The Gecko catshark (Galeus eastmani) is a species of catshark, belonging to the family Scyliorhinidae. It can be found in the northwestern Pacific Ocean from southern Japan to Taiwan, and possibly also off Vietnam. It is a common, demersal species found at depths of 328-2,953 feet, and not of any interest to fisheries. Its body is slender, with a pattern of dark saddles and blotches. The dorsal and caudal fins are edged in white, and there is a prominent crest of enlarged dermal denticles along the dorsal edge of the caudal fin. It also has a white mouth lining.
Family: Scyliorhinidae – Catsharks
Genus: Galeus
Species: eastmani
Phylum– Chordata
Class– Chondrichthyles
Common Name– Ground Sharks
Family– Scyliorhinidae
Common Name– Catsharks
Genus– Galeus
Species– eastmani
Status: IUCN Red List LEAST CONCERN
Average Size and Length: Mature males have been measured between 31-32 cm/1 foot. Mature females have been measured between 36-37 cm/1.2 feet. The maximum is possibly 50 cm/1.6 feet long. One immature male was recorded at 38 cm/1.2 feet.
Current Rare Mythical Sightings: The first known specimen of the Gecko catshark, a 35 cm long female caught off the Izu Peninsula of Japan, was presented to American ichthyologists David Starr Jordan and John Otterbein Snyder by Alan Owston, a shipmaster from Yokohama. Jordan and Snyder described the species as Pristiurus eastmani in a 1904 volume of the scientific journal Smithsonian Miscellaneous Collections. Later authors have recognized Pristiurus as a junior synonym of Galeus. A 2005 phylogenetic analysis, based on mitochondrial and nuclear DNA, found that this species, G. gracilis, and G. sauteri form a clade apart from G. melastomus and G. murinus.
Teeth and Jaw: The Gecko catshark has a white mouth lining. The mouth is large 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 tooth has a narrow central cusp and typically two pairs of smaller cusplets on the sides.
Head: They have 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 nictitating membranes and indistinct ridges underneath.
Denticles: There is a distinct crest of enlarged dermal denticles along the upper margin of the tail. The skin is covered by small, overlapping dermal denticles. Each dermal denticle has a leaf-shaped crown with a horizontal ridge and three marginal teeth.
Tail: The tail is elongated. The caudal peduncle is almost cylindrical, and leads to a low caudal fin with a subtle lower lobe and a ventral notch near the tip of the upper lobe.
Demographic, Distribution, Habitat, Environment and Range: They can be found in the northwest Pacific in Japan, the east China Sea and possibly Vietnam. It has been found off the Shizuoka and Mie Prefectures of Honshu and the main islands of Shikoku and Kyushu, to the East China Sea including Taiwan. They can be found in deep water on or near the bottom between 328-2,953 feet. They are considered bathydemersal.
Diet: They more than likely eat bony fishes, cephalopods, and crustaceans. Some include lanternfish, squid, and even krill. The relative importance of the three prey categories varies between geographical areas and seasons, likely reflecting what is most available in the environment.
Aesthetic Identification: The Gecko catshark has white-edged dorsal and caudal fins. They are obscurely patterned with a slender and firm body and a somewhat small anal fin. The five pairs of gill slits are short, with the fourth pair about level with the pectoral fin origins. The first dorsal fin has a blunt apex and is positioned over the latter half of the pelvic fin bases. The second dorsal fin resembles the first but is slightly smaller, and is positioned over the latter third of the anal fin base. The pectoral fins are rather large and broad, with rounded corners. The pelvic fins are small with angular margins; the claspers 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.
Biology and Reproduction: They are oviparous. Egg cases are laid in pairs; one egg case per oviduct. Mature eggs are contained within smooth, translucent yellow, vase-shaped egg case measuring roughly 6 cm/2.4 inches long and 1.6 cm/ 0.63 inches across, with the top squared off and the bottom converging on a short projection. One study in Suruga Bay recorded females with large yolked ova 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 (Horie, T.; S. Tanaka (2000). “Reproduction and food habits of two species of sawtail catsharks, Galeus eastmani and G. nipponensis, in Suruga Bay, Japan“. Fisheries Science. 6: 812–825.).
Behavioral Traits, Sensing and Intelligence: They could possibly school. It seems to exhibit strong spatial segregation by sex.
Gecko Catshark Future and Conservation: They are of least concern. They are common in Japanese waters and are not of any interest to fisheries.
Gecko Catshark Recorded Attacks on Humans: Not a threat to humans.