Chain catshark
The chain catshark or chain dogfish (Scyliorhinus retifer) is a small, spotted shark that has a characteristic fluorescent activity. The species is common from George’s Bank in Massachusetts, to Nicaragua. The species is considered harmless and rarely encountered by humans. It has very similar reproductive traits to Scyliorhinus canicula .


Mikhail Matz, a professor of marine biology
Marine biology
Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather...

 at the University of Florida
University of Florida
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...

, was the first to document the shark's previously unknown fluorescent properties. A specimen that proved to be a chain catshark was filmed by Matz off the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...

 in August 2005, a few days before Hurricane Katrina
Hurricane Katrina
Hurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall...

 passed through the area. The purpose of the shark’s fluorescence is still unclear.

Distribution and Size

In the Mid-Atlantic Bight, the Chain dogfish is found along the outer continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...

 and upper slope. The shark occupies depths of 58 to 359 meters and occupies shallower depths in the northern region compared to southern areas. Due to the shark’s depth distribution, it has been suggested that the shark does not perform large-scale migrations.

Temperature is thought to limit the shark’s distribution in northern areas, particularly during the winter. Although bands of warm water at the edge of the shelf have been observed, the temperature varies seasonally, thus limiting this non-migratory species.

Sizes of the species range from 0.36 ft. (immature), to 1.5 ft. (adult). Females tend to be larger at maturity, being 1.7 ft. long compared to their male counterparts at 1.64 ft.

Habitat and Behavior

The catshark spends the daytime resting at the bottom, usually in contact with certain structures. It has been observed with large burrowing cerianthid anemone
Anemone , is a genus of about 120 species of flowering plants in the buttercup family Ranunculaceae in the north and south temperate zones...

 tubes and boulders. The bottom rubble is thought to be used as a camouflage with the shark’s spotted surface. Adult sharks tend to prefer rough bottoms, creating a difficulty for trawl sampling, while the immature forms are found near smoother regions. The chain catshark has been known to feed on squid, bony fish, polychaetes and crustaceans. In aquaria, they are relatively motionless, only swimming occasionally.

Sexual Maturity

In the female chain catshark, follicle development has been correlated to nidamental gland
Nidamental gland
The nidamental gland is an internal organ found in some elasmobranchs and certain molluscs, including cephalopods and gastropods....

 size, thus, they are considered mature when they have a fully developed nidamental gland or shell gland. This is marked by the glands growth to 18 mm or more in width. Sexual maturity in the female is seen at 520 mm in length under normal conditions. There has been evidence however that some northern populations of the shark may mature at a smaller size (410 mm).

In the male catshark, testis development is correlated to clasper size, thus maturity is marked when it develops hardened claspers that are 30 mm or more in length. Claspers have been observed to develop after the shark is 490 mm and become mature at 500 mm.


Observed mating between the species suggests biting plays an element and that mating occurs repeatedly. Behavioral observations include the male biting the female until it can get a firm grasp and subsequently wraps its body around the female for copulation. After copulation, the male releases his bite and both separate.


The chain catshark prefers vertical structures for egg deposition and always deposits eggs in pairs. The interval between pairs of eggs ranges from a few minutes to 8 days. Development rates average 1mm diameter per 7.7 days although temperature has also been seen to affect follicle development.

Sperm storage and egg cases

The female chain dogfish is able to store sperm and lay eggs several days after initial copulation. The shark has been known to store sperm up to 843 days although, there are some circumstances of poor egg development in eggs laid later. It is suggested that this could be due to a number of factors including, senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...

, low sperm viability, or water quality factors.

Egg cases found in the oviduct are soft, pale yellow and translucent. They also feature two coiled tendrils, a key adaptation which allows snagging on rocks or man made structures, providing grounding and safety. When deposited, they become hardened and become dark amber with white bands.


Embyos take 8 – 12 months to develop due to temperature variations in the environment. The catshark lays eggs in their blastodisc form. The following exhibits a typical developmental timeline:

10 mm - it has well-defined gill arches and has a thin ventral finfold.
21 mm - dorsal and pelvic fin buds appear
33 mm - embryo has protruding eyes and well-developed gill filaments.
43 mm – it has lost its translucency and develops slits in the egg case, allowing fluid exchange from surrounding seawater and the interior
58 mm – the finfold starts to decay
66 mm – the finfold and gill filaments are reduced or absent
74 mm - external appearance is complete but yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...

is still being absorbed
100–110 mm - hatching

In aquaria

In an article for Aquarium Fish Magazine, Scott W. Michael described the chain catshark as "gorgeous," and "an ideal candidate" for being bred in captivity.

Further reading

Database entry includes justification for why this species is of least concern
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.