Gebiacantha richeri, Ngoc-Ho, 1989

Ngoc-Ho, Nguyen, 2014, Six species of Axiidea and Gebiidea from the Indo-West Pacific (Crustacea, Decapoda), Zoosystema 36 (3), pp. 545-561 : 558-560

Gebiacantha richeri Ngoc-Ho, 1989 ( Fig. 6 )

Gebiacantha richeri Ngoc-Ho, 1989: 137, fig. 8.

MATERIAL EXAMINED. — Vietnam. Can-gio, HochiMinh ville, Nguyen thi Du coll., 1996: 1 ovig. ♀, cl 13.5 mm, tl 30.5 mm, both pereopod 1, both pereopods 5, left pereopod 3 present ; 1 ♂, cl 5.5 mm, tl 12.5 mm, left pereopod 2, left pereopod 3 present, both specimens in poor conditions with thin carapace ( MNHN Th 1619) .

OTHER MATERIAL EXAMINED. — New Caledonia. Lagon

Est, Richer – ORSTOM col. 12.VIII.1986, holotype:

♂, tl 28 mm ( MNHN Th 957). DISTRIBUTION. — New Caledonia, Vietnam.

DESCRIPTION

Rostrum ( Fig. 6A ) slightly longer than broad at base in female specimen, longer in the male, bearing three large infra-rostral spines (two in the male) strongly projecting forward; lateral border with eight spiniform teeth, fine and faint median longitudinal groove bordered with small rounded tubercles.Lateral groove of carapace moderately broad bordered with tubercles; lateral ridge with six to eight small teeth. Antero-lateral border of carapace ( Fig. 6B ) with five spinules; antero-lateral region of carapace (between antero-lateral border and cervical groove) with three or four spinules. Cervical groove deep with five or six spinules on either side. Telson ( Fig. 6C ) about 1.3 times as broad as long, with faint inverted U-shaped carina dorsally, lateral border convex in proximal third, posterolateral angle rounded, posterior border concave medially.

Antennule with large lower spine on first peduncular article.

Antenna ( Fig. 6B ) second article with small upper spine; third article with lower subdistal spine; fourth article with three large lower spines, antennal scale small terminating in two spinules.

Pereopod 1 ( Fig. 6D, E ) subcheliform. Ischium with lower spine. Merus about three times as long as broad, with upper subdistal spine and 11 lower spines.Carpus with lower distal spine; lateral surface with light longitudinal crest on lower third bearing small tubercles, dorsal surface with several spinules covered with dense setae; mesial surface ( Fig. 6E ) with upper row of six large spines increasing in size distally and a median distal spine. Propodus slightly twisted, as in G. lagonensis Ngoc-Ho, 1989 (Ngoc- Ho 1989: fig. 7), with main part of mesial surface turned upwards, densely setose and bearing several spinules, 12 large upper spines, oblique row of six spines on lower third, larger distally, fixed finger with one or two denticles. Dactylus with corneous tip.

Uropods ( Fig. 6C ) exopod about 1.5 times as long as telson, posterior border rounded; endopod approximately elongated triangular; protopod with spinule and tubercle

REMARKS

The genus Gebiacantha was established by Ngoc-Ho in 1989 and redefined in 2001. Sakai (2006: 13; 2011b: 1130) synonymised it with Upogebia Leach, 1814 , arguing that it was created based on the presence of infrarostral spines “that are not considered so significant a character to distinguish one genus from another”( Sakai 2011b: 1130).

Gebiacantha was actually established not upon one character but a set of characters including those of mouth appendages; only specimens possessing all of these were assigned to the genus. The question is discussed in Ngoc-Ho(2008:158)and Poore (2008:422).

The present specimen from Vietnam agrees with the type in the morphology of the infrarostral spines that are strongly projecting forward, and also in the morphology and spinulation of the appendages. The first pereopod especially has the mesial surface of the propodus slightly twisted with dense setae and several spinules.

There are difference in the length of the rostrum which is shorter in the female specimen from Vietnam ( Fig. 6A ) than in the type (Ngoc-Ho 1989: fig.8A), a male from New Caledonia.It can be noted that the male specimen from Vietnam examined is smaller with a difference in tl of 12.5 mm, but has a longer rostrum than in the female, similar to that of the type.

The telson bears a faint inverted U-shaped carina, as in the type but the transverse branch is simple (double in the type).

Figures

FIG. 6. — Gebiacantha richeri Ngoc-Ho, 1989, ♀, tl 30.5 mm (MNHN Th 1619): A, B, anterior part of carapace in dorsal and lateral views; C, telson and uropod; D, pereopod 1; E, distal part of pereopod 1 in mesial view. Scale bars: 1 mm.