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

Syscenus springthorpei Bruce, 997 (Fig. 36)
Syscenus springthorpei Bruce, 1997: 114, figs 1–4.– Bruce, Lew
Ton & Poore, 2002: 63.
materiaL examined: ♂? (39 mm), Tui Oceanographic
Cruise, Auckland University Zoology, AUZ 098 4 ,
locality not known, probable New Zealand EEZ;
previously dissected (label in Hurley’s handwriting:
“ex Kussakin: 23 , 269”); dissected appendages in fair
condition but specimen seems to have subsequently
deteriorated (NIWA 2378).
desCription (after Bruce 997a): Body 3.0 as long as
greatest width, dorsal surfaces smooth, widest at pereonite
5, lateral margins subparallel. Eyes absent. Rostrum
simple, anteriorly rounded. Coxae 2–3 each with
posteroventral angle rounded; 5–7 without oblique
carina. Pleon with pleonite visible in dorsal view;
pleonite 4 with posterolateral margins not extending
to posterior margin of pleonite 5; pleonite 5 with posterolateral
angles acute. Pleotelson .2 times as long as
anterior width, dorsal surface smooth; lateral margins
weakly convex, posterior margin with distinct median
point, with 0 RS.
Antennule peduncle article 3 0.6 times as long as
combined lengths of articles and 2, .6 times as
long as wide; flagellum with 7 articles, extending to
anterior of pereonite . Antenna peduncle article 3 2.5
times as long as article 2, .5 times as long as wide;
article 4 .3 times as long as article 3, .8 times as long
as wide, inferior margin with 3 plumose setae (long),
and 0 simple setae; 2.7 times as long as wide, inferior
margin with 10 setae (long, plumose); flagellum with
20 articles (approximately), extending to posterior of
pereonite 3.
Frontal lamina longer than greatest width, anteriorly
acute.
Mandible molar process absent; palp article 2 with
2 marginal distolateral setae, and 3 long distolateral
setae; palp article 3 with 9 setae. Maxillule with 5 RS (4
large, apically curved, slender, straight). Maxilla mesial
lobe with 0 hooked RS; lateral lobe with 2 hooked
RS. Maxilliped palp article distomesial angle with
RS; article 2 with 3 hooked RS; article 3 with hooked
RS (and two short simple setae).
Pereopod 1 basis 2.3 times as long as greatest width;
ischium 0.4 times as long as basis, inferior margin with
0 RS, superior distal margin with 5 setae; merus inferior
margin with RS (large, distal), superior distal angle
with 2 setae; carpus .0 as long as merus, inferior margin
with RS (with numerous simple setae); propodus
.6 times as long as proximal width, propodal palm
simple, without blade or process, inferior margin with
RS (distal); dactylus .3 times as long as propodus.
Pereopods 2 and 3 similar to pereopod . Pereopod 6
208
similar to pereopod 7. Pereopod 7 basis 2.4 times as
long as greatest width; ischium 0.8 as long as basis,
inferior margin with 0 RS, superior distal angle with 2
RS (and numerous simple setae), inferior distal angle
with 4 RS (and numerous simple setae); merus 0.6 times
as long as ischium, .7 times as long as wide, inferior
margin with 2 RS, superior distal angle with 6 RS (and
~5 simple setae), inferior distal angle with 4 RS (and
~4 simple setae); carpus .3 times as long as ischium,
2.7 times as long as wide, inferior margin with 2 RS,
superior distal angle with 8 RS, inferior distal angle
with 4 RS; propodus 0.9 as long as ischium, 3.7 times
as long as wide, inferior margin with RS, superior
distal angle with 0 slender setae, inferior distal angle
with RS. Pereopods distal margins of ischium to
carpus with abundant simple setae; without strong
carina on basis.
Penes low tubercles; penial openings separated by
% of sternal width.
Pleopod 1 exopod 2.0 as long as wide, lateral margin
weakly convex, mesial margin weakly convex, with
PMS on distal three-quarters; endopod 2.5 times as
long as wide, lateral margin weakly convex, with PMS
on distal margin only, mesial margin with PMS on
distal three-quarters; peduncle mesial margin with 9
coupling hooks. Pleopod 2 appendix masculina distally
narrow, 0.9 times as long as endopod, distally acute.
Pleopods 2–5 peduncle distolateral margin each with
acute RS.
Uropod peduncle ventrolateral margin with 0 RS,
posterior lobe about one-third as long as endopod.
Uropod rami with endopod and exopod co-planar,
rami not extending to pleotelson apex. Endopod lateral
margin weakly convex, lateral margin with 0 RS, mesial
margin weakly convex, with 0 RS. Exopod not extending
to end of endopod, 3.7 times as long as greatest width;
lateral margin weakly convex, with 0 RS; mesial margin
convex, with 0 RS; distal margin rounded.
femaLe: No female had been positively identified.
size: Holotype 36 mm; New Zealand specimen 39
mm.
Variation: The New Zealand specimen is in poor condition
and meaningful assessment is not possible.
remarks: The single specimen is in very poor condition,
appearing to have dried out at some point after it was
dissected (the dissected appendages are in adequate
condition) and also having suffered a mould infection.
In addition, the locality of the specimen is not known,
although, having been collected by the RV Tui, it will
have been within the New Zealand region. For these
reasons the descriptions and figures are taken from
Bruce ( 997a).