Integrative taxonomy study of brackish water crabs of the genus Ptychognathus Stimpson, 1858 (Crustacea: Brachyura: Varunidae) from Polynesia, with description of two new species
Author
Mazancourt, Valentin De
Muséum national d’Histoire naturelle, UMR BOREA, CP 026, 57, rue Cuvier, F- 75231 Paris, Cedex 05, France.
Author
Mazel, Virgile
Ichtyo-Pacific, Virgile Mazel BP 381816 Punavai, 98718 Punaauia, Tahiti, Polynésie française.
Author
Marquet, Gérard
96 rue de Richelieu, 75002, Paris.
Author
Poupin, Joseph
Ecole Navale, CC 600, Lanvéoc, F- 29240 Brest, France.
Author
Keith, Philippe
0000-0002-1600-4909
Muséum national d’Histoire naturelle, UMR BOREA, CP 026, 57, rue Cuvier, F- 75231 Paris, Cedex 05, France.
keith@mnhn.fr
text
Zootaxa
2024
2024-07-04
5476
1
267
297
http://dx.doi.org/10.11646/zootaxa.5476.1.23
journal article
299703
10.11646/zootaxa.5476.1.23
f19cec98-eb1f-4305-8027-69ce085404c9
1175-5326
12681748
4250D709-E06C-4CFF-84D6-7A9E62427FE2
Ptychognathus barbatus
(A.
Milne-Edwards, 1873
)
(
Fig. 11A–H
,
12A–B
)
Gnathograpsus barbatus
A.
Milne-Edwards, 1873: 316
, pl. 17: 4.
Ptychognathus barbatus
.—
De Man, 1895: 105
.—
Fransen
et al.
, 1997: 127
.
Type material
. (All
New Caledonia
)
Syntypes
: MNHN-IU-2000-10877 (=
MNHN-B10877
),
3 ♂
(dry material, mounted on board) 9.0–
9.8 mm
× 11.0–
12.7 mm
, coll.
B. Balansa
;
MNHN-IU-2000-3395 (=
MNHN-B3395
),
1 ♂
(dry material), coll.
B. Balansa
;
MNHN-IU-2000-3401 (=
MNHN-B3401
),
2 ♂
(dry material), coll.
B. Balansa
;
MNHN-IU-2000-3394 (=
MNHN-B3394
),
2 ♂
(dry material),
♂
10.0 mm × 12.0 mm,
♂
9.6 ×
11.6 mm
, coll.
B. Balansa
;
MNHN-IU-2008-10675 (=
MNHN-B12605
),
1 ♂
(in ethanol, regenerated dry material), coll.
B. Balansa
;
RMNH-D192
,
1 ♂
(
12.3 mm
× 10.0 mm), coll.
B. Balansa
; USNM-20308:
3 ♂
(
9.5–11.9 mm
× 8.0–
9.8 mm
),
2 ♀
(
9.4–9.6 mm
×
7.8 mm
), coll. B. Balansa.
Other material examined
.
NEW CALEDONIA
.
MNHN-IU-2019-210 (DNA voucher:
CA2467
),
1 ♂
,
9.6 mm
× 8.0 mm,
Wadjana
waterfall,
22°17.603'S
,
167°0.859'E
, coll.
G. Marquet
&
V
.
de Mazancourt
,
13 September 2018
; MNHN-IU-2022-4124,
1 ♂
,
8.8 mm
×
7.7 mm
,
Wadjana
waterfall,
22°17.603'S
,
167°0.859'E
, coll.
G. Marquet
&
V
.
de Mazancourt
,
13 September 2018
;MNHN-IU-2017-8250,
3 ♂
,
9.4 mm
× 8.0 mm to
9.8 mm
×
9.1 mm
,
2 ♀
,
8.7 mm
×
7.7 mm
, 9.0 mm ×
7.9 mm
, coll.
B. Balansa.
Diagnosis.
Carapace subquadrate, dorsal surface smooth, flat; front broad, anterior margin slightly concave medially; anterolateral margin with 3 teeth including orbital tooth. Merus of third maxilliped with anteroexternal angle broad; exopod, 0.7–1.2 times broader than ischium. Chelipeds large, symmetrical in males, fingers with small tuft of setae at tips of pollex. Single pulvinus at base of fingers. Merus and carpus of ambulatory legs glabrous.
Description.
Carapace (
Fig. 11A
) subquadrate, slightly broader than long, 1.2 times as broad as long, flat, dorsal surface smooth and glabrous. Regions poorly defined, central H-shaped grooves distinct; epigastric cristae barely visible. Front broad, anterior margin, divided into 2 lobes, slightly concave medially. Frontal width 0.47–0.51 times CW, fronto-orbital width 0.84–0.90 times CW. Anterolateral margins and supraorbital margins lined with small granules. Upper margin of orbit weakly sinuous. Anterolateral margins each with 3 teeth including orbital tooth; first tooth largest and more distinct, second and third blunt, third tooth indistinct or notch. Posterolateral margins divergent posteriorly, moderately sloping outwards. Lateral and posterolateral margins regularly furnished with short, soft setae.
Third maxillipeds (
Fig. 11B
) with ischium subequal in proximal and distal widths, lateral margin concave, ventral surface with longitudinal median ridge. Merus with anterolateral angle broad; ventral surface with oblique ridge on mesial part. Exopod broad, inflated, greatest width 0.9–1.2 (
♂
), 0.7–1.0 (
♀
) times of median width of ischium.
Male chelipeds (
Fig. 11C
) symmetrical, not granular at all. Merus longer than broad (length to width ratio 1.1– 2.2); anterior and posterior margins glabrous, posterior distal margins bluntly carinate. Carpus, unarmed, strongly inflated, slightly shorter than wide (length to width ration 0.8–1.0). Palm inflated, smooth, without distinct granules; inner surface glabrous. Fingers with tuft of long setae on outer surface restricted at base of fingers. Dactylus shorter than palm, 0.7–1.0 times as long as palm, terminating in small, hoof-shaped corneous claw bearing 9 or 10 small blunt teeth. Pollex with 4 or 5 larger blunt teeth. Proximal half of fingers with long dense soft setae; single pulvinus at base of fingers.
Female chelipeds (
Fig. 11D
) distinctly smaller than those of male, chela much narrower than that of male. Fingers with smaller and fewer enlarged teeth. Proximal half of fingers without long dense soft setae; without pulvinus at base of fingers; pollex with ridge consisting of large granules toward palm and ending with distal tuft of setae.
Ambulatory legs (P2–5) comparatively long, slender, somewhat compressed laterally; P4 longest (male: length 1.3–1.4 times carapace width) P5 shortest. Merus elongated, subrectangular in lateral view, unarmed; anterior margins and posterior margins of merus of P2–5 glabrous. Anterior margin of carpus with few short setae, posterior margin glabrous. Propodus with dense short setae on anterior margins and dense short setae and long setae on posterior margins. Ventral surface with rows of short setae. Dactylus terminating in subacute corneous claw, with dense short setae on anterior and posterior margins; dorsal and ventral surface with rows of short setae. P3 merus (
Fig. 11E
) length to width ratio 1.9–3.3, carpus length to width ratio 1.8–2.1, propodus length to width ratio 1.3–2.0, dactylus length to width ratio 4.1–4.5, dactylus 0.7–1.3 times as long as propodus. P5 merus (
Fig. 11F
) length to width ratio 2.2–3.3, carpus length to width ratio 1.6–2.6, propodus length to width ratio 1.1–1.9, dactylus length to width ratio 2.6–3.9, dactylus 0.7–0.9 times as long as propodus.
Male pleon (
Fig. 11G
) narrow, broadly triangular, nearly smooth, distinctly narrowed at base of telson; lateral margins of first to fifth somites nearly straight; margins covered with short setae, distal margin of telson with tuft of setae. Telson linguiform, terminal margin broadly rounded; length 1.1 times basal width, 1.0–1.4 times longer than sixth somite, sixth somite 1.1–1.7 times longer than fifth somite.
Female pleon (
Fig. 11H
) very broad, covering most of thoracic sternum, fourth somite broadest. Telson broadly subtriangular, terminal margin broadly rounded, length 0.43–0.51 of basal width, 1.1 times longer than sixth somite, sixth somite 1.0–1.1 times longer than fifth somite, measured on midline.
Male G1 (
Fig. 11I
) slender, 6 times as long as wide, slightly curving dorsally; tip bluntly rounded, forming short chitinous structure; subdistal lobe obtuse, partially obscured by stiff setae.
Colouration in life.
Body, chelipeds and legs orange (
Fig. 12A and B
).
Size.
Small-sized. The largest male specimen examined is
9.6 mm
× 8.0 mm and the largest female 9.0 mm ×
7.9 mm
.
Habitat.
Ptychognathus barbatus
lives on seashores influenced by freshwater flows. Indeed, it was found under rocks on a beach next to the estuary of the Wadjana waterfall in the
South Province
of
New Caledonia
(
Fig. 12D
).
FIGURE 11.
Ptychognathus barbatus
(A.
Milne-Edwards, 1873
)
: A, carapace; B, left third maxilliped; C, male cheliped; D, female cheliped; E, third pereiopod; F, fifth pereiopod; G, male pleon; H, female pleon; I, right male first gonopod. MNHN-IU-2019-210 (A–C, E–G, I) male from New Caledonia; MNHN-IU-2017-8250 (D, H) female from New Caledonia.
FIGURE 12.
Ptychognathus barbatus
(A.
Milne-Edwards, 1868
)
: A, dorsal view of a living specimen from New Caledonia (MNHN-IU-2019-210); B, ventral view of the same; D, typical habitat of the species, Wadjana mouth of waterfall, New Caledonia.
Ptychognathus ngankeeae
sp. nov.
: C, dorsal view of a living specimen from Futuna Island. Photo credits: V. de Mazancourt (A, B, D) and J. Poupin (C).
Distribution.
Apparently endemic to
New Caledonia
(
Fig. 6
).
Remarks.
Ptychognathus barbatus
is not known from Polynesia but is re-described herein for comparison purposes. It was reported from Banda
Aceh
(
Indonesia
) and
Penang
Island (
Malaysia
) by
De Man (1895: 105–111
, fig. 23), from
Japan
by
Sakai (1939: 638–639
, text-fig. 348) and from
Madagascar
by
Crosnier (1965: 36–38
, figs. 42–45) but this species seems to be in fact restricted to
New Caledonia
. It can be distinguished from the other species previously reported under this name by features of the frontal region, setae on ambulatory legs and telson of male (see next species).