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Observations on the Subfamily Aetholaiminae Jairajpuri, 1965 (Nygolaimidae: Nematoda)

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Observations on the Subfamily Aetholaiminae Jairajpuri, 1965 (Nygolaimidae: Nematoda) 82 PROCEEDINGS OF THE HELMINTHOLOGICAL SOCIETY Hampshire. N.H. Fish and Game Dept, Div. in Biological Research. W. H. Freeman and of Inland and Marine Fisheries. Co., San Francisco. Schmidt, G. D., and O. W. Olsen. 1964. Life Spaeth, F. W. 1951. The influence of acantho- cycle and development of Prosthorhynchus cephalan parasites and radium emanations formosus (Van Cleave 1918) Travassos 1926, on the sexual characters of Hyalella (Crusta- an acanthocephalan parasite of birds. J. Par- cea: Amphipoda). J. Morphol. 88: 361-373. asitol. 50: 721-730. Spencer, L. T. 1974. Parasitism of Garnmanis Seidenberg, A. J. 1973. Ecology of the acan- lacustris (Crustacea: Amphipoda) by Poly- thocephalan, Acanthocephalw dims (Van morphus minutus (Acanthocephala) in Colo- Cleave 1931) in its intermediate host, Asellus rado. Am. Midi. Nat. 91: 505-509. intermediiis Forbes (Crustacea: Isopoda). J. Stark, G. T. C. 1965. Diplocotijle (Eucestoda), Parasitol. 59: 957-962. a parasite of Gammarus zaddachi in the estu- Sokal, R. R., and F. J. Rohlf. 1969. Biom- ary of the Yorkshire Esk, Britain. Parasitol- etry, the Principles and Practice of Statistics ogy 55: 415-420. Observations on the Subfamily Aetholaiminae Jairajpuri, 1965 (Nygolaimidae: Nematoda) A. COOMANS AND P. A. A. LOOF Instituut voor Dierkunde, Rijksuniversiteit, Gent, Belgium and Laboratorium voor Nernatologie, Landbouwhogeschool, Wageningen, Netherlands ABSTRACT: Mylocliscus nanus Thorne, 1939 is redescribed from specimens collected in the State of Bahia, Brazil. It has an axial odontostyle and therefore does not belong with Aetholaimus Williams, 1962 to the Nygolaimidae, subfamily Aetholaiminae. The abrupt esophageal expansion, location of dorsal esophageal gland orifice, and presence of oval organs in the lateral chord indicate that it be- longs to Discolaimidae. Donjlaimus rotundicauda de Man, 1880, currently placed under Carcharo- laimus Thorne, 1939, is redescribed from specimens collected in the Netherlands and Switzerland. The presence of a mural tooth and of three "cardiac glands" show that it belongs to the Nygolaimidae; it is transferred to Aetholaimus. The latter genus now contains four species and is briefly reviewed. In 1939 Thorne described a new genus and tween Aetholaimus and Mylocliscus. In 1965 species Mylocliscus nanus from a single fe- Jairajpuri united these two genera into the male collected on the Island of Sumatra, In- new subfamily Aetholaiminae—recently raised donesia. He placed this genus in the subfamily to family rank by Andrassy (1976); again he Actinolaiminae of the family Dorylaimidae be- noted that the position of Mijlodiscus required cause of the presence of sclerotization in the further clarification. stomatal region. He could not decide whether During a survey of plant parasitic nema- it had an axial stylet or a mural tooth. todes in the State of Bahia, Brazil, carried out In 1962 Williams described a new genus in cooperation with Dr. R. D. Sharma, the and species Aetholaimus bucculentus from the second author collected several females and Island of Mauritius, which he placed in the juveniles of Mijlodiscus, so that redescription family Nygolaimidae because it possessed a is possible and its taxonomic position can be mural tooth instead of an axial odontostyle. clarified. Paratypes of Aetholaimus buccu- He noted, however, that this species also pos- lentus were kindly put at our disposal by Mr. sessed a character reminiscent of the Actino- D. J. Hooper, Rothamsted, England, and Dr. laiminae, viz. sclerotization in the stomatal M. S. Jairajpuri lent a specimen from India, region; and he noted certain resemblances be- identified by him as Ae. indicus. Copyright © 2011, The Helminthological Society of Washington OF WASHINGTON, VOLUME 45, NUMBER 1, JANUARY 1978 83 Before dealing with these species, however, Krnjaic and Loof (1976) placed Carcharolai- we want to discuss the taxonomic value of mus in the family Discolaimidae. stomatal sclerotization in the Dorylaimoidea. It thus appears that the superfamily Actino- In our opinion this value has been strongly laimoidea as conceived by Thorne is an arti- overrated. Thorne (1939) united all dorylaims ficial taxon. The families Actinolaimidae, Neo- which possess such sclerotization, viz. the gen- actinolaimidae and Paractinolaimidae have era Actinolaimus Cobb, 1913 (in its old wide such close connections with Dorylaimidae that sense), Antholaimus Cobb, 1913, Carcha.ro- we think it best to place them as a single laimus Thorne, 1939, Mylodiscus Thorne, 1939 family beside the Dorylaimidae (see Baqri et and Trachypleura Thorne, 1939, to a subfamily al., 1975). Stomatal sclerotization may evi- Actinolaiminae of the Dorylaimidae. Meyl dently develop independently in several groups (1957) raised the group to family rank; of dorylaims, and the presence of such sclero- Thorne (1967) made it a superfamily Actino- tization in Aetholaimus should not a priori be laimoidea with six families: Actinolaimidae, interpreted as evidence of actinolaimid rela- Neoactinolaimidae, Paractinolaimidae, Trachy- tionship. pleurosidae, Carcharolaimidae and Mylodisci- dae. Leaving aside the Trachypleurosidae— Mylodiscus nanus Thorne, 1939 based upon two insufficiently known species (Fig. 1; Diagram 1) —we can say that the first three families con- tain species with long-tailed females and short- DIMENSIONS (based on 13 females): L = tailed males (Brittonema Thorne, 1967 was 1.09-1.78 mm; width = 36-53 /xm; a = 24- defined as having long-tailed males, but 38; b = 3.1-4.1; c = 56-72; V = °-1756- Thome's drawing suggests that the long male 599-18. odontostyle = 10-12 /xm; odontophore tail of B. sulcatwn is an artifact, and males are = 23-26 /-on; T/ABW = 0.7-0.9. unknown in all other species; the genus may Body ventrally curved after fixation; cylin- be identical with Actinca Andrassy, 1964. drical throughout the greater part of its length Thorne also reported a long-tailed male of the but markedly narrowing near the anterior end. genus Practinocephalus Andrassy, 1973 [ = Cuticle 2-3 /am thick in midbody, increasing Actinocephalus Thorne, 1967 nee Stein, 1848] to 6-9 /xm on tail; with fine but distinct trans- but did not describe or illustrate it), whereas verse striae. Lateral chord 3-6 /xm wide or %— the Carcharolaimidae and Mylodiscidae have Vi2 of body width at midbody. Lateral body short tails, generally rounded (except in a pores in single line along the dorsal side of few species of Carcharolaimus), and no sexual the chords; in one specimen there were 35: dimorphism. The first three families stand, in 11 in the neck region, 23 between esophagus general morphology, close to certain genera base and tail, and one on the tail. of the Dorylaimidae sensu stricto such as Dory- Lip region 12-15 /xm wide or two fifths laimus, Laimijdorus and Ischiodorylaimus: the to one third as wide as the base of the neck; cuticle may possess longitudinal ridges; the disclike with inner bowl-shaped sclerotized esophagus widens more or less gradually, and lining, the bottom of which is thickened and the orifice of the dorsal gland lies in the ex- has radiating ridges. Lips clearly demarcated, pansion region; in some groups the supple- with the usual set of six inner and ten outer ments are concentrated into a few clusters; papillae. Amphids with triangular pouch, 5- the lip region is usually almost continuous. 8 ^m wide or about three fifths the width of The Carcharolaimidae, on the other hand, have the base of the lip region. Seiisillae situated the lip region strongly offset by constriction; opposite the base of the odontophore, 34—40 the lateral chord contains a series of large, /xm behind head end. Oral opening a dorso- conspicuous oval organs, each connected with ventral slit. Odontostyle slender and conical, the body surface by a large pore; the esopha- about 0.80X as long as lip region width; with gus widens very abruptly and the orifice of thickened tip and small aperture. Odonto- the dorsal gland lies well behind the expansion phore linear, 23—26 /xm long. Guiding ring zone. In all these characters the Carcharo- "double," fixed ring 8.5-12 /xm or slightly less laimidae agree with Discolaimus. Following than one lip region width from head end. a suggestion of Loof and Coomans (1970), The esophagus measures 326-395 /xm; an- Copyright © 2011, The Helminthological Society of Washington 84 PROCEEDINGS OF THE HELMINTHOLOGICAL SOCIETY Copyright © 2011, The Helminthological Society of Washington OF WASHINGTON, VOLUME 45, NUMBER 1, JANUARY 1978 85 terior part a narrow tube except for the odon- columnar cells. Prerectum 67-96 fan or 2.1— tophore region, which is wider and spindle- 3.5 anal body diameters long; rectum 22-36 shaped. At 53-58% of the neck length the /xm or about equal to anal body width. esophagus expands suddenly, forming the Female reproductive system didelphic, am- heavily muscular posterior part. Dorsal gland phidelphic; each branch composed of a re- outlet 26—35 /xm behind the expansion or 8— flexed ovary, well-developed ovarial sac, dis- 9% of neck length. Dorsal esophageal gland tally slender and proximally enlarged oviduct, nucleus oval, measuring 6-8 X 4-5 fun, with sphincter, and uterus consisting of two about rounded nucleolus 3 /xm in diameter; located equally long parts: a distal glandular one 11-19 /xm behind the outlet of the gland. and a proximal one that connects with the First pair of ventrosublateral gland nuclei vagina. The vagina extends about halfway about 15 tirn apart; the nuclei are rather small into the body and is surrounded by a well-de- (3.0—3.5 /xm, nucleolus 1.5 /mi), oval to veloped sphincter consisting of five muscle rounded to somewhat triangular. Second pair bands. Vulva a transverse slit, with very of ventrosublateral gland nuclei at about the faintly sclerotized lips. One intrauterine egg same level; measuring 3.5—5.5 /am, nucleolus measures 109 X 41 /xm. 2-2.5 /x.m; rounded. Tail 20-25 /xm long; dorsally convex-conoid LOCATIONS: (gland nuclei and orifices of with broadly rounded terminus; usually two 5 females): DO 63-67%; DN 68-71%; DO- caudal pores present on each side, in some DN 3.3-5.8%; S^ 77-80%; S^ 81-83%; specimens only one.
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