Salmoneus ortmanni ( Rankin, 1898 )

Anker, Arthur, 2007, New species and records of alpheid shrimps, genera Salmoneus Holthuis and Parabetaeus Coutière, from the tropical western Atlantic (Decapoda, Caridea), Zootaxa 1653, pp. 21-39 : 23-26

Salmoneus ortmanni ( Rankin, 1898)

Fig. 1 , 2

Athanas ortmanni Rankin, 1898: 251 ; Verrill, 1900: 579.

Jousseaumea ortmanni – Coutière, 1900: 356; Verrill, 1922: 122; Schmitt, 1936: 367.

Salmoneus ortmanni – Chace, 1972: 79 (part.?); Banner & Banner, 1981: 56; Martínez-Iglesias et al., 1996: 35; Christoffersen, 1998: 362 (part.).

Not Salmoneus ortmanni – Carvacho, 1979: 453; Christoffersen, 1980: 137; Christoffersen, 1982: 94; Christoffersen, 1998: 362 (part.); Coelho dos Santos & Coelho, 2001: 78 (= S. carvachoi n. sp., see below).

(?) Not Salmoneus ortmanni – Carvacho & Ríos, 1983: 283; Ríos & Carvacho, 1983: 462; Christoffersen & Ramos, 1988: 63; Villalobos Hiriart et al., 1989: 16; Ríos, 1989: 154; Ríos, 1992: 7; Wicksten & Hendrickx, 1992: 6; Wicksten, 1993: 151; Villalobos, 2000: 74; Wicksten & Hendrickx, 2003: 66 (= Salmoneus sp. aff ortmanni ; see below).

Salmoneus evermanni (lap. cal.) – Holthuis, 1990: 111.

Salmoneus sp. – Rodríguez, 1986: 180.

Material examined: 2 ovig. females, MNRJ 20213, Brazil, Atol das Rocas (AR), LT 800, Ilha do Cemitério, intertidal, coll. C. Serejo and M.C. Rayol, 20 Oct 2001 [1 specimen dissected]; 1 ovig. female, MNRJ 20214, LT 795, Brazil, Atol das Rocas , between Ilha do Farol and Ilha do Cemitério, low tide, coll. C. Serejo and M.C. Rayol, 31 Oct 2001; 2 ovig. females, MNRJ 20215, Brazil, Atol das Rocas , between Ilha do Farol and Ilha do Cemitério, low tide, coll. C. Serejo and M.C. Rayol, 25 Oct 2001; 1 non-ovigerous specimen (male?), MNHN-Na 15686, Aruba, Pos Chiquito, from coral rocks, depth 0.5–1 m, coll. A. Anker, 7–8 Dec 2003; 1 ovig. female, MNHN-Na 15685, Aruba, Baby Beach, from coral rubble and porous rocks, depth 1–1.5 m, coll. A. Anker, 6 Dec 2003.

Description: Carapace slightly setose ( Fig. 1 a, c). Rostrum as long as broad, reaching half length of second segment of antennular peduncle, with acute tip ( Fig. 1 b); lateral margins slightly convex proximally; ventral margin unarmed ( Fig. 1 c); rostral carina distinct, reaching beyond eyes posteriorly ( Fig. 1 b). Orbital spines acute, slightly mesially directed ( Fig. 1 b). Pterygostomial margin protruding anteriorly, rounded ( Fig. 1 a, c). Eyes covered in dorsal and lateral view ( Fig. 1 a, b). Antennule with stylocerite reaching or slightly overreaching distal margin of second segment of antennular peduncle, with acute tip; second segment as long as wide ( Fig. 1 b). Antenna with basicerite bearing acute distoventral spine ( Fig. 1 c); scaphocerite broadly ovate, distolateral spine small, acute ( Fig. 1 b). Third maxilliped with rounded lateral plate; tip of ultimate segment with short apical and subapical spiniform setae ( Fig. 1 d, e). Chelipeds strongly asymmetrical in shape, unequal in size ( Fig. 2 ). Major cheliped ( Fig. 2 a–e) with unarmed ischium; merus inflated distally, ventrally flattened; carpus elongated, ventrally flattened to slightly depressed, distally lobed ( Fig. 2 c); chela excavated ventrally, flattened mesially ( Fig. 2 a, c); fingers about half as long as palm, cutting edges serrated, with about 10–12 rounded teeth ( Fig. 2 e). Minor cheliped ( Fig. 2 f, g) with ischium subequal to merus, both unarmed; carpus slightly shorter than merus; chela small, simple, with fingers subequal to palm. Second pereiopod ( Fig. 1 f) with unarmed ischium; carpus bearing five segments, first segment longer than sum of four other segments. Third pereiopod ( Fig. 1 g) with ischium bearing one ventrolateral spiniform seta; merus about four times as long as wide; carpus unarmed except for one slender distoventral spiniform seta; propodus with four slender ventral spiniform setae, including distal spiniform seta; dactylus simple, conical, moderately slender, less than half length of propodus. Fifth abdominal somite with subacute posteroventral angle. Sixth abdominal somite without articulated plate, with subacute posteroventral projection; preanal plate rounded ( Fig. 1 i). Second pleopod with appendix masculina subequal to appendix interna, furnished with slender setae on apex and along outer margin ( Fig. 1 h). Uropod with sinuous diaeresis and slender distolateral spinform seta ( Fig. 1 j). Telson about twice as long as wide proximally, tapering posteriorly, with two pairs of dorsal spiniform setae, inserted at about mid-length and 3/4 telson length, respectively ( Fig. 1 j); posterior margin with rounded median notch and two pairs of spiniform setae at posterolateral angles, mesial setae distinctly longer than lateral setae ( Fig. 1 j). Gill/exopod formula typical for genus: 5 pleurobranchs (above P1-5); 1 arthrobranch (above Mxp3); 0 podobranch; 2 lobe-shaped epipods (Mxp1-2); 5 mastigobranchs or strap-like epipods (Mxp3, P1-4); 5 sets of setobranchs (P1-5); 3 exopods (Mxp1-3).

Colour: The specimens from Aruba were uniformly yellow-orange.

Size: The largest AR specimen has CL 4.5 mm, TL 13.5 mm.

Ecology: The Aruba specimens were found in crevices of coral rubble and rocks in a depth of 1–1.5 m; the AR specimens were collected intertidally, probably under rocks. In the Caribbean, S. ortmanni occurs under rocks from the tide pool level down to about 3–4 m, and on turtle grass flats, under rocks and rubble ( Chace, 1972; pers. obs.), occasionally also in tide pools near low tide level ( Chace, 1972) and inside empty Strombus shells and among mangrove roots ( Rodríguez, 1986).

Type locality: Nassau, New Providence, Bahamas.

Distribution: Western Atlantic: Caribbean Sea: Bahamas, Cuba, W Mexico (?), Lesser Antilles, Aruba, Venezuela; Bermuda ( Rankin, 1898; Verrill, 1922; Chace, 1972; Christoffersen, 1982, 1998; Rodríguez, 1986; Martínez-Iglesias et al., 1996; present study), Brazil: Atol das Rocas (present study). Christoffersen’s (1982) record of S. ortmanni from southern Brazil most likely refers to S. carvachoi , n. sp. (see below). The records of S. ortmanni from the eastern Pacific (Ríos & Carvacho, 1983; Villalobos Hiriart et al., 1989; Ríos, 1989, 1992; Wicksten, 1993; Villalobos, 2000) most probably refer to closely related, undescribed species (see below).

Remarks: Salmoneus ortmanni belongs to the S. ortmanni species group (see Anker & Marin, 2006 for definition of species groups). Members of this group are unique in having a major cheliped with inflated and ventrally excavated merus and carpus. Until now, all western Atlantic and eastern Pacific specimens with this features were assigned to S. ortmanni (e.g., Carvacho, 1979; Christoffersen, 1998; Wicksten & Hendrickx, 2003). However, variation in the proportions of the major chela and especially in the shape of the dactylus of the third to fifth pereiopods suggests that S. ortmanni is a species complex, with two distinct forms in the western Atlantic (and perhaps one or two distinct forms in the eastern Pacific, see below).

In Christoffersen’s specimens from southern Brazil (São Paulo and Paraná), the major chela is 2.5–3 times longer than wide, compared to only twice as long as wide in the type ( Rankin, 1898: 251). In the AR specimens, the major chela appears to be stouter compared to that of the specimen from São Paulo illustrated by Christoffersen (1982), and approaching the ratio of the chela in the original figure by Rankin (1898). Furthermore, the dactylus of the third pereiopod of the AR specimens is moderately slender, only about half as long as the propodus, and so very similar to the proportions of the dactylus in Rankin’s figure, as well as in the Caribbean material reported by Chace (1972). In contrast to this, Christoffersen’s (1982) specimens had a very slender dactylus, with a ratio dactylus/propodus equal to 5/7. A similar ratio is also found in specimens from Guadeloupe reported by Carvacho (1979) (see below). Also, the merus and propodus of the third pereiopod are significantly broader in the AR specimens compared to the specimen from São Paulo (cf. Fig. 1 g and Christoffersen, 1982: 99, fig. 2f).

Christoffersen (1982) also reported variation in the shape of the rostrum and length of the scaphocerite. In the AR specimens, the rostrum is indeed slightly broader than in Christoffersen’s specimen from São Paulo (cf. Fig. 1 b and Christoffersen, 1982: 98, fig. 1a). Furthermore, in the AR specimens, the telson is broader and has a more pronounced median notch on the posterior margin (cf. Fig. 1 j and Christoffersen, 1982: 98, fig. 1d). Notably, both Christoffersen’s and Carvacho’s specimens with the elongate P3-5 dactyli were found on mud bottoms in mangrove-estuarine conditions, while the AR and Aruba specimens with a stouter P3-5 dactyli were collected on mixed sand-rubble bottoms. This ecological difference seem to corroborate the differences in morphology, suggesting that two species are currently confused under S. ortmanni : a coral rubbleseagrass species, with stouter P3-5 dactyli – S. ortmanni sensu stricto (sensu Rankin, 1898), and a mangroveestuarine species with longer and more slender P3-5 dactyli – S. ortmanni sensu Carvacho (1979) and Christoffersen (1982). The latter species is described below as new.

The specimens from Los Roques, Venezuela, reported as “ Salmoneus sp.” by Rodríguez (1986) agree almost perfectly with the AR specimens, including the shape of the rostrum and the broad telson bearing a shallow rounded median notch.

The records of S. ortmanni from the Gulf of California and Galapagos (e.g., Ríos & Carvacho, 1983; Ríos, 1989, 1992; Wicksten, 1993; Villalobos, 2000) should be regarded as questionable. Ríos (1989, 1992) examined and compared specimens from the Gulf of California (Bahía Concepición and Rio Mulegé), Laguna Percebú (Baja California), and Guadeloupe, French Antilles (Carvacho’s specimens), and noted that the posterior margin of the telson sometimes has a “vestigial” median notch. However, this notch – an important taxonomic character of the Salmoneus species - is quite deep in the AR specimens ( Fig. 1 j) and Los Roques specimens ( Rodríguez, 1986). Ríos (1992) noted that the ischium of the third and fourth pereiopods may bear either one or two spiniform setae. Ríos also found that the specimens from the Gulf of California differ from the specimens from Guadeloupe (described below as S. carvachoi n. sp.) by the absence of the ischial spiniform seta on the second pereiopod; this seta also lacks in the AR specimens ( Fig. 1 f). The present author examined several specimens of S. cf. ortmanni collected by Rafael Robles (University of Louisiana, Lafayette, LA, USA) from the mudflats of the Rio Mulegé estuary, northern Gulf of California, and specimens identified as S. ortmanni from Bahía Málaga, Pacific coast of Colombia (USNM 244251). All these specimens appear not to represent S. ortmanni sensu Rankin, 1898 . The above-listed differences, if shown to be consistent, could prove to be important characters in the separation of the eastern Pacific form (or forms) from both S. ortmanni and S. carvachoi n. sp. However, the status of the eastern Pacific specimens of S. ortmanni s. lat. will be subject of a separate study.

Figures

FIGURE 1. Salmoneus ortmanni Rankin, 1898, ovigerous specimen from Atol das Rocas, Brazil (MNRJ 20213): acephalothorax and major cheliped, lateral view; b—frontal region, dorsal view; c—same, lateral view; d—third maxilliped, lateral view; e—same, tip of ultimate segment; f—second pereiopod, lateral view; g—third pereiopod, lateral view; h—second pleopod with eggs, mesial view; i—preanal plate of sixth abdominal somite, ventral view; j—telson and right uropod, dorsal view. Scale bars = 1 mm.

FIGURE 2. Salmoneus ortmanni Rankin, 1898: ovigerous specimen from Atol das Rocas, Brazil (MNRJ 20213): amajor cheliped, mesial view; b—same, coxa to carpus, lateral view; c—same, chela, ventrolateral view; d—same, dorsolateral view; e—same, chela with opened fingers, lateral view; f—minor cheliped, lateral view; g—same, carpus and chela, mesial view. Scale bar = 1 mm.