A new species of Afropinnotheres Manning, 1993 (Crustacea, Brachyura, Pinnotheridae) from southwestern India, the first record of the genus from the Indian Ocean, with a review of the Pinnotheridae of India and adjacent seas
Author
Ng, Peter K. L.
Author
Kumar, Appukuttannair Biju
text
Zootaxa
2015
3947
2
264
274
journal article
10.11646/zootaxa.3947.2.8
6dd42c11-3a42-4438-99d7-8059fbd68516
1175-5326
239085
B7F32AB1-3F28-467C-916F-A72EE3307D02
Genus
Afropinnotheres
Manning, 1993
Afropinnotheres
Manning, 1993
: 130
.
Remarks
.
Manning (1993)
substantially changed the generic system for the species placed in
Pinnotheres
Bosc, 1802
, differentiating genera mainly on the basis of the structure of the MXP3 (notably the structure of the dactylus and its point of articulation with the propodus) and the proportions of their P2–P5 (notably the dactylus). Using these and characters of the carapace in some instances, over a dozen genera are now recognised (see Ng
et al.
2008).
In reviewing the generic status of many of the Atlantic species,
Manning (1993)
established a new genus,
Afropinnotheres
, for species that share the following characters: a rounded to subovate carapace, the propodus of the P2–P5 are laterally flattened and appear expanded; the P2–P5 dactyli are subequal; propodus of the MXP3 is distinctly coniform and is shorter than the carpus; dactylus of the third MXP3 is elongated, extending beyond the tip of the propodus and articulates near the base of the propodus; all the male abdominal somites are free; and the male first gonopod is simple and slender.
Afropinnotheres
is similar to
Pinnotheres
Bosc, 1802
s. str., and
Nepinnotheres
Manning, 1993
, but in these genera, the propodus of the MXP3 is distinctly more elongated (much longer than the carpus), with the dactylus either long, reaching to or over-reaching the tip of the propodus and inserted at or near the middle or the proximal third of the propodus (
Nepinnotheres
), or the MXP3 is shorter, not reaching the tip of the propodus and inserted near the base of the propodus (
Pinnotheres
s. str.
). Another character shared by all
Afropinnotheres
species is the proportionately slender male abdomen. The known male abdomens of
Pinnotheres
and
Nepinnotheres
are proportionately broader, with the first few somites much wider, giving the structure a more triangular appearance (see
Ahyong & Ng 2007
).
Four species of
Afropinnotheres
have been described, all from western Africa:
A. crosnieri
Manning, 1993
(
Congo
;
type
species);
A. guinotae
Manning, 1993
(
Angola
)
;
A. larissae
(Machkevskiy, 1992)
(
Senegal
,
Guinea
,
Ivory Coast
); and
A. monodi
Manning, 1993
(
Morocco
,
Mauritania
).
Ng & Manning (2003)
subsequently transferred a number of species of holothurian-dwelling
Pinnotheres
to a new genus,
Holotheres
, members of which share carapace and ambulatory leg characteristics with
Afropinnotheres
. In addition to their host preference (all
Afropinnotheres
are from bivalves), however,
Holotheres
can be separated by the elongated propodus of the MXP3 (much longer than the carpus) and a more distinctly spatulate dactylus which is as long as or longer than the propodus; the male abdomen is more triangular in shape and the G1 is gently sinuous (cf.
Ng & Manning 2003
: fig. 1B, H, I).
Afropinnotheres
also closely resembles species of
Pinnaxodes
Heller, 1865
, with regard to the carapace shape and symmetrical P2–P5. The MXP3 of
Pinnaxodes
is superficially similar to that of
Afropinnotheres
except that the propodus is elongated and much longer than the carpus (rather than short and conical in
Afropinnotheres
) and the more spatuliform dactylus is inserted on the proximal one-third or middle of the propodus (cf.
Garth 1958
: figs. 10D, 11B;
Wells & Wells 1961
: fig. 2F, G;
Campos
et al.
1998
: fig. 2B, D; Takeda & Prince Masahito 2000: figs. 2C, E, G, 4C;
Ng & Manning 1993
: figs. 6B, F, 7A, B; De Melo & Boehs 2014: fig. 4). The male abdomen of
Pinnaxodes
species is also relatively wider and more triangular in shape and the telson may be expanded such that it is wider than somite 6 (cf.
Garth 1958
: fig. 11A;
Wells & Wells 1961
: fig. 1F;
Campos
et al.
1998
: fig. 3A, C; Takeda & Prince Masahito 2000: figs. 4B, 5L; De Melo & Boehs 2014: fig. 6).
There has been some discussion about the taxonomy of
Pinnaxodes
Heller, 1865
, and
Holothuriophilus
Nauck, 1880
. Although Takeda & Prince Masahito’s (2000) suggestions on these genera were provisional, De
Melo & Boehs (2004)
followed their arguments for transferring the Japanese
Pinnaxodes mutuensis
Sakai, 1939
, to
Holothuriophilus
and placed the South American
P. tomentosus
Ortmann, 1894
, there as well.
Ng & Manning (2003)
showed that
Pinnaxodes
and
Holothuriophilus
are easily separated by the carapace shape (ovate in
Pinnaxodes
, transversely subrectangular in
Holothuriophilus
) and form of the MXP3 (i.e. presence of a faint suture separating the ischium and merus in
Pinnaxodes
; completely fused ischium and merus in
Holothuriophilus
) (see also
Ahyong & Ng 2007
;
Campos
et al.
2012
); and retained
P. mutuensis
in
Pinnaxodes
. Six species are now recognised in
Pinnaxodes
:
P. chilensis
(H. Milne Edwards, 1837)
(=
Pinnaxodes hirtipes
Heller, 1865
) [
Chile
to Per];
P. f l o r i d e ns i s
Wells & Wells, 1961
[Florida,
USA
];
P. gigas
Green, 1992
[Sonora,
Mexico
];
P. m a j o r
Ortmann, 1894 [
Japan
and northeastern
Russia
];
P. m ut uensis
Sakai, 1939 [
Japan
and northeastern
Russia
];
P. tomentosus
Ortmann, 1894
[
Brazil
] (Ng
et al.
2008).
The matter of fusion between the MXP3 ischium and merus requires discussion. Of the many genera associated with
Pinnotheres
s. lato in the past, only
Pinnaxodes
Heller, 1865
, has these two structures separated by a suture, faint or otherwise (see
Manning 1993
: 128). Takeda & Prince Masahito (2000) noted that while it is present, they regard it as a less important character since it is not always apparent and can be hard to see.
Ng & Manning (2003)
noted that it was always present but may be shallow, with the suture more pronounced on the inner surface of the MXP3 and best observed under transmitted light. All known species of
Pinnaxodes
possess this suture. The present new species from
India
,
Afropinnotheres ratnakara
n. sp.
, also has a trace of this suture. There is a faint suture visible under transmitted light between the merus and ischium in the larger female specimens (
Fig. 2
D), but it is not distinct even on the inner surface of the structure unlike
Pinnaxodes
. This suture is even less distinct in the smaller males (
Fig. 3
B) and may be absent.
Manning (1993)
did not report any trace of a suture for the four African species of
Afropinnotheres
he studied, but he may have overlooked this feature; the MXP3 of the African
Afropinnotheres
require restudy.
The discovery of the present new species from
India
is noteworthy because all other
Afropinnotheres
species have previously been reported from the eastern Atlantic (
Manning 1993
). The characters of
Afropinnotheres ratnakara
n. sp.
, however, are distinct for the genus. As discussed earlier, there are affiliations with
Pinnaxodes
as well, but this genus is also not known from the Indian Ocean. While it is possible that the presence of the new species in
India
is a consequence of introduction from the Atlantic, the fact remains that it may be the same species as specimens of
Pinnotheres
sp. reported by
Doflein (1904)
and
Tirmizi & Ghani (1996)
from
South Africa
and
Pakistan
, respectively (see species discussion), many years earlier. Another possibility of course is that the host
Perna perna
may have been introduced from Africa to
India
decades or even centuries ago with the crab. This mussel has a rather disjunct distribution, occurring in East and
South Africa
as well as southwestern
India
; and the
Perna
in
India
may have come from
South Africa
, especially since Doflein’s (1904)
Pinnotheres
sp. is probably conspecific with
Afropinnotheres ratnakara
n. sp.
In any case, the current evidence suggests that
Afropinnotheres
is naturally present in the western Indian Ocean.