Holophryxus giardi Richardson 1908

HOLOPHRYXUS GIARDI RICHARDSON, 1908

Original description: Richardson (1908): 690–693, figs 1–3 (adult and immature ♀♀).

Host: Boreogennema borealis (Dendrobranchiata, Benthesicymidae).

Distribution: North Pacific Ocean (Table 2).

Differential diagnosis: Holophryxus. Body length 8 mm (immature ♀), 39 mm (adult ♀; N = 1) (Richardson, 1908). Colour uniformly light yellow in ♀; unconfirmed in ♂.

FEMALE: Body spindle shaped, about 2.2 times as long as maximum width. Cephalon demarcated from pereon by lateral constrictions in dorsal aspect and by shallow dorsal fold in lateral aspect; dorsal prominence with emarginate (bilobed) anterior margin; with broad hood-like extension with virtually straight anterior margin and rounded frontolateral corners; ventral cephalic ridge not discernible in dorsal aspect, relatively small and slightly arched, about 0.3 times as long as wide, anterior margin slightly rounded, presence of pit organs unconfirmed; posterolateral corners of cephalic ridge produced into weakly developed pointed processes, representing coxal plates of incorporated first pereonite. Maxilliped and sternal plate not observed. Pereon with five pairs of incubatory plates; shape of oostegite 1 unconfirmed; oostegite 5 unilobate, covering about 60% of ventral side of body, posterior margin with minute spiniform extensions but number unconfirmed. Coxal plates of pereopods 2–5 expressed, represented by spinous processes on lateroventral margins of pereon, separated by transverse folds. Presence/absence of ventrolateral papillae on posterior part of pereon unconfirmed. Pleon demarcated from pereon by lateral and (particularly) ventral constrictions; about 15% of total body length; lobate with posterior margin broadly rounded.