Salmoneus malagensis, Anker, Arthur & Lazarus, Juan Felipe, 2015

Anker, Arthur & Lazarus, Juan Felipe, 2015, On two new species of the shrimp genus Salmoneus Holthuis, 1955 (Decapoda, Caridea, Alpheidae) from the tropical eastern Pacific, Zootaxa 3957 (5), pp. 520-534 : 526-531

publication ID	https://doi.org/ 10.11646/zootaxa.3957.5.2
publication LSID	lsid:zoobank.org:pub:C3BCE0B2-2277-4D54-95C2-4E99D1277D38
DOI	https://doi.org/10.5281/zenodo.3508367
persistent identifier	https://treatment.plazi.org/id/03EC879F-2140-FFCD-48A8-93E7A18FFA9C
treatment provided by	Plazi
scientific name	Salmoneus malagensis
status	sp. nov.

Treatment

Salmoneus malagensis View in CoL sp. nov.

( Figs. 4–6 View FIGURE 4 View FIGURE 5 View FIGURE 6 , 7 View FIGURE 7 A, B)

Salmoneus cf. carvachoi View in CoL — Anker 2010: 201 View Cited Treatment [not S. carvachoi Anker, 2007 View in CoL ].

Type material. Colombia. Holotype: ov. specimen (cl 4.2 mm), INV CRU8367, Bahía Málaga, Curichichi, 03°59’37.8”N 77°19’03.9”W, intertidal mudflat exposed at low tide, in burrow (suction pump), coll. A. Anker, 26.iv.2009 [fcn COL-00402]. Paratypes: 1 non-ov. specimen (cl 3.0 mm), INV CRU8368, Bahía Málaga, Mayordomo, 04°01’40.4”N 77°18’38.6”W, intertidal mudflat with scarce rocks, 0–0.5 m at low tide, in burrow (suction pump), coll. A. Anker, 24.iv.2009 [fcn COL-00066]; 1 non-ov. specimens (cl 2.7, 2.9 mm), INV CRU8369, same collection data [fcn COL-00078]; 1 non-ov. specimen (cl 3.3 mm), MZUSP 33197, same collection data [fcn COL-00058]; 2 non-ov. specimens (cl 3.2, 3.5 mm), OUMNH.ZC. 2015.01.0 91, Bahía Málaga, La Plata, 04°02’N 77°13”W, intertidal mudflat exposed at low tide, in burrow (suction pump), coll. A. Anker, 25.iv.2009 [fcn COL-00108]; 1 ov. specimen (cl 4.4 mm), OUMNH.ZC. 2015.01.0 92, same collection data [fcn COL-00117].

Description. Carapace with numerous scattered setae ( Fig. 4 View FIGURE 4 B). Rostrum triangular in dorsal view, longer than wide at base, reaching beyond distal margin of first article of antennular peduncle, but not reaching mid-length of second article, with acute tip; lateral margins broadly concave proximally; ventral margin distally unarmed; rostral carina very short, not extending beyond proximal half of rostrum posteriorly, sometimes inconspicuous; areas lateral to rostral carina not particularly depressed ( Fig. 4 View FIGURE 4 A, B). Orbital teeth strong, acute, directed anteriorly ( Fig. 4 View FIGURE 4 A, B). Pterygostomial margin somewhat protruding anteriorly, rounded ( Fig. 4 View FIGURE 4 B).

Eyes completely concealed in dorsal view, anterior-most portion usually visible in lateral view; anteromesial margin of eyestalk with conical or rounded tubercle, better developed in larger specimens; cornea well developed ( Figs. 4 View FIGURE 4 A, B, 7A, B). Epistomial sclerites each with small sharp tooth.

First to third pleura rounded posteroventrally; fourth and fifth pleura with posteroventral angle produced into small tooth, more conspicuous on fifth pleuron; sixth somite without articulated plate ( Fig. 4 View FIGURE 4 C); preanal plate rounded distally. Telson about 2.7–2.8 times as long as wide proximally, tapering posteriorly, with two pairs of small dorsal spiniform setae situated at about 0.7–0.75 and 0.8–0.9 of telson length, respectively; posterior margin broadly incised centrally, with two pairs of stout spiniform setae, latter more or less equal in robustness and length, and two pairs of long plumose setae between mesial spiniform setae ( Fig. 4 View FIGURE 4 D, E).

Antennule moderately robust; stylocerite distinctly overreaching distal margin of first article, not reaching mid-length of second article, with acute tip; ventromesial carina of first article with sharp, anteriorly directed tooth; second article about 1.2 times as long as wide; lateral flagellum bifurcating at about third or fourth segment, secondary ramus well developed, with typically three groups of aesthetascs ( Fig. 4 View FIGURE 4 A, B). Antenna with basicerite bearing sharp distoventral tooth; scaphocerite broadly ovate, slightly elongate, with strong acute distolateral tooth and relatively broad blade, latter with convex anterior margin reaching distinctly past distolateral tooth; carpocerite short, not reaching mid-length of scaphocerite ( Fig. 4 View FIGURE 4 A, B, F).

Mouthparts not specific, typical for genus. Third maxilliped with rounded lateral plate; ultimate article tapering distally, ending in small corneous, apparently immovable spine, distodorsal surface with some slender stiff setae, without stout spiniform setae ( Fig. 4 View FIGURE 4 G).

Chelipeds strongly asymmetrical in shape and unequal in size; major cheliped by far most conspicuous in general view ( Figs. 5 View FIGURE 5 , 6 View FIGURE 6 ). Major cheliped with ischium unarmed, depressed ventrally; merus moderately inflated, widening distally, excavated ventrally (especially distally); carpus long, with depressed ventral margin; chela stout, with fingers about 0.6 length of palm; palm conspicuously flattened ventromesially, excavated ventrally; fingers rather slender, with strongly curved, crossing tips; cutting edges of both fingers with about 12 subtriangular or rounded teeth extending from finger base to 0.9 of finger length ( Fig. 5 View FIGURE 5 C–D). Minor cheliped with ischium shorter than merus, unarmed; merus equal to carpus; carpus cylindrical, widening distally; chela small, simple, with fingers longer than palm, slightly gaping; finger cutting edges unarmed ( Fig. 5 View FIGURE 5 E, F).

Second pereiopod relatively short, slender; ischium armed with one spiniform seta on ventrolateral surface; merus longer than ischium; carpus five-jointed, first joint noticeably longer than sum of remaining joints ( Fig. 4 View FIGURE 4 H). Third pereiopod slender; ischium with two spiniform setae on ventrolateral surface; merus about eight times as long as wide; carpus without distoventral spiniform seta; propodus with one slender spiniform setae on ventral margin and one longer and stouter spiniform seta adjacent to dactylus; dactylus at least 0.7 length of propodus, very slender, conical, simple, smoothly curving distally ( Fig. 4 View FIGURE 4 I). Fourth pereiopod generally similar to third; ischium with one spiniform seta on ventrolateral surface. Fifth pereiopod longer and more slender than third; ischium shorter than that of third pereiopod, unarmed; merus shorter and wider than carpus; propodus without spiniform setae on ventral margin, with well-developed setal brush distally ( Fig. 4 View FIGURE 4 J).

Second pleopod with appendix masculina subequal in length to appendix interna, with stiff setae on and near apex ( Fig. 4 View FIGURE 4 K). Uropod with moderately narrow exopod and endopod; diaeresis sinuous, with blunt distolateral tooth adjacent to stout distolateral spiniform seta ( Fig. 4 View FIGURE 4 L, M).

Gill/exopod formula typical for genus (see Anker 2010).

Colouration. Semitransparent greyish with purple-bluish transverse bands, one near posterior margin of carapace, and six across posterior area of each abdominal somite, bands becoming narrower towards posterior somites; antennular and antennal peduncles with purplish areas, flagella conspicuously pale red-orange; major chela greyish with purplish tinge, fingers hyaline-white; second to fifth pereiopods mostly colourless; tail fan with some reddish-purplish areas; ovaries reddish orange ( Fig. 6 View FIGURE 6 ).

Etymology. The new species is named after the type locality, Bahía Málaga, Colombia; used as an adjective.

Type locality. Bahía Málaga, Colombia.

Distribution. Tropical eastern Pacific: presently known only from Colombia (Bahía Málaga).

Ecology. Estuarine intertidal mudflats, sometimes with scattered rocks partly submerged in mud; all type specimens were collected from burrows of unknown hosts, very lkely Alpheus colombiensis Wicksten, 1988 (based on burrow entrance type and collection of several specimens of A. colombiensis at La Plata, one of the collection sites of S. malagensis sp. nov.); during a more recent survey, several additional specimens S. malagensis sp. nov. were collected together with A. colombiensis , although some were obtained from a burrow of an unidentified orange-coloured echiuran (J.F. Lazarus, pers. obs.).

Remarks. Salmoneus malagensis sp. nov. represents beyond any doubt the eastern Pacific sister species of the western Atlantic S. carvachoi ranging from the Caribbean Sea ( Mexico: Yucatan Peninsula, French Antilles: Martinique, Guadeloupe) to Brazil (e.g., Paraíba, Bahia, São Paulo, Paraná) ( Anker 2007, 2010; present study). The two species are morphologically almost identical, with the exception of two characters (see below), and also share the same colour pattern (cf. Fig. 6 View FIGURE 6 and Anker 2007: fig. 14f; Almeida et al. 2012: fig. 2F). In addition, both species have a similar ecology, occurring in estuarine, mud-dominated habitats, in contrast to most other western Atlantic members of the genus Salmoneus .

The new species can be reliably separated from S. carvachoi only by the length of the stylocerite and position of the posterior pair of the dorsal spiniform setae of the telson. In all examined specimens of S. malagensis sp. nov., the stylocerite either falls short of the mid-length of the second article of the antennular peduncle or slightly overreaches it ( Fig. 4 View FIGURE 4 A); in some specimens it barely overreaches the distal margin of the first article. In contrast, in all examined specimens of S. carvachoi , the stylocerite distinctly overreaches the mid-length of the second article of the antennular peduncle, often reaching or almost reaching the distal margin of this article ( Anker 2007: fig. 3a; see also Christoffersen 1982: fig. 1a, as S. ortmanni ). In all examined specimens of S. malagensis sp. nov., the posterior pair of the dorsal spiniform setae is situated very close to the posterior margin; the distance is typically equal or slightly more than the full length of an individual spiniform seta ( Fig. 4 View FIGURE 4 D). In all examined specimens of S. carvachoi , the posterior pair of the dorsal spiniform setae on the telson is removed from the posterior margin by at least three times the length of an individual spiniform seta ( Anker 2007: fig. 3m; see also Christoffersen 1982: fig. 1d, as S. ortmanni ).

The posterior margin of the telson appears to be variable in both species, ranging from slightly convex centrally to perfectly straight, broadly concave or shallowly incised centrally. Most specimens of S. carvachoi have a spiniform seta on the ischium of the second pereiopod, as illustrated by Anker (2007: fig. 3i); however, in a few specimens (e.g. one female from lot MZUSP 31611), this spiniform seta is lacking or at least not recognisable (see also Christoffersen 1982: fig. 1e).

In the course of the interspecific comparison between S. malagensis sp. nov. and S. carvachoi , we made several interesting observations on the eyestalks of both species. Anker (2007) did not describe in detail the eyestalks of S. carvachoi and in his illustration of the frontal region of a paratype specimen ( Anker 2007: fig. 3b), no particular features can be seen on the anterior surface of the eyes. However, the material of S. carvachoi examined in this study shows that in this species, the anteromesial margin of each eyestalk is armed with a robust, conical or distally rounded tubercle, which in some specimens is visible in lateral view of the frontal region ( Fig. 7 View FIGURE 7 C). A similar tubercle is also present in S. malagensis sp. nov. ( Fig. 7 View FIGURE 7 A, B), constituting another morphological synapomorphy of the two transisthmian sister species.

Salmoneus malagensis View in CoL sp. nov. can be easily separated from S. alvarezi View in CoL sp. nov., S. ortmanni View in CoL , and S. wehrtmanni View in CoL by the much longer and more slender dactyli of the third to fifth pereiopods, the distinctly more slender merus of the major cheliped, the presence of a spiniform seta on the ischium of the second pereiopod, and in life, also by the distinctive banded colour pattern (cf. Fig. 6 View FIGURE 6 and Fig. 3 View FIGURE 3 , Anker 2010: fig. 14d, e; Anker et al. 2013: fig. 3). Both S. malagensis View in CoL sp. nov. and S. carvachoi View in CoL also differ ecologically from S. alvarezi View in CoL sp. nov., S. ortmanni View in CoL and S. wehrtmanni View in CoL , preferring muddier bottoms (mangroves, estuarine mudflats) and living “commensally” in burrows of larger snapping shrimps, Alpheus colombiensis View in CoL for S. malagensis View in CoL sp. nov. and A. estuariensis Christoffersen, 1984 View in CoL for S. carvachoi ( Almeida et al. 2012) View in CoL .