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

and carpus larger, 5 RS on inferior margin of carpus).
Pereopods 5–7 inferior margins of ischium–carpus with
short RS. Pereopod 6 similar to pereopod 7 (shorter,
with more and longer RS; carpus inferior margin with
+ 2 RS). Pereopod 7 basis 2.8 times as long as greatest
width, inferior margins with 9 palmate setae; ischium
0.4 as long as basis, inferior margin with 5 RS (set as ,
2 and 2), superior distal angle with 2 RS, inferior distal
angle with 2 RS (small); merus .3 as long as ischium,
2.5 times as long as wide, inferior margin with 2 RS
(set as and ), superior distal angle with 3 RS, inferior
distal angle with 2 RS; carpus .5 as long as ischium,
3.3 times as long as wide, inferior margin with 2 RS
(single cluster), superior distal angle with 9 RS (many
biserrate), inferior distal angle with 6 RS; propodus .3
as long as ischium, 4.0 times as long as wide, inferior
margin with 2 RS (single cluster), superior distal angle
with 4 slender setae ( RS, plumose and 2 simple),
inferior distal angle with 3 RS.
Penes opening flush with surface of sternite 7; penial
openings separated by 8% of sternal width.
Pleopod 1 exopod .6 times as long as wide, distally
narrowly rounded, mesial margin weakly oblique,
lateral margin weakly convex, mesial margin strongly
convex, with PMS on distal half, with ~36 PMS; endopod
.9 times as long as wide, distally rounded, lateral
margin convex, with PMS on distal half, mesial
margin with PMS on distal one-third, endopod with
~2 PMS; peduncle .9 times as wide as long, mesial
margin with 7 coupling hooks. Pleopod 2 exopod with
~43 PMS, endopod with ~27 PMS; appendix masculina
with straight margins, .2 times as long as endopod
(extending beyond distal margin of ramus), distally
narrowly rounded. Pleopod 3 exopod with ~48 PMS,
endopod with ~ 3 PMS. Pleopod 4 exopod with ~42
PMS, endopod with ~8 PMS. Pleopod 5 exopod with
~38 PMS. Exopods of pleopods –3 each with distolateral
margin digitate; endopods of pleopods 3–5
each without distolateral point; pleopods 2–4 peduncle
distolateral margin with prominent acute RS.
Uropod peduncle ventrolateral margin with 2 RS,
posterior lobe about one-half as long as endopod. Endopod
apically shallowly bifid, lateral margin proximally
convex, without prominent excision, proximal lateral
margin with 0 RS, distal lateral margin with RS, mesial
margin straight, with 3–4 RS. Exopod extending to
end of endopod, 2.8 times as long as greatest width,
apically sub-bifid, mesial process prominent; lateral
margin convex, with 8 RS; mesial margin convex, with
3 RS.
femaLe: Similar to males, but wider (2. times as long as
greatest width at pereonite 6); the pleon is proportionally
shorter ( 8% BL) than in the male (2 % BL).
02
size: Average lengths of type material: males 7.7 mm (n
= 6), ovigerous females 2.0 mm (n = 6), non-ovigerous
females 2.8 mm (n = 22); emergent mancas measured
3.0–4.3 mm, and eggs measured .4– .6 mm.
Variation: Robust setae: (n = 5) pleotelson always
without RS. Uropod exopod mesial margin 3 (50%)
or 4 (40%), 2 and 5 occurring, lateral margin 9 (83%),
0 RS occurring once, 8 RS 3 times (possibly owing
to damage); uropod endopod mesial margin with 2
(20%) or 3 (73%) 4 and 5 occurring once each, lateral
margin with only large RS distal to the pappose seta.
There is no discernable difference between males and
females. The most distal robust setae are often very
fine and occasionally absent, accounting for most of
the observed variation.
The lateral margin of the uropodal endopod has
a small robust seta set inside the bifid apex. This seta
is largely obscured by the apical slender setae, and
proved to be too small to observe by light microscopy
and was not counted.
The small size of the robust setae on pereopods
and 2 precluded making accurate direct counts of pereopod
robust setae using light microscopy.
remarks: Aegiochus gordoni is characterised by having
large but well-separated eyes, the antennule flagellum
extending to pereonite 2 and a shield-shaped pleo-
telson, which is finely serrate and totally lacking robust
setae or notches; the uropods are provided with small
and fine robust setae, the smallest of which are difficult
to observe under light microscopy; the uropodal endopod
lateral margin is markedly straight. The anterior
pereopods are weakly ‘spined’ with the small robust
setae close-set to the inferior margin, particularly on
the propodus; the pleopods have the exopod disto-
lateral margin with digitate serrations, and the appendix
masculina extends well beyond the distal margin
of the endopod.
There are three Southern Ocean species which appear
similar. All of these species are described from
single specimens only, and most descriptions lack
sufficient detail for accurate comparisons to be made.
These species are Aegiochus crozetensis (Kussakin &
Vasina, 982) (Crozet Islands, southern Indian Ocean,
280 metres), Aegiochus pushkini Kussakin and Vasina,
982 (Ob’ Bank, southern Indian Ocean, 4 0 m; here
recorded from New Zealand) and Aegiochus uschakovi
Kussakin, 967 (Drake Passage, Argentina, 95– 20
m). All species share a similar appearance, but were
described as having pleotelson ‘denticles’, taken here
to mean robust setae.
Aegiochus pushkini, redescribed herein, is nearly
twice the size of A. gordoni, has narrower eyes, the pleopod
rami lack marginal serrations and the pleotelson
and uropods are provided with robust setae.