| Gecko catshark | |
|---|---|
 | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Division: | Selachii |
| Order: | Carcharhiniformes |
| Family: | Pentanchidae |
| Genus: | Galeus |
| Species: | G. eastmani |
| Binomial name | |
| Galeus eastmani (D. S. Jordan &Snyder, 1904) | |
 | |
| Range of the gecko catshark | |
| Synonyms | |
Pristiurus eastmaniD. S. Jordan & Snyder, 1904 | |
Thegecko catshark (Galeus eastmani) is aspecies of deepwater catshark, belonging to thefamilyPentanchidae, native to the northwesternPacific Ocean from southernJapan toTaiwan, and possibly also offVietnam. It is a common,demersal species found at depths of 100–900 m (330–2,950 ft). Its body is slender, with a pattern of dark saddles and blotches. Thedorsal andcaudal fins are edged in white, and there is a prominent crest of enlargeddermal denticles along the dorsal edge of the caudal fin. The gecko catshark is aschooling, opportunisticpredator ofbony fishes,cephalopods, andcrustaceans. It isoviparous, with females producing two vase-shapedegg capsules at a time. This species is captured asbycatch, but does not appear to be threatened byfishery activities at present and has been assessed asLeast Concern by theInternational Union for Conservation of Nature (IUCN).
Although the honor for this Catshark is not named, it is possibly in honor of fish paleontologistCharles Rochester Eastman (1868-1918).[2]
The first known specimen of the gecko catshark, a 35 cm (14 in) long female caught off theIzu Peninsula ofJapan, was presented to AmericanichthyologistsDavid Starr Jordan andJohn Otterbein Snyder by Alan Owston, ashipmaster fromYokohama. Jordan and Snyder described the species asPristiurus eastmani in a 1904 volume of thescientific journalSmithsonian Miscellaneous Collections.[3] Later authors have recognizedPristiurus as ajunior synonym ofGaleus.[4] A 2005phylogenetic analysis, based onmitochondrial andnuclear DNA, found that this species,G. gracilis, andG. sauteri form aclade apart fromG. melastomus andG. murinus.[5]
The range of the gecko catshark extends from southern Japan, where it occurs off theShizuoka andMie Prefectures ofHonshu and the main islands ofShikoku andKyushu, to theEast China Sea includingTaiwan. It is extremely abundant in Japanese waters. Further records from offVietnam may be erroneous. This species is found in water 100–900 m (330–2,950 ft) deep, on or close to thesea floor.[1][4] It seems to exhibit strong spatial segregation by sex.[4][6]
Attaining 40 cm (16 in), possibly 50 cm (20 in) in length, the gecko catshark has a slim, firm body and a fairly short head that comprises less than one-fifth of the total length. The snout is flattened with a blunt tip. The nostrils are large and divided by triangular flaps of skin on their anterior rims. The eyes are large and horizontally oval, with rudimentarynictitating membranes (protective third eyelids) and indistinct ridges underneath. The mouth is sizable and forms a long arch; there are well-developed furrows around the corners. The teeth are small and number around 47 rows in the upper jaw and 50 rows in the lower jaw; each has a narrow central cusp and typically two pairs of smaller cusplets on the sides. The five pairs ofgill slits are short, with the fourth pair about level with thepectoral fin origins.[4][6][7]
The firstdorsal fin has a blunt apex and is positioned over the latter half of thepelvic fin bases. The second dorsal fin resembles the first but is slightly smaller, and is positioned over the latter third of theanal fin base. The pectoral fins are rather large and broad, with rounded corners. The pelvic fins are small with angular margins; theclaspers of adult males are short and do not reach the anal fin. The anal fin base measures roughly 12% of the total length, shorter than the distance between the dorsal fins but longer than the distance between the pelvic and anal fins. Thecaudal peduncle is almost cylindrical, and leads to a lowcaudal fin with a subtle lower lobe and a ventral notch near the tip of the upper lobe. The skin is covered by small, overlappingdermal denticles; each has a leaf-shaped crown with a horizontal ridge and three marginal teeth. There is a crest of enlarged denticles along the upper edge of the caudal fin. This species is grayish above and patterned with darker, fuzzy-edged saddles and blotches along the body and tail. The underside, dorsal and caudal fin trailing margins, and interior of the mouth are white.[4][6]
Schooling in nature,[6] the gecko catshark feeds opportunistically on a wide variety ofbony fishes (includinglanternfish),cephalopods (includingsepiolid andenoploteuthidsquid), andcrustaceans (includingisopods,amphipods,krill, anddecapods). The relative importance of the three prey categories varies between geographical areas and seasons, likely reflecting what is most available in the environment.[8] This species isoviparous; adult females have a single functionalovary, on the right, and two functionaloviducts. A single egg matures within each oviduct at a time.[8] Mature eggs are contained within smooth, translucent yellow, vase-shapedcapsules measuring roughly 6 cm (2.4 in) long and 1.6 cm (0.63 in) across, with the top squared off and the bottom converging on a short projection.[4][6] One study inSuruga Bay recorded females with largeyolkedova inside the ovary year-round, but females in the western part of the bay were only found to carry egg cases from October to January, suggesting that the interval between egg depositions is shorter at that time.[8] Males and females attainsexual maturity at approximately 31–32 cm (12–13 in) and 36–37 cm (14–15 in) long respectively. However, there is a Taiwanese record of an immature male 38 cm (15 in) long.[1]
Uncertain numbers of gecko catsharks arecaught incidentally bycommercialtrawlfisheries. In Taiwan, it is occasionally brought to market and processed intofishmeal foraquacultural use. This species' small size and oviparous mode of reproduction may make it more resilient to fishing pressure than other sharks. As the gecko catshark remains common off Japan and may be protected from fishing in the deeper parts of its range, theInternational Union for Conservation of Nature (IUCN) has assessed it as ofLeast Concern.[1]
