The Marine Fauna of New Zealand: Isopoda, Aegidae (Crustacea)

Figure 86. Aegiochus riwha sp. nov. C, male paratype, NIWA 7934; remainder holotype. A–C, pereopods , 2 and 7,
respectively; D, pereopod , inferior margin of merus and carpus.
Variation: There were only two intact specimens
available at time of description, therefore the details
here are of range only. Robust setae on the pleotelson
ranged from 0 or . Uropod endopod mesial margin
8– 2 RS, lateral margin always 2 RS; uropod exopod
mesial margin 5 or 6 RS, lateral margin 2 or 3 RS. In
both specimens there were 3 minute RS set within the
apical notch.
remarks: Aegiochus riwha sp. nov. is most similar to
A. beri, but has coxae that are more blunt, more robust
pereopods with a shorter dactylus ( .0 times as long
as propodus v. .4 times as long in A. beri), ventral
surface of frontal lamina is flat (angled in A. beri), the
uropod rami and pleotelson margins are weakly serrate
(strongly serrate in A. beri), the appendix masculina is
weakly spatulate and as long as the endopod (terminally
acute and shorter than the endopod in A. beri)
and the apices of the uropodal rami are more widely
bifid that in A. beri (narrowly bifid). In addition A. riwha
has all dorsal body surfaces covered by brown chro-
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matophores (A. beri is without such both in holotype
and Lord Howe material), although without access to
fresh or freshly preserved material it is not possible to
place much reliance on colour difference. Given the
proximity of the locations for the two species and the
possibility of their being sympatric in part, these differences
are considered to be of species-specific value.
The difference in coxal shape readily and easily
distinguishes Aegiochus riwha from Aegiochus beri. The
anteriorly truncate notch on the pleotelson posterior
margin separates these two species from all other
southwestern Pacific and Southern Ocean species.
Aegiochus quadratisinus (Richardson, 903) (Bruce 983)
is known only from Hawai’i but, while similar to A.
riwha, has smaller eyes and the anterior margins of the
frontal lamina are concave.
The maxilla appears to have the mesial lobe fused to
the larger lateral lobe, and I could not distinguish the
point of join under stereomicroscopy nor compound
microscopy using DIC light interference.