THE NAUTILUS 122(4):252-25.S. 20()S
Patie 252
A new species o^ Chkimi/cJoconcha Dall, 1884, from southeastern
Brazil (Bivalvia: Chlamydoconchidae^
Luiz Ricardo I^. Siinone
MiLscLi dc Z()ologi;i da Unnc-rsidade de Sao Paulo
CaL\a Post;J 42494
04299-970 Sao Paulo, BRAZIL
[email protected]
ABSTRACT
The second species in die genus Chlaimjdoconcha is
described. Clilainijdocoiiclia avalvis new species, occurs oii
the coast of Rio de Janeiro coast, in southeastern Brazil. The
new species has very reduced valves and a mantle surrounding
the entire body, two features of the genus. The outer surface of
the mantle lacks papillae e.xcept for a single one located close
to the excurrent siphon. These are distinctive characters of
ChUimi/doconcha orcutti Dall, 1884, from the eastern Pacific
coast ot North America, the single other knowm species of the
genus. Some of the more interesting anatomical characters of
the new species are: posterior pair of retractor nuiscles of foot
free from valves, absence of adductoi' muscles, gastric st\le sac
totally separated from intestine, and the presence of a single
(excurrent) siphon.
AdditioiKil kri/ivords: Anatomv, western Atlantic, Rio de
laneirf)
INTRODUCTION
The geniLS Clilamxdoconcha Dall, 1884 (tspe species by
original designation: C. orcutti Dall, 1884) has l:)een
known to be monotypic. Chlamijdoconcha orcutti occurs
from California to western Mexico (Carlton, 1979;
VIorton, 1981). The species is characterized by reduction
ol the shell, which is restricted to the anterior region of a
spherical mantle cover; the mantle outer surface has
many, somewhat equidistantly distributed papillae. After
the original description, furthei' anatomical studies of
C. orcutti were done by Bernard (1897) and Morton
(1981).
A sample collected by Ijiologist \'inii'ins Padula on the
coast of Rio de Janeiro was sent to the autlior for study.
The analysis ol the material revealed a new species of
Cidaintjcloconcha, formally described herein. This paper
is also the first discoveiy of the genus in (lie Atlantic
Ocean, representing the second known species in the
genus. The present description also includes a detailed
anatomy, which is discussed in comparison lo C orcutti
(Bernard, 1897; Morion, 1981).
The tiLXonomie allocation ol the genus Chhtuufdo-
concha has been pj-obleniatic. It has been included in
the Galeommatidae (Morton, 1981), but full family
status has been assigned (Chlamydoconchidae, Bernard,
1983), as part of the Galeommatoidea. Full superfamily
status was also considered (Chlamydoconchacea, Keen,
1969). The Galeommatoidea, are mostly moUusks with
usual bivalve shells, but may also include highly modi-
fied, slug-like animals, y\'ith iutei'nal and reduced shells.
MATERIALS AND METHODS
The specimen was delivered presened in 70% EtOH.
A photo of the li\ing specimen was taken before pi'e-
seivation. The dissection of the presened animal was
performed by standard teclniiques, under a stereo
microscope, with the specimen immersed in the alcohol.
All dissection steps were also photographed (e.g..
Figures 3-5). Drawings were made with aid of a camera
Incida.
Abbreviations used in ligiu'es are: an, anus; au, auri-
cle; by, byssal gland; cc, gill ciliaiy connection; ce, cere-
bral ganglion; co, cerebro-\isceral connecti\'e; tld, ducts
to digestive diverticulae; dh, dorsal hood; di, inner
demibranch; do, outer demibranch; es, esophagus; fg,
gill food groove; fni, posterior loot retractor muscle; fr,
anterior foot retractor muscle; ft, foot; ga, genital aper-
ture; gi, gill; go, gonad; gs. gastric shield; in, intestine;
ip, inner hemipalp; ki, kidne\; nib, m;mtle bojilcr; mo,
mouth; mt, niantic; ne. iiephiopore; op, outer hemi-
palp; pa, pedal apeitmc of nuintk'; pc, pericardium
pg, pedal ganglia; pi, p:illial papilla; pni. pallial muscles
pp, palp; rt, rectum; sh, shell; si, excurrent siphon
ss, st\li' sac; st, stomach; ty, t\phlosolis; ve, \'entricle
vg, visceral ganglia; vm, viscenil nuiss.
Institutional abbreviation: MZSP; Musen de Zoologia
da Universidade de Sao Paulo, Brazil
SYSTEMATICS
C.ldauuidocoiuhii avalvis new species
(Figures l-2()j
BioStor
