Salmoneus camaroncito, Anker, 2010
Anker, Arthur, 2010, The shrimp genus Salmoneus Holthuis, 1955 (Crustacea, Decapoda, Alpheidae) in the tropical western Atlantic, with description of five new species *, Zootaxa 2372 (1), pp. 177-205 : 184-188
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Salmoneus camaroncito sp. nov.
Type material. Holotype: breeding female (cl 2.5 mm, tl 7.0 mm), USNM 1124211 View Materials , Panama, Caribbean coast, Isla Grande, western point, under rock on coarse sand mixed with rubble, 0.5 m depth, leg. A. Anker, 10.VI.2006 [fcn 06-427].
Additional material examined. 1 breeding female (cl 2.4 mm, tl approx. 7.0 mm), USNM 1124212 View Materials , Panama, San Blas Islands , small cay in the Cayos Los Grullos NE of Cartí Suitupo, 0.5–1.5 m depth, under rocks on coarse sand, leg. A. Anker & I. Marin, 22. V.2007 [fcn 07-181]; 1 breeding female (cl 2.4 mm, tl 6.2 mm), OUMNH. ZC 2007-20 - 074 , Honduras, Utila , Stingray Point, 16°04.131'N 86°57.334'W, hand collecting under stone, 10 m depth, leg. A. Anker & S. De Grave, 5.VII.2007 GoogleMaps .
Description. Carapace smooth, only sparsely covered with small setae ( Figs. 5a–b View FIGURE 5 ). Rostrum triangular in dorsal view, at base about one quarter broader than long, reaching just past distal margin of first segment of antennular peduncle, tip acute ( Fig. 5a View FIGURE 5 ); lateral margins slightly concave; ventral margin with minute blunt subapical tooth ( Fig. 5b View FIGURE 5 ); rostral carina feebly developed, not reaching level of eyes. Orbital teeth relatively small, acute, directed anteromesially ( Figs. 5a–b View FIGURE 5 ). Pterygostomial margin not protruding anteriorly, rounded ( Fig. 5b View FIGURE 5 ). Eyes completely covered in dorsal and lateral views ( Figs. 5a–b View FIGURE 5 ); cornea slightly reduced; anteromesial margin of eyestalk without projection.
Antennule with stylocerite reaching well beyond mid-length of second peduncular segment, with acute or subacute tip; ventromesial carina of first segment with small sharp tooth ( Fig. 5c View FIGURE 5 ); second segment very short, wider than long ( Fig. 5a View FIGURE 5 ); lateral flagellum bifurcating at second segment, secondary ramus well developed, with several groups of aesthetascs ( Fig. 5b View FIGURE 5 ). Antenna with basicerite bearing acute distoventral tooth ( Fig. 5b View FIGURE 5 ); scaphocerite broadly ovate, with acute distolateral tooth and broadly rounded blade ( Fig. 5a View FIGURE 5 ); carpocerite short, not reaching mid-length of scaphocerite.
Third maxilliped with blunt lateral plate ( Fig. 5e View FIGURE 5 ); ultimate segment tapering, tip apparently without spines (or at least with minute spinules).
Chelipeds strongly asymmetrical in shape, unequal in size ( Figs. 6a–d View FIGURE 6 ). Major cheliped ( Figs. 6a–c View FIGURE 6 ) with ischium bearing one spine on ventrolateral surface; merus not inflated, depressed ventrally; carpus vaseshaped, widening distally; chela slender, with fingers slightly longer than palm; palm with shallow groove on dorsal side; fingers slender, straight except for curved crossing tips, cutting edges serrated, with seven or eight irregular, triangular, more or less spaced teeth ( Fig. 6c View FIGURE 6 ). Minor cheliped ( Figs. 6d–e View FIGURE 6 ) with ischium shorter than merus, armed with one small spine on ventrolateral margin; carpus half as long as merus, cylindrical, widening distally; chela simple, smooth, with fingers shorter than palm, cutting edges armed with three or four small rounded spaced teeth ( Fig. 6e View FIGURE 6 ).
Second pereiopod ( Fig. 5f View FIGURE 5 ) moderately slender; ischium bearing one small spine on ventrolateral surface, at about mid-length; merus longer than ischium; carpus five-segmented, first segment being almost equal to sum of remaining four segments. Third pereiopod ( Fig. 5g View FIGURE 5 ) moderately slender; ischium with two ventrolateral spines; merus about four times as long as wide; carpus more slender than merus, with stiff distoventral seta; propodus with two small ventral spinules and pair of longer stouter distal spinules; dactylus simple, conical, moderately slender, about half-length of propodus. Fourth pereiopod similar to third. Fifth pereiopod with ischium unarmed; propodus with setal brush distally.
First to fourth pleura rounded; fifth pleuron forming blunt angle posteroventrally ( Fig. 5i View FIGURE 5 ); sixth pleurite without articulated plate, subacute posteroventrally; preanal plate triangular, acutely produced posteriorly ( Fig. 5j View FIGURE 5 ). Telson ( Fig. 5l View FIGURE 5 ) about 2.2 times as long as wide proximally, tapering posteriorly, with two pairs of dorsal spines situated both in posterior half of telson; posterior margin straight, without median notch, fringed by one pair of plumose setae and two pairs of stouter spines closer to posterolateral angle, lateral being slightly shorter than mesial ( Fig. 5n View FIGURE 5 ) [spines broken in holotype ( Fig. 5l View FIGURE 5 )].
Second pleopod with appendix masculina slightly shorter than appendix interna, furnished with stout setae apically ( Fig. 1h View FIGURE 1 ). Uropod ( Fig. 5k View FIGURE 5 ) with narrow exopod and endopod; diaeresis sinuous; distolateral tooth very small, adjacent distolateral spine fairly stout.
Gill/exopod formula typical for genus (see under first species).
Size. Holotype: cl 2.5 mm, tl 7.0 mm; non-type specimens: cl 2.4 mm, tl 6.2–7.0 mm. One of the smallest alpheid shrimps.
Colour in life. Semitransparent, whitish; gonads and embryos yellow ( Fig. 14b View FIGURE 14 ).
Etymology. Derived from the Spanish word camaroncito, meaning “little shrimp” and obviously alluring to its small size; used as noun in opposition.
Type locality. Isla Grande, Panama.
Distribution. Presently known only from the Caribbean coast of Panama ( Isla Grande, San Blas Islands) and Honduras (Utila).
Ecology. Near-shore coarse sand flats with abundant pieces of coral rubble, usually with seagrass; all specimens were collected under rubble at depths of 0.5–1.5 m.
Variation. The non-type specimens from Utila and San Blas agree with the holotype in all features except for the absence of a subapical tooth on the ventral margin of the rostrum in the Utila and San Blas specimens ( Fig. 5m View FIGURE 5 ) and the presence of a minute median notch on the posterior margin of the telson in the San Blas specimen ( Fig. 5n View FIGURE 5 ); this notch is absent or at least appears to be indistinct in the holotype ( Fig. 5l View FIGURE 5 ). The San Blas specimen is missing its major cheliped, but most other features, including the very characteristic frontal margin and the presence of small spaced teeth on the cutting edges of the minor cheliped fingers leave no doubt that it belongs to S. camaroncito sp. nov.
Remarks. Salmoneus camaroncito sp. nov. belongs to the S. serratidigitus species group and is closely related to S. arubae , a poorly known species reported only twice from the Netherlands Antilles ( Aruba, Schmitt 1936; Curaçao, Holthuis 1990). However, there are numerous differences between the new species and S. arubae , e.g., in the length of the stylocerite, which surpasses the distal margin of the second segment of the antennular peduncle in S. arubae , but reaches to only 0.75 length of the second segment in S. camaroncito sp. nov.; the absence of subapical tooth on the ventral side of rostrum in S. arubae (a small but distinct tooth is present in S. camaroncito sp. nov.); the ischia of the minor cheliped and second and third pereiopods not having spine(s) in S. arubae vs. with one (P1, 2) or two (P3) spines in S. camaroncito sp. nov.; the more mesially directed orbital teeth in S. camaroncito sp. nov., and the cutting edges of fingers of the minor chela being, which are straight in S. arubae vs. armed with minute spaced teeth in S. camaroncito sp. nov. (compare Figs. 5–6 View FIGURE 5 View FIGURE 6 and Schmitt 1936: figs. 2a–g).
Holthuis (1990) provided detailed drawings of the major cheliped and second and third pereiopods of several specimens from Curaçao that he assigned to S. arubae . The major cheliped, which was missing in the holotype, differs from that of S. camaroncito sp. nov. in the higher number of teeth on the finger cutting edges (7–8 in S. camaroncito sp. nov. vs. 14–15 in S. arubae ). However, the third pereiopod of Holthuis’ S. arubae differs from that of Schmitt’s S. arubae in two important details. The third pereiopod illustrated by Holthuis is generally slender, with a fairly narrow and long dactylus (~0.4 propodus length), and with a small spine on the ischium ( Holthuis 1990: fig. 1d). The third pereiopod figured by Schmitt is generally stouter, with a stout, short dactylus (~0.3 propodus length), and without spine on the ischium ( Schmitt 1936: fig. 2e). These differences raise questions about the correctness of either Schmitt’s drawings or Holthuis’s identification. Both Schmitt’s and Holthuis’ specimens of S. arubae should be re-examined and refigured more completely. Noteworthy, the third pereiopod of S. camaroncito sp. nov. ( Fig. 5g View FIGURE 5 ) is similar to the one illustrated by Holthuis (1990) for the Curaçao specimens of S. arubae .
The remaining western Atlantic species of the S. serratidigitus group, viz. S. teres from Ascension Island and the eastern Caribbean Sea ( Guadeloupe), S. setosus from Ascension Island and NE Brazil (Atol das Rocas), and S. rocas from NE Brazil (Atol das Rocas), appear to be more distantly related to S. camaroncito sp. nov. All three species differ from S. camaroncito sp. nov. by the much more swollen major chela, the absence of a small subapical tooth on the ventral rostral margin (although this character seems to be variable in S. camaroncito sp. nov., see above), and the presence of a deep median notch on the posterior margin of the telson (see Manning & Chace 1990; Anker 2007). In addition, S. rocas differs from the new species by the shape of the frontal margin of the carapace, with stronger orbital teeth, and the absence of a spine on the ischium of the minor cheliped ( Anker 2007), whereas S. setosus is immediately recognisable by the thickened erect setae covering the carapace, abdomen and telson ( Manning & Chace 1990; Anker 2007). None of the currently known Indo-West Pacific species is closely related to S. camaroncito sp. nov.
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