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

Aegidae White, 850
Aegidae White, 850: 68.– Dana, 852 : 304; 853: 765.–
Hansen, 890: 3 5, 405.– Richardson, 905a: 66.–
Menzies & Glynn, 968: 44.– Menzies & George, 972:
9.9.– Kussakin, 979: 23 .– Brusca, 980: 229; 983:
6.– Menzies & Kruczynski, 983: 6 .– Kensley & Schotte,
989: 5.– Bruce, 993: 54.– Wetzer & Brusca, 997:
30.– Roman & Dalens, 999: 228.– Bruce, Lew Ton
& Poore, 2002: 59.– Keable, Poore & Wilson, 2002:
unpaginated.
Aeginae.– Menzies, 962: 7.
diagnosis: Eyes large, often medially united. Mouthparts
forming buccal cone; maxillule styliform, with
terminal and mesial robust setae; maxilla with single
distomesial basal endite; maxilliped palp with conspicuous
recurved (‘hooked’) RS. Pereopods –3 robust,
with dactylus as long as or longer than propodus,
usually strongly recurved.
desCription: Body evenly vaulted or dorsally depressed.
Eyes lateral or dorso-lateral, usually large, sometimes
contiguous or nearly so; occasionally absent. Antennae
and antennule well developed; division between
peduncle and flagellum distinct; flagellae multi-articulate;
antennule shorter than antenna, peduncle
4-articled; antennal peduncle 5-articled. Frontal lamina
present, varied in shape, occasionally absent, usually
not abutting clypeus; clypeus and labrum present,
often indistinct. Mouthparts forming buccal cone.
Mandible incisor narrow, small molar process present,
occasionally absent, lamellar and triangular when
present; lacinia mobilis and spine row absent. Maxillule
styliform, with flattened terminal RS, may be distally
hooked; mesial lobe present or absent. Maxilla with
small distomesial basal endite joined to larger mesial
lobe; each lobe with or more broad, usually apically
curved (hooked) RS. Maxilliped endite present (Aega
group of genera and Rocinela) or absent (Syscenus and
Xenuraega); palp with 3–5 articles, at least articles 3 and
4 with large hooked RS. Pereopods robust; pereopods
–3 with strongly curved dactylus (i.e. prehensile),
about as long or longer than propodus (occasionally
weakly curved or shorter than propodus); with few
slender setae. Pereopods 4–7 ambulatory, articles not
compressed or flattened, basis without long plumose
marginal setae; ischium to propodus inferior and distal
margins with RS. Pleopod rami lamellar, without
ridges or folding, with plumose marginal setae on both
rami of pleopods and 2, setation variously reduced
or absent on endopods of pleopods 3–5; pleopod 5
endopod without setae.
remarks: There are few unique character states that can
be used to define the Aegidae (see ‘Analysis’ p. 22).
There is a pagination error in this publication, with page
304 printed as 204.
26
Within the Cymothoida the styliform maxillule, with
terminal robust setae is a character shared with both the
Tridentellidae and Cymothoidae, and a maxillule that
has mesial (i.e. subterminal) as well as terminal robust
setae is shared only with the Tridentellidae. The maxilla
with a single distomesial endite is a character shared
only with the Cymothoidae. The Tridentellidae have
ambulatory pereopods –3 and lack hooked robust
setae on the maxilliped, and are further characterised
by having an elongate maxilliped endite. The Aegidae
is the only family in which all but a very few species
have greatly enlarged eyes, a state that is in general
rare within the Isopoda. There are some Corallanidae
that have large eyes, but in most species the eyes are
similar in size to those of the Cirolanidae. The Corallanidae
lack hooked robust setae on the maxilliped,
pereopods –3 are ambulatory, and the family has the
unique character states of strongly hooked maxillule
and vestigial maxilla with no endites. The Aegidae,
lack of wholly unique characters notwithstanding, can
be readily identified by the combination of characters
listed in the diagnosis.
Key to the marine genera of aegidae
A key to all genera was provided by Bruce ( 993a),
which included the only estuarine and freshwater genus
Alitropus (known only from tropical Australia and
Asia). Regional keys have been given to the East Pacific
by Brusca ( 983), the Caribbean (Kensley & Schotte
989), and to northern cold-water seas by Kussakin
( 979, in Russian).
Although the marine genus Xenuraega Tattersall,
909 has not been recorded from New Zealand it is
included in this key. The true extent of the distribution
of this genus is far from certain, but mesopelagic and
pelagic isopods often have extensive distributions,
sometimes in all oceans (e.g. Metacirolana caeca, see
Svavarsson and Bruce 2000, and Aega monophthalma
herein). For this reason it is considered entirely possible
that Xenuraega could be taken in New Zealand
waters.
Pleonite abruptly narrower than pereonite 7;
pleonite 5 lateral margins entirely free; eyes usually
absent ...............................................................2
– Pleonite not abruptly narrower than pereonite 7;
pleonite 5 lateral margins partly or entirely overlapped
by pleonite 4; eyes present, often large .3
2. Frontal lamina present; maxilliped palp 3-articled;
both uropod rami lamellar ........Syscenus [p. 98]
– Frontal lamina absent; maxilliped palp 2-articled;
uropodal rami with endopod stub-like, exopod
filamentous................................Xenuraega [p. 2 5]