21 July 1994
PRac. BIaL. Sac. WASH.
107(2), 1994, pp. 283-290
A NEW GENUS AND SPECIES OF CIROLANID
ISOPOD FROM THE WESTERN INDIAN OCEAN
(CRUSTACEA: PERACARIDA)
Abstract. -Seychellana expansa new genus, new species, is diagnosed and
described from shallow water off the Seychelles Islands, western Indian Ocean.
The genus is characterized by the possession of a slender, blade-like frontal
lamina, a somewhat reduced pereopod 7, a strongly bipartite epimeron on
pleonite 2, a broadly expanded epimeron on pleonite 3, and a ventrally inserted
uropod.
Records of the cirolanid isopod fauna of
the western Indian Ocean are scattered
through a number of publications (see Bruce
& lones 1978, Bruce & laved 1987, laved
& Yasmeen 1990); the steady stream of new
taxa being described, though, would indi-
cate that many new forms await discovery.
To date, the majority of records are from
coastal intertidal and very shallow waters.
Very little is known of the peracaridan fauna
of the tropical oceanic islands of the Indian
Ocean, as is demonstrated by the present
record ofa new genus from what is relatively
shallow water in the Seychelles, an area that
has received less attention than some.
The material was collected in the course
of an environmental survey carried out for
the government of the Republic of Sey-
chelles, and was submitted to the Smith-
sonian Institution for identification.
Suborder Flabellifera
Family Cirolanidae
Seychellana, new genus
Diagnosis. -Cephalon lacking rostrum.
Frontal lamina slender, blade-like, poste-
riorly well separated from flattened, non-
projecting clypeus. Mandibular molar not
reduced; incisor broad. Maxillipedal endite
having 2 coupling hooks. Pereopods 1-3
with merus anterodistally somewhat pro-
duced. Pereopods 4-7 ambulatory, articles
not markedly flattened, bases lacking na-
tatory setae. Pereopod 7 noticeably shorter
and more slender than pereopod 6. Epi-
meron of pleonite 2 bipartite, consisting of
strong acute dorsal and ventral parts. Epi-
meron of pleonite 3 enormously enlarged,
overlapping pleonites 4 and 5 laterally.
Pleonite 5 with free lateral margin over-
lapped by epimeron 3. Endopods of pleo-
pods 3 and 4 with marginal setae, of pIeopod
5 lacking setae; all exopods with marginal
setae. Uropod inserted ventrally; peduncle
produced along mesial margin of endopod;
latter fairly slender, lateral margin excavate.
Type species. - By present designation,
Seychellana expansa, new species.
Discussion. - The present material essen-
tially resembles a species of Eurydice, over-
lain with a number of specializations. The
similarities with Eurydice can be seen in the
structure of the frontal lamina, clypeus, an-
tennule, pleon, and in the ventral insertion
of the uropods. The specializations include
the reduced pereopod 7 (one-third shorter
and less robust than pereopod 6); the lack
of a complete transverse suture on any of
the pleopodal rami; the strongly bipartite
epimeron of pleonite 2 embracing that of
pleonite 3; the enormously enlarged epi-
meron ofpleonite 3 which completely over-
laps those ofpleonites 4 and 5. While some
of these features appear individually in some
other cirolanid genera, e.g., the slender fron-
tal lamina of Pseudolana, Eurydice, and Na-
tatolana, the plate-like epimera ofpleonites
2 and 3 in Booralana, the strongly expanded
epimeron of pleonite 3 as in Aatolana
schioedtei (Miers 1884) (see Bruce 1986, fig.
135c; 1993:5, 9), none of the presently rec-
ognized genera exhibit all of these special-
izations, along with a considerably reduced
pereopod 7 (compared to pereopod 6), and
ventrally inserted uropods.
Etymology. - The generic name is a com-
bination of Seychelles, the type locality, and
'lana', the suffix frequently used in cirolanid
taxonomy.
Seychellana expansa, new species
Figs. 1-4
Material. -Holotype, USNM 252889, 5
tl 6.6 mm, Paratypes, USNM 252890, 5 tl
6.3 mm, '2 tl 4.2 mm, sta C2RI, 6/1/92; 5
tl 6.0 mm, SEM whole mount, sta C2R2; 5
tl 6.4 mm, sta C2R3, 6/1/92 (dissected);
4?4I'N, 55?33'E, 30 m, Van Veen grab on
sandy bottom, off Anse aux Pins, Mahe,
Seychelles, coli. J. Elliott, S. Elliott, & P.
Harper, I Jun 1992.
Description. - Male: Body length about 3
times greatest width at pereonite 3. Red-
brown chromatophores scattered over most
of dorsum of cephalon, pereonites and
pleonites, pleotelson dorsally almost unpig-
mented. Cephal on with anterior margin
mesially broadly rounded but lacking dis-
tinct rostrum; bases of antennules separat-
ing cephalon from frontal lamina; latter an-
teriorly rounded in ventral view, posteriorly
elongate, narrowed, well separated from
broadly rounded clypeus. Eyes large, well
pigmented. Coxal plates ofpereonites 2 and
3 posteriorly truncate, ofpereonites 4-6 be-
coming larger and slightly produced, of pe-
reonite 7 posteriorly acute, much smaller
than and almost hidden by coxa ofpereonite
6. Posterior margins ofpereonites and pleo-
nites finely denticulate. Pleonites 1-5 free;
pleonite I short, with very short free epi-
meron; pleonites 2-4 subequal in length,
epimeron ofpleonite 2 bipartite, with strong
acute dorsal and ventral portions embracing
enlarged epimeron of pleonite 3; latter
broadly ovate, reaching posteriorly beyond
pleonites to protopod ofuropod, completely
covering short epimera of pleonites 4 and
5; pleonite 5 longer than 4, with posterior
margin mesially convex. Pleotelson as long
as wide, strongly arched, with finely cren-
ulate posterior margin broadly rounded,
bearing 12 short plumose setae; lateral and
posterior margins directed ventrally.
Antennular peduncle with articles 2 and
3 each bearing 2 spines on inner (ventral)
surface; flagellum consisting of 9 articles,
row of 3 or 4 aesthetascs on articles 2-7,
penultimate article with single aesthetasc.
Antennal peduncle articles I and 2 short,
articles 3-5 increasing in length distally, ar-
ticle 4 with 2 stout distal spines, article 5
with 5 distal spines; flagellum of 21 articles,
reaching posteriorly to level of pereonite 5.
Mandibular incisor of 3 cusps on each side,
mesial cusp somewhat elongate and acute,
2 lateral cusps rounded; 7 or 8 spines in
spine row; molar having row of 20 spines
on upper surface; palp of 3 articles, article
I subequal in length to article 3; article 2
2.5 times length of article I, bearing 10 setae
on distal half of lateral margin; article 3
bearing 13 fringed spines increasing in length
distally. Maxilla I, endopod having 3 stout
mesiodistal circum plumose setae; exopod
having 8 distal entire, comb, and denticu-
late setae. Maxilla 2, palp bearing 2 distal
elongate setae; exopod with 7 mesiodistal
setae; endopod broadly rounded, with sev-
eral simple and circum plumose setae on
mesial margin. Maxillipedal endite reaching
base of article 2 of palp, bearing 4 sparsely
plumose setae distally, 2 coupling hooks on
mesial margin of both left and right ap-
pendage; palp articles 2-5 bearing setae on
mesial and lateral margins.
Pereopod I, merus somewhat anterodis-
tally produced, bearing strong terminal
Fig. I. Seychellana expansa. A, Holotype in dorsal view, scale = 1 mm; B, Holotype in lateral view; C,
Lateral pleon enlarged, with epimera I, 2, and 3 indicated. D, Antennule; E, Antenna; F, Left and right mandibles;
G, Maxilla I; H, Maxilla 2; I, Maxilliped; J, Mandibular palp; K, Uropod.

spine, posterior margin having single elon-
gate and several short spines; carpus short,
triangular, lacking free anterior margin;
propodus with 5 short spines on posterior
margin; dactylar unguis lacking accessory
spine. Pereopod 2, basis with 2 elongate se-
tae on anterior margin; ischium with single
strong anteromesial and posteromesial
spine; merus with short anteromesial lobe
bearing several spines; carpus having free
anterior and posterior margin, with 2 short
posterodistal spines; propodus with 2 pos-
terodistal spines. Pereopod 3, basis with row
of palmate setae on anterior margin; ischi-
um with few small spines at posterodistal
angle, single strong spine at anterodistal an-
gle; merus with several strong anterodistal
spines, posterior margin sinuous, bearing
Fig. 4. Seychellana expansa. A, Cephalon, antennular bases, and apex of frontal lamina in dorsal view; B,
Anterior cephalon in ventral view; C, Dactylar unguis of pereopod I; 0, Dactylar unguis of pereopod 5; E, Pleon
in lateral view; F, Pleon in ventral view, showing ventral insertion ofuropods (protopods indicated by arrows).
about 7 short and long spines; carpus, prop-
odus, and dactylus as in pereopod 2. Pereo-
pod 4, basis with row of elongate setae on
lateral surface; ischium with anterodistal
clump of spines, clump of spines at mid-
length and at posterodistal angle of poste-
rior margin; merus and carpus each with
anterodistal and posterodistal clump of
spines; propodus slender, elongate, with sin-
gle spine at about midlength of posterior
margin, 2 small posterodistal spines. Pereo-
pods 5 and 6 similar, basis with double row
of setae; ischium with 3 clumps of spines
on posterior margin, clump of anterodistal
spines; merus and carpus with clump of
spines at midlength of posterior margin, plus
anterodistal and posterodistal clump; prop-
odus with clump of spines at midlength of
posterior margin, 2 small posterodistal
spines. Pereopod 7 about one-third shorter
and less robust than pereopods 5 and 6,
basis with double row of setae; ischium with
slender spines and setae on anterior and
posterior margins; merus with clumps of
slender spines at midlength of posterior
margin, anterodistal and posterodistal an-
gles; carpus with numerous slender distal
spines; propodus with single spine at mid-
length of posterior margin, 2 spines at pos-
terodistal and anterodistal angles. Penes on
sternite 7 well separated low rounded struc-
tures.
Pleopod I, protopod with 4 retinaculae;
endopod slightly longer and narrower than
exopod, with few distal plumose marginal
setae; exopod ovate, with distal third of me-
sial margin and all oflateral margin bearing
plumose setae. Pleopod 2, proto pod with 3
retinaculae; copulatory stylet articulating at
base of endopod, slender, distally curved
and barely surpassing apex of rami; ovate
exopod with plumose marginal setae on dis-
tal third of mesial margin and all of lateral
margin. Pleopods 3 and 4 similar, proto pod
with 3 retinaculae; endopod with mesial
margin straight, few plumose marginal setae
distally; exopod ovate, with plumose mar-
ginal setae on distal third of mesial margin
and all of lateral margin, latter having in-
complete suture forming small notch at
about midlength. Pleopod 5, proto pod lack-
ing retinaculae; endopod ovate, having
rounded proximomesiallobe; exopod ovate,
bearing plumose marginal setae on distal
third of mesial margin and all oflateral mar-
gin, with incomplete suture forming small
notch just short of mid length of both mesial
and lateral margins. Uropodal protopod in-
serted ventrally and completely hidden by
pleotelson in dorsal view, produced dis-
tomesially for about one-third length of en-
dopod; latter with lateral margin excavate,
ramus appearing flexed, with numerous se-
tae on distomesial margin, few spines and
setae on lateral margin; exopod slender, lan-
ceolate, with 4 short spines and few setae
along lateral margin, several setae along me-
sial margin, apex having 2 short spines.
Etymology. - The specific epithet, from
the Latin expansus, expanded or spread out,
refers to the expanded character of the epi-
meron of pleonite 3.
Acknowledgments
We thank Jim Elliott, Susan Elliott, and
Patricia Harper of Ogden Environmental
and Energy Services of San Diego, Califor-
nia, for collecting the material and making
it available for study. The material was col-
lected under a subcontract to Black and
Veatch International. Funding was provid-
ed by The African Development Bank
through a contract let and administered by
the Seychelles Public Utilities Corporation.
We thank Mrs. Susann Braden for assis-
tance with production of the SEM photo-
graphs. We are grateful to Dr. Richard Brus-
ca, The University of Charleston, South
Carolina, and to two anonymous reviewers
for their valuable comments on this paper.
Bruce, N. L. 1986. Cirolanidae (Crustacea: Isopoda)
of Australia.-Records of the Australian Mu-
seum, supplement 6: 1-240.
1993. Two new genera of marine isopod crus-
taceans (Ciro lanidae) from Madang, Papua New
Guinea.-Memoirs of the Queensland Museum
31(1): 1-15.
---, & W. Javed. 1987. A new genus and two new
species of cirolanid isopod Crustacea from the
northern Indian Ocean.-Journal of Natural
History 21:1451-1460.
---, & D. A. Jones. 1978. The systematics of some
Red Sea Isopoda (Family Cirolanidae) with de-
scriptions of two new species.-Journal of Zo-
ology, London 185:395-413.
Javed, W., & R. Yasmeen. 1990. A new species of
cirolanid isopod of the genus Neocirolana from
Pakistan with a review of the genus.-Crusta-
ceana 58(1):67-73.
Miers, E. J. 1884. Crustacea. Isopoda. Pp. 299-31 I,
Report of the zoological collections made in the
Indo-Pacific Ocean during the voyage ofH.M.S.
"Alert," 1881-1882. TrusteesoftheBritish Mu-
seum (Natural History), London.
Department ofInvertebrate Zoology, Na-
tional Museum of Natural History, Smith-
sonian Institution, Washington, D.C. 20560,
U.S.A.