Alpheopsis paratrigona, Anker, 2017

Anker, Arthur, 2017, Strongly carinate species of Alpheopsis Coutière, 1897 of the tropical Atlantic and eastern Pacific, with redescription of A. trigona (Rathbun, 1901) and description of three new species (Malacostraca: Decapoda: Alpheidae), Zootaxa 4277 (2), pp. 199-227 : 207-214

Alpheopsis paratrigona sp. nov.

( Fig. 5–10 )

Alpheopsis trigonus — Chace 1972: 56 (partim, material from Barbuda and Yucatan) [not A. trigona ( Rathbun, 1901) ] Alpheopsis sp. 1— Rodriguez 1986: 121, fig. 29.

Alpheopsis sp. aff. trigonus — Anker 2001: 163.

Type material. Holotype: male (cl 4.5 mm), MZUSP 34222 , Panama, Caribbean coast, Portobelo, Drake, 11–12 m, silt-covered reef, under coral rubble, coll. A. Anker & D. Roche, 21 July 2007 [fcn 07-204].

Additional material examined: 1 male (cl 5.0 mm), USNM 107089 , Bermuda, under rocks along southern shore, coll. B.A. Hazlett & H.E. Winn, 11 August 1960 ; 1 male (cl 4.0 mm), USNM 135846 , Antigua & Barbuda, Barbuda Island, west and south of Spanish Point , Smithsonian-Bredin Caribbean Expedition sta. 112A-58, from coral, 28 April 1958 ; 1 male (cl 3.1 mm), USNM 1292510 , Belize, Carrie Bow Cay, 16°48’8.5”N 88°04’54.3”W, reef flat with Porites , from broken-up conchs, coll. D.L. Felder et al., 23 February 2009 ; 1 ovig. female (cl 5.5 mm), USNM 1171216 , Belize, Carrie Bow Cay , 16°48’N 88°05’W, depth: 2 m, coll. K. Ruetzler, 2 May 1976 ; 1 male (cl 3.6 mm), OUMNH.ZC. 2009.01.0 0 68, Belize, Carrie Bow Cay, 16°48.138’N 88°04.842’W, outer reef, intertidal coral rubble, coll. D.L. Felder et al., 22 February 2009 ; 1 male (cl 5.4 mm, missing both chelipeds), OUMNH.ZC. 2009.01.0 0 63, Belize, Carrie Bow Cay , northeastern shore, coral rubble, depth: 0.5–1 m, coll. D.L. Felder et al., 20 February 2009 ; 1 male (cl 4.5 mm), 1 female (cl 4.4 mm), ULLZ 8939 , Belize, Carrie Bow Cay, back reef, sand flat with sea grass, depth: less than 2 m, in dead conch shell, coll. D.L. Felder et al., 4 April 2007 ; 1 male (cl 4.0 mm, missing both chelipeds), Mexico, Quintana Roo, Bahía del Espíritu Santo, Smithsonian-Bredin Caribbean Expedition sta. 41-60, west side of reef, east of anchorage, depth: 1–3 m, 6 April 1960 ; 1 male (cl 6.0 mm), 1 female (cl 6.2 mm), USNM 134762 , US Virgin Islands, St. John Island, Lameshur Bay , canyon base, depth: 20 m, scuba diving, from empty conch shell, coll. C. Mahnken 24 March 1969 ; 1 male (cl 3.5 mm), 1 ovig. female (cl 4.4 mm), USNM 134763, same collection data; 2 males (cl 3.5, 5.1 mm), 1 female (cl 3.3 mm), MNHN-2014- IU-19473, French Antilles, Guadeloupe, Grand Cul de Sac, coll. F. Fasquel, 2000 ; 1 female (cl 4.4 mm), MNHN- IU-2013-12143, French Antilles, KARUBENTHOS 2012, sta. GD20, Baie de Baille-Argent , 16°15.54’N 61°48.71’W, 35 m, coll. MNHN team, 12.v.2012 ; 1 male (cl 3.5 mm), MNHN-IU-2013-12150, same collection data; 1 male (cl 2.9 mm, missing both chelipeds), MZUSP 18179 , Brazil, continental shelf off southern Paraíba, REVIZEE—Score NE II, sta. 32-2, sand-mud, 31 January 1997 (tentative identification, see below).

Description. Medium-sized species of Alpheopsis (present material: maximum cl 6.2 mm). Carapace with one strong MDC extending from rostral tip to almost posterior margin of carapace; each side of carapace with one strong ASC running in parallel and lateral to MDC, starting at almost frontal margin of carapace and abruptly ending at about 0.7 length of carapace, sometimes forming short high crest above eye; one strong PSC running in parallel and lateral to MDC, starting posterior and sometimes slightly ventral to ASC, not extending ventrolaterally at anterior end; one very low, short, sometimes barely noticeable or obsolete VLC, running slightly obliquely from postorbital-hepatic area to about 0.4 carapace length; and one strong ABC running along and somewhat above branchiostegial margin to about 0.1–0.2 carapace length, with stout subacute tooth at anterior end, latter protruding well beyond anterolateral margin, occasionally ABC reduced to short ridge posterior to strong anterior tooth ( Figs. 5 a–d; 7a–d, m–o; 8a–c, o, p).

Rostrum well developed, about 1.3–1.6 times as long as wide at base, with strong carina, subacute distally, tip reaching or slightly overreaching distal margin of first article of antennular peduncle, reaching at most to 0.3 length of second article ( Figs. 5 c, d, 7c, d, n, o; 8b, c, o). Orbital hoods with distinct orbital teeth, latter ranging from broadly subtriangular and obtuse lobes to triangular and strongly projecting, distally acute teeth; tips of orbital teeth reaching to level just beyond rostral base to about 0.3 of rostral length ( Figs. 5 c, d, 7c, d, n, o; 8b, c, o). Pterygostomial angle below strong ABC tooth broadly rounded ( Figs. 5 a, c; 7c, n; 8a, c, p).

First and second pleomeres with well-marked, high MDC-PL1 and low MDC-PL2, continuing MDC of carapace; third to sixth pleomeres unarmed dorsally; all pleura rounded ventrally; fifth pleuron with posteroventral angle rounded; sixth somite with bluntly projecting posterior lobe and well-delimited, triangular, articulated plate ( Figs. 5 a, b, e; 7a, b). Telson moderately broad, tapering distally, about 2.3–2.5 as long as anterior width; dorsal surface with shallow median longitudinal depression and two pairs of stout spiniform setae inserted far from lateral margin, at about 0.5 and 0.75 telson length, respectively; posterior margin slightly less than half as long as anterior margin, broadly rounded; each posterolateral angle with one pair of stout spiniform setae, mesial much longer than lateral ( Fig. 5 f; 8d, e).

Eyes completely concealed by orbital hoods, not visible in dorsal and lateral views; eyestalk with wellpigmented cornea ( Fig. 5 c, d). Epistomial sclerite each with strong sharp process.

Antennular peduncles stout; stylocerite strong, with sharp tip, latter overreaching distal margin of second article; ventromesial carina with anteriorly directed, acute tooth; second article 1.2–1.3 times as long as wide; lateral flagellum biramous; fused portion short, with three or so joints; accessory ramus long, with several groups of long aesthetascs ( Figs. 5 c, d, g; 7c, d, n, o; 8b, c, o, p). Antenna with basicerite ending in sharp tooth distoventrally; scaphocerite ovate, with anteriorly rounded blade and sharp distolateral tooth, latter not reaching beyond anterior margin of blade; anterior margin of scaphocerite not exceeding distal margin of antennular peduncles; carpocerite reaching or slightly overreaching end of scaphocerite ( Figs. 5 c, d; 7c, d, n, o; 8b, c, o, p).

Mouthparts typical for genus in external view. Third maxilliped slender, pediform; coxa with distally subacute lateral plate above mastigobranch; penultimate article about 2.5 times as long as wide proximally; ultimate article tapering to slender corneous tip, with one stiff subdistal spiniform seta mesiodorsally; arthrobranch well developed ( Figs. 5 h, i; 8f).

Chelipeds subequal or somewhat unequal in size, subsymmetrical or slightly asymmetrical in shape and armature on finger cutting edges, carried extended when not in use ( Figs. 6 a–c; 7e–g, k, l; 8g –i, k, l). Ischium stout, short, with stout spiniform seta distodorsally ( Figs. 6 a; 8e). Merus stout, usually somewhat longer as wide in adult males, slenderer, noticeably longer than wide in females, broadening distally, distinctly triangular in cross-section, with three well-defined margins, dorsal margin ending in very conspicuous blunt tooth, proximodorsal margin usually with stout spiniform seta ( Figs. 6 a, b; 7e; 8g). Carpus very stout, short, cup-shaped, widening distally, usually with strong dorsal constriction, ventral margin typically with one stiff seta ( Figs. 6 a–c; 7e, k; 8g). Chela moderately robust, with palm somewhat flattened on mesial surface and fingers about 0.8–0.9 length of palm; dorsomesial-proximal surface of palm without process; cutting edges of fingers unarmed (male minor cheliped, some female chelipeds) or armed with three to five moderately developed, rounded or subtriangular, teeth (male and female major cheliped); fingers somewhat gaping, crossing distally, usually with row of short setae parallel to cutting edge; dactylus of minor cheliped not noticeably flattened; adhesive disks not distinct ( Figs. 6 a–c; 7f, g, k, l; 8g –i, k, l).

Second pereiopod relatively slender; ischium subequal or slightly longer than merus; carpus with five joints; ratio of carpal joints (from proximal to distal) approximately equal to: 3.5: 1: 1: 1: 1.8; chela longer than distal carpal article, with fingers equal to palm in length, simple ( Figs. 6 d; 7h). Third pereiopod moderately slender; ischium with one spiniform setae on ventrolateral surface; merus about 5.5 times as long as wide, unarmed; carpus about 0.5 length of merus, much slenderer, with slender spiniform seta on distoventral margin; propodus with three spiniform setae along ventral margin and pair of distal spiniform setae adjacent to dactylus; dactylus about 0.4–0.5 length of propodus, slender, simple, conical, gradually curving distally ( Figs. 6 e; 7i). Fourth pereiopod very similar to third pereiopod. Fifth pereiopod more slender than third and fourth pereiopods; ischium unarmed on ventrolateral surface; merus about 5.7 times as long as wide, unarmed; carpus about 0.8 length of merus; propodus long, slender, with four or five spiniform setae along ventral margin, one long distal spiniform setae adjacent to dactylus, and several rows of short serrulate setae on distolateral surface; dactylus about 0.4 length of propodus, similar to that of third pereiopod ( Fig. 6 f).

Male second pleopod with appendix masculina exceeding appendix interna; apex with several long stiff setae ( Fig. 5 j). Uropod with lateral lobe of protopod ending in stout sharp tooth; endopod and exopod broadly ovate; exopod with distolateral tooth and adjacent spiniform seta both moderately developed; diaeresis with blunt tooth adjacent to spiniform seta and sinuous mesial portion ( Figs. 5 k, 8n).

Gill-exopod formula as in A. trigona (see above).

Colour pattern. Background semitransparent whitish; carapace covered with bright red chromatophores, except for anterior-most dorsal and posterior-most lateral portions; pleon typically with two broad adjacent transverse bands of red chromatophores running across posterior half of third pleomere and most of fourth pleomere, sometimes with only one band on either third or fourth pleomere; antennular and antennal flagella pale orange; chelipeds hyaline white; walking legs and tail fan whitish ( Figs. 9 , 10 ).

Etymology. The specific name refers to the general resemblance of the new species to A. trigona .

Type locality. Portobelo , Caribbean coast of Panama.

Distribution. Western Atlantic: Bermuda ( Chace 1972, as A. trigonus ; present study); Caribbean Sea: Panama (Portobelo, present study), Mexico (Yucatan, Chace 1972, as A. trigonus ; present study), Venezuela (Los Roques Archipelago, Rodriguez 1982, as Alpheopsis sp. 1), French Antilles ( Guadeloupe, Anker 2001, as A. sp. aff. trigonus ), British Virgin Islands (Guana Island, photographic record, see Fig. 10 ); US Virgin Islands (St. John Island), Barbuda ( Chace 1972, as A. trigonus ), Belize (Carrie Bow Cay) (present study); possibly also Brazil: off Paraíba (see below).

Ecology. Coral reefs and associated shallow flats with abundance of coral rubble, also on rocky-sandy mixed bottoms; in crevices of dead corals, under coral rubble and rocks, in shells of dead queen conchs, Lobatus gigas (L.); shallow subtidal (1–2 m) to at least 12 m ( Rodriguez 1986; present study), possibly in deeper water in Brazil (see below).

Remarks. Alpheopsis paratrigona sp. nov., as its name suggests, is closely related to A. trigona , differing from it by the presence of only one feebly developed carina (presumably VLC) on the carapace (cf. Figs. 5 a–d; 7a– c, m–o) vs. two well developed carinae (DLC and VLC) in A. trigona ( Figs. 2 a–d; 4a, d–g; see also Rathbun 1901: fig. 21); the frontal margin of the carapace with orbital teeth, ranging from distinctly projecting and sharp teeth to rounded or blunt-angular lobes ( Figs. 5 d; 7d, o), vs. without orbital teeth in A. trigona ( Figs. 2 b, d; 4a, e, g; see also Rathbun 1901: fig. 21); the dorsomesial-proximal surface of the cheliped palm unarmed (cf. Fig. 6 a–c; 7e, f; 8g –l) vs. with a strong curved process in A. trigona ( Figs. 3 b, c; 4b, c, h, k); and the fingers of the major cheliped palm moderately gaping and unarmed or armed with three to five rounded-triangular low teeth, all more or less similar in size ( Figs. 6 c; 7f, g; 8h, i; see also Rodríguez 1986: fig. 29e) vs. strongly gaping and armed with three much stouter teeth, especially the distal-most tooth of the pollex ( Fig. 4 h, i). Because of the notable variation in the development of the orbital teeth and VLC and ABC in A. paratrigona sp. nov., the variation in the extension of DLC (including development of PLC) in A. trigona , as well as the likely sympatry of these two taxa over at least part of their distribution ranges, a genetic analysis (e.g. comparison of the COI gene sequences) is desirable to verify the validity of the here-proposed new species.

The colour patterns of A. trigona and A. paratrigona sp. nov. are very similar, although the pleon of the former species appears to have an anterior transverse band across the first pleomere, extending laterally onto the second pleomere ( Soledade et al. 2015: fig. 3A), which is absent in the new species ( Figs. 9 , 10 ). However, since firstly, A. paratrigona sp. nov. displays some variation in the development of the posterior two bands (one vs. more typically two, Figs. 9 , 10 ), and secondly, the specimen of A. trigona in Soledade et al. (2015) was photographed postmortem (which sometimes results in fading or displacement of pigments), the importance of the colour pattern in the separation of the two species remains to be evaluated.

The Brazilian specimen tentatively identified as A. paratrigona sp. nov. is an incomplete juvenile male lacking most of its pereiopods, including both chelipeds. The orbital margins of this specimen are produced anteriorly into distally acute teeth. The carapace shows no trace of ALC or ABC. On the other hand, MDC is relatively well marked and the carapace also seems to have, albeit poorly developed, a longer ASC and a shorter PSC. Based on these features, this specimen is identifiable as A. paratrigona sp. nov., however, collection of more complete and/ or adult specimens from Brazil is necessary to confirm its presence in the southwestern Atlantic.

Figures

FIGURE 2. Alpheopsis trigona (Rathbun, 1901), female (cl 5.5 mm) from Fort Pierce, Florida, USA (MZUSP 34221): acarapace and anterior pleon, lateral; b—same, dorsal; c—anterior region of carapace and frontal appendages, lateral; d—same, dorsal; e—posterior pleon, lateral; f—telson, dorsal; g—ventromesial tooth on first article of antennular peduncle, lateral; hthird maxilliped, lateral; i—same, tip of ultimate article, mesial; j—uropod, dorsal.

FIGURE 3. Alpheopsis trigona (Rathbun, 1901), female (cl 5.5 mm) from Fort Pierce, Florida, USA (MZUSP 34221): aright cheliped, lateral; b—same, mesial (proximal articles detached); c—same, chela, mesial; d—same, chela fingers, lateral; e—second pereiopod, lateral; f—third pereiopod, lateral; g—same, distal propodus and dactylus, lateral; h—fifth pereiopod, lateral.

FIGURE 4. Alpheopsis trigona (Rathbun, 1901), female holotype (cl 5.5 mm) from off Vieques Island, Puerto Rico (USNM 23785) [a – c]; male (cl 5.4 mm) from Peter Island, US Virgin Islands (USNM 135844); a—carapace, lateral; b—left cheliped, mesial; c—same, dorsolateral; d—carapace and anterior pleon, lateral; e—same, dorsal; f—anterior region of carapace and frontal appendages, lateral; g—same, dorsal; h—right (major) cheliped, mesial; i—same, carpus and chela, lateral; j—left (minor) cheliped, mesial; k—same, lateral; l—second pereiopod, lateral; m—third pereiopod, lateral. Modified from Anker (2001).

FIGURE 5. Alpheopsis paratrigona sp. nov., male holotype (cl 4.5 mm) from Portobelo, Caribbean coast of Panama (MZUSP 34222): a—carapace and anterior pleon, lateral; b—same, dorsal; c—anterior region of carapace and frontal appendages, lateral; d—same, dorsal; e—posterior pleon, lateral; f—telson, dorsal; g—ventromesial tooth on first article of antennular peduncle, lateral; h—third maxilliped, lateral; i—same, tip of ultimate article, mesial; j—second pleopod, lateral; k—uropod, dorsal.

FIGURE 6. Alpheopsis paratrigona sp. nov., male holotype (cl 4.5 mm) from Portobelo, Caribbean coast of Panama (MZUSP 34222): a—left cheliped, lateral; b—same, mesial; c—same, chela, lateral; d—second pereiopod, lateral; e—third pereiopod, lateral; f—fifth pereiopod, lateral.

FIGURE 7. Alpheopsis paratrigona sp. nov., male (cl 4.0 mm) from Barbuda, Antigua & Barbuda (USNM 135846) [a – i]; ovig. female (cl 4.4 mm) from St. John Island, US Virgin Islands (USNM 134763) [j – l]; male (cl 5.0 mm) from Bermuda (USNM 107089) [m – o]; a—carapace and anterior pleon, lateral; b—same, dorsal; c—anterior region of carapace and frontal appendages, lateral; d—same, dorsal; e—left cheliped, mesial; f—same, chela, mesial; g—same, chela fingers (open), lateral; h—second pereiopod, lateral; i—third pereiopod, lateral; j—anterior region of carapace, lateral; k—left cheliped, mesial; lsame, lateral; m—carapace and anterior pleon, lateral; n—anterior region of carapace and frontal appendages, lateral; o—same, dorsal. Modified from Anker (2001), except for j, k, l (drawings prepared, but not used in Anker 2001).

FIGURE 8. Alpheopsis paratrigona sp. nov., male (cl 5.1 mm) [a – n] and female (cl 3.3 mm) [o, p] from Guadeloupe, French Antilles (MNHN- 2014 - IU- 19473); a—carapace, lateral; b—anterior region of carapace and frontal appendages, dorsal; csame, lateral; d—telson, dorsal; e—same, detail of posterolateral spiniform setae, dorsal; f—third maxilliped, lateral; g—left (major) cheliped, lateral; h—same, chela, mesial; i—same, chela fingers, lateral; j—right (minor) cheliped, mesial; k, same, chela, mesial; l—same, mesial; m—third pereiopod, lateral; n—uropod, dorsal; o—anterior region of carapace and frontal appendages, dorsal; p—same, lateral. Drawings prepared, but not used in Anker (2001); (e) drawn without scale.

FIGURE 9. Alpheopsis paratrigona sp. nov., male holotype (cl 4.5 mm) from Portobelo, Caribbean coast of Panama (MZUSP 34222) [a]; male (cl 4.5 mm) from Carrie Bow Cay, Belize (ULLZ 8939) [b]. Photographs: A. Anker (a) and Darryl L. Felder (b).

FIGURE 10. Alpheopsis paratrigona sp. nov., male (cl not measured) from Guana Island, British Virgin Islands, in dorsal [a] and lateral [b] views (specimen possibly deposited in the Natural History Museum of Los Angeles Country, LACM, not available for study). Photographs: Todd Zimmerman (a, b).