Macrobrachium australe (Guérin-Méneville, 1838 (Guerin-Meneville, 1838)

Castelin, Magalie, Mazancourt, Valentin de, Marquet, Gérard, Zimmerman, Gabrielle & Keith, Philippe, 2017, Genetic and morphological evidence for cryptic species in Macrobrachium australe and resurrection of M. ustulatum (Crustacea, Palaemonidae), European Journal of Taxonomy 289, pp. 1-27 : 9-14

Macrobrachium australe (Guérin-Méneville, 1838 in Guérin-Méneville 1829 –1838) Fig. 3 , Table 2

Palaemon australis Guérin-Méneville, 1838 in Guérin-Méneville 1829–1838: 37 (“Île de Taïti” = Tahiti). Palaemon danae Heller, 1865: 120 , pl. 11, fig. 4 (”Sydney”; synonymy considered erroneous by Short 2004).

Palaemon dispar von Martens, 1868: 41 (“ Insel Adenare, unweit Flores” = Adenare Island, near Flores). Palaemon alphonsianus Hoffmann, 1874: 33 , pl. 9, figs 63–65 (“l’île de la Réunion ” = Reunion Island). Palaemon parvus Hoffmann, 1874: 35 , pl. 7, fig. 59 (“l’île de Nossy-Faly” = Nosy Faly Island).

Palaemon malliardi Richters, 1880: 166 , pl. 18, figs 1–3 (“Creole River, Black River, Mauritius Is.”).

Leander lepidus de Man, 1915: 410 , pl. 28, figs 6–6d (”Mündung des kleinen Flusses zu Oinaké, einem Dorfe an der Küste östlich von der Humboldt-Bai” = mouth of a small river at Oinaké, a coastal village east of Humboldt Bay (Yos Sudarso Bay), Papua).

Material examined

Neotype

COOK ISLANDS: 1 ♂, Rarotonga Island , Avana River, 21.2461° S, 159.7316° W, 11 Jul. 2010, 15.3 mm CL (MNHN-IU-2013-13198).

Other material

COOK ISLANDS: 1 ♂, same collection data, 12 mm CL (MNHN-IU-2013-13196); 1 ♂, 14.5 mm CL (MNHN-IU-2013-13197).

COMOROS: 1 ♂, Anjouan Island, Jomani River, 12.246° S, 44.529° E, 2 Nov. 2005, 16.2 mm CL (MNHN-IU-2013-13199).

VANUATU: 1 ♂, Pentecost Island, Warbot River, 15.957° S, 168.195° E, 26 Jan. 2010, 14.3 mm CL (MNHN-IU-2013-13200).

Description

ROSTRUM. Moderately long, reaching to or slightly beyond end of scaphocerite ( Fig. 3A ); tip slightly upcurved; dorsal margin with 10–11 teeth, including 2–3 teeth on carapace; ventral margin with 3–4 teeth; teeth large, evenly spaced; sometimes distance between ultimate and penultimate teeth much larger than distances between other teeth; sometimes distance between 1 st and 2 nd teeth larger than between 2 nd and 3 rd teeth.

GENERAL CEPHALON. Eyes well developed; cornea as long as, but broader than peduncle; stylocerite distinctly pointed, reaching beyond basal segment; inferior orbit bluntly angular ( Fig. 3A ); postantennular carapace margin straight or slightly concave; protective setation absent on carapace; epistome lobes narrowly separated, not strongly diverging anteriorly ( Fig. 3B ); TS4 unarmed ( Fig. 3C ).

SECOND CHELIPEDS (fully developed ♂). Very unequal sizes, non-isomorphic. Major P2 ( Fig. 3D ) long, subcylindrical, merus extending beyond scaphocerite; carpus 0.78–0.97 CHL, 1.18–1.40 PL. Fingers slender, 0.32–0.55 PL; dactylus shorter than FF. Cutting edges ( Fig. 3E ) with 4–5 conical teeth at base (3 rd largest) followed by 9–14 evenly spaced, small, blunt teeth along entire length; teeth diminishing in size distally; FF elongated, curved inwards; teeth arrangement similar to that of dactylus; basal part armed with 5–6 conical teeth (3 rd largest) followed by 9–16 evenly spaced, small, blunt teeth along entire length; teeth diminishing in size distally. Largest tooth of FF lies after largest tooth of dactylus. Cheliped with numerous large spiniform setae on inner edge, smaller and denser on outer edge. Some scattered long setae present on cheliped, but very distinct on fingers. Merus 0.51–0.60 CAL, ischium 0.48–0.76 MEL. Minor P2 ( Fig. 3F ) with entire carpus beyond scaphocerite. Carpus 0.79–1.04 CHL, 1.19–1.60 PL. Fingers slender, 0.46–0.53 PL. Palm and bases of fingers densely packed with velvety setae. CED ( Fig. 3G ) with 6–13 teeth along entire length diminishing in size. CEFF with 9–15 teeth, similar teeth arrangement to that of dactylus, but teeth smaller. Pereiopods with numerous spiniform setae, denser on lower edge. MEL 0.60–0.81 CAL, IL 0.76–0.81 MEL.

ABDOMEN. Smooth, inter-uropodal sclerite with preanal carina.

Remarks

Since the type specimen of P. australis is lost, and because of the taxonomic problems discussed above, a specimen from the Avana River on Rarotonga Island ( Cook Islands, Central Pacific), which is geographically close to the type locality of P. australis (Tahiti) , is herein designated as the neotype of M. australe in order to stabilize the taxonomy of the species. One specimen in our sample was collected from Moorea, which is closer to Tahiti. However, the specimen was in a less good condition than specimens from Rarotonga; thus, diagnostic morphological characters defined in this study were less obvious. Specimens from Rarotonga and from Moorea, however, showed no genetic variation in both the 28S and the 16S genes.

Distribution

From the Indian Ocean ( Madagascar, Comoros and Mascarenes Islands) to the Central Pacific Ocean ( French Polynesia and Cook Islands). Syntopic with M. ustulatum in the Northwest Pacific Ocean ( Taiwan, Philippines, Indonesia, Papua New Guinea and Palau) and the Southwest Pacific Ocean ( Vanuatu) ( Fig. 1 ).

Habitat

Lentic habitats in the lower courses of rivers and at the edge of rivers, in water plant communities ( Keith et al. 2013).

Color patterns

Body colors ( Fig. 4A ) tend to match the substrate, varying from grey to brown, rather translucent, with three reddish stripes on each side of the cephalothorax.

Figures

Fig. 3. Macrobrachium australe (Guérin-Méneville, 1838 in Guérin-Méneville 1829–1838), MNHN- IU-2013-13198. A. Cephalothorax. B. Epistome. C. Fourth thoracic sternite. D. Major second pereiopod. E. Major second pereiopod finger. F. Minor second pereiopod. G. Minor second pereiopod finger. Scale bars: A, E, G = 2 mm; B–C = 1 mm; D, F = 4 mm.

Fig. 1. Map of the Indo-Pacific showing localities where Macrobrachium australe (Guérin-Méneville, 1838 in Guérin-Méneville 1829–1838) (black area) and M. ustulatum (Nobili, 1899) (red area) were collected and/or recorded. Capitalized locality names correspond to the 7 localities sampled for this study. Non-capitalized locality names correspond to the localities reported from the literature. Stars shows the type localities of the synonyms of M. australe (black stars) and M. ustulatum (red star).

Fig. 4. A. Live coloration of Macrobrachium australe (Guérin-Méneville, 1838 in Guérin-Méneville 1829–1838) (photo: E. Vigneux). B. Live coloration of M. ustulatum (Nobili, 1899) (photo: P. Keith).