Asian Journal of Biology

4(4): 1-7, 2017; Article no.AJOB.37805 ISSN: 2456-7124

First Record of Bluntnose Sixgill griseus (Bonnaterre, 1788) (, Hexanchidae) from Hadhramout Coast, Gulf of Aden

Moteah Sheikh Aideed1 and Ali Attaala Mukhaysin2*

1Freelance Marine Biology, Mukalla, Yemen. 2Faculty of Environmental Sciences and Marine Biology, Hadhramout University, Yemen.

Authors’ contributions

This work was carried out in collaboration between both authors. Author MSA is interested in searching and studied the fauna of the region, including the subject of the current study. He measured and wrote the first draft of the manuscript. Author AAM designed the final study, performed and managed the analyses of the study, the literature searches. Both authors read and approved the final manuscript.

Article Information

DOI: 10.9734/AJOB/2017/37805 Editor(s): (1) Paola Angelini, Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy. (2) P. Dhasarathan, Department of Biotechnology, Prathyusha Engineering College, Anna University, India. Reviewers: (1) Renato Massaaki Honji, Universidade de São Paulo Rua do Matão, Brasil. (2) André Lincoln Barroso Magalhães, Universidade Federal de São João Del Rei, Brasil. (3) Carmen Georgeta Nicolae, University of Agronomic Sciences and Veterinary Medicine of Bucharest, Romania. (4) K. V. Akhilesh, Central Marine Fisheries Research Institute, India. Complete Peer review History: http://prh.sdiarticle3.com/review-history/22591

Received 29th October 2017 Accepted 16th December 2017 Original Research Article Published 4th January 2018

ABSTRACT

The new record of Hexanchus griseus (Bonnaterre, 1788) based on 148.1cm as total length was collected during the traditional fishing activities in Hadhramout coast, north east Gulf of Aden, Yemen. It is compared with the specimen from the same species in the literature in terms of morphometrics and lower teeth. The analysis of the teeth of the current specie with H. nakamurai, do not let doubt that these characteristics linked to the new record of Hexanchus griseus in the Gulf of Aden for first time.

Keywords: Shark; ; Hexanchus griseus; Gulf of Aden; Hadhramout coast; morphometric.

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*Corresponding author: E-mail: [email protected]; Aideed and Mukhaysin; AJOB, 4(4): 1-7, 2017; Article no.AJOB.37805

1. INTRODUCTION have been recorded species of deep [8,9] in addition to the development of the potential of Arabian Sea and Gulf of Aden fauna were the fishing methods in the Yemeni coast, it is subject of active research of scientists, but only expected that there are some species of in recent decades have some monographic must be explored for scientific and commercial studies of various groups of (Ebert and purposes. Mostarda, 2013; Jabado and Ebert, 2015). The objective of the present study is to contribute Little is known about the deep sea sharks that the project of the specific census of Hadhramout are catch by drifting, bottom long lines and gill coast fish, which is adopted by Hadhramout nets and occasionally by bottom trawlers along University. the coast of Gulf of Aden. 2. MATERIALS AND METHODS Hexanchiformes is primitive group which survive to the present time, this includes the Blunt nose Bluntnose six gill shark H. griseus sample was six gill sharks Hexanchus which first appeared in collected in Al Mukalla bay (N:14.25.073, E the middle Jurassic time [1]. 049.06.584) from depth 480 meter, the sample was collected by traditional bottom long line on 3 Hexanchus griseus occur globally in all oceans mile off shore in 2009 (Fig. 1). and one of four species and three living genera belong to the family Hexanchidae [2], these Morphometric measurements of the shark has sharks live and thrive in the most widespread been taken by measure tape as TL The total distribution of all known sharks [3]. Hexanchus length, HDL Head length, PCL precaudal length griseus is mainly a deep water shark, rarely and Prepectoral length in centimeters, and total found at depths of less than 100 m. The species weight were recorded as Kilograms. seems to usually stay close to the bottom, near rocky reefs or soft sediments. The deepest one Usually the tooth morphology have been has been found was about 2500 m. regarded as key diagnostic characters allowing distinction between the two living species, H. These sharks are vertical migratory; they are griseus and H. nakamurai Teng, 1962 in many nocturnal and remain in the deep oceans during hand books [10]. the day but rise towards the surface at night. H. griseus also seasonally migrates to shallower We extracted the lower and upper jaws for coastal waters, these sharks can occasionally be further identification. We used the teeth as found in shallower waters at depths of 23 to 39 m characters used to describe the genus during the day and as shallow as 3 m at night [4]. Hexanchus, which usually based on morphology of the degrees of cusp serration and root The most obvious diagnostic features of these enlargement. However, few studies on specific sharks are the presence of six gill slits and only variation have been undertaken when describing one and anterolateral lower teeth with a Recent or fossil teeth of Hexanchidae [11,12]. saw blade appearance which most commonly described as comb like [5]. Hexanchidea are 3. RESULTS often described as morphologically primitive in nature based on the presence of six gill openings This description based on single specimen with and strongly dimorphic top and bottom teeth [6] 148.1cm total length (TL), 105.8 precaudal fin and characteristic by strong dimorphism in teeth, (PCL), 32.6 Head length (DHL), 32.9 Prepectoral the male has more erect primary cusps than fin length (PP1) and Total weight 31.9 Kg for female, especially noticeable on anterior most preadult Female (Fig. 2). cusps of enlarged lower anterior teeth of male, which is about 50% longer than the secondary 3.1 Morphometry (cm) cusp that follows it [7]. Unfortunately Yemen doesn’t realize that part of all fish (especially Some measurements were listed here as: Fork shark) species live their whole lives below 400 length 116; Pre-caudal length 104.8; Head length meters deep. Since it is known that the coast of 32.6; Pre-gill length 24.4; Pre-orbital length 5.5; Hadhramout as part of the Gulf of Aden and the Eye length 2.6; Pre-dorsal length 83; First dorsal exclusive economic zone includes deep depths, fin base 10; Pre-pectoral length 32.9; Pectoral fin up to more than 2000 meters, and that there length 19.8; Pre-pelvic length 75; Pelvic fin

2 Aideed and Mukhaysin; AJOB, 4(4): 1-7, 2017; Article no.AJOB.37805 length 13.2; Pre-anal length 87.9; Anal fin base rounded. The large teardrop-shaped eye, with 8; Anal-caudal length 10; Dorsal caudal space color is a fluorescent blue green are found 7.9 cm. anterior to the mouth.

This is the first record of the bluntnose Hexanchus griseus has only one dorsal fin six gill shark H. griseus (Bonnaterre, 1788) in located close to the caudal fin. Its origin is just Hadhramout coast, Gulf of Aden. behind the insertion point of the pelvic fins, while the dorsal fin has a rounded apex and slightly 3.2 Distinctive Features convex back margin. The pectoral fins have wide bases and rounded tips. The anal fin is small H. griseus has a heavy fusiform body with a than the dorsal fin and the pelvic fins have close flattened broad head. The rounded snout is blunt to straight margins and rounded tips. The caudal and there are six long gill slits on each side of the peduncle is short and stout and the ventral lobe head that discriminate this order and family, the of the caudal fin is not very obvious with only ventrally located mouth is wide and broadly moderate development.

Fig. 1. Maps of the locations Mukalla bay ( ) where specimen of Blunt nose six gill shark Hexanchus griseus was fished

Fig. 2. Blunt nose Sixgill Shark, Hexanchus griseus: Juvenile obtained during fishing by Traditional fishermen Almukalla bay, Hadrahmout Governorate, in September 2009. Length 148.1 cm and weight 31.9 Kg

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3.3 Dentition The shark H. griseus has three rows and one illusory of replacement lower teeth along the A distinguishing character, Hexanchus griseus inner jaw margins behind the front teeth (Fig. 4), has six broad, saw like teeth on each side of the as the front teeth are lost, the other move into lower jaw and the present of median erect cusp place from behind. (Figs. 3, 4). The upper jaw has nine smaller, serrated, single-cusped teeth on each side. 4. DISCUSSION

The length of the lower tooth 15mm, and have fin In Yemen Elasmobranches are caught in coastal serration on the mesial side of the first cusp, fisheries using lines and gillnets. Landings of while on the apical seven cusps that get smaller elasmobranches currently remain over 5,000t toward the distal end, and thin, flat rectangular [13], with Yemen being the fifth largest country in base or root on the distal side (Fig. 3). The the region in terms of reported elasmobranches oblique on cusps of the lower teeth are the most landings. There is considerable trade in shark important feature of the female than male. fins to Asia, and particularly to Hong Kong

Fig. 3. The lower and upper of Hexanchus griseus teeth identification diagram, obtained from the single specimen from AlMukalla bay, Yemen

Fig. 4. Diagram shows the three rows of replacement of inner jaw of the lower cusped teeth and the presence of median erect cusp

4 Aideed and Mukhaysin; AJOB, 4(4): 1-7, 2017; Article no.AJOB.37805

Fig. 5. Diagram shows the whole jaw of Hexanchus griseus and the saw like teeth on each side of the lower jaw appear statistics of which shows that imports from Based on a literature review its reproduction and Yemen as the fifth highest at 350t (dry weight) in aspects of reproductive biology were proved, 2000 [14]. from east and west coast of South Africa and the coasts of France, Spain, Italy, , Algeria and H. griseus was never recorded before in the fish Tunisia [23,24,25]. Confirming such statement, literature in the Gulf of Aden, and was limited on [26] reported an additional capture of a young of several regions in the : Pakistan H. griseus from Iskenderun Bay, . and Indian coasts, Oman, east coast of South Consequently, the records reported throughout Africa, southern Mozambique, , the and the southern Black Aldabra Island group, Comoros Islands [7,15, Sea and showed that the species could not 16]. This shark was absent in the main literature considered as threatened in both seas despite of Field identification guide to the sharks and the consideration of Cook and Compagno [27] rays of the Red Sea and Gulf of Aden [17]. that this species as near threatened but not totally depleted. The current registration and recurrence of this species in the northern Arabian Sea and the Hexanchus griseus have wide geographic Indian Ocean [16], in addition to the expansion of distribution in boreal and cold temperate to its spread in the Indian Ocean, it confirms the tropical seas. This strange distributional pattern suitability of this region as an environment for its happen due to different oceanographic coexistence. Furthermore the discovery of a phenomena in the Indian ocean include changes species outside of their usual area of distribution in the currents, migration undertaken by these may be due to an increase of traditional species, hereby causing wide geographic prospection, or to the use of newer techniques distribution [7,28]. which allow the exploration of otherwise unaccessible depths and habitat [18,19]. Results show that the record species of H. griseus have a similar dental development to that In some areas such as the Turkish waters, the described by Compagno [7]. The detection of the species appears to be commonly caught. It teeth in our species indicating the presence of 6 reported from the Turkish coast of the Black Sea rows of lower bladelike, comb-shaped teeth on [20,21,22]. Thus the species is known in all each side in the lower jaw which close related to directions of Mediterranean basin. H. griseus (Fig. 5), while there are 5 rows of

5 Aideed and Mukhaysin; AJOB, 4(4): 1-7, 2017; Article no.AJOB.37805 lower teeth on each side in the lower jaw of H. 5. Kemp NR. Detailed comparisons of the nakamurai. Where distinguish by the teeth dentitions of extant Hexanchid sharks and between the two living species from each other, tertiary Hexanchid teeth from South has been used as efficient method [7,11]. Australia and Victoria, Australia (Selachii: Hexanchidae). National Museum, Victoria. Hexanchus griseus shows close similarity with H. Memoirs.1978;39:61–83. nakamurai by the single dorsal fin along with the 6. Ellis R. The book of sharks. Harcourt six gill slits which help to distinguish these sharks Brace Jovanovich. San Diego. 1983;256. from most other species, but differs strongly in 7. Compagno LJV. FAO species catalogue. some morphomeristic characters, where H. Vol. 4. Sharks of the world. An annotated griseus has a blunt snout while the H. nakamurai and illustrated catalogue of shark species is smaller and has a more pointed snout. known to date. Part 1. Hexanchiformes to Lamniformes. FAO Fisheries Synopsis, 5. CONCLUSION Rome. 1984;249. 8. Ali Mukhaysin, Laith Jawad, and Aideed The recorded species in this report was never Sheikh. First record of Neoharriotta pinnata before mentioned in the fish fauna literature of (Osteichthys: Rhinochimaeridae) and the Gulf of Aden [7,17], but it is recorded in second record of Satyrichthys adeni Oman gulf, Pakistan and Indian coasts [15,16]. (Osteichthys: Peristediidae) from Gulf of Documentation the Family Hexanchidae in Gulf Aden, Republic of Yemen. Marine of Aden would be a further addition to the Biodiversity Records, Marine Biological scientific collections and deep sea fish fauna in Association of the United Kingdom. 2009; the Arabian Sea and Indian Ocean. 2(e170):1-4. DOI: 10.1017/S1755267209990972 ETHICAL APPROVAL 9. Ali AM, McNoon AH. Additions to benthopelagic fish fauna of Aden Gulf – As per international standard or university Arabian Sea (Actinopterygii: Bramidae and standard written ethical approval has been Sternoptychidae). Journal of Fisheries and collected and preserved by the authors. Aquatic Science. 2010;5(1):23-32. 10. Whitehead PJP, Bauchot ML, Hureau JC, COMPETING INTERESTS Nielsen J, Tortonese E. Fishes of the Northeastern Atlantic and the Authors have declared that no competing Mediterranean. UNESCO, Paris. 1984;1: interests exist. 510. 11. Welton BJ. Late Cretaceous and Cenozoic REFERENCES Squalomorphii of the Northwest Pacific Ocean (PhD Thesis). University of 1. Beaumont G. de. Contribution to the study California, Berkeley. 1979;553. of the genera Orthaccords Woodward and 12. Kaneko M, Fujii K, Takayama Y, and Notidanus Cuvier (Selachii). Swiss Sakamoto O. Analysis of dental formula Memory of Paleontology, 1960;77:4–36. based on 315 fossil teeth of Hexanchus sp. (In France) from the Miocene in the Chichibu basin, 2. Adnet S. Biometric analysis of the Central . Bulletin of the Saitama teeth of fossil and recent hexanchid sharks Museum of Natural History. 1997;15:17– and its taxonomic implications. Acta 32. Palaeontologica Polonica. 2006;51(3): 13. FAO (Food and Agriculture Organization of 477–488. the United Nations). FISHSTAT Plus, 3. McFarlane G, King J, Saunders M. Capture Production Database, 1970–2000, Preliminary study on the use of neural and Commodities Trade and Production arches in the age determination of Database 1976–2000. v. 2.30; 2002. bluntnose sixgill sharks. Fishery Bulletin. 14. Anon. Import, export and re-export 2002;100(4):861-864. statistics by commodity code (2000 data). 4. Musick JA, McMillan B. The shark Hong Kong Census and Statistics chronicles: A scientist tracks the Department, Hong Kong Special consummate predator. Times Books, New Administration Region Government; 2001. York. 2002;256. Unpublished data.

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