Alpheopsis gotrina Anker 2017, sp. nov.

Alpheopsis gotrina sp. nov.

(Figs. 11–15)

Type material. Holotype: ovigerous female (cl 7.0 mm), MZUSP 34507, Panama, Pacific coast, Playa Venao (west of Panama Canal), rocky intertidal exposed at low tide, under large rocks on sand, coll. A. Anker & I.N. Marin, 18 April 2007 [fcn 07-107b].

Additional material examined. 1 male (cl 5.2 mm, missing major cheliped), INV CRU 8407, Colombia, Pacific coast, Los Negros Islands near entrance to Bahía Málaga, 03°59’22.7’’N 77°17’46.6’’W, sand and rock bottom, artificial reef substrate, depth: 2 m, coll. J.F. Lazarus et al., 25 April 2009 [fcn COL 00147]; 1 male (cl 4.8 mm), OUMNH.ZC. 2017.01.0 21, Colombia, Pacific coast, Bahía Málaga, Curichichi, 03°59’38.8’’N 77°18’45.1’’W, mud and silt bottom with rocks, artificial reef substrate, depth: 6.5–7 m, coll. J.F. Lazarus et al., 26 April 2009 [fcn COL 00188].

Description. Medium-sized species of Alpheopsis (present material: maximum cl 7.0 mm). Carapace with one strong MDC extending either from rostral tip to almost posterior margin of carapace (non-type specimens), or interrupted by wide gap between approximately 0.2 and 0.4 carapace length, this gap bearing very short low transverse crescent-shaped ridges converging to mid-dorsal line (holotype); each side of carapace with one strong ASC running in parallel and lateral to MDC, starting at frontal margin of carapace and abruptly ending at about 0.7 length of carapace; one PSC running in parallel and lateral to MDC, starting posterior to ASC, with anterior end extending ventrolaterally as fairly well-marked CSR; one DLC running slightly obliquely from postorbital area to about 0.6 carapace length, stopping shortly before CSR; one VLC running ventral and in parallel to DLC, starting well anterior to DLC and either reaching or falling short of carapace mid-length; one PLC ventrolateral to PSC, somewhat oblique, with posterior end adjacent to cardiac notch, sometimes very short (holotype); and one strong ABC running along and somewhat above branchiostegial margin to at most 0.3 carapace length, with stout subacute tooth at anterior end, latter protruding well beyond anterolateral margin (Figs. 11 a–c, e; 13a, b).

Rostrum well developed, up to twice as long as wide at base, with strong dorsal carina conspicuously sloping shortly before reaching acute tip, latter overreaching distal margin of first article of antennular peduncle, sometimes reaching mid-length of second article (Figs. 11 a–e; 13a, b). Orbital hoods protruding anteriorly as broad rounded-angular orbital teeth (Figs. 11 c, e; 13b). Pterygostomial angle below strong tooth of ABC broadly rounded (Figs. 11 a, c; 13a).

First pleomere with strong MDC-PL1 continuing MDC of carapace; second 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. 11 a, f; 13a). Telson moderately broad, tapering distally, about 2.3 as long as anterior width; dorsal surface with median longitudinal depression and two pairs of stout spiniform setae inserted far from lateral margin, at about 0.5 and 0.7 telson length, respectively; posterior margin about half as long as anterior margin, broadly rounded; each posterolateral angle with one pair of stout spiniform setae, mesial much longer than lateral (Figs. 11 g; 13c, note: telson of holotype with posterior margin damaged on right side).

Eyes completely concealed by orbital hoods, not visible in dorsal and lateral view; eyestalk with wellpigmented cornea (Fig. 11 c, e; 13b). Epistomial sclerites each with strong sharp process.

Antennular peduncles stout; stylocerite strong, with sharp tip greatly overreaching distal margin of second article, sometimes reaching almost to end of third article; ventromesial carina with anteriorly directed, acute tooth; second article about 1.2 times as long as wide; lateral flagellum biramous; fused portion short, with three or four joints; accessory ramus well developed, with several groups of long aesthetascs (Figs. 11 c, e, h; 13b). Antenna with basicerite ending in stout sharp tooth distoventrally; scaphocerite ovate, with anteriorly rounded blade and sharp distolateral tooth, latter reaching beyond anterior margin of blade; anterior margin of scaphocerite not or only slightly exceeding distal margin of antennular peduncles; carpocerite reaching to end of scaphocerite (Figs. 11 c, e; 13b, d).

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 several thick subdistal setae; arthrobranch well developed (Fig. 11 i, j).

Chelipeds subequal or slightly unequal in size and asymmetrical in shape and armature on finger cutting edges (at least in adult males), carried extended when not in use (Figs. 12 a–d; 14a–f; 15a, b). Ischium stout, short, with stout spiniform seta distodorsally (Figs. 12 a–c; 14a, b, d). Merus almost as long as wide in males, noticeably longer than wide in females, broadening distally, triangular in cross-section, with three well-defined margins, dorsal margin ending in very conspicuous blunt tooth, proximodorsal margin with stout spiniform seta (Figs. 12 a–c; 14a, b, d). Carpus very stout, short, cup-shaped, widening distally, with deep dorsal constriction, ventral margin without stiff seta (Figs. 12 a–c; 14a, b, d). Male major chela robust, with palm conspicuously flattened on mesial surface and fingers about 0.6 length of palm; dorsomesial-proximal surface of palm with strong, usually somewhat dorsally and/or anteriorly projecting, distally curved process; fingers somewhat gaping, crossing distally; cutting edges of fingers with few strong, rounded or subtriangular teeth, three on dactylus and four on pollex, distal-most teeth very large, especially on pollex; adhesive disks moderately developed (Fig. 14 d–f). Male minor chela with palm flattened on mesial surface and fingers about 0.9 length of palm; dorsomesial-proximal surface of palm with strong, dorsally and/or anteriorly projecting, distally curved process, latter similar to that of major chela; dactylus distinctly flattened and somewhat expanded dorsally; cutting edges of fingers finely and irregularly dentate (Fig. 14 a–c). Female minor chela (or one of chelae) generally similar to male minor chela, less robust, with slenderer fingers; dorsomesial-proximal surface of palm with strongly projecting, distally curved process as in males; cutting edges of fingers armed with small spaced irregular teeth (Fig. 12 a–d).

Second pereiopod moderately slender; ischium shorter than merus; carpus five-jointed; ratio of carpal joints (from proximal to distal) approximately equal to: 3: 1.2: 1: 1: 2; chela longer than distal carpal article, with fingers equal to palm in length, simple (Figs. 12 e; 13e). Third pereiopod moderately slender; ischium with one stout spiniform setae on ventrolateral surface; merus about 4.8–5.1 times as long as wide, unarmed; carpus about half-length of merus, much slenderer, without or with minute 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 length of propodus, slender, simple, conical, gradually curving distally (Figs. 12 f, g; 13f). Fourth pereiopod generally similar to third pereiopod. Fifth pereiopod more slender than third and fourth pereiopods; ischium unarmed on ventrolateral surface; merus about five times as long as wide, unarmed; carpus about 0.7 length of merus; propodus long, slender, with at least four spiniform setae along ventral margin, one long distal spiniform setae adjacent to dactylus, and several rows of serrulate setae on distolateral surface; dactylus about 0.45 length of propodus, similar to that of third pereiopod (Fig. 12 h; 13g).

Male second pleopod with appendix masculina well developed, as long as appendix interna; appendix masculina with several long stiff setae on apex and along margin. Uropod with lateral lobe of protopod ending in long sharp tooth; endopod and exopod broadly ovate; exopod with distolateral tooth and adjacent spiniform seta both strong; diaeresis with distinct subtriangular tooth adjacent to spiniform seta and sinuous mesial portion (Figs. 11 k; 13i).

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

Colour pattern. Background semitransparent whitish or pale yellowish; carapace covered with red chromatophores, except for anterior-most dorsal and posterior-most lateral portions; pleon with two broad adjacent transverse bands of red chromatophores running across posterior half of third pleomere and most of fourth pleomere (red bands either very intense or faded, depending on contraction state of chromatophores and shrimp’s physiological condition); antennular and antennal flagella pale orange; chelipeds hyaline white; walking legs and tail fan whitish (Fig. 15).

Etymology. The new species’ name is an anagram of the specific epithet of its presumed closest relative, A. trigona (see below).

Type locality. Playa Venao, Pacific coast of Panama.

Distribution. Eastern Pacific: Colombia (Bahía Málaga), Panama (Playa Venao), and possibly Costa Rica (photographic record, see below and Fig. 15 c).

Ecology. Rocky-sandy shores; under rocks and rubble; intertidal and shallow subtidal (1–2 m).

Remarks. Alpheopsis gotrina sp. nov. is closely related to the western Atlantic A. trigona and A. paratrigona sp. nov., especially to the former species based on the shared presence of well-developed DLC and VLC and a strong curved proximal process on the cheliped palm, both features being absent in the latter species. On the other hand, A. gotrina sp. nov. shares with A. paratrigona sp. nov. the presence of orbital teeth, which are absent in A. trigona.

The Pacific species can be separated from A. trigona by the presence of blunt-angular orbital teeth (Fig. 11 e; 13b), which are absent in A. trigona (Figs. 2 d; 4g); the absence of MDC-PL2 (Fig. 11 a, b; 13a), which is present albeit relatively low in A. trigona (cf. 2a, b; 4e); and the stronger distolateral tooth of the scaphocerite, usually reaching beyond the anterior margin of the blade (Figs. 11 e; 13b, d) vs. not reaching this margin in A. trigona (Figs. 2 d; 4g). Alpheopsis gotrina sp. nov. may be separated from A. paratrigona sp. nov. using essentially the same criteria as for A. trigona (presence of DLC and VLC on the carapace and proximal process on the cheliped palm, see above), but also by the shape of the rostral carina, i.e. abruptly sloping in A. gotrina sp. nov. (Figs. 11 d; 13a) vs. gently sloping or not sloping in A. paratrigona sp. nov. (Figs. 5 c; 8a, c). In addition, in A. gotrina sp. nov., the ventral surface of the cheliped carpus does not possess a long stiff seta (Figs. 12 a–c; 14a, b, d), which is typically present in both A. trigona and A. paratrigona sp. nov. (cf. Figs. 3 b; 4h; 6a, b; 7e).

The rather obvious and marked differences in the configuration of the carapacial carinae between the holotype from Panama and the two non-type specimens from Colombia (cf. Figs. 11 a, b; 13a) are here tentatively interpreted as intraspecific variation. The extreme condition seen in the holotype could be interpreted as (1) typical development of the carinae in very large specimens or (2) some sort of abnormal development, perhaps due to an early injury or genetic aberration. The Colombian specimens also differ from the holotype by the somewhat shorter scaphocerite and longer rostrum (cf. Figs. 11 e; 13b). Clearly, more material of A. gotrina sp. nov. is needed to clarify these issues.

The Costa Rican record is based on a photograph of a specimen from Isla Tortuga in the Nicoya Gulf (Fig. 15 c). Although the photographed shrimp has been collected and preserved, it was not located in the crustacean collection of the Universidad de Costa Rica, San José (most probably, it was lost during transportation to San José, Ingo S. Wehrtmann, pers. comm.). Although the presence of yet another species in the eastern Pacific cannot be totally excluded, this photographic record is tentatively assigned to A. gotrina sp. nov., awaiting collection of new material along the Pacific coast of Costa Rica.