ASPECTS OF THE BIOLOGY OF Argulus
by
QUINTON TAM
DISSERTATION
Submitted in partial fulfillment of the requirements for the degree
MASTER OF SCIENCE
in
ZOOLOGY
in the
FACULTY OF SCIENCE
at the
UNIVERSITY OF JOHANNESBURG
SUPERVISOR: PROF A AVENANT-OLDEWAGE
NOVEMBER 2005
DEDICATION
This work is dedicated to the LORD, for if it was not for him the completion of
this dissertation would not be possible.
FOOTPRINTS
One night a man had a dream. He dreamed he was walking along the beach with the LORD. Across the sky flashed scenes from his life. For each scene, he noticed two sets of footprints in the sand; one belonging to him, and the other to the LORD.
When the last scene of his life flashed before him, he looked back at the footprints in the sand. He noticed that many times along the path of his life there was only one set of footprints. He also noticed that it happened at the very lowest and saddest times in his life.
This really bothered him and he questioned the LORD about it. “LORD, you said that once I decided to follow you, you’d walk with me all the way. But I have noticed that during the most troublesome times in my life, there is only one set of footprints. I don’t understand why when I needed you most you would leave me.”
The LORD replied, “My precious, precious child. I love you and I would never leave you. During your times of trial and suffering, when you see only one set of footprints, it was when I carried you.”
--- Author unknown
ACKNOWLEDGEMENTS
1. Prof. Annemarié Avenant-Oldewage, for her guidance, patience and
encouragement during this study.
2. My mother, for her support and encouragement.
3. Edie Lutsch, for her patience and help with the preparation of the
microscope slides.
4. The National Research Foundation, Sasol and the University of
Johannesburg for funding this study.
5. I would also like to acknowledge the support and assistance of the
following people:
Ebrahim Karim, Emmerentia Potgieter, Nico-Ronaldo Retief, Professor
Elizabeth Snyman, Mkhacani Mathonsi, Gina Walsh, Simon John
Milne, Solly Tshabalala, Anna Mbokoleng Tsotetsi, Dr. Richard
Greenfield, Dr Nico Smit, Herman Van Niekerk, Louie Lodewyk
Coetzee, Dr. Willie Oldewage (for printing the exquisite photo sheets).
ABSTRACT
At present 35 species of Argulus are recognized in Africa. From a summary of the literature available for Argulus species in Africa it is clear that species descriptions are often the only information available for the majority of species. Information on the anatomy and histology of African Argulus species is even more scant. However, previous literature reveals that the anatomy and histology of the digestive system is similar in most branchiurans. The first study includes a description of a poorly known Argulus species described using SEM. Sixteen male and one female specimen of Argulus personatus
Cunnington, 1913, were collected from Bathybates ferox Boulenger, 1898, from Lake Tanganyika in northern Zambia. Results from light and scanning electron microscopy (SEM) examinations documented a thickening of cuticle located on the dorsal surface between the last thoracic segment and abdomen, which was rectangular in shape; the pre-oral spine and the proboscis ornamented with simple scales; a set of 3 large simple setae on the distal end of the basal plate; the dorsal distal end of second podomere of the maxillae ornamented with scales resembling those of a fish; the second and third podomeres of maxillae ornamented with two types of pectinate scales
(with fine bristle-like ends and scales with large pointed ends); the ventral distal end of third and fourth maxillary podomeres bearing large teardrop- shaped scales; a pair of tubular structures present adjacent to the anterior projection; a peg on the fourth pairs of legs of males bearing shallow grooves running irregularly across surface; and an accessory cushion bearing minute
i projections. These characters found in A. personatus were addressed in a redescription.
The digestive system of Argulus japonicus metanauplii is described following reconstruction from serial sections. The similarities between the larval and adult digestive system are described. Both digestive systems consist of an oesophagus, oesophageal funnel, anterior midgut, midgut enteral diverticula, posterior midgut and a hindgut. Histologically, the foregut of both the adult and larva consist of cuboidal epithelium and both the adult and larval hindguts are composed of columnar epithelium. Despite the similarities between the adults and larvae some differences exist. Differences include that the epithelium lining of the midgut of newly hatched larvae contain yolk. The midgut diverticula are less ramified than in the adult. The posterior midgut is lined with large swollen cuboidal epithelium with large vacuoles and a ciliated border whereas the adult posterior midgut is lined by large papilliform cells.
Argulus japonicus larvae only survive a day after hatching without nutrition from a host and once the first stage larvae start to feed on host tissue they feed mainly on epithelial cells and mucus. There was no blood observed in the lumen of the digestive system. It is concluded from the study that much work remains concerning the taxonomy of African species. Many of the species remains inadequately described and new identification keys must be created.
New environmentally safe treatments should be a focus of future development. Also, many physiological aspects of the argulid digestive system remain unknown and provide another focus of future research.
ii OPSOMMING
Huidiglik word 35 spesies van die genus Argulus in Afrika erken. Uit ‘n oorsig van literatuur van Argulus spesies in Afrika blyk dit dat spesiebeskrywings dikwels die enigste inligting is wat vir die meerderheid spesies beskikbaar is.
Inligting met betrekking tot die anatomie en histology van Argulus spesies in
Afrika is selfs nog skaarser. Uit bestaande literatuur blyk dit dat die spysverteringstelsels van verteenwoordigers van die Branchiura oor ‘n soortgelyke histologie en anatomie beskik. In die eerste gedeelte van die verhandeling word ‘n onvolledig beskryfde spesie van die genus Argulus verder beskryf met behulp van SEM. Sestien mannetjie- en een wyfie eksemplaar van Argulus personatus Cunnington, 1913, individue is versamel op Bathybates ferox Boulenger, 1989, uit die Tanganjikameer in noordelike
Zambië. Lig- en skandeerelektronmikroskopie (SEM) demonstreer ‘n reghoekige verdikking van die kutikula op die dorsale oppervlak, tussen die laaste segment van die toraks en abdomen. eenvoudige skubbe was waargeneem op die basale gedeelte van die pre-orale stekel en proboskis; drie groot, eenvoudige setas was waargeneem op die distale punt van die basale plaat; die dorsale distale punt van die tweede podomeer van die maksillae word bedek met skubbe soortgelyk aan die van ‘n vis; die tweede en derde podomere van die maksillae word bedek met twee tipes blaarvormige skubbe (met fyn borselagtige punte en skubbe met groot punte); groot traanvormige skubbe word gedra op die ventrodistale punt van die derde en vierde maksillêre podomeer; langs die anterior projeksie is ‘n paar buisvormige strukture gelëe. Die pen is geleë op die vierde paar swempote
iii van die mannetjie met diep groewe wat onrëelmatig oor die oppervlak voorkom; en klein projeksies op ‘n bykomende kussing. Hierdie eienskappe het van die oorspronklike beskrywing van A. personatus verskil, en word herbeskryf.
Die spysverteringstelsel van die eerste stadium larwe van Argulus japonicus
Thiele, 1900, word beskryf deur die rekonstuksie vanaf seriessnëe. Die morfologie van die verteringskanaal is soortgelyk aan die van volwasse verteenwoordigers van die Branchiura. Die veteringskanaal van die larva bestaan uit ʼn esofagus, esofageale tregter, anterior midderm (krop), enteriese divertikula, posterior midderm (intestinum) en ʼn endderm. Die epiteelselle wat die midderm van die nuweling larwe uitvoer bevat groot hoeveelhede dooier.
Die midderm divertikula is minder boomvormig vergeleke met volwassenes en ontstaan van die anterior midderm as twee arms wat verder anterior en posterior in die karapaks verdeel. Die posterior midderm bestaan uit groot uitstulpte kubiese epiteelselle met groot vakuole en ‘n gesillieerde rant. In teenstelling hiermee is die posterior midderm van die volwassenes met groot papilvormige selle uitgevoer. Larwes van Argulus japonicus oorleef vir slegs ‘n dag na uitbroeing sonder voeding op ‘n gasheer, en wanneer die eerste larwe stadium begin voed op gasheerweefsel, voed hulle hoofsaaklik op epiteelselle en slym. Geen bloed was in die lumen van die veteringstelsel waargeneem nie. Samevattend, daar is steeds baie gapings betreffende die taksonomie van Afrika verteenwoordigers van Argulus. Baie spesies is steeds ontoereikend beskryf en nuwe identifikasie sleutels moet saamgestel word.
Nuwe omgewingsvriendelike behandelingsmetodes behoort ‘n fokuspunt in
iv toekomstige navorsing te wees. Fisiologiese aspekte van die spysverteringstelsels is steeds onbekend en bied ‘n ander fokuspunt vir toekomstige studies.
v TABLE OF CONTENTS
ABSTRACT…………………………………………………………………………..i
TABLE OF CONTENTS…………………………………………………………...vi
LIST OF FIGURES………………………………………………………………..viii
LIST OF TABLES…………………………………………………………………..ix
CHAPTER 1: INTRODUCTION: Argulus IN AFRICA
1.1 Distribution and morphology of the Branchiura ...... ….1 1.1.1 Distribution of the Branchiura...... 1 1.1.2 Morphological differences between the branchiuran genera...... 1
1.2 Importance of branchiuran parasites...... 2 1.2.1 Pathogenic effects of branchiuran parasites ...... 2 1.2.2 Pathogenic effects caused by Argulus ...... 4 1.2.3 Treatment of Argulus infestations ...... 5
1.3. Distribution of Argulus species in Africa...... 6 1.3.1 Distribution of Argulus in Southern Africa...... 13 1.3.2 Distribution of Argulus in East-Central Africa ...... 14 1.3.3 Distribution of Argulus in Northern Africa ...... 14
1.4. Previous knowledge on African Argulus species ...... 15 1.4.1 SEM studies conducted on African species ...... 20 1.4.2 Anatomical and Histological studies conducted on African species...... 21
1.5. Objectives of this study...... 24
1.6. An outline of the dissertation ...... 25
vi
CHAPTER 2: ULTRASTRUCTURAL INVESTIGATION OF Argulus personatus Cunnington, 1913
2.1. INTRODUCTION...... 28
2.2. MATERIALS AND METHODS ...... 29
2.3. RESULTS ...... 31
2.4. DISCUSSION AND CONCLUSION...... 40
CHAPTER 3: THE DIGESTIVE SYSTEM OF LARVAL Argulus japonicus Thiele, 1900
3.1. INTRODUCTION...... 44
3.2. MATERIALS AND METODS ...... 45
3.3. RESULTS ...... 46
3.3.1. Foregut...... 49
3.3.2. Anterior Midgut...... 50
3.3.3. Posterior Midgut...... 54
3.3.4. Hindgut...... 54
3.4. DISCUSSION...... 55
CHAPTER 4: SUMMATIVE DISCUSSION AND FUTURE RESEARCH...... 62
LITERATURE REFERENCES...... 70
vii
LIST OF FIGURES
Figure 1.1. Schematic representations of Branchiurans to show basic structure…………………………………………….…………………...3 Figure 1.2. A. Map of African continent. B. Map of Southern Africa showing the geographic locations of the various Argulus species …………………………………………...……………………..7
Figure 1.3. A. Map of African continent. B. Map of East-Central Africa showing the geographic locations of the various Argulus species………………………………...………………………………...9
Figure 1.4. A. Map of African continent. B Map of Northern Africa showing the geographic locations of various Argulus species…………………………………………………………………12
Figure 2.1. Schematic diagram of Argulus personatus to indicate the position where measurements were taken; A, male, dorsal view; B, female, dorsal view…………………………………30
Figures 2.2.A-G Scanning electron micrographs of Argulus personatus…………..33
Figures 2.2.H-M Scanning electron micrographs of Argulus personatus…………..35
Figures 2.2.N-S Scanning electron micrographs of Argulus personatus………...... 37
Figures 2.2.T-Y Scanning electron micrographs of Argulus personatus…………..39
Figure 3.1 Argulus japonicus larva. Graphic reconstruction of the digestive system………………………………………………………47
Figures 3.2.A-I Argulus japonicus larva. Schematic drawings of transverse sections through the digestive system……………………...……...48
Figures 3.3.A-I Photomicrographs of Argulus japonicus larva…………………....52
Figures 3.3.J-N Photomicrographs of Argulus japonicus larva……………..……..55
viii LIST OF TABLES
Table 1.1.1 Table accompanying Figure 1.2 indicating letter symbols that correspond to each locality where a specific species of Argulus was recorded in Southern Africa……………….…….8
Table 1.1.2 Table accompanying Figure 1.3 indicating letter symbols that correspond to each locality where a specific species of Argulus was recorded in East-Central Africa……….……….10
Table 1.1.3 Table accompanying Figure 1.4 indicating letter symbols that correspond to each locality where a specific species of Argulus was recorded in Northern Africa……………….……13
Table 1.2.1 Summary of information available on whole mount, histological and SEM studies on Argulus species in Southern Africa….16
Table 1.2.2 Summary of information available on whole mount, histological and SEM studies on Argulus species in East-Central Africa……………………………………………………………. 17
Table 1.2.3 Summary of information available on whole mount, histological and SEM studies on Argulus species in Northern Africa.....19
ix
CHAPTER 1
INTRODUCTION: Argulus IN AFRICA
GENERAL INTRODUCTION
1.1. Distribution and morphology of the Branchiura
1.1.1. Distribution of the Branchiura
The Branchiura is a relatively small group of ectoparasitic crustaceans which
include less than 150 species. This taxon of parasites traditionally infects fishes
but is also known to infect frogs (Wilson, 1903, Bower-Shore, 1940 and Wolfe et
al. 2001). The group comprises 4 genera including Argulus, Müller (1785),
Dolops Audouin (1837), Chonopeltis, Thiele (1900) and Dipteropeltis, Calman
(1912), The genus Chonopeltis is endemic to Africa. Dipteropeltis is represented
by a single species D. hirudino Calman (1912) and this genus is endemic to
South America. A single species of Dolops (D. ranarum) is present in Africa and
another species in Tasmania, the other eleven species are found in South
America. The genus Argulus is the only genus with a cosmopolitan distribution
and is found in Africa, Europe, Asia, Australia, as well as North and South
America (Ringuelet, 1943, Yamaguti 1963, Fryer, 1968, Hewitt and Hine, 1972,
Byrnes, 1985).
1.1.2. Morphological differences between the branchiuran genera
The carapace lobes of D. hirundo are extremely elongated and extend past the
abdominal lobes and they are also lanceolate in shape. An oral papilla is present
which is unique to the genus (refer to Fig.1.A and B). In Dolops, the maxillules
are robust hooks for attachment; whereas in the other three genera the
maxillules are transformed into large, strong, cup-shaped suckers (refer to Fig.1C
and D). In Chonopeltis, morphological differences include the absence of a pre-
CHAPTER 1 1 GENERAL INTRODUCTION
oral spine, trifoliate carapace and the absence of antennules (refer to Fig. 1E and
F). Species of Argulus are the only ones to possess an oral spine (refer to Fig.1G
and H).
1.2. Importance of branchiuran parasites
1.2.1. Pathogenic effects of branchiuran parasites
The attachment and feeding appendages such as the maxillules and proboscis,
as depicted in Figure 1, are responsible for the numerous pathogenic effects.
The pathogenic effects of Dipteropeltis and Chonopeltis haven’t been studied as
yet. However, since Chonopeltis and Argulus possess suckers as their primary
appendages of attachment, the pathogenic effects caused by Chonopeltis would
be similar to Argulus. The suckers are known to cause damage to the epidermal
layer of the skin. The hooked maxillules in Dolops cause the most significant
damage. They are known to penetrate both the epidermal and dermal layers and
even break blood vessels causing anemia (Avenant-Oldewage, 1994). Argulus
causes blood loss by sucking blood while Chonopeltis feeds on mucus only. The
pathogenic effects caused by Chonopeltis are probably less severe. Argulus is
also the only genus known to transmit other pathogens through their feeding
habits. Fish farmers fear branchiurans above many other parasites, and of all the
branchiuran parasites Argulus is said to be the most feared (Reichenbach-Klink
and Elkan, 1973) possibly because the pathogenic effects caused by Argulus are
relatively more severe when compared to other branchiuran genera. The
pathogenic effects caused by Argulus are described below.
CHAPTER 1 2 GENERAL INTRODUCTION
Fig 1.1. Schematic representations of Branchiurans to show basic structure; A, Ventral view of Dipeteropeltis hirundo; B, Dorsal view of Dipteropeltis hirundo (Redrawn from Calman, 1912); C, Ventral view of Dolops ranarum; D, Dorsal view of Dolops ranarum (Redrawn from Avenant- Oldewage and Van As, 1990); E, Ventral view of Chonopeltis flaccifrons; Dorsal view of Chonopeltis flaccifrons (Redrawn from Fryer, 1960); G, Ventral view of Argulus japonicus; H, Dorsal view of Argulus japonicus (Redrawn from Cesare, 1986); A, abdomen; An, antennule; Ant, antenna; C, carapace; CE, compound eye; L, swimming leg; LL, lanceolate lobe of carapace; Max, maxilla; Maxl, maxillule; OP, oral papilla; P, proboscis; PS, preoral spine; T, thorax; TC, trifoliate carapace.
CHAPTER 1 3 GENERAL INTRODUCTION
1.2.2. Pathogenic effects caused by Argulus
Parasites which infect fish under natural conditions are less of a threat than to
those under artificial enclosed conditions (Walker et al. 2004). The increased
interest of fish farming during the decades of the 1970’s, 80’s and 90’s has
helped to focus argulid research mainly on host-parasite interaction under
artificial conditions, and the treatment there of. Under artificial conditions fish
parasites such as Argulus are known to cause large economic losses on fish
farms, where they are able to increase their numbers exponentially and destroy
fish. Studies with regards to Argulus infestations on fish farms include Okaeme et
al. (1988), Behrent (1994), Buchmann et al. (1995), Grignard et al. (1996),
Buchmann and Bresciani (1997) and Northscott et al. (1997). Pathogenic effects
include skin damage to their hosts and manifest themselves as skin lesions
(dermatitis) (Oprean and Vulpe, 2002). These lesions could become secondarily
infected by bacteria (Yldz and Kumantas, 2002). The dermatitis is due to the
damaging effect of the suckers and proboscis. The rim of the suckers
compresses epithelial cells in the shape of a ring, whereas the vacuum action of
the sucker causes the elevation and loss of cohesion of cells in the center of the
ring (Watson and Avenant-Oldewage, 1996). Anemia is another significant
pathological effect caused by feeding. Hindle (1948) reported fishes infested with
Argulus were sluggish and isolated themselves in the corners of aquariums. In
addition to the pathogenic effects mentioned above, Argulus is also known to be
a vector of certain viruses, such as Rhabdovirus carpio or spring viraemia (Pfeil-
Putzien, 1977 and Pfeil-Putzien and Baath, 1978) and carp pox or viral
epithelioma (Timur, 1991). They are vectors for nematode larvae of the family
CHAPTER 1 4 GENERAL INTRODUCTION
Skrjabillanidae (Rudometova, 1974, Tikhomirova, 1971, 1975 and 1983,
Moravec, 1978, Molnar and Szekely, 1998 and Moravec et al. 1999) and of the
order Dranunculoidea (Molnar and Moravec, 1997). Reports of parasitic
crustacean infection have increased the number of researchers in this specific
study area (Walker et al. 2004). The significance of these pathogenic effects has
spawned numerous methods of treatment which include both chemical and non-
chemical means.
1.2.3. Treatment of Argulus infestations
The treatments of Argulus infestations include the use of common chemicals
such as salt (NaCl) (Singhal et al. 1986, Rydlo, 1989 and Wolfe et al. 2001).
Other common chemicals used in experimentation include formaldehyde (Rydlo,
1989), potassium permanganate (Singhal et al. 1986 and Jafri et al. 1994)
formalin (Singhal et al. 1986 and Rezeka, 1998) and powered quicklime (Jafri et
al. 1994). Treatments such as trichlorfon (Shoshov and Kolarova, 1997, Inoue et
al. 1980, Schmahl et al. 1989 and Tavares et al. 1999), emamectin benzoate
(Hakalahti et al. 2004) nuvan (Padmavathi et al. 1998) and gammexane (Singhal
et al. 1986) have also been used to eradicate Argulus. Gault et al. (2002)
developed a way of using egg-laying boards which imply boards are supplied and
once females had laid their eggs on the boards they are removed and burned.
Most of the previous fish farming and treatment research were conducted
primarily on the adults of a European argulid i.e.: A. foliaceus Linnaeus (1758),
and to a lesser extent on the adults of another European species A. coregoni
Thorell (1864) as well as on the Asian species A. japonicus Thiele (1900).
CHAPTER 1 5 GENERAL INTRODUCTION
Literature of this nature on African species is almost non-existent. However,
Okaeme et al. (1988) and Opara and Okon (2002) reported on information
collected from fish farms in Nigeria where A. africanus played a role in
infestation. No treatment was mentioned.
1.3. Distribution of Argulus species in Africa
The following figures (1.2, 1.3, and 1.4) and tables (1.1.2, 1.1.3 and 1.1.4)
summarize the distribution of Argulus species in Africa. Due to the large number
of species, the African continent (Fig 1.2.A, 1.3.A and 1.4.A) was divided into
three regions, namely Southern Africa (Fig 1.2.B), East-Central Africa (Fig 1.3.B)
and Northern Africa (Fig 1.4.B). Each figure shows the specific localities where
an Argulus species was recorded.
CHAPTER 1 6 GENERAL INTRODUCTION
A
B
Figure 1.2. A Map of African continent. B Map of Southern Africa showing the geographic locations of the various Argulus species.
CHAPTER 1 7 GENERAL INTRODUCTION
Table 1.1.1. Table accompanying Figure 1.2 indicating letter symbols which correspond to each locality where a specific species of Argulus was recorded in Southern Africa.
Corresponding Locality Argulus species Reference/s symbol in Figure 1.2.B A Zoetendals vlei, Western Cape Argulus capensis Barnard (1955) B KwaZulu/Natal coast Argulus belones Van Kampen (1909) C Lake St. Lucia, KwaZulu/Natal Argulus izintwala Van As et al. (2001)
Barberspan, Vaal River System, Argulus japonicus Kruger et al. (1983) D Northwest Province Van As and Basson (1984)
Bloemhof Dam, Vaal River Argulus japonicus Kruger et al. (1983) D1 System, Free State Van As and Basson (1984) D2 Boskop Dam, Vaal River System, Northwest Province Argulus japonicus Van As and Basson (1984)
Hartebeespoort Dam, Crocodile Argulus japonicus Van As and Basson (1984) D3 River, Northern Province D4 Loskop Dam, Olifants River System, Northern Province Argulus japonicus Avenant-Oldewage (2001)
Lydenburg (Provincial Fisheries Argulus japonicus Van As and Basson (1984) D5 Institute), Mpumalanga D6 Roodeplaat Dam, Crocodile River Northern Province Argulus japonicus Van As and Basson (1984) E Avenant-Oldewage and Kosi Bay, KwaZulu/Natal Argulus kosus Oldewage (1994) F Richards Bay, KwaZulu/Natal Argulus multipocula Barnard (1955) F1 Berg River Estuary, Western Cape Argulus multipocula Smit et al. (2005) G Algoa Bay, near Port Elizabeth, Eastern Cape Argulus smalei Avenant-Oldewage (1995) H Port Alexander, Angola Argulus alexandrensis Wilson (1923)
CHAPTER 1 8 GENERAL INTRODUCTION
A
B
Fig 1.3. A Map of African continent. B Map of East-Central Africa showing the geographic locations of the various Argulus species
CHAPTER 1 9 GENERAL INTRODUCTION
Table 1.1.2. Table accompanying Figure 1.3 indicating letter symbols which correspond to each locality where a specific species of Argulus was recorded in East-Central Africa.
Corresponding Locality Argulus species Reference/s symbol in Figure 1.3.B A Lake No Argulus rhipidiophorus Fryer (1959) B Lake Zwai Argulus rhipidiophorus Fryer (1964) C Lake Oitu (Langano) Argulus rhipidiophorus Fryer (1964) D Lake Abaya (Margherita) Argulus rhipidiophorus Fryer (1964) E Lake Awassa (Awusa) Argulus rhipidiophorus Fryer (1964) F Lake Turkana (Rudolf) Argulus brachypeltis, Argulus Rushton-Mellor (1994) fryeri Argulus rhipidiophorus Fryer (1959)
G Lake Kioga Argulus africanus Fryer (1968) H Lake Albert Argulus cunningtoni Fryer (1964)
Argulus rhipidiophorus Monod (1931) Argulus ambloplites Wilson (1920)
I Wilson (1920), Rushton – Dungu River Argulus confusus Mellor (1994) Argulus africanus Argulus ambloplites
Argulus angusticeps, Argulus
exiguus, Argulus personatus, Argulus incisus, Argulus Fryer (1968) rubescens, Argulus rubropunctatus, Argulus striatus,
Argulus monodi, Argulus
reticulatus, Argulus schoutedeni, J Zaire/Congo River Argulus rijkmansii, System Brian (1940), Fryer (1959)
Argulus dartevelli and Fryer (1968)
Argulus wilsonii Brian (1940) and Fryer
(1968)
CHAPTER 1 10 GENERAL INTRODUCTION
Lake Edward Argulus africanus Fryer (1964) K
Argulus rhipidiophorus Fryer (1965)
L Lake Kivu Argulus rhipidiophorus Fryer (1968) M Lake Mweru Argulus africanus Fryer (1965) N Bukama Argulus schoutedeni Monod (1928) Argulus africanus, Argulus Fryer (1958) ambloplites O Lake Bangweulu Argulus brachypeltis , Argulus Fryer (1958 and 1968) monodi Argulus africanus, Argulus Zambezi River System ambloplites, Argulus ambloplites Fryer (1968) P jollymani Argulus africanus, Argulus Fryer (1968) ambloplites, Q Lake Malawi
Argulus ambloplites jollymani Fryer (1956 and 1959)
R Lake Rukwa Argulus africanus Fryer (1968)
Argulus africanus Cunnington (1913) and Fryer (1965)
Argulus angusticeps, Argulus Cunnington (1913), Fryer
exiguus, Argulus incisus, Argulus (1965) and Lake Tanganyika S personatus, Argulus rubescens, Fryer (1968) Argulus rubropunctatus, Argulus striatus
Argulus schoutedeni Fryer (1965 and 1968)
Argulus gracilis Rushton-Mellor (1994) T Lake Kitangiri Argulus africanus Fryer (1968)
U Lake George Argulus rhipidiophorus Fryer (1968) V Lake Victoria Argulus africanus Fryer (1968) W Lake Naivasha Argulus rhipidiophorus Fryer (1959)
CHAPTER 1 11 GENERAL INTRODUCTION
A
B
Fig 1.4. A Map of African continent. B Map of Northern Africa showing the geographic locations of various Argulus species
CHAPTER 1 12 GENERAL INTRODUCTION
Table 1.1.3. Table accompanying Figure 1.4 indicating letter symbols which correspond to each locality where a specific species of Argulus was recorded in Northern Africa.
Corresponding Locality Argulus species Reference/s symbol in Figure 1.4.B A Near Algerian coast Argulus purpureus Wilson (1902) B Between Cape White and Argulus zei Brian (1924) Mauritania C Bay of Dakar, Senegal Argulus melita Van Beneden (1891) D Niger River System Argulus dageti Dollfus (1960) and Fryer (1968) E Bay of Douala, Cameroon Argulus trachynoti Brian (1927) F Kribi, Cameroon Argulus otolithi/ Argulus Brian (1927) and Cuenot arcassonensis (1912) Argulus africanus Fryer (1968)
Argulus brachypeltis Fryer (1958) Nile River System, Egypt G Argulus japonicus Fryer (1968) and Paperna (1980)
Argulus rhipidiophorus Fryer (1964)
1.3.1. Distribution of Argulus in Southern Africa
There are 36 species of Argulus recorded in and around the African continent.
However, Monod (1928) synonomised A. alexandrensis Wilson (1912) recorded
on the coast of Angola, with A. zei Brian (1924), recorded on the coast of
Cameroon. Therefore the number of species is reduced to 35. A freshwater
species has been introduced into Africa namely, A. japonicus. This species
resides in the Nile River system in Northern Africa and in rivers in South Africa. In
South Africa A. japonicus has received the reputation of being a major pest. This
could be due to the lack of host specificity of A. japonicus (LaMarre and Cochran,
CHAPTER 1 13 GENERAL INTRODUCTION
1992). Argulus japonicus was originally found in the Orange – Vaal River
systems, but was more recently found in the Olifants river system as well.
According to Avenant-Oldewage (2001), the parasite was probably transferred to
this system from the Grootdraai Dam in the Vaal River system.
1.3.2. Distribution of Argulus in East-Central Africa
As shown in Figure 1.3.B the species in the East-Central African region live in
large freshwater bodies such as the Great African lakes. The majority of the
Argulus species known in Africa come from this region. Many of the endemic
species can be found in multiple localities (refer to Table 1.1.3). Argulus
japonicus has not been recorded in any of the water bodies in this region.
1.3.3. Distribution of Argulus in Northern Africa
There are far less species and parasitologists working on these in the north of
Africa (Figure 1.4.B and table 1.1.4) with A. africanus Thiele (1900) and A. dageti
Dollfus (1960) being the only two endemic freshwater species in the Niger River
System. The remainder are marine or estuarine and are found along the coast of
Northern Africa. Most marine species of Argulus are also found in other areas of
the world due to host migration. Some of the same species are also found along
the coasts of the Mediterranean and Europe. For instance, Monod (1928) found
A. arcassonensis Cuenot (1912) was the same as A. otolithi Brian (1924) and
synonomised them. Rushton-Mellor (1994b) has confirmed they are identical.
CHAPTER 1 14 GENERAL INTRODUCTION
1.4. Previous knowledge on African Argulus species
The following tables (1.2.1, 1.2.2 and 1.2.3) contain a summary of information on
all the African Argulus species. The tables indicate whether research was done
using whole mount specimens, and whether any SEM or histological studies
were conducted.
CHAPTER 1 15 GENERAL INTRODUCTION
Table 1.2.1. Summary of information available on whole mount, histological and SEM studies on Argulus species in Southern Africa.
Species Whole mount Histological SEM Reference/s studies studies studies
1. Argulus alexandrensis Yes No No Wilson (1923), Monod (1928), (Wilson 1923) and Rushton- Mellor (1994b)
2. Argulus capensis Yes No No Barnard (1955), Rushton- Barnard (1955) Mellor (1994b)
3. Argulus belones* Yes No No Van Kampen (1909) Van Kampen (1909) Rushton-Mellor (1994b)
4. Argulus izintwala Van As J.G and Van Yes No Yes Van As et al. (2001) As L.L. (2001)
5. Argulus japonicus* Yes Yes Yes Thiele (1900), Avenant- Thiele (1900) Oldewage and Swanepoel (1992 and 1993), Ikuta and Makioka (1993, 1994, 1995 and 1997), Gresty et al. (1993) and Rushton- Mellor (1994b)
6. Argulus kosus Yes No Yes Avenant-Oldewage and Avenant-Oldewage (1994) Oldewage (1994), Van As et al. (1999)
7. Argulus multipocula Yes No Yes Barnard (1955), Barnard (1995) Smit et al. (2005) and Rushton-Mellor (1994b)
8. Argulus smalei Yes No No Avenant-Oldewage (1995) Avenant- Oldewage and Oldewage (1995) * Not an endemic species to Africa
CHAPTER 1 16 GENERAL INTRODUCTION
Table 1.2.2. Summary of information available on whole mount, histological and SEM studies on Argulus species in East-Central Africa.
Species Whole mount Histological SEM Reference/s studies Studies studies
1. Argulus africanus Yes No No Thiele (1900 and 1904), Thiele (1900) Cunnington (1913), Monod (1928), (1956, 1958, 1964, 1965 and 1968) and Rushton-Mellor (1994b)
2. Argulus amboplites Yes No No Wilson (1920), Fryer (1958, 1959 Wilson (1920) and 1968) and Rushton-Mellor (1994b)
3. Argulus ambloplites Yes No No Fryer (1956, 1959 and 1968) jollymani Fryer (1956) and Rushton-Mellor (1994b)
4. Argulus angusticeps Yes No No Cunnington (1913), Fryer (1968) Cunnington (1913) and Rushton-Mellor (1994 a and b)
5. Argulus brachypeltis Yes No No Fryer (1958 and 1968), Rushton- Fryer (1958) Mellor(1994 and 1994b)
6. Argulus confusus Yes No No Wilson (1920) and Rushton-Mellor Wilson (1920) (1994 and 1994b)
7. Argulus cunningtoni Yes No No Fryer (1964) and Rushton-Mellor Fryer (1964) (1994b)
8. Argulus dartevelli Yes No No Brian (1940), Fryer (1959 and Brian (1940) 1968) and Rushton-Mellor (1994b)
9. Argulus exiguus Yes No No Cunnington (1913), Fryer (1968), Cunnington (1913) Rushton-Mellor (1994 a and b)
10. Argulus fryeri Yes No No Rushton-Mellor (1994 and 1994b) Rushton-Mellor (1994)
CHAPTER 1 17 GENERAL INTRODUCTION
11. Argulus gracilis Yes No No Rushton-Mellor (1994 and 1994b) Rushton-Mellor (1994)
12. Argulus incisus Yes No No Cunnington (1913), Fryer (1968), Cunnington (1913) Rushton-Mellor (1994 a and b)
13. Argulus monodi Yes No No Fryer (1958 and 1968) and Fryer (1958) Rushton-Mellor (1994b)
14. Argulus personatus Yes No No Cunnington (1913), Fryer (1965 Cunnington (1913) and 1968) Rushton-Mellor (1994 a and b)
15. Argulus reticulatus Yes No No Wilson (1920), Fryer (1968) Wilson (1920) and Rushton-Mellor (1994b)
16. Argulus rhipidiophorus Yes No No Fryer (1965 and 1968) Monod (1931) Rushton-Mellor (1994b)
17. Argulus rijkmansii Yes No No Brian (1940), Barnard (1955) and Brian (1940) Rushton-Mellor (1994b)
18. Argulus rubescens Yes No No Cunnington (1913), Fryer (1968) Cunnington (1913) and Rushton-Mellor (1994 a and b)
19. Argulus rubropunctatus Yes No No Cunnington (1913), Monod (1928), Cunnington (1913) (1965 and 1968), Rushton-Mellor (1994 a and b)
20. Argulus schoutedeni Yes No No Monod (1928), Fryer (1965 and Monod (1928) 1968) Rushton-Mellor (1994b)
21. Argulus striatus Yes No No Cunnington (1913), Fryer (1965 Cunnington (1913) and 1968), Rushton-Mellor (1994 a and b)
22. Argulus wilsonii Yes No No Brian (1940), Fryer (1968) Brian (1940) and Rushton-Mellor (1994b)
CHAPTER 1 18 GENERAL INTRODUCTION
Table 1.2.3. Summary of information available on whole mount, histological and SEM studies on Argulus species in Northern Africa
Species Whole mount Histological SEM Reference/s Studies Studies studies
1. Argulus africanus Yes No No Monod (1928), Fryer (1961 and 1968) Thiele (1900) and Rushton-Mellor (1994b)
2. Argulus brachypeltis Yes No No Fryer (1958) and Rushton-Mellor Fryer (1958) (1994b)
3. Argulus dageti Yes No No Dollfus (1960), Fryer (1968) Dollfus (1960) and Rushton-Mellor (1994b)
4. Argulus japonicus* Yes Yes Yes Thiele (1900), Avenant-Oldewage Thiele (1900) and Swanepoel (1992 and 1993), Ikuta and Makioka (1993, 1994, 1995 and 1997), Gresty et al. (1993) and Rushton- Mellor (1994b)
5. Argulus melita Yes No No Van Beneden (1891), Wilson (1902), Van Beneden (1891) Monod (1928), Rushton-Mellor (1994b)
6. Argulus arcassonensis Yes No No Cuenot (1912), Brian (1927), Monod Cuenot (1912) (synonym is (1928) and Rushton-Mellor (1994b) Argulus otolithi Brian (1927))
7. Argulus purpureus Yes No No Wilson (1902), Monod (1928) Risso (1826) and Rushton-Mellor (1994b)
8. Argulus rhipidiophorus Yes No No Fryer (1959 and 1965) and Rushton Monod (1931) Mellor (1994b)
9. Argulus trachynoti Yes No No Brian (1927), Monod (1928) and Brian (1927) Rushton-Mellor (1994b)
CHAPTER 1 19 GENERAL INTRODUCTION
10. Argulus alexandrensis Yes No No Brian (1924), Monod (1928) Wilson (1923) (synonym is and Rushton-Mellor (1994b) Argulus zei Brian (1924)) * Not an endemic species to Africa
1.4.1 SEM studies conducted on African species
Tables 1.2.1, 1.2.2 and 1.2.3 reveal that in Africa specifically, much of the
research conducted on Argulus was based on whole mounts. With regards to the
species in South Africa, only 4 of the 8 species were studied with SEM (A.
izintwala, A. japonicus, A. kosus and A. multipocula). All of the SEM studies on
A. japonicus were conducted by researchers in South Africa (Avenant-Oldewage
and Swanepoel, 1992 and 1993) and from other parts of the world (Gresty et al.
1993), but none from northern Africa. In the regions of East-Central Africa and
Northern Africa, SEM studies have not yet been conducted on any of the
species. Therefore, the majority of species endemic to Africa have not been
studied with SEM.
The most recent up-to-date identification key available on African species was
compiled by Rushton-Mellor (1994b), based on whole mount studies and
includes all the known species except A. izintwala, A. kosus and A. smalei.
However, despite the depth of the key, information on many of the male
specimens remains undescribed or inadequately described (Rushton-Mellor,
1994b). The conspicuous accessory copulatory structures present on the third
and fourth pairs of legs of males allows for easy species identification (Rushton-
Mellor, 1994b). However, since many of the descriptions and drawings of the
CHAPTER 1 20 GENERAL INTRODUCTION
males are not included in the key, identification of a species is more difficult.
Conducting SEM work on all species would greatly contribute to the creation of
future identification keys and possibly eradicate many taxonomic problems in this
group.
1.4.2 Anatomical and Histological studies conducted on African species
The tables (1.2.1, 1.2.2 and 1.2.3) above reveal that histological information on
African argulids is non-existent. Information is only available for the introduced A.
japonicus, and two European species i.e. A. foliaceus and A. coregoni. Similarly
much of the literature concerning fish farming and treatment are on the
previously mentioned species (see section 1.2.2 and 1.2.3). One of the
explanations for the wealth of literature on the above mentioned species
(especially A. foliaceus) is because biologists had begun studying these species
during the late 19th century and continued their studies into the 20th century.
Authors including Jurine (1806), Claus (1875), Leydig (1850 and 1889), Grobben
(1908), Martin (1932), Debaisieux (1953) and Madsen (1964), produced literature
on the morphology, anatomy, and histology of various organs such as the eyes,
nervous system, circulatory system, reproductive system and digestive system.
Wilson (1902) wrote on similar aspects of biology of American species (A.
americanus and A. megalops). Ikuta and Makioka (1993, 1994, 1995 and 1997),
produced a series of articles on the adult female reproductive system of A.
japonicus and Avenant-Oldewage and Swanepoel (1993) on the adult male
reproductive system of A. japonicus. They also produced a publication on the
pre-oral spine (Avenant-Oldewage and Swanepoel, 1992).
CHAPTER 1 21 GENERAL INTRODUCTION
Despite the relatively comprehensive information available on their biology,
mostly the morphology, anatomy and histology research concentrated mainly on
the adults and information on the larvae is scant and limited to the morphology of
various lifestages. Both the older literature (Claus, 1875, Leydig, 1850 and 1889,
Wilson, 1902) and more recent literature (Tokioka, 1936, Stammer, 1959,
Shimura, 1981 and Rushton-Mellor, 1993) give detailed accounts on the
metamorphosis of Argulus larvae.
When considering the aspects of the internal anatomy such as the digestive
system for instance, the adult digestive system of Argulus (A. foliaceus) is well-
known. Studies on the adult digestive systems of other branchiuran genera also
exist and include Dolops ranarum, Stuhlmann (1891) (Avenant-Oldewage and
Van As 1990) and Chonopeltis australis, Boxshall (1976) (Avenant-Oldewage et
al. 1994). Overstreet et al. (1993) produced a paper on the Branchiura which
included the histology of the adult digestive systems. These studies revealed the
digestive systems of all three genera are similar to each other. Therefore
conducting studies on the digestive systems of other African Argulus species
would produce similar information. However, the digestive system of larval
argulids is largely unknown. Previous authors have merely observed that the
morphology and anatomy of the larval digestive system is superficially similar to
the adult, and none of the authors conducted studies on the histology of the
larval digestive system. Furthermore, some authors such as Bower-Shore
(1940), Shimura (1981), Schram (1986) and Lester and Roubal (1995) have also
reported that Argulus larvae become parasitic during their first naupliar stage.
CHAPTER 1 22 GENERAL INTRODUCTION
Most species of crustacean larvae hatch with yolk supplies in their digestive tract
and many of them are not parasitic during their first few lifestages. Lernaea
cyprinacea Linnaeus (1758), for example, undergoes a few molts before
becoming parasitic (Benedetti et al. 1992). In contrast, other authors have
reported yolk present in the Argulus larval digestive system after hatching (Claus,
1875) and this may indicate feeding does not take place during their first lifestage
despite being attached to them. Therefore this may contradict what previous
authors have reported. However, due to the scant information available on the
larval digestive system, previous claims on the parasitic nature of larvae during
their first stage are unreliable.
There is no conclusive evidence to prove the digestive system of the larvae and
adult are similar or different to each other morphologically, anatomically or
histologically. Also, despite previous reports that Argulus attach to hosts during
their first stage; there is no conclusive evidence to show they are parasitic as
previous authors have not commented on the role of yolk in Argulus larvae.
The lack of knowledge in certain aspects of Argulus biology, as discussed in this
introductory chapter, provides the foundation for the hypothesis and also the
study objectives of this dissertation.
CHAPTER 1 23 GENERAL INTRODUCTION
1.5. Objectives of this study
During the year 2000, specimens of an unidentified Argulus were donated to
Prof. Avenant-Oldewage at the University of Johannesburg. They were collected
from Lake Tanganyika in the East-Central African region (see Figure 3 and table
3.1)
Therefore the first objective of this study is to:
5.1 Conduct a detailed ultrastructural study on a species from East-Central
Africa by:
a. investigating the donated specimens by the use of SEM
b. describing previously unrecognized characters of this African species
to further contribute to identification and taxonomy
Detailed information on the Argulus larval digestive tract is unavailable and the
evidence on the parasitic nature of the first stage metanauplii is unconfirmed. A.
japonicus was chosen as the subject of this particular study due to their
abundance in South Africa and ease of sampling.
Therefore the second objective of this study is to:
CHAPTER 1 24 GENERAL INTRODUCTION
5.2 Conduct a detailed study of the Argulus larval digestive
system by:
a. reconstructing and describing the morphology, anatomy and histology
the larval digestive system
1.6. An outline of the dissertation
Different aspects of this study are discussed in separate chapters. Chapter 1 is a
literature review on Argulus in Africa. Each chapter succeeding chapter 1
consists of an introduction, materials and methods, discussion and conclusion.
These chapters are organized as follows:
Chapter 2 contains an ultrastructural description of Argulus personatus
Cunnington (1913). This chapter has been published in African
Zoology, Journal of. as Tam, Q, Avenant-Oldewage, A. and Williams
E.H. Jr. 2005. An ultrastructural investigation of Argulus personatus
Cunnington 1913 (Crustacea: Branchiura) from Lake Tanganyika,
northern Zambia. African Zoology. 40 (2): 301-308.
Chapter 3 contains a detailed anatomical and histological description of the
larval digestive tract of Argulus japonicus Thiele (1900) and was
submitted to the Journal of Crustacean Biology as Tam, Q. and
Avenant-Oldewage, A. In press. The Digestive System of Larval
Argulus japonicus (Branchiura). Accepted in the Journal of Crustacean
Biology.
Chapter 4 is a summative discussion of the study and gives suggestions for
future research on Argulus.
CHAPTER 1 25 GENERAL INTRODUCTION
Chapter 5 is a reference list of all the literature cited in the different chapters of
the thesis.
In addition to the publication mentioned above, the following outputs were
delivered.
Conference contributions
1) Q. Tam and A. Avenant-Oldewage. 2004. Aspects of the Biology of Argulus
and other branchiurans. Post-graduate symposium of the Department of
Zoology at the University of Johannesburg. 26 October 2004. Recipient of the
Zoology Department award for best oral presentation.
2) Q. Tam and A. Avenant-Oldewage. 2004. Aspects of the Ultrastructure of
Argulus personatus Cunnington, 1913 (Crustacea: Branchiura) from Lake
Tanganyika, northern Zambia. 2004. 43rd Annual congress of the Microscopic
Society of Southern Africa. Groenkloof Campus of the University of Pretoria.
30th of November – 3rd of December 2004. Attached as (Appendix A).
3) Tam, Q and Avenant-Oldewage, A. 2005. Investigation of the gastrointestinal
tract of Laval and Juvenile Argulus japonicus Thiele: 1900. 34th Congress of
Parasitological Society of Southern Africa. Magoesbaskloof. 25-28 September
2005. – Provided as Appendix B. Recipient of the Senior Oral Presentation
Award.
Published abstract.
Tam, Q. and Avenant-Oldewage, A. In Press. Investigation of the
gastrointestinal tract of Larval and Juvenile Argulus japonicus Thiele: 1900.
Abstract accepted for publication in the Onderstepoort Journal of Veterinary
Research.
CHAPTER 1 26 GENERAL INTRODUCTION
4) Q. Tam and Avenant-Oldewage. 2005. The Digestive System of Larval
Argulus japonicus. Post-graduate symposium of the Department of Zoology
at the University of Johannesburg. 10 November 2005.
All chapters are written according to the format of African Zoology.
CHAPTER 1 27
CHAPTER 2
ULTRASTRUCTURAL INVESTIGATION OF Argulus personatus Cunnington, 1913
ULTRASTRUCTURE OF Argulus personatus
2.1. INTRODUCTION
Lake Tanganyika harbours eight Argulus species of which seven species are endemic to the lake (Cunnington, 1913). These species were originally discovered during the third expedition to Lake Tanganyika conducted by W.A.
Cunnington in 1904 and 1905. The seven species endemic to Lake
Tanganyika include A. angusticeps, A. exiguus, A. incisus, A. personatus, A. rubescens, A. rubropunctatus, and A. striatus. The non-endemic species,
Argulus africanus, was present in Lake Tanganyika also (Cunnington, 1913).
However, Fryer (1960) later discovered that many of the A. africanus collected in the Great African lakes region were in fact A. rhipidiophorus. He mentions some of the lakes with L. Albert in particular, the same lake in which
Cunnington sampled his specimens. However, Fryer does not mention Lake
Tanganyika specifically. Cunnington reiterates his findings in his subsequent publication of 1920 without mentioning anything new. Since Cunnington’s publications on L. Tanganyika (Cunnington, 1913 and 1920), there has been current updated information regarding the argulids of this lake. Therefore there is no updated confirmation as to whether A. africanus truly exists there.
Cunnington’s first descriptions of these seven endemic Argulus also lacked much morphological detail and subsequent redescriptions of these species were conducted by Rushton-Mellor (1994a and b). She examined
Cunnington’s type-material and gave detailed redescriptions of these endemic species in Lake Tanganyika. A detailed key for identification was also created for most of the African Argulus species. The A. personatus collected in
Zambia were compared to the literature (Rushton-Mellor 1994a and b,
Cunnington, 1913) and the British Museum of Natural History type specimens
CHAPTER 2 28 ULTRASTRUCTURE OF Argulus personatus
(cotypes 46-49). Previous research on A. personatus was conducted with light microscopy only. Therefore SEM was conducted on the specimens to add characteristics previously undescribed. Morphological examinations with light and scanning electron microscopy documented differences from Rushton-
Mellor 1994a and b which were incorporated into a redescription of the species. It must also be noted that the object of this paper is not to rearrange the taxonomy of African argulids but merely to provide additional morphological and ultrastructural information regarding A. personatus.
2.2. MATERIALS AND METHODS
Seventeen Argulus personatus were sampled from the buccal cavities of
Bathybates ferox Boulenger, 1898 (Perciformes: Cichlidae) on 4 July 2000 near the city of Mpulunga in northern Zambia. The fishes were collected from
Lake Tanganyika (35 in total) by four persons of whom one is a fish specialist,
Dr. Joseph R. Sullivan (see acknowledgements). This pelagic fish is endemic to this lake and has some commercial importance as a food and aquarium fish. Sixteen males and one female of Argulus personatus were immediately preserved in vodka (40% ethanol) and subsequently transferred to 10% formalin. The specimens were donated to Williams who subsequently donated them to Avenant-Oldewage. They were rinsed under running tap water prior to examination, dehydrated in an ascending ethanol series to 70%, cleared in
90% lactic acid containing Dimethylamino azo-benzine sodium sulphonate for light microscopy with a Wild M5 dissection microscope and Zeiss Lab 18 compound microscope both with drawing tubes. Eight male specimens were mounted on slides and examined with light microscopy. The single female
CHAPTER 2 29 ULTRASTRUCTURE OF Argulus personatus along with other eight male specimens was used for scanning electron microscopy. Specimens for scanning microscopy, following hydration, were freeze-dried and sputter coated with gold prior to examination with a JEOL
JSM-5600. Micro-dissection was performed to reveal the internal structure of the mouthparts. The specimens from the Natural History Museum (London) were examined with a dissection and a compound microscope.
Measurements of specimens were taken as indicated in Fig. 2.1. The length of the carapace was measured from the right side only.
The remaining specimens were deposited in the collection of the
Albany Museum, Grahamstown, South Africa (Argulus personatus. RAU 10 A-
H).
Locality. Off the south coast near Mpulunga, Lake Tanganyika.
Fig 2.1. Schematic diagram of Argulus personatus to indicate the position where measurements were taken; A, male, dorsal view; B, female, dorsal view (AbL, abdomen length; AbS, Abdomen sinus; AbW, abdomen width; CL, carapace length; CW, carapace width; TL, total length); C, male abdomen showing testes (TsL, testes length; TsW, testes width); D, female abdomen showing spermathecae (SpL, spermathecal length; SpW, spermathecal width).
CHAPTER 2 30 ULTRASTRUCTURE OF Argulus personatus
2.3. RESULTS
Description of adult male: Measurements based on eight specimens- Body
shape elongated; average length 5.5 mm, range 4.68 - 7.2 mm. Anterolateral
depressions pronounced, carapace almost as broad as it is long; average
length of carapace 3.03 mm, range 2.42 – 4.05 mm, percentage range 48% -
57% (53% of overall body length). No variation in the length of the carapace
lobes was visible. Average width of carapace 2.9 mm, range 2.37 – 3.95 mm,
carapace lobes extend to anterior midline of third pair of swimming legs.
Compound eyes large, nauplius eye visible, distance between compound
eyes, and distance between compound eyes and nauplius eye form an
equilateral triangle. Nauplius eye composed of 3 ocelli, 1 ocellus facing
anteriorly and 2 facing posteriorly. Thorax consists of four segments. Two
dorsal anterior facing projections located on fourth segment. Thickening of
cuticle present between fourth thoracic segment and abdomen, thickening
rectangular in shape (Fig. 2.2.Y). Abdomen elongated, average length of
abdomen 2.1 mm, range 2 - 2.47 mm, percentage range 37% - 41% (39% of
total length). Posterior part of abdomen separated into two tapering lobes,
ending in sharp points. Abdomen sinus comprises 41% of abdomen length,
range of sinus length 0.84 – 1mm, percentage range 40% - 48%. Average
abdomen width 0.93 mm, range 0.84 – 1.26 mm. Furcal rami very small and
located at junction of abdominal sinus, adjacent to anus. Each bulbous ramus
carries 4 simple setae. Length of testes comprises 61% of abdomen length,
range 0.8 – 1.9 mm, percentage range 45% - 77% average width of 1 testis
0.39 mm (42% of abdomen width of one abdominal lobe), and range 0.32 -
0.58 mm, percentage range 38% - 46%.
CHAPTER 2 31 ULTRASTRUCTURE OF Argulus personatus
Antennules and antennae: Antennules divided into four podomeres (Fig.
2.2.A). First basal podomere consists of large posterior spine, second podomere large and stout, positioned horizontally, composed of a straight anterior spine, minute medial spine pointing towards posterior. Second podomere ends in slender, tapering terminal hook. Third podomere located ventral to terminal hook, elongated and slender with large, single seta located on distal end. Fourth podomere minute and short, ending in four apical setae positioned on distal end of podomere. Antennae separated into four podomeres. First podomere larger and stouter than the three other podomeres, minute posterior spine positioned on proximal end of first podomere (Fig. 2.2.C). A series of five minute, closely arranged, simple setae present adjacent to posterior spine, two setae extending medially from podomere above posterior spine. A group of four setae positioned on ventral distal end of podomere. Large, elongated seta present on distal end of first podomere, with two smaller setae present directly above larger seta, single smaller seta present directly ventral to larger seta (Fig. 2.2.B). Second podomere elongated and slender, series of four setae found on distal end.
Third podomere shorter than second, series of four simple setae present on distal end. Fourth podomere shortest, bears four apical setae on distal end.
Two large pointed post-antennal spines present ventrally on carapace.
Scales on ventral carapace surface: Scales on ventral anterolateral and lateral surfaces of carapace are simple in shape and pointed. Scales on ventral anterolateral surface dented on one side, broad at their bases and curve towards tapered end (Fig. 2.2.D).
CHAPTER 2 32 ULTRASTRUCTURE OF Argulus personatus
Figs 2.2.A-G. Scanning electron micrographs of Argulus personatus; A, antennule and antennae (AS, anterior spine; MS, medial spine; PS, posterior spine; TH, terminal hook); B-C, first podomere of antenna (arrows indicating position of various groups of setae); D, simple scales on ventral anterolateral surface of carapace; E, maxillule of male showing damaged/malformed rods; F, maxillule of female; G, pre-oral spine. Scale bars: A = 100 µm, B and C = 20 µm, D = 10 µm, E and F = 20 µm, G = 100 µm.
CHAPTER 2 33 ULTRASTRUCTURE OF Argulus personatus
Respiratory areas: Consists of two large areas located on each lateral lobe of carapace. Outer area larger and located near to edge of carapace lobes, area is slightly C-shaped. Smaller respiratory area encompassed within larger outer area.
Maxillules/Suckers: Suckers relatively large, outermost circumference bordered by closely arranged single layer of setae. Number of rods in sucker
49 with no variation observed. Variations regarding the shape or number of sclerites were not found in the anterior and posterior supporting rods. Anterior and posterior supporting rods regularly arranged, composed of crucible- shaped sclerites fitting into one another, diminishing in size towards periphery.
Basal sclerites elongated and vase-shaped. Variation was observed where some rods became fused with one another (Fig. 2.2.E) other rods possessed five or six deformed sclerites which deviated from the normal crucible shape.
Only the sclerites in the normal rods were counted. Number of sclerites in normal rods ranges from eight to ten; adjacent rods parallel.
Pre-oral spine and proboscis: Retractable pre-oral spine elongated, located midway between maxillules and ornamented with simple scales (Fig. 2.2.G).
Proboscis present posterior to pre-oral spine and surface covered by simple scales (Fig. 2.2.H). Labrum square-shaped, lateral walls of labrum arch bears pair of minute sharp projections, which originate from a shallow circular depression, and a row of pectinate outgrowths extend from each wall of labrum arch (Fig. 2.2.I).
CHAPTER 2 34 ULTRASTRUCTURE OF Argulus personatus
Figs 2.2.H-M. Scanning electron micrographs of Argulus personatus; H, proboscis with simple scales; I, ventral view of proboscis; J, labial tubules and part of labrum wall (Lt, labial tubule; MP, minute projection; PO, pectinate outgrowth); K, ventral view of mandible (arrow showing recurved denticles); L, lateral view of mandible; M, maxilla showing podomeres (S1, first podomere; S2 second podomere; S3, third podomere; S4, fourth podomere; S5, fifth podomere). Scale bars: 9 = 50 µm, 10 = 20 µm, J-L = 10 µm, M = 100 µm.
CHAPTER 2 35 ULTRASTRUCTURE OF Argulus personatus
Two labial tubules present within mouth tube (Fig. 2.2.J). Labium unadorned with scales but bears fine rows of serrations on surface. Two mandibles present within mouth tube, each consists of two sections. Basal section stout and second section stout and bulbous, tapers towards a flat plate-like tip, bearing row of conspicuous, curved denticles. Series of denticles extend all around tip to proximal edge where three larger, recurved denticles are present on a small projection situated at a 90° angle to former (Figs 2.2.K and 2.2.L).
Maxillae: Consists of five podomeres (Fig. 2.2.M) with first basal podomere bearing three spines. Spines elongated and sharp, basal plate large and ornamented with simple slender scales, three elongated simple setae present at posterior end of basal plate (Fig. 2.2.N). Rushton-Mellor (1994a) previously stated that the basal plate lacked setae. Dorsal surface of second
podomere adorned with minute scales resembling those of fish arranged in
patches, scales positioned at distal end of podomere (Fig. 2.2.O). Ventral
surface of second podomere bears two types of pectinate scales (with fine, bristle-like ends; or with large, thick ends) (Fig. 2.2.P). Third podomere bears both types of pectinate scales; distal end of podomere bears patches of tear- drop shaped scales. Fourth podomere bears teardrop-shaped scales at distal end of podomere (Fig. 2.2.Q). Fifth podomere ends in a blunt, terminal extension, conspicuously separated into two sections, distal part with a pair of claws situated ventrally to terminal extension (Fig. 2.2.R). Pair of accessory solid and curved thoracic spines situated on either side of midline, and pair of post maxillary spines situated on anterior end of first thoracic segment.
CHAPTER 2 36 ULTRASTRUCTURE OF Argulus personatus
Figs 2.2.N-S. Scanning electron micrographs of Argulus personatus; N, basal plate of maxilla showing scales, setae and spines (arrow indicating group of three simple setae); O, second podomere of maxilla showing area of fish-like scales at dorsal distal end; P, pectinate scales on second and third podomere of maxilla, ventral view; Q, teardrop- shaped scales on distal end of third podomere; R, fourth and fifth podomeres of maxilla (arrows showing terminal extension and pair of claws); S, proximal posterior midline of second pair of biramous appendages showing plate covered in simple scales. Scale bars: N = 100 µm, O = 10 µm, P = 50 µm, Q = 10 µm, R = 50 µm, S = 20 µm.
CHAPTER 2 37 ULTRASTRUCTURE OF Argulus personatus
Swimming legs: Ventral surface of thorax and swimming legs covered by simple elongated scales. Four pairs of biramous legs present. First and
second pair of legs divided into three podomeres, third and fourth pairs divided into two podomeres. First and second pairs each bear flagellum on
basipodite, flagella positioned on dorsal surface of basipodite, extending
medially across podomere. Second pair of legs bears a conical projection on
posterior midline of precoxae, projection ornamented with elongated, simple
scales (Fig. 2.2.S). Third and fourth pair of legs bears accessory copulatory
structures (Fig. 2.2.T). On third leg, a rounded extension is present on anterior midline of basipodite adjacent to exopodite, covered all over by narrow bristle-shaped scales (Fig. 2.2.V). Adjacent to projection two tubular structures are present (Fig. 2.2.U). On posterior side of third leg, socket present on proximal end. Socket consists of deep cavity surrounded by folds.
Fourth pair of legs slightly shorter than third pair; large peg present on distal end of basipodite, originating from proximal end, extending medially across
basipodite. Peg bears minute indentation patterns and minute scales on
surface (Fig. 2.2.W). Accessory cushion originates medially from ventral
surface of basipodite. Cushion also ornamented with minute scales (Fig.
2.2.X).
Description of female: Measurements based on one specimen - length 5.6
mm, carapace length 3.7 mm (66% of total length), carapace width 3.4 mm.
Carapace lobes extend to anterior midline of third pair of legs. Abdomen shorter and broader than male abdomen, lobes rounded terminally, abdomen length 1.5 - mm (comprises 27% of total body length), abdomen width is 0.9
CHAPTER 2 38 ULTRASTRUCTURE OF Argulus personatus mm, and abdomen sinus 0.57 mm (comprises approximately 38% of total length of abdomen). Spermathecae small and oval in shape, positioned on the anterior end of abdomen, length of spermathecae is 0.3 mm and the width is 0.18 mm
Fig 2.2.T-Y. Scanning electron micrographs of Argulus personatus; T, third and fourth pairs of legs showing accessory copulatory organs (AC, accessory cushion; AP, anterior projection; P, peg on fourth leg; So, socket on third leg; T, tubules); U, pair of tubular structures on third leg of male; V, anterior projection showing narrow bristled scales; W, peg on fourth leg of male; X accessory cushion on fourth leg of male; Y, light micrograph of male, dorsal view (DP, dorsal projections; RT, rectangular thickening) Scale bars: T = 100 µm; U-X = 10 µm.
Maxillules/suckers: Very similar to male maxillule, with rods composed of crucible shaped sclerites. Sclerites numbering from 8-10 in each rod (Fig.
2.2.F). Variation in number or shape of sclerites was not observed. (Only one specimen collected)
CHAPTER 2 39 ULTRASTRUCTURE OF Argulus personatus
Swimming legs: Absence accessory copulatory structures on third and fourth pair of legs. Large natatory lobe present, positioned between fourth segment of thorax and coxapodite of fourth pair of legs. Outgrowth present on proximal edge of natatory lobes and edge of natatory lobes carries a single layer of setules.
2.4. DISCUSSION AND CONCLUSION
This redescription adds numerous characters which were not previously recognized; possibly because this was the first examination done on A. personatus by SEM. The study also helped to verify morphological characters from previous descriptions. Cunnington’s original description (1913) is generally concurrent with this one; specifically with regards to the different body measurements and the various descriptions of the appendages such as the antennae, suckers, etc. His description of the male accessory copulatory structures is also the same. He mentions the males possessing a large conical projection on the anterior face of the leg. The specimens examined in this study also have this conical projection. He also mentions a projection on the proximal end of the posterior midline of the second pair of legs. This projection was also observed in the SEM study. Rushton-Mellor’s description of this species is also generally concurrent, but with very few minor differences. In this study, it was observed that the proboscis was ornamented with simple scales. This is in contrast to the finding of Rushton-Mellor (1994a) that the proboscis is ornamented with pectinate scales. Rushton-Mellor
(1994a) also found that the basal plate lacks setae. However, in this study it was observed that these specimens do indeed have setae (three elongated
CHAPTER 2 40 ULTRASTRUCTURE OF Argulus personatus simple setae) at the base of the plate. During the SEM study it was common to observe the setae detaching from their basal plates when being handled. It was also found that the shape of the respiratory areas of the male specimens were similar in shape to the respiratory areas of the female specimens illustrated in Rushton-Mellor (1994a and b). The “anteriorly directed processes located on dorsal surface of fourth thoracic segment” mentioned in Rushton-
Mellor (1994a) were also present in the male specimens studied. However, the processes were not as pronounced as they were in her illustration or in the museum specimens examined. It was also noted that the number and arrangement of setae on the first podomere of the antennae were also different to Rushton-Mellor’s illustrations. In Rushton-Mellor (1994a), she illustrates the first podomere with setae extending medially from the podomere, with large single setae on the distal end of the podomere. In this study, it was observed that there were various groups of setae situated on different areas of the first antennal podomere. It was observed in some instances 2 or 3 (out of 49) of the supporting rods in the suckers were fused with one another, possibly resulting from natural damage or malformation while the parasites were still alive. Fused rods were still counted as two separate ones but they were not used to determine the variation in the number of sclerites. The sclerites in these rods deviated from the normal crucible shape and it was common to see five or six in a rod. Some rods were not fused with its adjacent counterpart but did possess deformed sclerites.
The rods with deformed sclerites were not included in the sclerite count due to the fact that the shape of these sclerites is not accepted as part of the normal taxonomic species identification of A. personatus, and because these deformities were probably caused by external environmental influences. The
CHAPTER 2 41 ULTRASTRUCTURE OF Argulus personatus typically formed rods usually consisted of eight to ten sclerites. The SEM micrographs also revealed that the female also possessed a variation between eight to ten sclerites whereas Rushton-Mellor (1994a) found that the sclerites numbered between twelve to thirteen sclerites in each rod. Fused rods were not observed in the specimen, nor were there any rods with deformed sclerites. It was also not possible to count the number of rods for the female as sections of the maxillules were heavily damaged. However, there was only a single female specimen to examine and therefore variations on morphology cannot be commented on. With regards to the additional information gleaned, the detailed morphology of various types of scales on the maxillae is described. Additional information regarding the ultrastructure of the male copulatory structures is also provided. The structure of the labrum, labium and mandibles are described for the first time and the rectangular thickening found between the fourth thoracic segment and abdomen. This thickening was also found in the museum specimens.
Due to the very detailed illustrations done by Rushton-Mellor (1994a and b) it is possible to identify the seven endemic Argulus species from each other by using superficial differences such as the shape of the carapace and the shape and length of the abdomen. However, another species (Argulus rubropunctatus) possesses body proportions similar to Argulus personatus.
The shape and proportions of their carapaces are only slightly different and both species have long abdomens with long tapering lobes and elongated testes. The eyes of both species offer an important difference in identification.
The eyes of A. rubropunctatus are far smaller than those of A. personatus.
Another difference is the antennules of A. personatus consist of four
CHAPTER 2 42 ULTRASTRUCTURE OF Argulus personatus podomeres while the antennule of A. rubropunctatus consists of three only.
Also, both species have similar structured accessory copulatory structures which include paired tubular structures on the anterior midline of each third pair of legs. However, the males of A. personatus possess a large projection on the distal anterior midline of the third pair of legs whereas A. rubropunctatus does not.
CHAPTER 2 43
CHAPTER 3
THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus Thiele, 1900
HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
3.1. INTRODUCTION
The literature on the adult branchiuran digestive system is scant when compared to the information available on morphology, ecology and development since most researchers focused on these aspects (Wilson,
1902, and 1904, Tokioka 1936, Meehan, 1940, Fryer 1956, Stammer 1959,
Shimura 1981 and Rushton-Mellor 1993, etc). However, a small number of authors (Jurine, 1806, Thorell, 1866, Claus, 1875, Leydig, 1850 and 1889,
Wilson, 1902, Thiele, 1904, Grobben, 1908, Martin, 1932, Debaisieux, 1953 and Madsen, 1964) have provided descriptions regarding the digestive system of Argulus. Most of the authors mentioned above provided anatomical information on the digestive system of Argulus foliaceus Linnaeus but with regards to the histology, only Grobben (1908), Martin (1932), Debaisieux
(1953) and Madsen (1964) gave figures and descriptions. Madsen (1964) also provided an account on the digestive systems of Argulus africanus Thiele,
1900 and Argulus coregoni Thorell. In the case of the genera Dolops and
Chonopeltis, Maidl (1912) and Avenant-Oldewage and Van As (1990) described the anatomy and histology of the digestive system of the species
Dolops ranarum, and Avenant-Oldewage et al. (1994) described the anatomy and histology of the digestive system of Chonopeltis australis Boxshall, 1976.
As far as the larvae are concerned, information on the morphology, anatomy and histology is not available. Leydig (1850), Claus (1875) and Wilson (1902) provided descriptions on the Argulus larval digestive system without any information on the histology. Lutsch and Avenant-Oldewage (1995) conducted an investigation of newly hatched Argulus japonicus Thiele, 1900 larvae but concentrated on their morphology. In the case of Dolops also, information on
CHAPTER 3 44 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus the larval digestive system is not available and the structure of the larval digestive system of Chonopeltis Thiele, 1900 was briefly commented on by
Fryer (1956). Argulus japonicus was chosen as the study subject due to their large abundance in South Africa and also due to their close phylogenetic relationship with A. foliaceus (Stammer, 1959).
A detailed description of the feeding habits, anatomy and histology of the
Argulus larval digestive canal is given. The histological information available on A. foliaceus was compared to the results gleaned from larval A. japonicus.
Comparisons were also made between other branchiuran species and their larvae.
3.2. MATERIALS AND METHODS
Adult Argulus japonicus were collected from the yellow fishes Labeobarbus
aeneus (Burchell, 1822) and Labeobarbus kimberleyensis (Gilchrist and
Thompson, 1913) in the Vaal Dam. The Vaal Dam is located in the Vaal River
system between the provinces of the Orange Free State and Gauteng,
Republic of South Africa. The live specimens were allowed to copulate and
lay eggs. After hatching, larvae were fixed in an acetic acid alcohol formalin
solution and preserved in 70% alcohol, and another group was put into a
small fish tank with goldfish, Carassius auratus (Linnaeus, 1758), while the
remainder was left in the glass bottles without any nourishment for
observations. The larvae with the goldfish were allowed to attach to their
hosts to feed and grow. Samples of each juvenile stage, as demarcated by
Tokioka (1936) were collected and fixed. Following fixation, specimens were
dehydrated in acetone and infiltrated with a low viscosity aliphatic epoxy resin.
CHAPTER 3 45 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
Serial sections at 5µm were obtained and stained with azan solution (Romeis,
1968). Some sections were also stained with Periodic acid-schiff solution
(PAS) (Pearse, 1985). However, the serial sections were not counterstained with haemotoxylin and fast green. Each juvenile stage was sectioned and examined until evidence of aliment was found inside the lumen of their digestive tracts. The presence of which would indicate the stage at which the parasites would have begun feeding. Graphic reconstructions of the sections of the alimentary canal were done according to the method of Pusey (1939).
3.3. RESULTS
The digestive tract of Argulus japonicus first stage larvae consists of the following parts (Figs. 3.1 and 3.2): the proboscis, esophagus (constituting the foregut), anterior midgut (crop), midgut glands (enteral diverticula), posterior midgut and hindgut.
CHAPTER 3 46 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
Fig. 3.1. Argulus japonicus. Graphic reconstruction of the larval digestive system, ventral view; amg, anterior midgut (crop); an, anus; ao, ascending esophagus; bc, buccal cavity; ed, enteral diverticula; fg, foregut; hg, hindgut; o, esophagus; of, esophageal funnel; pmg, posterior midgut (intestine). Proboscis is folded back on esophagus. Arrows indicate position of cross sections illustrated in Figs. 3.3.
CHAPTER 3 47 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
Fig. 3.2.A-I. Argulus japonicus larva. Schematic drawings of transverse sections through the digestive system; A, esophageal funnel; B, anterior region of anterior midgut; C, posterior end of anterior midgut; D, enteral diverticula near the vicinity of the main arms; E, enteral diverticula near the terminal end; F, sphincter/transition zone between anterior and posterior midgut; G, posterior midgut. Scale bars for figs. 3.2.A – G = 50 µm; H, anterior hindgut; I, posterior midgut in the vicinity of the gonads. Scale bars for figs. 3.2.H and 3.2.I = 25 µm. C, cuticle; CC, cuboidal epithelium; CE, columnar epithelium; CL, cilia layer; CM, circular muscle; L, lumen; N, nucleus; V, vacuole.
CHAPTER 3 48 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
3.3.1. Foregut
The proboscis is extremely short and stout, and is a fusion of the distal ends of the labrum and metastome. The foregut consists of a preoral cavity, an oral cavity with mandibles and tongue, an ascending esophagus and a horizontal esophagus which extends into an esophageal funnel. The entire foregut is lined with compressed cuboidal epithelium possessing large flattened nuclei.
The lumen is lined with a thick cuticle. Labial tubules were not observed in the preoral region. Both the preoral and oral cavities possessed longitudinal and circular muscles. Setae were absent on the floor of the oral cavity. Posterior to the mandibles, a tongue is present on the floor of the oral cavity. The glandular cells of the tongue are large and contain cytoplasm which stains deep blue with azan (Fig. 3.3.C). These gland cells have large nuclei and probably serve a salivary function.
There are two pairs of muscles attached to the tongue and consists of the anterior and the posterior tongue muscles (Fig. 3.3.C, D and E). The anterior
Y-shaped tongue muscles are attached obliquely to two separate tendons
(Fig. 3.3.C) located dorsally to the nerve ring. The posterior tongue muscles are attached longitudinally to a common tendon known as the median tendon, located ventral to the horizontal esophagus. These muscles penetrate through the nerve ring and attach to the tongue (Fig. 3.3.D and E). Dentigerous plates were absent in the oral cavity. The lumen of the proboscis is triangular shaped in the preoral and oral cavities and gradually becomes rounder and narrower towards the ascending esophagus. The inner wall of the ascending esophagus (Fig. 3.3.B) is formed by a single layer of large cuboidal shaped
CHAPTER 3 49 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus epithelial cells lined with cuticle. The epithelium is surrounded by a thin layer of longitudinal muscle. This muscle layer in turn is surrounded by a thick series of strong, conspicuous circular muscles (Fig. 3.3.A). The horizontal esophagus is a narrow tube lined with large epithelial cells with large basal nuclei and a granular cytoplasm. The horizontal esophagus is surrounded by a thin circular muscle layer; and a longitudinal muscle layer was not observed
(Fig. 3.3.D and E). The horizontal esophagus extends into the esophageal funnel (Fig. 3.3.F), and the esophagus is an extension of the esophageal wall into the lumen of the anterior midgut. The wall of the esophagus folds back on itself and creates an inner and recurrent wall, both of which are lined with cuboidal epithelium covered by cuticle. A thin layer of circular muscle is present between the inner and recurrent walls. The epithelial wall of the inner surface of the anterior midgut in this region is ciliated.
3.3.2. Anterior Midgut
The anterior midgut or crop is composed of a single layer of epithelial cells surrounded by a conspicuous layer of circular muscle (Fig. 3.3.G). The epithelial cells of the anterior portion of the anterior midgut swell into the lumen (Fig. 3.3.G) whereas those in the posterior portion remain flat (Fig.
3.3.L). The anterior midgut produces two large branches which expand laterally then diverge anteriorly and posteriorly in the lobes of the carapace.
The branches extend throughout the carapace. The anterior branches are simple, and are not ramified. The posterior branches each have a smaller branch which projects posteriorly in the carapace (Fig. 3.1). The anterior and posterior midgut epithelium of the newly hatched larvae contains large
CHAPTER 3 50 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus granules which stained orange with azan (Fig. 3.3.K). These granules were extremely large in some cases and caused massive enlargement of the epithelial cells. The granules stained negatively for PAS and therefore are composed mainly of proteins and not mucopolysaccharides. Newly hatched larvae died within a day of hatching if they did not gain access to a host. In most of the larvae observed the yolk is completely depleted within 4 hrs of hatching, although a small number of second stage larvae contain negligible amounts of yolk. Apparently the yolk observed is probably insufficient in sustaining the juvenile. The parasites start to feed on hosts during the first larval stage, and the epithelial cells undergo conspicuous changes. Visible signs of damage were not observed on the hosts. When the yolk is exhausted, the cells are flatter and less distorted. The cells are of a cuboidal type and the nuclei grow exponentially in size. Vacuoles are also conspicuous within the cells. The nuclei are basally situated with the vacuoles situated dorsally to the former. In some parts of the anterior midgut, the cells are distorted and swell into the lumen.
CHAPTER 3 51 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
Fig. 3.3.A-I. Photomicrographs of Argulus japonicus larva. A, cross section showing the circular and longitudinal muscles surrounding the ascending esophagus; B, photomicrograph of a cross section showing the lumen of the ascending esophagus; C, cross section through proboscis and esophagus showing anterior tongue muscles; D, cross section through proboscis and esophagus showing posterior tongue muscles; E, cross section through esophagus and proboscis showing mandibles F, esophageal funnel in the region of the anterior midgut G, anterior region of anterior midgut showing swollen cuboidal cells; H, cross section of enteral diverticula branch terminally; I, cross section of enteral diverticula nearer to the main arms; Scale bars 3.3.A - I = 50 µm. AT, anterior tongue muscles; BL, basal lamina; C, cuticle; CL, cilia layer; CM, circular muscle; F, food bolus; LM, longitudinal muscles; M, muscle; MT, median tendon; N, nucleus; NR, nerve ring; O, esophagus; PT, posterior tongue muscles; T, tendon; To, tongue; V, vacuole.
CHAPTER 3 52 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
The larval diverticula consist of two large arms which originate laterally from the anterior midgut into the carapace. The diverticula extend towards the lateral ends of the carapace and then split into anterior and posterior orientated branches. The anterior branches do not extend into smaller, thinner branches. The posterior branches each have a smaller branch connected to them and these sub-branches extend proximally. The epithelial cells of the diverticula are similar in shape and size to the cells of the midgut.
Vacuoles are more abundant in the epithelium where the two main branches join the crop (Fig. 3.3.I). The lumen of the anterior midgut and diverticula is lined with cilia and the anterior midgut is surrounded by a thin layer of circular muscles. The epithelium contains a large number of melanophores probably taken from host epithelial cells. Very large gland cells surround the midgut and the enteral diverticula and these gland cells release their contents into the diverticula (Fig. 3.3.J). The food of larval argulids consists of what appears to be host mucus and epithelial cells. The mucus stained blue with
Heidenhain’s Azan. Host blood cells were not observed in the lumen of the digestive system.
The anterior midgut is separated from the posterior midgut by a sphincter or
transitional zone. The posterior end of the anterior midgut folds over the
dorsal wall of the anterior end of the posterior midgut, giving the incorrect
impression that there could be a tube separating the midguts. However, in
Argulus the midguts are separated abruptly with a flap of thick tissue. The flap
is an incomplete septum which is a downwards extension of the dorsal
anterior wall of the posterior midgut.
CHAPTER 3 53 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
3.3.3. Posterior Midgut
The vacuoles of the epithelial cells of the posterior midgut are filled with yolk granules. In adult branchiurans, two types of epithelial cells can be distinguished - large papillated cells interdispersed among columnar epithelium. The yolk filled cells are neither columnar nor papilliform in shape.
Instead, the cells are similar to those found in the anterior midgut of the larvae. Even during the feeding stage, the epithelium of the posterior midgut remains flattened and appears squamous due to the swollen nuclei (Fig.
3.3.M). Large vacuoles are present in the cells and the surfaces of the cells bear a ciliated brush border. Melanophores are absent in the cells of the posterior midgut. Digested food was observed within the lumen. A thin circular muscle layer surrounds the organ.
3.3.4. Hindgut
The onset of the hindgut is marked by very tall columnar epithelial cells with a thick layer of cuticle on their surfaces (Fig. 3.3.N). The anterior section of the hindgut has a large diameter and the lumen is conspicuous. As the hindgut proceeds towards the posterior, the epithelium fills the entire lumen. At the posterior end, in the region of the undeveloped gonads, a very large, conspicuous cell with a large nucleus is present on the dorsal wall of the posterior hindgut (Fig. 3.3.N). The nucleus fills almost the entire cell and stained bright red with azocarmine indicating the high activity of the cell. The entire midgut is surrounded by a thin layer of circular muscles. The hindgut makes an abrupt turn dorsally and opens out into the anus located between the two furcal rami.
CHAPTER 3 54 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus
Fig. 3.3.J-N. Photomicrographs of Argulus japonicus larva. J, cross section of main arm of the enteral diverticula showing bolus of food in the midgut lumen; K, photomicrograph of main arm of the enteral diverticula immediately after hatching showing large yolk granules in epithelial cells; L, cross section of posterior end of anterior midgut showing epithelial cells; M, cross section through posterior midgut; Scale bars for Figs. 3.3.J – K = 50 µm; N, cross section through posterior hindgut showing large dorsal cell. Scale bar for Fig. 3.3.N = 25µm. BL, basal lamina; C, cuticle; CL, cilia layer; CM, circular muscle; F, food bolus; GC, glandular cell; N, nucleus; S, secretion of glandular cell; V, vacuole; YG, yolk granule.
3.4. DISCUSSION
In some of the crustacean species studied, yolk granules were present in the
midgut of the larval stages. Walley (1969) studied the larval development of
Balanus balanoides and found remnants of yolk in the epithelial cells of the
midgut. He also found the lumina of the fore- and hindguts closed and
underdeveloped. She concluded the larvae were not able to feed. Anderson
(1969) studied the embryological development of the cirripede crustaceans,
Tetraclita purpurascens, Chthamalus antennatusa and Chamaesipho
columnar and noticed that feeding did not occur until the larvae reached the
CHAPTER 3 55 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus third naupliar stage. Benedetti et al. 1992 investigated the gut development of the parasitic copepod Lernaea cyprinacea Linnaeus (1758). They found yolk present in the third naupliar stage and the midgut not fully developed.
Previous studies therefore indicate some crustacean species are able to survive on their yolk supplies without taking in food. Argulus is not an exception and authors such as Leydig (1850), Claus (1875) and Wilson
(1902) observed the presence of yolk in the digestive system of argulid nauplii. However, the length of time taken for the depletion of the yolk supply is unknown. Shimura (1981) reported newly hatched larvae of A. coregoni fed on host mucus but did not mention whether they could survive a short length of time without a host. Schram (1986) and Lester and Roubal (1995) also stated that the first stage larvae are parasitic. Previous researchers have therefore established argulids are parasitic during their first stage. Wilson
(1902), Meehan, 1940, Fryer (1956), Shimura (1981) and Schram (1986) stated Argulus species can be divided roughly into two categories depending on the type of larvae which is produced. Some species produce a primitive, naupliar type larva whereas other species produce a more developed
“juvenile adult” larva resembling the adults. The juvenile type larvae spend a longer period embryonating inside the egg. Thomas (1961) investigated A. puthenveliensis Ramakrishna, a species which produces the juvenile adult type larva and reported they immediately attach themselves to a host after hatching. Perhaps the “juvenile adult “type larvae exhaust their yolk supply while still in the egg and hatch with the need to feed immediately. The three common species including A. foliaceus, A. japonicus and A. coregoni produce naupliar larvae which are difficult to distinguish morphologically. The yolk in the larval midgut of Argulus japonicus was depleted within 4 hrs of hatching
CHAPTER 3 56 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus and the larvae needed to start feeding within one day. However, Bauer (1962) reported A. foliaceus newly hatched larvae are able to survive 2-3 days without a host. Kollatsch (1959) also noted the larvae of A. foliaceus die within a few days if a host is not located in time. Taking into consideration the three above-mentioned species are closely related (similar morphologies and lifestages) the larvae of these species would be expected to deplete their yolk supplies within a similar length of time. Other authors who reported branchiuran larvae feeding during their first stages include Fryer (1961) who reported Chonopeltis larvae feeding on host tissue during the earliest stages.
Fryer (1956) investigated the newly hatched larvae of Chonopeltis and found they could survive eight days without a host. He mentioned their eventual death may have been caused by the inability to find the correct food, or due to the drop in nocturnal temperatures at Lake Nyasa. He did not mention whether yolk had played a role in their survival. Fryer (1961) noted that
Chonopeltis larvae are far less mobile than their Argulus counterparts. This disadvantage makes the location of hosts far more difficult. One possibility could be that Chonopeltis larvae have a larger amount of yolk in their midguts to compensate for their disadvantage or as Fryer stated, that the larvae have evolved to feed on non-host materials temporarily until a host is found.
Leydig (1850) described the alimentary canal of A. foliaceus larvae microscopically and his description indicated that the digestive system was generally similar to the adult. Claus (1875) also observed that the digestive system was similar to the adult, and Wilson (1902) merely reiterated Claus’ findings. Fryer (1956) described the larval alimentary canal of Chonopeltis as a simple tube but did not mention the enteral diverticula. Since the anatomy of
CHAPTER 3 57 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus the larvae was similar to the adults, previous scientists perhaps thought that the histology would be similar as well, and therefore further research was unwarranted. Despite the overall commonalities in the anatomy and histology, there exist some differences. The foregut is like the adult and is composed of flattened cuboidal epithelium lined with a thick cuticle. However, the mandibles and proboscis of larval A. japonicus are far smaller than the adult.
Measurements extrapolated from SEM micrographs of the larval proboscis
(Fig. 2.A) of Lutsch and Avenant-Oldewage (1995) indicated the mandibular blades were approximately 15 µm in length and the length of the proboscis approximately 40-50 µm. However, the epidermis of a cyprinid host is approximately 100 µm in thickness (Yonkos et al. 2000). The mandibles are situated very close to the entrance of the proboscis and the length of the proboscis influences the depth at which the mandibles penetrate the host tissue. Therefore the short length of the larval proboscis allows the penetration of the epidermis but not the dermis where the blood vessels are situated and may explain the absence of blood cells in the midgut lumen. This may also indicate that they are not able to cause any visible, significant damage to their hosts.
The epithelium of the enteral diverticula of the larvae is similar to the adult and is composed of a ciliated cuboidal type. However, the enteral diverticula of the larvae are less ramified when compared to the adult (Wilson, 1902, Tokioka
1936, Meehan, 1940, Stammer 1959) and because they occupy a smaller surface area in the carapace perhaps the diverticula are far less efficient in digestion and absorption. Thorell (1864) reported that in A. purpureus the main diverticula extends further into inner and outer branches whereas A.
CHAPTER 3 58 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus foliaceus extends sub-branches only on the outer side. From the reconstructed figure of the adult A. japonicus digestive system (Baker and
Avenant-Oldewage, 1990), the thinner sub–branches are portrayed extending inwards and outwards within the carapace. The lack of thickness of the carapace restricts the development of branches forming dorsally and ventrally to the main branches. The simpler ramification of the diverticula may reduce the efficiency of digestion and absorption in the midgut. Overstreet et al.
(1993) mentioned that in some branchiuran species the cells of the midgut diverticula are not lined with cilia. In this study, however, the cuboidal epithelium in the larval diverticula is lined with cilia. The anterior and posterior midguts are separated by a sphincter or transition zone. This sphincter was also observed in the adult by previous authors such as Grobben, 1908,
Martin, 1932 and Debaisieux, 1953. The sphincter is generally similar in the larvae and in the adult. In adult branchiurans such as Dolops ranarum
(Avenant-Oldewage and Van As, 1990) a narrow isthmus is formed between the anterior and posterior midgut. In Chonopeltis (Avenant-Oldewage et al.
1994) an S-shaped tube separates the midguts.
The main difference between the histology of the larval and adult alimentary canals involves the posterior midgut. Previous researchers, (Leydig, 1850,
Grobben, 1908, Martin, 1932, Debaisieux, 1953, Madsen, 1964, Avenant-
Oldewage and Van As, 1990, Avenant-Oldewage et al. 1994 and Schram
1986) showed histologically that the epithelium of the posterior midgut of adult branchiurans consists of cuboidal epithelium interdispersed with large papilliform cells. In Chonopeltis australis the cuboidal epithelium of the posterior midgut is replaced with tall columnar epithelium. The height of these
CHAPTER 3 59 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus cells indicates that the cells are heavily involved in digestion and absorption of nutrients (Avenant-Oldewage et al. 1994). The papilliform cells of Chonopeltis australis fill up almost the entire lumen of the gut (Avenant-Oldewage et al.
1994). Grobben (1908) conducted a histological study on the digestive system of A. foliaceus. He noted the large papillated cells and stated these cells were perhaps used to ferment digested food (fermentzellen). Grobben (1908) also noted the granular appearance of the vacuoles. Similar cells were found in other parasitic crustaceans such as Ergasilus sieboldi (Nordmann)
(Einszporn, 1965) and in the copepod Pseudocycnus armatus (John and Nair,
1975). According to Briggs (1977) and Overstreet et al. (1993) the columnar cells are involved in the absorption of nutrients whereas the papilliform cells are involved in phagocytosis. Briggs (1977) observed these cells in
Paranthessius anemoniae (Claus) actively taking in digested material. He suggested these cells have a secretory function as Einszporn (1965) and
John and Nair (1975) did. After the necessary nutrients are taken up by the ameboid vacuole, the apical vacuole of the cells are broken off and released into the lumen and constitute the fecal pellet. Einszporn (1965) suggested the papilliform cells in E. sieboldi undergo holocrine type secretion.
Since ciliated cuboidal epithelium lines the posterior midgut of the larvae (and consequently occupies less surface area), questions are raised with regard to the efficiency of absorption and digestion in this part of the alimentary canal.
Even in the second stage juvenile (Tokioka, 1936) or third stage juvenile
(Stammer, 1959), cuboidal epithelium persists in the posterior midgut and papillated cells were not observed. The cuboidal epithelium could be sufficient in sustaining the young larvae by digesting and absorbing mucus and other
CHAPTER 3 60 HISTOLOGY OF THE LARVAL DIGESTIVE SYSTEM OF Argulus japonicus food particles only. This finding perhaps correlates with the information of
Bower-Shore (1940), who observed the larvae of A. foliaceus congregating on areas of the fish with the most mucus. The stage in which the papilliform cells develop is not known. The papillated cells cover a larger surface area and perhaps are better at providing nourishment for larger adult parasites. Briggs
(1977) also noted that when Paranthessius anemoniae was starved the papilliform cells decreased in size. Avenant-Oldewage et al. (1994) observed a similar result when Chonopeltis australis specimens were starved of food.
TEM studies on the digestive cells of adult branchiuran digestive tracts are not available. Therefore comparison between the larval and adult digestive cells was not possible.
The larval hindgut is a relatively uncomplicated organ in lower crustaceans
(Dall and Moriaty, 1983) consisting of a simple tube composed of columnar epithelium lined with a thick cuticle. In the larvae the hindgut is similar to the adult. Furthermore, a large cell is present on the dorsal wall of the posterior hindgut. The cell is relatively much larger than the surrounding cells and possesses a large active nucleus which occupies almost the entire cell.
Whether this type of cell is present in the adults is unknown.
Comparison between the larval and adult Argulus digestive system yields many morphological and histological similarities. There is however, a major difference in the histology of the posterior midgut of the larvae and the adult.
This difference is thought to decrease the digestive and absorptive capabilities of larvae.
CHAPTER 3 61
CHAPTER 4
SUMMATIVE DISCUSSION AND FUTURE RESEARCH
GENERAL DISCUSSION AND FUTURE RESEARCH
The general objectives of this study were achieved. The function of this chapter is to elucidate future related research possibilities on Argulus. A detailed SEM study was conducted on an African species (Argulus personatus, a species from East Central Africa) increasing the number of
SEM studies on African species. The digestive tract of larval Argulus japonicus was reconstructed and its histology studied. It was confirmed that the parasite does indeed feed during its first stage as reported by Shimura
(1981), Schram (1986), Bouchet (1985) and Lester and Roubal (1995).
The information in the introductory chapter reveals the scant information available on the ultrastructural and anatomical aspects of Argulus, not only in
Africa but generally in the world. Further SEM, anatomical, histological and physiological studies on Argulus (especially on African species) would contribute greatly to the understanding of Argulus. Future research regarding treatment could also be explored. The information gleaned from studying
Argulus could possibly provide an understanding of other branchiurans.
Possible future studies concerning the above mentioned biological aspects on
Argulus are discussed below.
An area of possible future study concerns the issue of treatment. Many of the fish farms around the world exist as arbitrary enclosures in lakes and rivers.
However, the treatment chemicals available are only suitable for isolated environmentally controlled fish tanks and aquariums. These treatment chemicals are not suitable for fish farms in lakes and rivers as they cause environmental damage by destroying other organisms. Therefore the
CHAPTER 4 62 GENERAL DISCUSSION AND FUTURE RESEARCH development of chemicals which are environmentally safe should be a future focus. The egg-laying boards developed by Gault et al. (2002) provide a promising momentum to develop other non chemical methods of treatment in future. Non chemical methods could also prove to be a cheaper alternative to chemicals and could prove to be an advantage to third world countries.
As far as the SEM study conducted on Argulus personatus is concerned, the results revealed minute morphological structures which are difficult to view under a light microscope. These include setae and scales of different sizes and shapes. SEM has proven to be useful when examining the morphology of fine microscopic structures in other organisms such as ticks (Chang et al.
1989, Gothe et al. 1991, Homsher et al. 1991 and Buczek et al. 1998).
Studies on the morphology of the complex, microscopic sensory structures on these parasites have helped to contribute to the understanding of their appearance and their function. Ticks possess a group of sensory setae on the distal end of their first pair of tarsi known as the Haller’s organ. SEM has helped scientists to determine the arrangement and number of setae in different species and this feature is used as a taxonomic tool (Chang et al.
1989, Gothe et al. 1991, Homsher et al. 1991 and Buczek et al. 1998). The specific number and arrangement of setae found on specific body parts of
Argulus species would be determined in a similar way, especially amongst the naupliar larvae. Many species produce larvae which closely resemble each other. The differences in the number of setae can be used to differentiate between species.
CHAPTER 4 63 GENERAL DISCUSSION AND FUTURE RESEARCH
Individual setae found in and around the Haller’s organ of ticks are known to have a specific sensory function. Researchers such as Li-Guamin et al.
(1992) conducted electrophysiological tests on these setae and found individual setae were responsible for detecting specific stimuli. SEM helped to identify the individual setae which were responsible for detecting a specific stimulus. SEM and electrophysiological studies have contributed to the understanding of physiology and behaviour of ticks, e.g. host and mate searching. The arrangement and placement of setae discussed in A. personatus indicates they serve specific functions, as the placement of the setae on the various body parts is not random. Similar studies on the larvae and adults of Argulus would be conducted in future and could contribute to the knowledge of Argulus in a similar way. The setae on the body surface of
Argulus could be used to detect various stimuli from their hosts and environment and certain types of behaviour would be elicited.
As far as the digestive system is concerned, the study revealed that the morphology and, to a lesser extent, the histology of the larval digestive system is similar to the adult. It was also discovered that the yolk present in the digestive system sustains the parasite for one day and the larvae die if a host is not found. When a host is found the metanauplii feed on mucus and epithelial cells.
Despite the overall similarity between the adult and larval digestive system, some differences exist. These differences include a short proboscis with smooth-edged mandibles (Lustch and Avenant-Oldewage, 1995), largely
CHAPTER 4 64 GENERAL DISCUSSION AND FUTURE RESEARCH unramified enteral diverticula, and a posterior midgut lined with cuboidal epithelium. The absence of blood in the lumen of the gastrointestinal tract is probably due to the short proboscis. It is likely the cuboidal cells of the posterior midgut of the larva have adapted to digest and absorb mucus. It could then follow that the papilliform cells in the posterior midgut of the adult would be efficient at digesting blood also. However, adults of the genus,
Chonopeltis, feed on mucus exclusively (Avenant-Oldewage et al. 1994) despite possessing similar papilliform cells in their posterior midguts
(Avenant-Oldewage et al. 1994). Another commonality Chonopeltis adults share with argulid larvae is a short proboscis and this may explain why this genus does not feed on blood. Therefore the papilliform cells are not indicative of the aliment the parasites digest and absorb. Chonopeltis adults live for roughly a day if deprived of food (Avenant-Oldewage, 2005). When adults of Argulus japonicus were taken off their hosts and observed, they were able to survive for up to 3 days. Dolops also feeds on blood and is able to survive up to a week (Avenant-Oldewage, 2005). Since Argulus and Dolops survive a longer period without food, this may indicates a blood feeding strategy is perhaps more advantageous than feeding on mucus alone.
However, the digestive physiology of branchiurans remains unknown and should receive more attention in future.
Previous researchers have produced literature on the digestive physiology of other crustacean groups. Through TEM studies the digestive cells of crustaceans were divided into categories depending on their cellular components and their functions (Brunet et al. 1994). These cells have been
CHAPTER 4 65 GENERAL DISCUSSION AND FUTURE RESEARCH studied in decapods, mysids and amphipods and there gut cells consists of several cells e.g. R-, F-, B-, E- or S- cells. Agreement has not been reached concerning the functioning of these cells. The digestive cells of lower crustaceans such as the Calanoida (Arnaud et al. 1978, 1980, 1984, 1987,
1991), Ostracoda and Harpacticoid Copepoda have also been studied. As of yet there are no existent TEM studies on the digestive epithelium of neither adult nor larval argulids. There is also a great variance in the digestive anatomy and histology of various crustaceans (Brunet et al. 1991) and it was not possible to classify and compare the digestive cells mentioned in previous ultrastructural studies to the digestive cells in Argulus. Perhaps some of the midgut cells present in argulids would be found to be similar to the cells in other parasitic copepods and would be categorized accordingly if further studies were conducted. The cells lining the midgut are presumably not the only ones involved in digestion. As it was previously mentioned in section
3.3.2 of chapter 3, large unicellular glands were observed releasing secretions into the lumen of the midgut. TEM and tests of physiology could reveal their nature. Ultrastructural studies conducted on all the digestive cells of branchiurans would provide momentum for future research.
The nutritional requirements, digestive system and feeding appendages of a parasite are intimately related to the pathological effects caused. They determine to some degree how pathogenic effects will manifest themselves.
The pre-oral spine and proboscis of Argulus are speculated to cause pathogenic effects but the specific effects are still largely unknown. Avenant-
Oldewage and Swanepoel (1992) examined the glandular complexes of both
CHAPTER 4 66 GENERAL DISCUSSION AND FUTURE RESEARCH the pre-oral spine and labial tubules of the proboscis in the adult. Generally, glands located in the dorsal regions of the carapace are associated with the pre-oral spine while the glands situated ventrally are associated with the labial tubules. The pre-oral spine is associated with 4 sets of glandular complexes; one set located anteriorly to the optic tracts and the other three situated posteriorly to the nauplius eye. The duct from the gland complex in the anterior region run caudally to join with the duct running anteriorly from the posteriorly situated glands to create a main duct before running through the pre-oral spine. The labial tubules are associated with three glandular complexes all situated anteriorly to the proboscis. The largest and farthest complex, from the labial tubules, is located beneath the optic tracts. Two of the ducts from this complex open in the oesophageal lumen while the other opens via the labial tubules. The second complex (glandula praeboscoidalis) is located at the base of the pre-oral spine and the ducts run caudally in the dorsal proboscis wall and open in the oesophageal lumen very close to the labral wall. The third glandular complex is located mid-ventrally below the first pair of thoracic ganglia. The ducts originating from this complex run caudally in the ventral proboscis wall and open in the labial part of the proboscis.
However, Avenant-Oldewage and Swanepoel (1992) did not comment on the substances produced by each of the various complexes. Shimura and Inoue
(1983) conducted studies on the toxic effects of the mouthparts of adult specimens of Argulus coregoni. They provided evidence indicating the mouthparts cause a haemorrhagic effect but not a haemolytic or cytolytic effect. However, they did not specify whether this effect was caused by the pre-oral spine, labial spines or by both structures. Overstreet et al. (1992)
CHAPTER 4 67 GENERAL DISCUSSION AND FUTURE RESEARCH speculate the labial tubules produce digestive secretions while other researchers speculate both the pre-oral spine and labial tubules produce digestive secretions (Boxshall, 2005). The specific substances produced by each complex are unknown. Although knowledge on the pathological effects caused by adults is still far from complete, nothing is known of the pathological effects caused by the metanauplii. Whether these glands associated with the pre-oral and labial tubules are present in the larvae and whether they are functional is not known. Martin (1932) observed the presence of labial tubules in metanauplii of Argulus foliaceus while Tokioka
(1936) did not observe these structures in larval Argulus japonicus. In this present study labial tubules were also not observed. Since the labial tubules are absent, perhaps the glandular complexes associated with the labial tubules are not functional in the first life stage.
The appendages concerned with feeding are only partially responsible for causing pathogenic effects. Other appendages include the claw-shaped maxillules the larvae use to attach to their hosts. Pathology regarding the maxillule suckers of argulid adults is known (Watson and Avenant-Oldewage,
1996). However, the possible effects caused by the larval maxillules would probably be more similar to those caused by Dolops. Members of this genus possess hooked maxillules and they are used to attach to the integument of is host. They are known to cause great damage to the epidermal and dermal layers resulting in loss of blood and secondary bacterial infection. The larvae of Dolops, Argulus and Chonopeltis possess hooked maxillules, and since they are many times smaller than Dolops adults the possible damage caused
CHAPTER 4 68 GENERAL DISCUSSION AND FUTURE RESEARCH by larval maxillules would be reduced. The pathology caused by the larvae provides another subject for future research, which could include histological, histochemical and SEM studies conducted on host skin infected with larval argulids.
Lastly, studies conducted on the ontogenic development could provide a more complete understanding of the functioning of organs and cells of Argulus.
Previous researchers have given accounts of embryo development; from the time the eggs are laid to the time of hatching, of various species (Wilson,
1902, Tokioka, 1936, Fryer, 1956, Bouchet, 1985, etc). However, these accounts were done based on observations only. Histological and TEM studies could be conducted on the various stages of embryo development within the egg.
CHAPTER 4 69
LITERATURE REFERENCES
REFERENCES
Anderson, D.T. 1969. On the Embryology of the Cirripede crustaceans
Tetraclita rosea (Krauss), Tetraclita purpurascens (Wood), Chthamalus
antennatus (Darwin), Chamaesipho columna (Spengler) and some
Considerations of Crustacean Relationships. Philosophical
Transactions of the Royal Society of London. Series B, Biological
Sciences, 256 (806): 183–235.
Arnaud, J., Brunet, M. and Mazza, J.A. 1978. Studies on the midgut of
Centropages typicus (Copepod, Calanoida). I. Structural and
ultrastructural data. Cell and Tissue Research, 187: 333-353.
Arnaud, J., Brunet, M. and Mazza, J. 1980. Structure et ultrastructure
comparées de I’intesin chez plusieurs espèces de copepods
calanoides (Crustacea). Zoomorphology, 95: 213-233.
Arnaud, J., Brunet, M. and Mazza, J. 1984. Cytochemical detection of
phosphatase and arylsulphatase activities in the midgut of
Centropages typicus (Copepod, Calanoida). Basic and Applied
Histochemistry, 28: 399-412.
Arnaud, J., Brunet, M. and Mazza, J. 1987. Rôle des cellules B de l’intesin
moyen chez Centropages typicus (Copepoda, Calanoida).
Reproduction Nutrition Développement, 27 (4): 817-827.
Arnaud, J., Brunet, M. and Mazza, J. 1991. Ultrastructural data proving the
selective character of endocytosis by midgut B-cells in Hemidiaptomus
ingens. (Copepoda, Calanoida). Comptes Rendus des Seances.
Academie de Sciences (Paris) Serie 3. Science de la vie: 495-501.
Avenant-Oldewage, A. 1994. A new specie of Argulus from Kosi Bay, South
Africa, and distribution records of this genus. Koedoe, 37 (2): 89-95.
CHAPTER 5 70 REFERENCES
Avenant-Oldewage, A. 2001. Argulus japonicus in the Olifants River system –
Possible conservation threat?. South African Journal of Wildlife
Research, 31 (1 and 2): 59-63.
Avenant-Oldewage, A. 2005. Professor at the University of Johannesburg.
[[email protected]]. Personal communication.
Avenant-Oldewage, A and Oldewage, W.H. 1995. A new species of Argulus
(Crustacea: Branchiura) from a bony fish in Algoa Bay. South African
Journal of Zoology, 30: 197-199.
Avenant-Oldewage, A and Swanepoel, J.H. 1992. Comments on the
morphology of the pre-oral spine in Argulus (Crustacea: Branchiura).
Journal of Morphology, 212 (2): 155-162.
Avenant-Oldewage, A and Swanepoel, J.H. 1993. The Male Reproductive
System and Mechanism of Sperm Transfer in Argulus japonicus
(Crustacea: Branchiura). Journal of Morphology, 215: 51-63.
Avenant-Oldewage, A., Swanepoel, J.H., and Knight, E. 1994.
Histomorphology of the digestive tract of Chonopeltis australis
(Crustacea: Branchiura). The South African Journal of Zoology, 29 (1):
74–81.
Avenant-Oldewage, A. and Van As, J.G. 1990. The digestive system of the
fish ectoparasite Dolops ranarum (Crustacea: Branchiura). Journal of
Morphology, 204: 103–112.
Baker, C and Avenant-Oldewage, A. 1990. On the morphology of the
digestive tract of Argulus japonicus Thiele, 1900 (Crustacea:
Branchiura). Electron Microscopy Society of South Africa, 20: 197–198.
Barnard, K.H. 1955. South African parasitic Copepoda. Annuals of the South
African Museum, 41: 223-312.
CHAPTER 5 71 REFERENCES
Bauer, O.M. 1962. Parasites of the freshwater fish and the biological basis for
their Control. Israel Program for Scientific Translations. Keter Press,
Jerusalem, 236 pp.
Benedetti, I., Mola, L. and Sabatini, M.A. 1992. Morphogenesis of the gut in
the nauplius stages of the parasitic copepod Lernaea cyprinacea.
Bollettino Di Zoologia, 59: 245-249.
Behrent, A. 1994. Lice - a ticklish problem for trout fisheries. Fish-Farmer, 17
(2): 52-53.
Bower-Shore, C. 1940. An investigation of the common fish louse, Argulus
foliaceus (Linn.). Parasitology, 32: 361-371.
Bouchet, G.C. 1985. Redescription of Argulus varians (Branchiura, Argulidae)
including a description of its early development and first larval stage.
Crustaceana, 49 (1): 30-35.
Boxshall, G. 2005. Crustacean parasites. Pp. 123-167 in K. Rhode, ed.
Marine Parasitology. CABI Publishing, Wallingford, U.K.
Brian, A.G.G. 1924. Copepoda. Copepodes commensaux et parasites des
cotes mauritaniennes. Parasitologica Mauritanica. Matériaux pour la
faune parasitologique en Mauritanie, 1(1): 1-66.
Brian, A.G.G. 1928. Crustacea II Copepoda parasitica. Faune Des Colonies
Francais, 1 (6): 571-587.
Brian, A.G.G. 1940. Sur quelque Argulide’s d’Afrique appartenant aux
collections du Musée du Congo Belge. Revue de Zoologie et de
Botanique Africaines, 33: 77-98.
Briggs, R.P. 1977. Structural observations on the alimentary canal of
Paranthessius anemoniae, a copepod associate of the snakelocks
CHAPTER 5 72 REFERENCES
anemone Anemonia sulcata. Journal of Zoology, London, 182: 353-
368.
Brunet, M., Arnaud, J. and Mazza, J. 1994. Gut structure and digestive
cellular processes in marine Crustacea. Oceanography and Marine
Biology: an Annual Review, 32: 335-367.
Buchmann, K and Bresciani, J. 1997. Parasitic infection in pond-reared
rainbow trout Oncorhynchus mykiss in Denmark. Diseases of Aquatic
Organisms, 28 (2): 125-138.
Buchmann, K, Uldal, A and Lyholt, H.C.K. 1995. Parasite infection in Danish
trout farms. Acta Veterinaria Scandinavica, 36 (3): 283-298.
Burnes, 1985 Byrnes, T. 1985. Two new Argulus species (Branchiura:
Argulidae) found on Australian bream (Acanthopagrus spp.). Australian
Zoologist, 21(7): 579-586.
Claus, C. 1875. Über die Entwickelung, Organisation und systematiche
Stellung der Arguliden. Zeitschrift für wissenschaftliche Zoologie, 25:
217–284 + pls XIV – XVIII.
Cunnington, W.A. 1913. Zoological results of the Third Tanganyika
Expedition, conducted by Dr. W.A. Cunnington, 1904-1905. Report on
the Branchiura. Proceedings of the Zoological Society of London, 127:
293-283.
Dall, W. and Moriaty, D.J. 1983. Functional aspects of the nutrition and
digestion. Pp. 215–261 in H. Mantel, ed. Internal anatomy and
physiological regulation. Academic Press, New York, U.S.A.
Debaisieux, P. 1953. Histologie et Histogenèse chez Argulus foliaceus.
Cellule, 55: 1–53.
CHAPTER 5 73 REFERENCES
Dollfus, R.P. 1960. Mission M. Blanc, F.d’Aubenton (1954) VII Copépodes
Parasites de Téléostéens du Niger. Bulletin de l'Institut Fondamental
d'Afrique Noire, Série A, Sciences Naturelles, 22: 170 -192.
Einzporn, T. 1965. Nutrition of Ergasilus sieboldi Nordmann. I. Histological
structure of the alimentary canal. Acta Parasitologica Polonica, 13 (31):
72 – 79 + pls I - X.
Einzporn, T. 1965. Nutrition of Ergasilus sieboldi Nordmann II. The uptake of
food and the food material. Acta Parasitologica polonica, 13 (37): 373-
380.
Fryer, G. 1956. A report on the parasitic Copepoda and Branchiura of the
fishes of Lake Nyasa. Proceedings of the Zoological Society of London,
127: 293-344.
Fryer, G. 1958. A report on the parasitic Copepoda and Branchiura of the
fishes of Lake Bangweulu (Northern Rodesia). Proceedings of the
Zoological Society of London, 132: 517-550.
Fryer, G. 1959. Studies on some parasitic Crustaceans on African freshwater
fishes, with descriptions of a new Copepod of the genus Ergasilus and
a new Branchiuran of the genus Chonopeltis. Proceedings Zoological
Society of London, 133: 629-647.
Fryer, G. 1961. Larval development in the genus Chonopeltis. Proceedings of
the Zoological Society of London, 137: 61–69.
Fryer, G. 1964. Parasitic Crustaceans of African freshwater fishes from the
Nile and the Niger systems. Proceedings of the Zoological society of
London, 145: 285-303.
Fryer, G. 1965. Crustacean Parasites of African freshwater fishes mostly
collected during expeditions to Lake Tanganyika, and to Lakes Kivu,
CHAPTER 5 74 REFERENCES
Edward and Albert by the Institute Royal des Bulletin de l'Institut Royal
des Sciences Naturelles de Belgique, Biologie, 41: 1-22.
Fryer, G. 1968. The Parasitic Crustacea of African freshwater fishes; their
biology and distribution. Journal of Zoology, London, 156: 45-95.
Gault, N.F.S., Kilpatrick, D.J. and Stewart, M.T. 2002. Biological control of the
fish louse in a rainbow trout fishery. Journal of Fish Biology, 60 (1):
226-237.
Gresty, K.A. and Boxshall, G.A. 1993. The fine structure and function of the
cephalic appendages of the branchiuran parasite, Argulus japonicus
Thiele. Philosophical Transaction of the Royal Society of London,
Series B, 339: 119-135.
Grobben, K. 1908. Beiträge zur Kenntnis der siphonostomen.
Sitzungsberichte. Koenigliche Preussische Akademie der
Wissenschaften, 25: 89–108.
Grignard, J.C., Melard, C. and Kestemont, P. 1996. A preliminary study of
parasites and diseases of perch in an intensive culture system. Journal
of Applied Ichthyology, 12 (3 and 4): 195-199.
Hakalahti, T., Laniken, Y. and Valtonen, E.T. Efficacy of emamectin benzoate
in the control of Argulus coregoni (Crustacea: Branchiura) on the
rainbow trout Oncorhynchus mykiss. Diseases of Aquatic Organisms,
60 (3): 197-204.
Hewitt, G.C. and Hine, P.M. 1972. Checklist of parasites of New Zealand
fishes and of their hosts. New Zealand Journal of Marine and
Freshwater Research, 6 (1 and 2): 69-114.
Hindle, E. 1948. Notes on the treatment of fish infested with Argulus.
Proceedings of the Zoological Society of London, 119: 79-81.
CHAPTER 5 75 REFERENCES
Inoue, K., Shimura, S., Saito, M. and Nishimura, K. 1980. Use of trichlorfon in
control of Argulus coregoni. Fish Pathology, 15 (1): 37-42.
Ikuta, K and Makioka, T. 1993. Structure of the ovary in Argulus japonicus
(Crustacea: Branchiura). Proceedings of the Arthropod Embryological
Society of Japan, 28: 1-2.
Ikuta, K and Makioka, T. 1994. Notes on the postembryonic development of
the ovary in Argulus japonicus (Crustacea: Branchiura). Proceedings
of the Athropod Embryological Society of Japan, 29: 15-17.
Ikuta, K and Makioka, T. 1995. Notes on the ultrastructure of female germ
cells in the adult ovary in Argulus japonicus (Crustacea: Branchiura).
Proceedings of the Athropod Embryological Society of Japan, 30: 9-11.
Ikuta, K and Makioka, T. 1997. Structure of the Adult Ovary and Oogenesis in
Argulus japonicus Thiele (Crustacea: Branchiura). Journal of
Morphology, 231: 29-37.
Jafri, S.I.H. and Ahmed, S.S. 1994. Some observations on mortality in major
carps due to fish lice and their control. Pakistan Journal of Zoology, 26
(3): 274-276.
John, S. and Nair, N.B. 1975. Functional morphology of the digestive system
in Pseudocycnus armatus (a parasitic copepod). Forma Functio, 8 (3):
361-386.
Jurine, L. 1806. Memoires sur l’ Argule foliacè (Argulus foliaceus). Annales du
Musee d’ Histoire Naturelle, 7: 431–458.
Kollatsch, D. 1959. Untersuchungen uber die biologie und okologie der
karpfenlause (Argulus foliaceus L.). Zoologische Beitraege, 5: 1-36.
CHAPTER 5 76 REFERENCES
Kruger. I, Van As, J.G. and Saayman, J.E. 1983. Observations on the
occurrence of the fish louse Argulus japonicus Thiele, 1900 in the
western Transvaal. South African Journal of Zoology, 18 (4): 408-410.
LaMarre, E and Cochran, P.A. 1992. Lack of host species selection by the
exotic parasitic crustacean, Argulus japonicus. Journal of Freshwater
Ecology, 7 (1):77-80.
Lester, R.J.G. and Roubal, F. 1995. Phylum Arthropoda. Pp. 475-598 in P.
Woo, ed. Fish Diseases and Disorders: Vol 1: Protozoan and
Metazoan Infections. CAB International. Wallingford, UK.
Leydig, F. 1850. Über Argulus foliaceus. Ein Beitrag zur Anatomie, Histologie
und Entwickelungsgeschichte dieses Thieres. Zeitschrift für
wissenschaftliche Zoologie, 2: 323–349.
Leydig, F. 1889. Über Argulus foliaceus. Neue Mitteilungen. Archiv fuer
Mikroskopische Anatomie und Entwicklungs mechanic, 33: 1–55.
Lustch, E. and Avenant-Oldewage, A. 1995. The ultrastructure of the newly
hatched Argulus japonicus Thiele, 1900 larvae (Branchiura).
Crustaceana, 68 (3): 329–340.
Maidl, F. 1912. Beiträge zur Kenntnis des anatomischen Baues der
Branchiurengattung Dolops. Arbeiten aus den zoologischen Instituten
der Universität Wien, 19: 317–330.
Madsen, N. 1964. The anatomy of Argulus foliaceus Linnè with notes on
Argulus coregoni Thorell and Argulus africanus Thiele. Part I:
Integument, central nervous system, sense organs, preoral spine and
digestive organs. Acta Universitatis Lundensis, 13: 1–33.
CHAPTER 5 77 REFERENCES
Martin, M. 1932. On the morphology and the classification of Argulus
(Crustacea). Proceedings of the Zoological Society of London, 103:
771–806.
Meehan, O.L. 1940. A review of the parasitic crustacea of the genus Argulus
in the collection of the United States Museum. Proceedings of the
United States Museum, 88 (3087): 459-522.
Molnar, K and Moravec, F. 1997. Skrjabillanus cyprinid n.sp. (Nematoda:
Dracunculoidea) from the scales of common carp Cyprinus carpio
(Pisces) from Hungary. Systematic Parasitology, 38 (2): 147-151.
Molnar, K. and Szekely, C. 1998. Occurrence of Skrjabillanid nematodes in
fishes of Hungary in the intermediate host, Argulus folicaeus L. Acta
Veterinaria Hungarica, 46 (4):451-463.
Monod, T. 1928. Les Argulides du Musée du Congo. Revue de Zoologie et de
Botanique Africaines, 16: 242-274.
Moravec, F. 1978. First record of Molnaria erythrophthalmi larvae in the
intermediate host in Czechoslovakia. Folia Parasitologia, 25 (2): 141-
142.
Moravec, F., Vidal-Martinez, V. and Aguirre-Macede, L. 1999. Branchiurids
(Argulus) as intermediate hosts of the daniconematid nematode. Folia
Parasitologica, 46 (1): 79.
Northcott, S.J., Lyndon, A.R. and Campbell, A.D. 1997. An outbreak of
freshwater fish lice, Argulus foliaceus L., seriously affecting a Scottish
stillwater fishery. Fisheries Management and Ecology, 4 (1): 73-75.
Okaeme, A.N., Obiekezie, A.I., Lehman, J., Antai, E.E. and Madu, C.T. 1988.
Parasites and disease of cultured fish of Lake Kainji area, Nigeria.
Journal of Fish Biology, 32 (3): 479-481.
CHAPTER 5 78 REFERENCES
Opara, K.N and Okon, A.O. 2002. Studies on the parasites of cultured
Oreochromis niloticus (Cichlidae) in rainforest pond South Eastern
Nigeria. Journal of Aquatic Sciences, 17 (1): 17-20.
Oprean, O.Z. and Vulpe, V. 2002. Morphology and diagnostic value of some
skin lesions of fish. Lucrai Stiinifice Medicina Veterinara Universitatea
de Stiinte Agricole si Medicina Veterinara ”lon lon escu de la Brad” lasi,
45 (4(1)): 231-235.
Overstreet, R.M., Dykova, I. and Hawkins, E. 1993. Branchiura. Pp. 385 – 413
in F.W. Harrison and A.G. Humes, ed. Microscopical Anatomy of the
Invertebrates. Vol 9 Crustacea. Wiley Liss Inc. New York.
Padmavathi, P and Prasad, M.K.D. 1998. An effective economically feasible
treatment of organophosphate pesticide and common salt to eradicate
the fish ectoparasite, Argulus japonicus Thiele in carp culture ponds.
Journal of Environmental Biology,19 (3): 193-203.
Paperna, I. 1980. Parasites, infections and diseases of fish in Africa.
Committee for the Inland Fisheries of Africa Technical paper, 7: 216.
Pearse, A.G.E. 1985. Histochemistry theoretical and applied. Vol 2: Analytical
technology. Churchill Livingstone. London, England. 1055pp.
Pfeil-Putzien, C. 1977. New results in the diagnosis of spring viraemia of carp
caused by experimental transmission of Rhabdovirus carpio with the
carp louse (Argulus foliaceus). Bulletin de l’ Office International des
Epizooties, 87 (5 and 6): 457.
Pfeil-Putzien, C. and Baath, C. 1978. Demonstration of Rhabdovirus carpio
infection among carp in the autumn. Berliner und Munchener
Tieraztliche Wochenschrift, 91 (22): 445-447.
CHAPTER 5 79 REFERENCES
Pusey, K.H. 1939. Methods of reconstruction from microscope sections.
Journal of the Royal Microscopical Society, 59: 232-251.
Rezeka, S. 1998. Trials for treatment and control of ectoparasites infesting
commercial penaeid shrimps “Penaeus vannamei”. 8th Scientific
Congress Faculty of Veterinary Medicine, Assiut University, Egypt, 15-
17 November, 1998: 844-855.
Ringuelet, R. 1943. Revisión de los Argúlidos Argentinos (Crustácea.
Branchiura) con el catálogo de las especies neotropicales. Revista del
Museo de La Plata, (Sección Zoología), 19 (3): 43-99.
Romeis, B. 1968. Microscopische Technik. R. Oldenburg, München,
Germany. 757pp.
Rudometova, N.K. 1974. The biology of Skrjabillanus amuri Garkawi, 1972
(Camallanata: Skrjabillanidae), a parasite of Ctenopharyngodon idella.
Sbornik Nauchnykh Trudov Vsesoyuznogo Nauchno Issledovatel’
skogo Instituta Prydovogo Rybnogo Khozyaistva, 11: 293-305.
Rushton-Mellor, S.K. 1994. The genus Argulus (Crustacea: Branchiura) in Africa:
two new species, A. fryeri and A. gracilis, previously undescribed male
of A. brachypeltis Fryer and the identity of the male described as A.
ambloplites Wilson. Systematic Parasitology, 28: 23-31.
Rushton-Mellor, S.K. 1994a. The genus Argulus (Crustacea: Branchiura) in
Africa: redescriptions of type-material collected by W.A. Cunnington
during the Lake Tanganyika Expedition in 1913 with notes on A.
giganteus Lucas and A. arcassonensis Cuénot. Systematic
Parasitology, 28: 33-49.
Rushton-Mellor, S.K. 1994b. The genus Argulus (Crustacea: Branchiura) in
Africa: identification keys. Systematic Parasitology, 28 (1): 51-63.
CHAPTER 5 80 REFERENCES
Rushton-Mellor, S.K. and Boxshall, G.A. 1994. The developmental sequence
of Argulus foliaceus (Crustacea: Branchiura). Journal of Natural History
28, (4): 763-785.
Rydlo, M, 1989. Comparative experiments on the control of some fish
ectoparasitoses. Current trends in fish therapy. Proceedings of a joint
WAVSFD and DVG meeting held in Munich on 25-26 April 1989: 76-
90.
Schram, F.R. 1986. Branchiura. Pp. 435–443 in Crustacea. Oxford University
Press, New York.
Schmahl, G., Taraschewski, H. and Melhorn, H. 1989. Chemotherapy of fish
parasites. Parasitology Research, 75 (7): 503-511.
Shimura, S. 1981. The larval development of Argulus coregoni. Journal of
Natural History, 15: 331-348.
Shimura, S. and Inoue, K. 1983. Toxic effects from the mouth-parts of Argulus
coregoni Thorell (Crustacea: Branchiura). Bulletin of the Japanese
Society of Scientific Fisheries, 50 (4): 729.
Shoshov, D and Kolarova, V. 1977. Action of trichlorfon on Argulus foliaceus
and Dactylogyrus extensus in carp. Veterinarnomeditinski Nauk,. 14
(8): 91-98.
Singhal, R.N., Jeet, S., Davies, R.W. 1986. Chemotherapy of six ectoparasitic
Diseases of cultured fish. Aquaculture, 54 (3): 165-171.
Smit, N.J., Van As, L.L. and Van As, J.G. 2005. Redescription of Argulus
multipocula Barnard, 1955 (Crustacea: Branchiura) collected on the
west coast of South Africa. Systematic Parasitology, 60: 75-80.
Stammer, J. 1959. Beiträge zur Morphologie, Biologie und Bekämpfung der
Karpfenläuse. Zeitschrift für Parasitenkunde, 19: 135-208.
CHAPTER 5 81 REFERENCES
Swanepoel, J.H. and Avenant-Oldewage, A. 1993. Functional morphology of
the foregut of Chonopeltis australis Boxshall (Branchiura). Journal of
Crustacean Biology, 13 (4): 656-666.
Tavares-Dias, M., Martins, M.L. and Kronka, S do N. 1999. Evaluation of the
haematological parameters in Piaractus mesopotamicus Holmberg
(Osteichthyes, Characidae) with Argulus sp. (Crustacea: Branchiura)
infestation and treatment with organophosphate. Revista Brasileira de
Zoologia, 16 (2): 553-555.
Thiele, J. 1904. Beiträge zur Morphologie der Arguliden. Mitteilungen Aus
Dem zoologischen museum in Berlin, 2: 1–51.
Timur, G. 1991. A histological study of a carp pox (Viral epithelioma) disease
in Turkey. Bulletin of the European Association of Fish Pathologists, 11
(5): 171-173.
Tikhomirova, V.A. 1971. Biology of Skrjabillanidae (Camallanata). Trudy Gel’
mintologicheskoi Laboratorii Teoreticheskie Voprosy Obshchei Gel’
Mintologii, 22: 208-211.
Tikhomirova, V.A. 1975. The life-cycle of nematodes of the family
Skrjabillanidae. Voprosy ekologii zhivotnykh Vypusk, 2: 100-113.
Tikhomirova, V.A. 1983. Carp lice- intermediate hosts of Skrjabillanidae
nematodes. Vliyanie antropogenykh faktorov nastrukturu i
funktsionirovanie ecosystem: 104-109.
Thomas, M.M. 1961. Observations on the habits and the post-embryonic
development of the parasitic branchiuran Argulus puthenveliensis
Ramakrishna. Journal of Marine Biology Association of India, 3 (1 and
2): 75-86.
CHAPTER 5 82 REFERENCES
Thorell, M.T. 1864. Om tvenne Europeikse Argulide, jemte anmärkningar om
Argulidernas morfologi och sustematiska ställning, samt en őfversigt af
de főr nävararande kände arterna af denna familj. Annals and
magazine of Natural History, 21: 7–71.
Tokioka, T. 1936. Larval development and metamorphosis of Argulus
japonicus. Memoirs of the college of Science Kyoto Imperial University
(B), 12 (1): 93-114.
Van As, J.G., Van Niekerk, J. P. And Oliver, P.A.S. 1999. Description of the
previously unknown male of Argulus kosus Avenant-Oldewage, 1994
(Crustacea: Branchiura). Systematic Parasitology, 43: 75-80.
Van As, J.G. and Van As, L.L. 2001. Argulus izintwala n.sp. (Crustacea:
Branchiura) from Lake St Lucia, South Africa. Systematic Parasitology,
48: 75-79.
Van As, J.G.and Basson, L. 1984. Checklist of freshwater fish parasites from
southern Africa. South African Journal of Wildlife Research, 14 (4): 9-
61.
Van Beneden, P.J. 1891. Un Argule nouveau des côtes d’Afrique. Bulletin de
i’ Academie royale de Belgique 3 serie, 22 (11): 369-378.
Van Kampen, P.N. 1909. Über Argulus belones n. sp. und A. indicus M.
Weber aus dem Indischen Archipel. Zoologischer Anzeiger, 34 (13 and
14): 443-447.
Walley, L. and Rees, E.I.S. 1969. Studies on the Larval Structure and
Metamorphosis of Balanus balanoides (L.). Philisophical Transactions
of the Royal Society of London. Series B, Biological Sciences, 256
(807): 237–280.
CHAPTER 5 83 REFERENCES
Walker, P.D., Flik, G. and Wendelaar Bonga, S.J. 2004. The biology of
parasites from the genus Argulus and a review of the interactions with
its host. Pp. 107—129 in G.F. Wiegertjes and G. Flik, ed. Host-Parasite
Interactions. Garland Science/BOIS Scientific Publishers. Hampshire,
UK.
Watson, R. and Avenant-Oldewage, A. 1996. Damage caused by the
attachment of Argulus japonicus to its fish host. Microscopy Society of
Southern Africa – Proceedings, 26: 126.
Wilson, C.B. 1902. North American parasitic copepods of the family Argulidae,
with a bibliography of the group and a systematic review of all known
species. Proceedings of the United States National Museum, 25: 635-
752.
Wilson, C.B. 1903. North American parasitic Copepods of the family
Argulidae, with a bibliography of the group and systematic reiew of all
known species. Proceedings of the United States National Museum,
25: 635-742.
Wilson, C.B. 1904. A new species of Argulus, with a more complete account
of two species already described. Proceedings of the United States
National Museum, 27: 627-655.
Wilson, C.B. 1920. Parasitic Copepods from the Congo Basin. Bulletin of the
American Museum of Natural History, 43: 1-8.
Wilson, C.B. 1923. New species of parasitic copepods from southern Africa.
Meddelanden Göteborgs Musei Zoologiska Avdelning, 25 (6):1-11 +
pls. 1-2.
CHAPTER 5 84 REFERENCES
Wolfe, B.A., Harms, C.A., Groves, J.D., and Loomis, M.R. 2001. Treatment of
Argulus sp. Infestations of river frogs. Contemporary Topics in
Laboratory Animal Science, 40 (6): 35-36.
Yamaguti, S. 1963. Parasitic Copepoda and Branchiura of fishes. Wiley
Interscience Publishers, New York. 1104 pp.
Yildiz, K and Kumantas, A. 2002. Argulus foliaceus infection in a goldfish
(Carassius auratus). Israel Journal of Veterinary Medicine, 57 (3): 118-
120.
Yonkos, L.T., Fisher, D.J., Reimschuessel, R., and Kane, A.S. 2000. Atlas of
fathead minnow normal histology. [http://aquaticpath.umd.edu/fhm].
Yoshiokoshi, K, and Yoshio, K. Histochemical localization of Hydrolase
activities in the alimentary canal of some parasitic copepods. Nippon
Suisan Gakkaishi, 57 (4): 613-618.
CHAPTER 5 85