Potamocarcinus garthi, (Pretzmann, 1971)

Magalhães, Célio, Campos, Martha R. & Türkay, Michael, 2013, Freshwater crabs from eastern Panamá: a new species of Potamocarcinus H. Milne Edwards, 1853, and new records of two little-known species (Crustacea: Decapoda: Pseudothelphusidae, Trichodactylidae), Zootaxa 3702 (4), pp. 348-356 : 352-354

Spirocarcinus garthi ( Pretzmann, 1971)

( Fig. 2 A–F)

Potamocarcinus (Potamocarcinus) garthi Pretzmann, 1971: 19 .— Rodríguez & Hobbs 1989: 189, fig. 4a–d.

Potamocarcinus (Spirocarcinus) garthi .— Pretzmann 1972: 67, figs. 363–365, 387–389.— Pretzmann 1975: 619, pl. 5, figs. 15- 17, pl. 7, figs. 24, 25.— Rodríguez 1982: 191.—Ng et al., 2008: 177 [in list].

Spirocarcinus garthi .— Villalobos & Álvarez, 2008: 295.

Material. Panamá, Panamá Province, male holotype (cw 78.8, cl 50.8, ch 29.2, fb 25.9), USNM 107096 , Icandi river, affluent of Bayano river, 13.Jun.1960, C.F. Bennett leg.; 1 male (cw 72.1, cl 46.2) , 1 female (cw 64.5, cl 42.5), USNM 1180976 , Canita river, at Pan American Highway , 24.Feb.1985, R.W. Bouchard leg.; 1 male (cw 46.3, cl 30.7), SMF 31704 , Platano river, bridge at Pan American Highway , between Las Margaritas and El Llano , 2.Mar.1996, C.D. Schubart. Darién Province, 1 male (cb 64.4, cl 41.9) 3 females (cw 39.9, cl 26.1; cb 60.9, cl 39.5; cw 90.8, cl 56.1), USNM 1180975 , Púcuro river, approximately 1000 m upstream from Tuira river, 12.Feb.1985, R.W. Bouchard leg.

Redescription of the male first gonopod ( Fig. 2 A–D). G1 robust, nearly straight, lateral border sinuous in mesio-caudal view, with irregular row of minute spines. Marginal suture situated on mesial side, displaced towards cephalic side distally, with proximal row of long, short setae. Marginal process indistinct, continuous with distal, rounded border of apex. Lateral suture incomplete, with distinct sulcus on proximal half of caudal side, faint sulcus on distal half. Distal part with 2 distinct conical teeth on latero-cephalic surface, cephalic tooth bifid; caudo-lateral surface with subapical tooth, slightly smaller, more distal that latero-cephalic teeth. Apex with short, semicircular subapical lobe on caudo-lateral surface; large, rounded apical lobe in cephalic, lateral views; smaller, shorter auriculariform lateral lobe; field of apical spines well developed along semicircular and lateral lobes of apex.

Distribution. This species was only known from its type locality, the Bayano river basin (currently a large area of the basin is flooded by the damming of the river in 1976 to form Bayano Lake). The present new records suggest that the species is more widely distributed in eastern Panamá, ranging from Bayano river and Chepo river basins to Tuira river basin, both draining into the Pacific ( Fig. 3 ).

Remarks. Pretzmann (1971) described this species as Potamocarcinus (Potamocarcinus) garthi from a single male and soon after erected the monotypic subgenus Spirocarcinus to accommodate it ( Pretzmann, 1972). Rodríguez (1982) could not examine the gonopods of the holotype and therefore treated it as incertae sedis because he judged Pretzmann's (1971, 1972) descriptions and illustrations to offer little diagnostic value. In the rearrangement of some groups within the Potamocarcini, Rodríguez and Hobbs (1989) considered some morphological characters of the G1 of P. (S.) garthi to be closer to those of the G1 of species of the Kingsleyini , particularly the open field of apical spines partially located longitudinally in an ear-like lobe directed towards the latero-cephalic side. They therefore raised Spirocarcinus to generic rank and transferred it to the tribe Kingsleyini .

The situation and position of the apical field of spines as well as the presence of apical lobes in Spirocarcinus resemble those in genera assigned to the Kingsleyini , which might represent a possible affinity between them. The G1 nevertheless shows a quite distinct organization in which the distal part is rather twisted as evidenced by the displacement of the marginal suture from the mesial to the cephalic surface on the distal sixth of the stem ( Fig. 2 A, D). The marginal process also reaches the apex of the gonopod, being continuous with its distal border. In Kingsleyini , the distal part is not twisted, the marginal suture is straight, with the marginal process distinctly shorter than the apical lobes, and ending either straight or oriented towards the caudo-lateral side. This cephalad torsion of the marginal suture seems to be unique to Spirocarcinus as it is also not apparent in representatives of the other tribes of Pseudothelphusinae . A slight twist towards the cephalic side can be noticed in some species of Epilobocerinae (see Rodríguez 1982: 26, fig. 4), a group distributed in the West Indies and considered to be the most primitive among the Pseudothelphusidae ( Rodríguez, 1982) . The length of the exopod of the third maxilliped is 0.50 times the length of the outer margin of the ischium in Spirocarcinus ( Fig. 2 E), which is similar to species of Potamocarcinus . In species of Kingsleyini , except Eudaniela spp., length does not exceed 0.3 the length of the outer margin of the ischium ( Rodríguez 1982; Campos & Magalhães 2004). The presence of large triangular teeth on the lateral margin of the carapace ( Fig. 2 F), though a rather uncommon feature among pseudothelphusids, can be found in a few species of both Potamocarcinini and Kingsleyini ( Pretzmann 1975; Rodríguez 1982; Magalhães 1986; Rodríguez & Hobbs 1989).

Whether those characters might indicate a closer affinity with Kingsleyini , Potamocarcinini or even with Epilobocerinae , remains to be investigated by a thorough morphological and molecular study that can help to evaluate the systematic relationships within the family ( Villalobos & Álvarez 2010).

The holotype of S. garthi (USNM 107096) is totally disarticulated, the anterolateral teeth broken or eroded, and both G1s detached from the body.

Figures

FIGURE 2. Spirocarcinus garthi (Pretzmann, 1971), male holotype (USNM 107096) (A – E). A, right male first gonopod, mesio-caudal view; B, distal part, lateral view; C, distal part, caudal-apical view; D, distal part, cephalic view; E, left third maxilliped; F, male, SMF 31704, outline of right side of lateral margin of carapace. Abbreviations: al, auriculariform lobe; ap, apical lobe; cl, semicircular subapical lobe; fs, field of apical spines; ls, lateral suture; lt, lateral-cephalic teeth; ms, marginal suture; st, subapical tooth. Scale bars, A – D, 1 mm, E, F, 5 mm.

FIGURE 3. Geographic distribution of Melocarcinus meekei (Pretzmann, 1968) (•), Potamocarcinus darienensis sp. n. (˔), and Spirocarcinus garthi (Pretzmann, 1971) (⋅) in eastern Panama, Central America.