Alpheus gallicus, Scioli & Anker, 2020

Scioli, Justin A. & Anker, Arthur, 2020, Description of Alpheus gallicus, a new deep-water snapping shrimp from Galicia Bank, northeastern Atlantic (Malacostraca, Decapoda, Alpheidae), Zootaxa 4731 (3), pp. 347-358 : 349-355

publication ID	https://doi.org/ 10.11646/zootaxa.4731.3.4
publication LSID	lsid:zoobank.org:pub:61966E54-BC89-4301-A8FA-671FA803597E
DOI	https://doi.org/10.5281/zenodo.3664913
persistent identifier	https://treatment.plazi.org/id/039987FC-9674-4D7B-FF4D-99FEFB0DAE61
treatment provided by	Plazi
scientific name	Alpheus gallicus
status	sp. nov.

Treatment

Alpheus gallicus View in CoL n. sp.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Alpheus cf. macrocheles — Cartes et al. 2014: 168 View in CoL ( Table 1 View TABLE 1 ) [not Alpheus macrocheles ( Hailstone, 1835) View in CoL ].

(?) Alpheus View in CoL macrocheles— García Raso 1996: 735 [not Alpheus macrocheles ( Hailstone, 1835) View in CoL , see discussion below].

Type material. Holotype: male (cl 11.5 mm), OUMNH. ZC.2017-01-061, Spain, Galicia Bank , expedition INDE- MARES 0711 , sta. V11 , 42º44.209’N 11º46.352’W, depth: 768 m, beam trawl, leg. J.E. Cartes et al., 9 August 2011 GoogleMaps . Paratypes: 1 female (CL 13 mm), OUMNH. ZC.2017-01-062, same collection data as for holotype GoogleMaps ; 1 female (cl 11.25 mm), OUMNH. ZC.2017-01-063, same collection data as for holotype GoogleMaps ; 1 female (cl 11.9 mm), ICM 002618 View Materials , same collection data as for holotype GoogleMaps ; 1 male (cl 9.6 mm), ICM 002619 View Materials , Spain, Galicia Bank , expedition INDE- MARES 0711 , sta. GOC3, 42º38.972’N 11º49.092’W, depth: 785 m, otter trawl / 2-doors trawl, leg. J.E. Cartes et al., 30 July 2011 GoogleMaps .

Diagnosis. Species of Alpheus macrocheles species group. Frontal margin of carapace with well-developed rostrum and orbital teeth; rostrum distally acute, about 1.3 times as long as wide at base, tip not reaching halflength of first article of antennular peduncle; orbital teeth narrow and acute; stylocerite of antennule not reaching distal margin of first article or antennular peduncle; second antennular article slender, four times as long as wide; scaphocerite with shallowly concave lateral margin, stout distolateral tooth, reaching far beyond distal margin of narrow blade; third maxilliped not especially modified; major cheliped much larger and stouter than minor cheliped; major cheliped ischium with small spiniform seta on ventromesial margin; major cheliped merus with several small spiniform setae on ventromesial margin and acute distomesial tooth; major chela with distinct inferior plaque and superior crests separated by superior and inferior grooves, as well as with superior and inferior transverse grooves; superior and inferior crests ending distally in acute, anteriorly directed teeth; distal portion of major cheliped pollex twisted laterally, cutting edge bearing small tooth and notch; major chela dactylus twisted laterally, dorsally convex; plunger reduced to small proximal protuberance; minor cheliped ischium bearing small stout spiniform seta on ventral margin; ventromesial margin of minor cheliped merus without spiniform setae, with acute distomesial tooth; minor cheliped dactylus compressed, twisted laterally, with high dorsal crest; length ratio of subdivisions of second pereiopod carpus approximately equal to 9: 5: 3: 3: 4; meri of third and fourth pereiopods without distoventral tooth, ventral margin without spiniform setae; dactyli of third to fifth pereiopods inconspicuously biunguiculate; male second pleopod with appendix masculina slightly overreaching appendix interna; uropod with distolateral spiniform seta flanked laterally by acute tooth, mesially by obtuse projection.

Description. Carapace glabrous, not setose; frontal margin with well-developed rostrum and orbital teeth; rostrum subtriangular, distally acute, about 1.3 times as long as wide at base, without setae, tip not reaching half-length of first article of antennular peduncle; rostral carina not distinct; orbital teeth narrow, distally acute, reaching halflength of rostrum, directed anteriorly and slightly mesially; frontal margin between rostrum and orbital teeth nearly straight at oblique angle; orbital hoods moderately swollen, completely enclosing eyes ( Fig. 1a, b View FIGURE 1 ). Pterygostomial angle rounded, not protruding anteriorly ( Fig. 1b View FIGURE 1 ); cardiac notch deep.

Telson about twice as long as basal width; lateral margin slightly constricted posterior to half-length, tapering distally; dorsal surface smooth, bearing two pairs of stout cuspidate setae; anterior pair inserted slightly anterior to telson mid-length; posterior pair inserted at about 0.7 telson length; posterior margin slightly convex, distolateral angles each bearing one pair of spiniform setae, mesial about four times longer than lateral; margin between spiniform setae without spinules ( Fig. 1c View FIGURE 1 ); anal tubercles well developed.

Antennular peduncle slender; stylocerite well developed, with acute tip, not reaching distal margin of first article of antennular peduncle ( Fig. 1a, b View FIGURE 1 ); ventromesial carina of first article subtriangular, with minute, anteriorly directed tooth ( Fig. 1d View FIGURE 1 ); second article about twice as long as visible portion of first, four times as long as wide; third article shortest, one-fourth length of second ( Fig. 1a, b View FIGURE 1 ); lateral flagellum with aesthetascs starting from about 15 th subdivision. Antenna with basicerite bearing short, acute distoventral tooth; carpocerite slender, about eight times as long as broad, overreaching both antennular peduncle and scaphocerite; scaphocerite with shallowly concave lateral margin; distolateral tooth stout, reaching far beyond distal margin of blade; blade fairly narrow, gradually tapering distally ( Fig. 1a, b View FIGURE 1 ).

Mouthparts typical for genus in external view. Third maxilliped slender, not especially modified; coxa with lateral plate not strongly produced, distal margin sparsely setose; exopod not overreaching penultimate article; antepenultimate article gradually flattening ventrally, ventral margin setose; penultimate article subcylindrical, slightly broadening distally, roughly 4.5 as long as maximal width; ultimate article long, slender, about 11 times as long as maximal width, unarmed distally, with transverse rows of serrulate setae on mesial surface ( Fig. 1e View FIGURE 1 ).

Major cheliped noticeably larger and stouter and somewhat longer than minor cheliped; ischium short, bearing small spiniform seta on ventromesial margin; merus broad, relatively short, subtriangular in cross-section, about 2.5 times as long as maximal width; ventrolateral margin unarmed; ventromesial margin bearing seven or so small spiniform setae and ending in sharp distal tooth; distodorsal margin bluntly protruding; carpus short, cup-shaped; chela somewhat compressed, twisted laterally; plaque crest deviating from dorsal margin in proximal third of chela, continuing as elevation on lateral surface; superior crest lamellar, dorsally rounded, ending distally in acute tooth; inferior crest distinct, ending distally as sharp acute tooth; superior groove deep, proximally extending beyond superior transverse groove; inferior groove originating shallowly near linea impressa, gradually deepening distally; superior transverse groove deep, with overhanging proximal shoulder; inferior depression deep, sharply delimited proximally; pollex short, distal portion twisted laterally, cutting edge bearing small tooth followed by triangular notch; dactylus twisted laterally, dorsally convex, flattened; tip with deep notch bearing tufts of setae; plunger greatly reduced to small proximal protuberance ( Fig. 2 View FIGURE 2 a–d).

Minor cheliped with ischium short, bearing small, stout spiniform seta on ventral margin; merus short, broad, subtriangular in cross-section, about 2.5 times longer than maximal width; ventrolateral margin smooth; ventromesial margin without spiniform setae, with acute distomesial tooth; distodorsal margin not protruding; carpus short, cup-shaped; chela strongly compressed, twisted laterally; crests and grooves on lateral face of chela similar to those of major chela but less distinct; fingers subequal to palm in length; pollex with ventral margin distally curving, cutting edge excavated; dactylus compressed, lamellar, twisted laterally, with high dorsal crest ( Fig. 2e, f View FIGURE 2 ).

Second pereiopod long, slender; ischium slightly longer than merus; carpus with five subdivisions with length ratio approximately equal to 9: 5: 3: 3: 4; chela simple, fingers slightly longer than palm, with distal tufts of setae ( Fig. 3a View FIGURE 3 ).

Third pereiopod long, slender; ischium with one cuspidate seta on ventrolateral surface; merus compressed, about 6.5 times as long as maximal width; ventral margin without spiniform setae and without distal tooth; carpus about half-length of merus, slenderer than latter, distal portion of dorsal margin obtusely projecting; propodus slen- der, subequal in length to carpus, armed with twelve or so slender spiniform setae on ventral margin, in addition to two distoventral spiniform setae flanking base of dactylus; dactylus inconspicuously biunguiculate, with proximal unguis much smaller and shorter than distal one, extensor margin bearing small distal notch ( Fig. 3 View FIGURE 3 b–d). Fourth pereiopod generally similar to third in armature and proportions of articles, somewhat slenderer. Fifth pereiopod slenderest; ischium bearing small cuspidate seta on ventrolateral surface; merus and carpus subequal in length, unarmed; propodus bearing 10 or so spiniform setae on ventral margin and setal brush on distolateral surface; dactylus generally similar to that of third pereiopod ( Fig. 3 View FIGURE 3 e–g).

Second pleopod with lateral margin of protopod unarmed, bearing long, fine setae; in males appendix masculina slightly overreaching appendix interna, but not overreaching distal margin of endopod, with numerous long distal setae ( Fig. 1f View FIGURE 1 ).

Uropod with protopod bearing large acute distolateral tooth; exopod with sinuous transverse suture (diaeresis); distolateral spiniform seta flanked by acute distolateral tooth laterally and broad obtuse projection mesially; endopod bearing row of minute spinules along distal margin ( Fig. 1g View FIGURE 1 ).

Colouration. Body uniformly reddish, with reddish chromatophores distributed throughout the body (carapace, pleon, telson); major and minor chelae orange-reddish; antennules, antennae and walking legs pale orange-reddish ( Fig. 4 View FIGURE 4 ).

Etymology. The new species’ name refers to the type locality, Galicia Bank, situated in the offshore waters of Galicia, an autonomous community of Spain ( gallicus —Latin adjective for Galician, with a masculine ending); used as an adjective.

Ecology. All specimens were trawled at considerable depths ranging from 768 to 785 m (type series), and down to 909 m (other material, see Cartes et al. 2014).

Remarks. The distinct pattern of crests and grooves on the chelipeds clearly place Alpheus gallicus n. sp. within the Alpheus macrocheles species group sensu Coutière (1905). Within this species group, A. gallicus n. sp. is morphologically closest to three deep-water species, viz. A. lentiginosus , A. romensky , and A. platydactylus , but also to the shallow-water A. macrocheles . These five taxa are indeed similar in the shape of the frontal margin of the carapace and also many features of the major and minor chelipeds, as well as the walking legs (third to fifth pereiopods). The most important morphological characters uniting these taxa are: (1) the well-developed rostrum and orbital teeth; (2) the major chela palm with well-developed crests and deep grooves, including a superior transverse groove; (3) the major chela dactylus with a greatly reduced plunger; (4) the major chela pollex not or only feebly reduced; (5) the meri of the third and fourth pereiopods without a sharp distoventral tooth; (6) the second article of the antennular peduncle slender (length to width ratio>3); and (7) the dorsal margin of the cheliped meri without spiniform setae.

Alpheus lentiginosus , presently known only from its type locality in the Gulf of Mexico, can be distinguished from A. gallicus n. sp. by the absence of a notch the extensor margin of the dactyli of the third to fifth pereiopods (present in A. gallicus n. sp.), and by the number of spiniform setae on the ventral margin of the cheliped ischia (three in A. lentiginosus vs. one in A. gallicus n. sp.) (cf. Anker & Nizinski 2011).

Alpheus romensky , was described from a single incomplete specimen collected from the Salas y Gomez Ridge in the Central Pacific. The frontal margin and major cheliped of this species are similar to those of A. gallicus n. sp., but it can be easily distinguished from the new species by the shape of the minor chela dactylus (slender, mesially somewhat concave in A. romensky vs. greatly expanded dorsally, distinctly convex in A. gallicus n. sp.), as well as the development of the superior transverse groove of the major chela (shallow in A. romensky vs. fairly deep in A. gallicus n. sp.) (cf. Burukovsky 1990).

Alpheus platydactylus is a deep-water eastern Atlantic species found at depths between 55 m and 600 m ( Coutière 1897; Crosnier & Forest 1966). Based on both previously published descriptions and the presently examined material (see comparative material), A. platydactylus is distinguishable from A. gallicus n. sp. mainly by the shape and setation of the minor chela. In A. platydactylus , the minor chela dactylus (cf. Crosnier & Forest 1966: fig. 2g) is slender and not expanded dorsally (vs. strongly expanded in A. gallicus n. sp.), and bears dense rows of elongate setae throughout its length (absent in A. gallicus n. sp.).

Alpheus macrocheles is a shallow to moderately deep-water species (typically 0–200 m, but see below) that has been reported from throughout the eastern Atlantic from Great Britain to Gabon, including the Mediterranean Sea, as well as from Ascension Island and St. Helena in the central Atlantic ( Holthuis 1951; Crosnier & Forest 1966; Chace 1966; Manning & Chance 1990, Soledade et al. 2019). Alpheus macrocheles may be distinguished from A. gallicus n. sp. by the shape of the dactyli of the third to fifth pereiopods (simple in A. macrocheles vs. minutely biunguiculate in A. gallicus n. sp.); the shorter and stouter antennular peduncles (length-with ratio of the second article 2.5–3 in A. macrochele s vs. closer to 4 in A. gallicus n. sp.); the length of the stylocerite (reaching or nearly reaching the distal margin of the first antennular article in A. macrocheles vs. not reaching its distal margin in A. gallicus n. sp.); and the number of spiniform setae on the ventral surface of the major cheliped ischium (three in A. macrocheles vs. one in A. gallicus n. sp.). The two species also differ by the colouration of the major chela, with A. macrocheles displaying a transverse, more or less W-shaped blotch on the distomesial face of the palm (cf. Anker & De Grave 2012: fig. 4A, B).

Several other members of the A. macrocheles species group seem to be more distantly related to A. gallicus n. sp. based on their morphological characteristics. Alpheus puapeba Christoffersen, 1979 is a moderately deep-water species (45–175 m) known from Brazil, Uruguay and Argentina ( Christoffersen 1979). It can be distinguished from A. gallicus n. sp. by the shape of the dactyli of the third to fifth pereiopods (simple in A. puapeba vs. minutely biunguiculate in A. gallicus n. sp.); the shape of the minor cheliped dactylus (not expanded in A. puapeba vs. dorsally expanded in A. gallicus n. sp.); and the development of the inferior transverse groove of the major chela (with strongly overhanging shoulder in A. puapeba vs. with very shallowly overhanging shoulder in A. gallicus n. sp.). The members of the Indo-West Pacific A. hailstonei species complex, which includes the non-monophyletic A. hailstonei (Scioli et al., in prep.), A. brachymerus Banner, 1953 and A. lanceostylus Banner, 1959 , can be distinguished from A. gallicus n. sp. by the presence of spiniform setae on the dorsal margin of the cheliped meri (present in most members of this complex, absent in A. gallicus n. sp.), as well as by several features on the minor cheliped, such as the proportions of articles and the general shape of the minor chela (cf. Coutière 1905; Banner 1953, 1959; Banner & Banner 1982).

The poorly known A. candei Guérin-Méneville, 1855 , originally described from Cuba, is a taxonomically highly problematic species that has not been collected since Coutière’s (1910) tentative identification of a single specimen from Dry Tortugas, Florida. Alpheus candei , if confirmed to be valid, can be easily distinguished from A. gallicus n. sp. by multiple characters of the frontal region (shape of the rostrum and orbital teeth, proportions of the antennular articles, much shorter scaphocerite blade, etc.) and minor cheliped (e.g. with the dactylus not expanded in A. candei vs. dorsally expanded in A. gallicus n. sp.). In addition, it appears to be a shallow-water species inhabiting coral reefs.

Genbank Accession No. OUMNH.ZC.2017-01-063: MN754223 View Materials , ICM 002618: MN754224 View Materials .