M. Sars, 1857
Description
— Generic features. No statocyst in endopod of uropod. Pleopods well developed in both sexes, natatory, unmodified. Pleural plates of abdominal somites distinct and moderately well developed; exopod of uropod undivided; outer margin naked and ending in a tooth. Maxillus without endopod. Antennal scale heart shaped, outer margin serrated. Marsupium with seven pairs of oostegites (brood lamellae).
— Species. Integument firm and moderately calcified. Carapace large, completely covering the thorax laterally, but deeply emarginated in the posterior mid-dorsal line leaving the last two thoracic somites, at least, exposed in dorsal view.
Antenna with peduncle of endopod three segmented, the third segment longer than the first and second together and armed with a strong curved spine on its inner distal corner.
Antennular peduncle robust, basal segment quadrangular, slightly broader than long; second segment very short with the outer distal corner produced into a long acute process with a few setae at the apex; third segment as long as the first two together and somewhat stouter.
Labrum triangular, longer than broad, with anterior angle acute and bluntly rounded.
Mandibles with strong incisor and molar processes; left with a broad lacinia mobilis, which works on a fixed cusp on the right mandible.
On the sternum of each of the thoracic somites 2-7 and the first abdominal somites of the male there is a long, acutely pointed, forwardly directed, median, scythe-like spine. It is absent on the last thoracic somites.
First abdominal somite with processes on the sterna.
Telson more than twice as long as the sixth abdominal somite, three times as long as broad at the base; lateral margins with three spines on the middle third of their length; apex armed with two pairs of strong spines.
Size
Length of adult specimens of both sexes, 18-22 mm.
Depth range
Hyperbenthic from 60-450 m.
Remarks
Lophogaster typicus is usually found on a muddy bottom or one where mud largely predominates. However, breeding females, which have the young almost ready to be liberated, become planktonic and rise almost to the surface. Here the young are set free and for some time remain planktonic.
The species is probably a raptorial feeder. The loss of the maxillulary endopod (palp) is probably correlated with the loss of the filter feeding habit.
Distribution in the North Sea
Northern North Sea, W Norway, Skagerrak.
World distribution
Eastern North Atlantic: <26 –63°N, Mediterranean, Indian Ocean; shelf to slope. Lophogaster typicus is known from the Atlantic slope of Europe from Norway to Spain, and from the Mediterranean in water of comparable depth.
[After Tattersall and Tattersall, 1951]