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

cle 2.0 as wide as long, mesial margin with 7 coupling
hooks. Pleopod 2 exopod with ~75 PMS, endopod with
~50 PMS (24 short PMS on mesial margin); appendix
masculina basally swollen, 0.96 times as long as endopod,
distally acute. Pleopod 3 exopod with ~78 PMS, endopod
with ~ 8 PMS. Pleopod 4 exopod with ~76 PMS,
endopod with ~ 4 PMS. Pleopod 5 exopod with ~67
PMS. Exopods of pleopods –5 each with distolateral
margin not deeply serrate; endopods of pleopods 3–5
each with mediodistal point; pleopods 2–5 peduncle
distolateral margin with prominent acute RS.
Uropod peduncle posterior lobe about one-half
as long as endopod. Uropod rami extending beyond
pleotelson. Endopod apically not bifid, lateral margin
straight, without prominent excision, proximal lateral
margin with RS, distal lateral margin with 2 RS, mesial
margin weakly convex, with 7 RS. Exopod not extending
to end of endopod, 2.3 times as long as greatest
width, apically not bifid; lateral margin convex, with
3 RS; mesial margin convex, with 5 RS.
femaLe: The single female, taken at the same station as
the New Zealand male, differs in a number of minor
characters, and its identity is here regarded as provisional
(see ‘Remarks’).
size: New Zealand material examined here 6.5– 7.0
mm; specimens from Bouvet Island, 6.0–25 mm.
Variation: Robust setae: pleotelson RS 4+4 (holotype)
and 5+5 (New Zealand). The holotype had only one
uropod, so no assessment was possible for uropodal
robust setae. The robust setae of the pereopods were
consistent between specimens, as illustrated (Figs 79F,
82). The Bouvet Island specimens are in good condition,
and have variable counts for robust setae: pleotelson
RS 4+4, 5+5 and 7+7; uropodal endopod mesial margin
7 (three times), 9 (twice) and 0 (once), lateral margin
+2 (all); uropodal exopod lateral margin with 0– 2
RS, mesial with 5 (twice) or 6 (four times). The coxae of
pereonites 5–7 on the Bouvet Island specimens have a
weakly concave posterior margin, while this is straight
in the New Zealand specimens and the holotype.
Bouvet Island specimens dorsally brown, laterally
with patches of white chromatophores on all or some
of pereonites 4–6.
remarks: The mesially narrow eyes, rectangular posterior
margins of coxal plates 2–4, wide and short frontal
lamina with the posterior margin forming a distinctly
concave blade, close-set penial openings in the males
and the presence (and pattern and number) of robust
setae on the uropods and pleotelson all allow identification
of this species.
40
Aegiochus pushkini belongs with a group of Aegiochus
species characterised by their relatively small size,
the posterior margin of the frontal lamina forming a
blade and relatively slender pereopods armed with
small robust setae. Two of these, Aegiochus nohinohi sp.
nov. and A. gordoni sp. nov., can be distinguished by
the rami of pleopod and 2 being deeply serrate and
lacking robust setae on the pleotelson. The remaining
species with similar pereopodal, uropodal and pleotelson
morphology can be separated by having the eyes
united (Aegiochus kakai sp. nov. and A. kanohi sp. nov.)
or by having the distal margin of the propodal palm of
pereopods –3 expanded (A. piihuka sp. nov.).
Other superficially similar species from the southern
Indian Ocean are Aegiochus crozetensis (Kussakin &
Vasina, 982), see p. 237, and A. uschakovi (Kussakin,
967) see p. 24 . The former has far larger eyes and a
narrower frontal lamina which has a convex posterior
margin, while the latter also has a narrower frontal
lamina and also has a far wider uropod endopod.
The specimens from three widely distant locations
show a degree of variation not usually observed within
a species. The holotype and male New Zealand specimen
agree closely, differing principally in the male
having a wider frontal lamina and two distal robust
setae on pereopod 2 merus. The female New Zealand
specimen is in good condition and shows rather more
differences that can be ascribed to sexual dimorphism.
These differences include a more strongly serrated
and posteriorly wider pleotelson margin, the antennal
flagellum extending to the posterior of pereonite
3 (it is more usual in dimorphic species that the male
has the longer antennal flagellae), coxae 7 are slightly
more acute. The specimens from Bouvet Island are in
close agreement with the New Zealand female, but
show considerable variation in pleotelson robust setae
(from 8 to 4), the large female has the posterior margin
of coxae 5–7 weakly concave and the small specimen
is similar to the New Zealand material; the pereopod
and uropod morphology seems identical in all of these
specimens. Without a larger series of specimens from
one location it is not possible to further assess the consistency
of such differences. In view of these differences
I consider the New Zealand male to be the same as
the holotype, but the remaining specimens to be only
provisionally determined as this species.
prey: Not known.
distribution: Recorded from the southern Indian Ocean
(Kussakin & Vasina 982); in the New Zealand region
off southern South Island, Macquarie Ridge; off Bouvet
Island (to Norway), South Atlantic; all localities
between 52° and 54° South. At depths from 22 to 4 0
metres.