Malagasya antongilensis ( Rathbun, 1905 ) Cumberlidge & Sternberg, 2002

Cumberlidge, Neil & Sternberg, Richard V., 2002, The freshwater crabs of Madagascar (Crustacea, Decapoda, Potamoidea), Zoosystema 24 (1), pp. 41-79 : 61-63

Malagasya antongilensis ( Rathbun, 1905) n. comb.

( Fig 1E ; 3E ; 4E ; 5E ; 6E ; 7I, J ; 8I ; 10C, D ; 11F )

Potamon (Parathelphusa) antongilensis Rathbun, 1905: 265 , 266, fig. 21, pl. 12, fig. 5. — Cumberlidge 1998: 210.

Hydrothelphusa (Acanthothelphusa) antongilensis – Bouvier 1921: 52.

Potamon (Geothelphusa) antongilensis – Balss 1929: 355, fig. 21.

Thelphusa madagascariensis – Balss 1929: 254 — Balss 1934: 520, pl. 1, fig. 1 [non madagascariensis H. Milne Edwards, 1872 ].

Gecarcinautes antongilensis antongilensis Bott, 1965: 337 , figs 1-3, figs 1-3; 338, pl. 1. — Vuillemin 1972: 135-166. — Ng & Takeda 1994: 163.

Gecarcinautes antongilensis vondrozi – Bott 1965: 338, pl. 1, figs 4, 5. — Cumberlidge et al. 2002: 75.

MATERIAL EXAMINED. — Madagascar. Antongil Bay, coll. M. Mocquerys, 1 holotype of Potamon (Parathelphusa) antongilensis Rathbun, 1905 , cw 22.3, cl 17.5 mm ( MNHN-B 5033). — Forest, Manambato Valley, 1927, coll. G. Petit, 1 subad. cw 19, cl 14.5 mm, 1 ad. cw 34, cl 25 mm ( MNHN-B 5035). — Ambilobé, coll. J. Millot, 1 ad. cw 34, cl 25 mm ( MNHN-B 5036). — Tamatave, coll. J. Millot, several specimens ( MNHN-B 5037). — Tamatave, 1924, coll. J. Millot, more than 10 specimens ( MNHN-B 5041). — Toamasina, Autumn 1922, coll. J. Millot, 2 ad. cw 32, cl 23.5, ch 12.5, fw 7.5 mm and cw 29.5, cl 23, ch 12, fw 7.5 mm, 1 subad. cw 27.5 mm, 1 ad. cw 32 mm, 1 ad. ovig. cw 29.5 mm, 1 subad. cw 22.5, cl 17.2 mm ( MNHN-B 5063). — Tsingalapaky, Fetoky, Fandiarano, Marotsy river, Tsimantsy (another label indicates Forêt de Périnet, Moramanga), 13.XII.1965, 5 specimens ( MNHN-B 25752). — Forêt de Périnet, I.1966, 1 specimen, 3 subad. cw 20.8, 19.8, 16 mm, 2 subad. cw 23.5, 21 mm, 1 juv. cw 14.3 mm ( MNHN-B 25764). — Grotte de la Mananjiba, Nosy-Bé, Ambilobe, 1924, coll. Waterlott, 2 juv. cw 12.8, 11.6 mm ( ZSM 1163/1). — Toamasina, coll. J. Millot, 2 ad.

cw 30.7, 30.4 mm, 2 juv. cw 18.9, 15.8 mm, 3 ad. cw 31.2, ovig., 29.0, ovig., 30.1 mm, 1 subad. cw 23.5 mm ( ZSM 1531/1). — Toamasina, 1 ad. cw 30, cl 22.5, ch 11.5, fw 8 mm ( SMF 2615).

TYPELOCALITY. — Potamon (Parathelphusa) antongilensis: Antongil Bay , Madagascar. Gecarcinautes antongilensis vondrozi: Vondrozo , crab in a hole in an old tree, in the forest.

DISTRIBUTION. — Madagascar ( Fig. 11F ).

DIAGNOSIS. — Pterygostomial region of carapace sidewall with small sparse hairs; suborbital, subhepatic regions of carapace sidewall finely granulated; ischium of third maxilliped with deep vertical sulcus. Third sternal sulcus s3/s4 straight, horizontal, completely crossing sternum; s6/s7 meeting a5/a6 junction; inner margin of propodus of p5 with distinct spines.

REDESCRIPTION

Carapace outline heart-shaped, elongated (cl/fw = 3), high (ch/fw = 1.6), very wide anteriorly (cw/fw = 3.8), tapering sharply, frontal, posterior margins narrow (cw 0.3 mm); entire dorsal carapace finely granulated, sculpted by grooves; branchial groove deep; semi-circular, urogastric, cardiac grooves deep; cervical grooves short; distinct gap between epigastric, postorbital crests; front sharply deflexed, almost vertical. Exorbital, epibranchial teeth equal, large, curved, pointed; anterolateral margin behind epibranchial tooth with five or more large pointed teeth; anterolateral margin curving inward, not continuous with posterolateral margin. Vertical sulcus on carapace sidewall running from base of epibranchial tooth to epimeral sulcus, dividing suborbital region from hepatic region, sidewall divided into three regions; suborbital, subhepatic regions of carapace sidewall finely granulated, pterygostomial region near third maxilliped with short, sparse hairs. Suborbital margin raised, smooth. Mandibular palp two-segmented, terminal segment with enlarged lobe-shaped anterior process (about 0.5 as big as terminal segment) at junction between segments. Third maxilliped exopod medium length, reaching to mid-point of merus, with long flagellum; ischium with deep vertical sulcus. Thoracic sternal sulcus s1/s2 not visible; sternal sulcus s2/s3 deep, horizontal; sternal sulcus s3/s4 horizontal, completely crossing sternum, meeting anterior margin of sternoabdominal cavity on sternite s4. Anterior sternum with conspicuous setae.

Adult male abdomen slim, triangular; a6 short, only as long as width of distal margin of a6; telson sides indented, bell-shaped. Gonopod 1 terminal article short, ratio length terminal article to subterminal segment 0.25, longitudinal groove on terminal article clearly visible on ventral, superior sides, not visible on dorsal side; lateral, medial folds of ventral side of terminal article equal in height, width; terminal article almost straight, directed slightly outward; slim tapering to upcurved tip with clear apical opening; subterminal segment of gonopod 1 with distinct triangular shoulder on external margin near junction with terminal article. Gonopod 1 terminal article/subterminal segment junction marked by deep sulcus; dorsal membrane broad. Gonopod 2 longer than gonopod 1; gonopod 2 terminal article long, flagellum-like, shorter than subterminal segment, ratio length terminal article to subterminal segment 0.62.

Dactylus of right, left chelipeds relatively narrow, straight (one-quarter height of palm); upper margin of dactylus smooth; finger of propodus slim (one-third height of palm) lower margin of propodus of cheliped slightly indent- ed. Fingers of propodus, dactylus with series of small teeth, no interspace when closed. Anterior, posterior inferior margins of ischium of p1 smooth. Inferior margins of merus of p1 toothed, distal margin with single pointed distal meral tooth; superior surface of merus granular. First carpal tooth on inner margin of carpus of p1 large, pointed, second carpal tooth smaller, pointed, followed by several smaller teeth. Anterior, posterior margins of propodus of p5 slightly serrated. Merus, carpus, propodus, dactylus of p2-p5 all conspicuously elongated, walking legs elongated, slender, ratio length merus p5/cw = 0.52.

Size

The adult size range is from cw 27.5-29 to 34 mm. The carapace proportions are given in Table 3.

REMARKS

Bott (1965) recognised one subspecies of M. antongilensis n. comb., which he called Gecarcinautes antongilensis vondrozi . We have examined the types of both taxa and we conclude that G. a. vondrozi should properly be viewed as a junior objective synonym of M. antongilensis , in agreement with the opinion of Cumberlidge et al. (2002).

Potamon (Potamon) pittarrelli Nobili, 1905 from Madagascar was overlooked in the study by Bott (1965) and its current taxonomic status is still uncertain. Ng & Takeda (1994) considered P. (P.) pittarrelli to resemble members of Skelosophusa . The type specimen of P. (P.) pittarrelli that was described and figured by Nobili (1905: 2, fig. 1) is unavailable, despite our best efforts to locate it. Ng & Takeda (1994) did not directly examine P. (P.) pittarrelli but nevertheless referred this taxon to Gecarcinautes based on a quote from Colosi (1920: 25): “Il palpo mandibolare è bilobo...”. However the next part of the same sentence in Colosi (1920: 25) continues “il lobo accesorio è piuttosto piccolo” which implies that the anterior lobe/process is distinctly smaller than the posterior segment: but this is also the case for Malagasya n. gen., Hydrothelphusa and Marojejy . The heart-shaped carapace outline and elongated, slender walking legs of P. (P.) pittarrelli place it closest to Malagasya n. gen. However, it has proved difficult to locate and borrow the type material of P. (P.) pittarrelli , and our opinion is based only on photographs and illustrations in Nobili (1905). In our opinion, P. (P.) pittarrelli is most likely M. antongilensis n. comb., however, without first-hand knowledge of the specimens in question, it is difficult to be more certain.

Vuillemin (1972) provided excellent ecological notes and a detailed description of the habitat of M. antongilensis n. comb. It is possible that some of her specimens may belong to Madagapotamon humberti which is similar in many respects, but an exact identification is difficult to make from the photographs supplied in that publication.

Figures

FIG. 1. — Dorsal view of the carapace of adult males of Madagascan freshwater crabs; A, Hydrothelphusa agilis A. Milne-Edwards, 1872; B, H. madagascariensis (A. Milne-Edwards, 1872); C, H. bombetokensis (Rathbun, 1904); D, H. goudoti (H. Milne Edwards, 1853) n. comb.; E, Malagasya antongilensis (Rathbun, 1905) n. comb.; F, M. goodmani (Cumberlidge, Boyko & Harvey, 2002) n. comb., holotype (FMNH 4651). Scale bar: A, 10.5 mm; B, 14.4 mm; C, 14.1 mm; D, 12.6 mm; E, 8.9 mm; F, 6.4 mm.

FIG. 3. — Inferior view of the sternum of adult males of Madagascan freshwater crabs; A, Hydrothelphusa agilis A. Milne-Edwards, 1872; B, H. madagascariensis (A. Milne-Edwards, 1872); C, H. bombetokensis (Rathbun, 1904); D, H. goudoti (H. Milne Edwards, 1853) n. comb.; E, Malagasya antongilensis (Rathbun, 1905) n. comb.; F, M. goodmani (Cumberlidge, Boyko & Harvey, 2002) n. comb., G, Madagapotamon humberti Bott, 1965; H, Marojejy longimerus Cumberlidge, Boyko & Harvey, 2002; I, Boreas uglowi n. gen., n. sp. Scale bar: A, 11.7 mm; B, 17.2 mm; C, 15.9 mm; D, 14.5 mm; E, 10.2 mm; F, 7 mm; G, 9.6 mm; H, 6.4 mm; I, 9.1 mm.

FIG. 4. — Left mandible of Madagascan freshwater crabs, frontal view showing the palp (J, K based on Ng & Takeda 1994); A, Hydrothelphusa agilis A. Milne-Edwards, 1872; B, H. madagascariensis (A. Milne-Edwards, 1872); C, H. bombetokensis (Rathbun, 1904); D, H. goudoti (H. Milne Edwards, 1853) n. comb.; E, Malagasya antongilensis (Rathbun, 1905) n. comb.; F, M. goodmani (Cumberlidge, Boyko & Harvey, 2000) n. comb.; G, Marojejy longimerus Cumberlidge, Boyko & Harvey, 2000; H, Boreas uglowi n. gen., n. sp.; I, Skeleosophusa gollhardi (Bott, 1965); J, S. prolixa Ng & Takeda, 1994; K, S. eumeces Ng & Takeda, 1994; L, Madagapotamon humberti Bott, 1965. Scale bar: A-I, K, L, 1.0 mm; J, 1.25 mm.

FIG. 5. — Left third maxilliped of Madagascan freshwater crabs, frontal view (J, K based on Ng & Takeda 1994); A, Hydrothelphusa agilis A. Milne-Edwards, 1872; B, H. madagascariensis (A. Milne-Edwards, 1872); C, H. bombetokensis (Rathbun, 1904); D, H. goudoti (H. Milne Edwards, 1853) n. comb.; E, Malagasya antongilensis (Rathbun, 1905) n. comb.; F, M. goodmani (Cumberlidge, Boyko & Harvey, 2002) n. comb.; G, Marojejy longimerus Cumberlidge, Boyko & Harvey, 2002; H, Madagapotamon humberti Bott, 1965; I, Skelosophusa gollhardi (Bott, 1965); J, S. prolixa Ng & Takeda, 1994; K, S. eumeces Ng & Takeda, 1994; L, Boreas uglowi n. gen., n. sp. Scale bar: A-D, 5.0 mm; E-L, 3.5 mm.

FIG. 6. — Superior view of the carpus of the cheliped (pereiopod 1) of adult males of Madagascan freshwater crabs (J, K based on Ng & Takeda 1994); A Hydrothelphusa agilis A. Milne-Edwards, 1872; B, H. madagascariensis (A. Milne-Edwards, 1872); C, H. bombetokensis (Rathbun, 1904); D, H. goudoti (H. Milne Edwards, 1853) n. comb.; E, Malagasya antongilensis (Rathbun, 1905) n. comb.; F, M. goodmani (Cumberlidge, Boyko & Harvey, 2002) n. comb.; G, Madagapotamon humberti Bott, 1965; H, Marojejy longimerus Cumberlidge, Boyko & Harvey, 2002; I, Skeleosophusa gollhardi (Bott, 1965); J, S. prolixa Ng & Takeda, 1994; K, S. eumeces Ng & Takeda, 1994; L, Boreas uglowi n. gen., n. sp. Scale bar: A-D, 5.5 mm; E-L, 3.5 mm.

FIG. 7. — Superior and inferior views of the merus of the cheliped (pereiopod 1) of adult males of Madagascan freshwater crabs; A, B, Hydrothelphusa agilis A. Milne-Edwards, 1872; C, D, H. madagascariensis (A. Milne-Edwards, 1872); E, F, H. bombetokensis (Rathbun, 1904); G, H, H. goudoti (H. Milne Edwards, 1853) n. comb.; I, J, Malagasya antongilensis (Rathbun, 1905) n. comb.; K, L, Madagapotamon humberti Bott, 1965; M, N, Skelosophusa gollhardi (Bott, 1965); O, P, Marojejy longimerus Cumberlidge, Boyko & Harvey, 2002; Q, R, Boreas uglowi n. gen., n. sp. Scale bar: A-H, 5.0 mm; I-T, 3.0 mm.

FIG. 8. — Last walking leg (pereiopod 5) of adult males of Madagascan freshwater crabs (H based on Ng & Takeda 1994); A, Hydrothelphusa agilis A. Milne-Edwards, 1872; B, H. madagascariensis (A. Milne-Edwards, 1872); C, H. bombetokensis (Rathbun, 1904); D, H. goudoti (H. Milne Edwards, 1853) n. comb.; E, Boreas uglowi n. gen., n. sp.; F, Marojejy longimerus Cumberlidge, Boyko & Harvey, 2002; G, Madagapotamon humberti Bott, 1965; H, Skelosophusa prolixa Ng & Takeda, 1994; I, Malagasya antongilensis (Rathbun, 1905) n. comb.; J, M. goodmani (Cumberlidge, Boyko & Harvey, 2002) n. comb. Scale bar: A-D, 5.0 mm; E-L, 2.6 mm.

FIG. 10. — Right first gonopod (dorsal and ventral views) of adult males of Madagascan freshwater crabs; A, B, Boreas uglowi n. gen., n. sp.; C, D, Malagasya antongilensis (Rathbun, 1905) n. comb.; E, F, Skeleosophusa gollhardi (Bott, 1965); G, H, Madagapotamon humberti Bott, 1965; I, J, Marojejy longimerus Cumberlidge, Boyko & Harvey, 2002. Scale bar: 4.0 mm.

FIG. 11. — Summaries of the known distribution of the Madagascan freshwater crabs; A, Hydrothelphusa agilis A. Milne-Edwards, 1872; B, H. madagascariensis (A. Milne-Edwards, 1872); C, H. bombetokensis (Rathbun, 1904); D, H. goudoti (H. Milne Edwards, 1853); E, Marojejy longimerus Cumberlidge, Boyko & Harvey, 2002; F, Malagasya antongilensis (Rathbun, 1905) n. comb.; G, M. goodmani (Cumberlidge, Boyko & Harvey, 2002) n. comb.; H, Madagapotamon humberti Bott, 1965; I, Skelosophusa gollhardi (Bott, 1965); J, S. prolixa Ng & Takeda, 1994; K, S. eumeces Ng & Takeda, 1994; L, Boreas uglowi n. gen., n. sp.