Mouse Catshark

The maximum length of the mouse catshark has been variously reported as 49 cm (19 in) and 85 cm (33 in). The larger figure comes from Iceland and is reflective of the aforementioned taxonomic confusion, as the specimen of P. jensenii described by Bjarni Sæmundsson was 63 cm (25 in) long. This species has a firm body with a rather long, blunt snout. The nostrils are divided by triangular flaps of skin in front. The eyes are horizontally oval and equipped with rudimentary nictitating membranes (protective third eyelids). A thin ridge is present beneath each eye, and a tiny spiracle behind. The large mouth forms a wide arch, and bears well-developed furrows at the corners. The teeth have a narrow central cusp and multiple lateral cusplets on either side. There are five pairs of gill slits. The first dorsal fin has a rounded tip and is positioned over the aft portion of the pelvic fins. The second dorsal fin is similar in size and shape as the first, and is positioned over the aft portion of the anal fin. The pectoral fins are large and broad. The pelvic fins are distinctive, being large and wide with an evenly rounded margin. In adult males, the inner margins of the pelvic fins are fused together to form an "apron" partially covering the claspers. …

Fairly common, the mouse catshark has recently been found to be more widespread in the northeastern Atlantic than previously thought, occurring from western Iceland and the Faroe Islands to the Hebrides, Scotland, and Ireland, to as far south as France and Western Sahara. This species is found on or near the bottom over the continental slope, in water 380–1,300 m (1,250–4,270 ft) deep. It has been reported from a depth of 656–1,731 m (2,152–5,679 ft) off Iceland, but the figure is confounded by taxonomic confusion.

The diet of the mouse catshark consists primarily of shrimp such as Pasiphaea multidentata and Sergestes robustus, other crustaceans such as Dorhynchus thomsoni, bony fishes such as Micromesistius poutassou, and cephalopods. Most prey organisms are captured on or close to the sea floor. Reproduction is oviparous; the female has two oviducts, with one egg maturing inside each at a time. The egg capsules are golden yellow and vase-shaped, measuring 5.4–5.6 cm (2.1–2.2 in) long and 1.4–1.7 cm (0.55–0.67 in) across. The top of the capsule is squared off, while the bottom comes to a short projection. The capsule surface is thickly covered by fibers, giving it a hairy appearance. The young are estimated to hatch at a length of approximately 8–9 cm (3.1–3.5 in).