CLASSIFICATION of CHILOSCYLLIUM
Phylum :- CHORDATA ( Notochord and dorsal tubular nerve cord present and gill-slits present)
Group :- CRANIATA ( Cranium with brain present ).
Subphylum :- VERTEBRATA (Vertebral column present ).
Division :- Gnathostomata ( Jaws and paired appendages present ).
Super class :- PISCES (Paired fins , gills and skin with scales)
Class :- CHONDRICHTHYES { =ELASMOBRANCHI } (Endoskeleton cartilaginous. Scales usually placoid. spiral valve in intestine. Opercula absent ).
Sub-class :- Selachi (Sharks and rays. Gills in seperate clefts. Cloaca present).
Order :- PLEUROTREMATA { =SQUALI } (Pleuro-sides , trema-opening. gill slits lateral, pectoral fins small.)
Family :- SCYLLIDAE (Asterospondylus. First dorsal fin without spine)
Genus :- CHILOSCYLLIUM (TRUE DOGFISH)
Geographical distribution
Chiloscyllium is abundantly distributed in temperate and tropical sea water. It ranges from U.S.A. to Indian Ocean. Australia, China and Japan.
Habit and habitat
Marine shark. found at a depth of about 700-800 meters.
GENERAL CHARACTERSTICS OF chiloscyllium : true dogfish
- Commonly called as true dogfish of moderate size.
- Body is laterally compressed and differentiated into head, trunk and tail.
- Surface of body is mottled with irregular black bands.
- Head is produced into snout and comprises ventral mouth, nostrils and eyes without nictitating membrane. Spiracle and 5 pairs of gill-slits are found behind eyes.
- Mouth contains small teeth provided with median cusps.
- Median fins dorsally consists of first dorsal and second dorsal fins. Ventrally paired fins pectoral fin, pelvic fin with clasper. anal fin, upper and lower lobes of caudal fin.
- Tail is very slightly curved upwards and possess caudal fin.
- Sexually dimorphic. Males have claspers which act as intromittent organ.
- Fertilization internal and oviparous.
Economic importance
Very important to fisheries as its liver contains oil rich in vitamin A.
Special features
This fish secretes Mermaid’s purse or case. The eggs are extremely yolky and they pass down the oviduct. become surrounded by watery albumen and then by horny mermaid’s case. Each case is roughly rectangular with four long coiled filaments. Females lay egg case among sea weeds. The filaments of the egg cases become entangled with the sea weeds soon after their emergence from the cloaca. In this condition they remain as such till the young ones come out.
Identification
Since this fish has irregular black spots and above features, hence it is Chiloscyllium.
