— Generic features. Closely related to the Genus Acanthomysis. Antennal scale setose all round; very long and narrow, terminating in an acute spine-like apex.
Tarsus of endopods of third-eighth limbs 3 or more segmented. Third pleopod of male rudimentary, fourth with short sympod, endopod unsegmented, exopod 2-segmented, very long armed distally with 2 very long setae. Pleopods in the female rudimentary , in the form of simpleunsegmented plates.
Telson long; lateral margins armed with many spines, apex small, armed with 2 spines.
Marsupium consisting of two pairs of brood lamellae; anterior pair with a posterior baling lobe. Median finger-like processes on the sterna of the last two or three thoracic somites in the breeding female.
— Species. Carapace leaving the last, and part of the seventh, thoracic somites exposed in dorsal view, produced anteriorly between the eyes into a short triangular rostral plate which does not extend forwards beyond the eyes, depressed in the central area, with slightly upturned margins and a prominent ventral keel, apex pointed; antero-lateral angles acutely pointed.
Antennular peduncle with the third segment of about the same length as the first but much stouter, setose lobe in the male as long as the last two segments of the peduncle; long and narrow, finger-shaped.
Antennal peduncle about one-third of the length of the scale, with second and third segments subequal.
Antennal scale long and narrow, from 10-12 times as long as broad, setose all round, terminating in an acutely spiniform apex, distal suture distinct; a prominent spine on the outer, distal angle of the sympod and a similar spine at the base if the peduncle.
Eyes about one and a half times as long as broad, somewhat pyriform in shape, cornea occupying the distal third of the whole eye, pigment black.
Thoracic limbs with a prominent gnathobasic lobe from the second segment of the endopod and with less prominent lobes on the succeeding segments. Thoracic limbs 3-8 with carpopropodus of the endopods divided into 6-8 subsegments, nail distinct; basal plate of the exopods with an acute spine on the outer distal corner. Genital organ of male short and barrel-shaped. Pleopods of the female all simple, unsegmented, short plates furnished with setae; of the male, first, second, third and fifth pairs rudimentary as in the female, fourth pair greatly elongated, extending backward half-way along the telson, sympod two-segmented; endopod a simple setose plate with a prominent setose lobe near the base; exopod two-segmented, first segment four and a half times as long as the second, armed with a single, short, distal seta; second segment terminating in two equal, strong, barbed setae which are one-fifth longer than the segment.
Telson long and narrow, longer than the sixth abdominal somite, triangular in shape, two and a quarter times as long as broad at the base; apex narrow but distinctly truncate and armed with two pairs of spines of which the outer are more than twice as long as the inner; no apical plumose setae; lateral margins armed throughout their entire length by a continuous series of 20-24 spines, crowded near the base and becoming gradually more spaced distally, more or less subequal in size, not arranged in series of larger spines with smaller ones between.
Uropods with endopod as long as the telson together with its terminal spines; armed with a dense row of comb-like spines, about 25 in number, on the ventral surface near the inner margin, extending from the distal end of the statocyst to about half the length of the endopod; exopod one and a half times as long as the telson; undivided and without spines, armed all round with setae.
Adult up to 17 mm.
Hyperbenthic, mainly in littoral and coastal waters.
The name integer, emphasises one of the most important characters of the species, the entire, uncleft telson. Neomysis integer is a euryhaline form with a wide range of salinity tolerance and considerably powers of adaptation to the changing salinity of the waters which it frequents. The species, like the great majority of the Mysicadea, is a filter feeder, living on organic detritus and microscopic animals and plants.
Distribution in the North Sea
All North Sea, Skagerrak, Wadden Sea, littoral, shallow, also brackish.
E North Atlantic: 44-71°N, Baltic, Mediterranean; estuarine, coastal.
[After Tattersall and Tattersall, 1951]