The genus Parapseudomma from the East Atlantic deep sea, with description of a new species (Mysida: Mysidae)

Revised diagnoses are given for the mysid genus Parapseudomma Nouvel and Lagardere, 1976, and its type species Parapseudomma calloplura (Holt and Tattersall, 1905) from the Northeast-Atlantic, Mediterranean and waters off Japan, depth range 94-1200 m. Parapseudomma stenurum n. sp. from the sea floor off Cape Verde Islands and the Angola Basin, depth range 3825-5460 m, is described as the second species of its genus. It differs from the type species mainly by an unsegmented antennal scale, the carpus of thoracic endopods 3-8 separated from the propodus by a transverse articulation, the digitus mobilis of the right mandible reduced to a slender spine, and by a more slender telson. Reduction of the right digitus is also found in Abyssomysis and Xenomysis, the latter with potential genetic affinity to Parapseudomma. The three genera also share reduced eyes as in many other deep-sea Erythropinae. Both species of Parapseudomma share recently detected, probably sensorial structures: a pit-like depression here named 'antennular bursa,' dorsally on the basal segment of the antennula, and a median 'eye-cyst' inside the fused 'eye-bar,' the cyst opening to the surface by a duct. The evidence in Parapseudomma raises expectations that these sensorial organs are potentially present in a great variety of Erythropinae taxa.