Alain raymondi, a new species of deepwater pinnotherid crab (Crustacea: Decapoda: Brachyura) from the Philippines, commensal with holothurians
Author
Ahyong, Shane T.
Author
Ng, Peter K. L.
text
Zootaxa
2008
1919
61
68
journal article
10.5281/zenodo.184681
dab15da6-86f0-4c1c-b925-2bbca111f049
1175-5326
184681
Alain
Manning, 1998
Alain
Manning, 1998
: 358
[
type
species:
Alain crosnieri
Manning, 1998
, by original designation].
Diagnosis.
Carapace with long, sparsely distributed simple dorsal setae and short, plumose setae lining margins. Pereopods covered with plumose setae. Carapace firm, subglobular, dorsal outline subcircular, widest near midlength. Maxilliped 3 palp 3-segmented, dactylus inserting proximal to midlength of lower margin of propodus; ischium and merus fused; exopod 3-segmented. Walking legs symmetrical from left to right; dactyli simple. Dactyli of P2–3 shorter than dactyli of P4–5. Abdomen comprising 7 free somites (including telson) in both sexes. Male abdomen hourglass-shaped, widest at somite 5; telson broader than long.
Composition.
A. crosnieri
Manning, 1998
;
A. raymondi
sp. nov.
Remarks.
Although
Manning (1998)
characterized
Alain crosnieri
as having a 6-segmented abdomen, reexamination of the
type
material in the MNHN confirmed that males possess a 7- rather than 6-segmented abdomen as originally diagnosed. Two factors probably contributed to the confusion over the male abdominal segmentation. First, abdominal somite 1 is usually partially concealed by the posterior margin of the carapace, and was probably overlooked as a result of the setose integument. Second, the bases of the gonopod of somite 2 (G2) and vestigial pleopods of somite 3 are more or less appressed owing to the arching of the abdomen. The G2 and pleopod 3 thus have the appearance of a common source, as would be expected if somites were fused. With corrected interpretation of male abdominal segmentation in
Alain
, Manning’s (1998) major distinguishing generic character is invalidated.
Alain
is in fact most similar to
Nepinnotheres
Manning, 1993
b, and
Viridotheres
Manning, 1996
, sharing a third maxilliped dactylus that is inserted at or slightly proximal to the propodal midlength, and walking legs that are left right symmetrical. Unfortunately, no single character or combination of characters will collectively distinguish both sexes of
Alain
from
Nepinnotheres
and
Viridotheres
.
Males of
Alain
differ from male
Nepinnotheres
and
Viridotheres
by the hourglass-shaped abdomen, which is widest at somite 5, rather than triangular or linguiform with the widest point at somite 3. The P4–5 dactyli in female
Alain
are distinctly longer than those of P
2–3 in
contrast to
Nepinnotheres
and
Viridotheres
in which the P2–3 dactyli are subequal to or longer than those of P4–5.