PHROSINIDAE Dana, 1852

Zeidler, Wolfgang, 2004, A review of the families and genera of the hyperiidean amphipod superfamily Phronimoidea Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 567, pp. 1-66 : 17-18

Family PHROSINIDAE Dana, 1852

Diagnosis

Body length 10–30 mm, rather compact with relatively thick cuticle, relatively transparent. Head large, globular, height more than length. Eyes large, occupying most of head surface. Pereonites all separate, or pereonites 1 & 2 fused. Coxae separate from pereonites. Antennae 1 reduced to two articles in females; multi­articulate, in males with enlarged callynophore, with aesthetasc brush composed of two asymmetrical fields located ventromedially and ventrolaterally. Antennae 2 rudimentary, or absent in females; multiarticulate in males. Mandibles with palp in males, without palp in females; molar welldeveloped. Maxillae 1 with palp and well­developed outer lobe, inner lobe absent. Maxillae 2 bilobed, well­developed. Maxilliped with slender outer lobes; inner lobe about halflength outer lobes. Gnathopods 1 & 2 simple. Pereopods 3–6 prehensile, or subchelate. Pereopod 5 the longest with large, denticulate subchela. Pereopods 5–7 with broad basis. Pereopod 7 reduced in size, sometimes with reduced number of articles. Uropods composed of single, foliaceous article. Telson small, not longer than half­length U3. Gills on pereonites 2–6. Oostegites on pereonites 2–5.

Three genera: Phrosina , Anchylomera and Primno .

Remarks

Species of this family are very distinctive, and are often present in plankton collections, sometimes in very large numbers. Phrosina and Anchylomera are monotypic, and Primno has been revised by Bowman (1978). Thus, only minimal additional information is provided here.

The structure of the uropods, each consisting of a single leaf­like article, is a unique feature amongst the Hyperiidea . They may serve as effective locomotory organs as phrosinids are known to be active swimmers, and sometimes occur in large swarms ( Lobel & Randall 1986).

Key to the genera of the Family PHROSINIDAE

1. Pereopods 3 & 4 distinctly subchelate, with large teeth on distal margin of carpus. Pereopod 7 reduced to basis and one tiny additional article ......... Phrosina Risso, 1822

­ Pereopods 3 & 4 simple, or if subchelate, with very small teeth, or bristles on distal margin of carpus. Pereopod 7 reduced, with at least 2 articles in addition to basis...... 2

2. Pereopods 3 & 4 simple. Pereonites 1 & 2 separate .... Primno Guérin­Méneville, 1836

­ Pereopods 3 & 4 distinctly subchelate. Pereonites 1 & 2 fused ...................................... ................................................................................ Anchylomera Milne­Edwards, 1830