Anisopagurus asteriscus, Lemaitre, 2020

Lemaitre, Rafael, 2020, New and rare micro-pagurid hermit crabs (Crustacea: Anomura: Paguridae) from the Caribbean Sea and Gulf of Mexico, Zootaxa 4722 (4), pp. 301-325 : 302-308

Anisopagurus asteriscus sp. nov.

( Figs 1–4 )

Type material. Holotype: male 3.7 mm, St. Martin, French Antilles , Caribbean Sea, BSTM-1144, STM-044, 18.118°N, 63.056°W, 1.5–6.1 m, reef at night, 19 Apr 2012, colls G. Paulay, J. Slapcinsky, A. Bemis ( UF 032279).

Paratypes: St. Martin, French Antilles , Caribbean Sea: 1 ov female 1.6 mm, Passe Espagnole, BSTM-0233, STM-011, 18.13°N, 63.005°W, 1.5–6.1 m 10.7–13.7 m, canyon with sponges, 11 Apr 2012, colls G. Paulay, J. Slapcinsky, A. Bemis ( UF 031910); 1 female 1.4 mm, Circus , off Tintamarre Island, BSTM-1140, STM-040, 18.118°N, 63.056°W, 12.2–18.3 m, reef, 19 Apr 2012, colls G. Paulay, J. Slapcinsky, A. Bemis ( UF 032275) .

Guadeloupe: 3 males 0.7–1.0 mm, KARUBENTHOS 2012, Petite Terre, GB 31, 16°09.71’N, 61°07.73’W, 15 m, 26 May 2012, photographed by D.L. Felder (MNHN-IU-2013-5472) .

Bocas del Toro Province, Panama, Caribbean Sea : 1 male 1.8 mm, Punta Puebla, 9.367°N, 82.291°W, BBDT- 0606, BCS2016-012, [no depth], 16 May 2016, colls M. Leray, F. Michonneau, R . Lasley ( UF 044312); 1 male 1.9 mm, same data as previous, BBDT-0607, BCS2016-012; 1 female 2.1 mm, Seagal, 9.289°N, 82.296°W, BBDT- 2888, BCS2016-043, 3–3.5 m, lagoon fringing reef, Agaricia reef framework, 27 May 2016, colls M. Leray, F. Michonneau, R . Lasley ( UF 052159); 1 female 2.1 mm, runway, 9.342°N, 82.260°W, BBDT-2089, BCS2016-034, [no depth], 23 May 2016, colls M. Leray, F. Michonneau, R . Lasley ( UF 044440); 1 male 1.8 mm, 1 female 1.5 mm, Popa Reef, 9.233°N, 82.112°W, BBDT-2423, BCS2016-036, [no depth], 24 May 2016, colls M. Leray, F. Michonneau, R . Lasley ( UF 044486) .

Description. Shield ( Fig. 1A ) subtriangular, terminating in sharp spine, approximately 1.2 times as long as broad; dorsal surface glabrous, lacking linea or groves except for weakly visible short linea-d and grooves separating narrow lateral lobe on each side; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; posterior margin roundly truncate. Rostrum acutely triangular, reaching distally beyond lateral projections. Lateral projections subtriangular, terminating in sharp spine.

Ocular peduncles relatively long, about 0.7 length of shield, weakly diminishing in length distally; dorsal surfaces nearly naked or at most with short setae medially and dorsodistally; corneas weakly dilated. Ocular acicles subtriangular, terminating in 2 or 3 sharp spines.

Antennular peduncles exceeding distal margins of cornea when fully extended by approximately one-third length of ultimate segment. Segments naked or with scattered short setae; basal segment with blunt ventromesial distal angle, and small spine on lateral face.

Antennal peduncles, when fully extended, exceeding distal margins of corneas by approximately half of fifth segment. Fifth segment slender, approximately 6 times as long as wide, unarmed except for scattered short setae. Fourth segment unarmed except for scattered short setae. Third segment with spine on ventrodistal angle. Second segment with dorsolateral distal angle produced into strong spine-like process with short laterodistal setae; dorsomesial distal angle with small spine. First segment with small lateral spine. Antennal acicles not exceeding distal margins of corneas, broadly curving outward, terminating in strong spine, with few tufts of setae on mesial margin and tuft of setae distally. Flagellum long, exceeding extended right cheliped, with few short setae 1 or less flagellar article in length.

Mouthparts not dissected. Third maxilliped ischium with crista dentata consisting of approximately 14 small teeth slightly diminishing in length distally, and accessory tooth.

Chelipeds strongly dissimilar in strength and shape, right distinctly larger and stronger than left. Right cheliped ( Fig. 2 A–C) suboperculate. Chela ovate, approximately 1. 8 times as long as broad; angle of articulation with carpus 90° or larger (viewed laterally); dorsal surface of palm and fingers surrounded by strong, corneous-tipped spines interspersed with long setae and directed nearly vertically forming crown-like shape; dactyl and fixed finger each terminating in inwardly curved blunt calcareous tips overlapping when closed; ventral surface glabrous except for scattered tufts of long setae. Dactyl about as long as palm; dorsal surface with low star-like tubercles bearing short bristle-like setae, and tufts of bristle-like setae near cutting edge and directed toward cutting edge of fixed finger; cutting edge with 8 strong, rounded calcareous teeth slightly diminishing in strength distally. Fixed finger armed on dorsal surface with a few strong spines basally, and tufts of bristle-like setae near cutting edge directed toward cutting edge of dactyl; cutting edge with 7 unequal calcareous teeth, middle tooth distinctly larger than others. Palm slightly longer than broad, with median region moderately elevated, armed with cluster of strong, corneous–tipped spines and surrounded by more or less flat surface covered with numerous low flat-topped, well-spaced star-like tubercles ( Fig. 2A, C ) that extend to fixed finger; proximal dorsal surface strongly sloping towards articulation with carpus. Carpus approximately as long as merus; dorsal surface with scattered tufts of setae and dorsomesial row of 4 corneous-tipped spines; dorsodistal margin with 1 small subdistal spine; ventral surface glabrous except for few tufts of setae; mesial surface nearly vertical, glabrous; lateral surface rounded; ventral surface glabrous, bulging proximally. Merus subtriangular in cross-section, naked or sparsely setose; dorsodistal margin armed with small median spine; ventrodistal margin with row of 4 small spines distally and row of long setae, ventromesial margin unarmed or with 1 small spines and row of long setae. Ischium unarmed. Coxa with row of setae on ventromesial distal angle.

Left cheliped ( Fig. 2E, F ) slender, approximately as long as right cheliped; fingers terminating in inwardly curved corneous tips crossed when closed, ventrodistal surface spoon-like. Dactyl slightly longer than palm, with low setose tubercles on dorsal surface; cutting edge with row of fused minute corneous spinules; lateral margin with long setae; ventral surfaces glabrous. Fixed finger with few tubercles and setae on dorsal surface, and row dorsolateral row of small tubercles on distal three-fourths; cutting edge with row of minute calcareous teeth and row of fused corneous spinules distally. Palm dorsolateral margin with prominent row of strong, corneous-tipped spines directed dorsolaterally with tips slightly curving forward and interspersed with long setae, row of spines continued to basal portion of fixed finger and diminishing slightly in size; dorsal surface with distinct median irregular row of prominent slender corneous-tipped spines; mesial surface rounded, with few low tubercles and scattered setae; ventral surface glabrous except for a scattered tufts of long setae. Carpus approximately as long as merus; dorsal surface with 2 rows of spines, and strong spine on dorsodistal margin; lateral and mesial surfaces glabrous; ventral surface unarmed; ventrodistal margin with small tubercles and 1 small spine laterally. Merus subtriangular in cross-section; dorsal margin with minute tubercles and short setae; lateral and mesial faces glabrous; ventrolateral margin with long setae and row of 4 strong spines, ventromesial margin with row of small tubercles and 1 distal spine. Ischium and coxa unarmed, latter with row of setae on ventromesial margin.

Pereopods 2 and 3 ( Fig. 3 A–D) sparsely setose, subequal left from right. Dactyl approximately as long as propodus, with few setae dorsally and scattered short setae ventrally; ventral margin nearly straight, dorsal margin broadly curved, terminating in sharp corneous claw curving ventrally; ventromesial margin with row of 6 or 7 distinct corneous spinules. Propodus nearly straight, approximately 1.3 times times as long as carpus, with few setae dorsally and well-spaced tufts of short setae ventrally; lacking spines except for 1 or 2 corneous spinules on ventrodistal angle. Carpus with small dorsodistal calcareous spine. Merus unarmed, with few tufts of setae dorsally and ventrally. Ischium unarmed. Anterior lobe of sternite XI (of pereopods 3; Fig. 1B ) subcircular, sparsely setose and armed with 2 small spines distally.

Pereopod 4 ( Fig. 3E, F ) semichelate. Dactyl nearly straight, slender, terminating in short, inwardly directed corneous claw; dorsal margin with long setae distally; ventral margin with short brush-like preungual process ( Fig. 3F ) at base of corneous claw, and row of short close-set corneous teeth. Propodal rasp with 2 or 3 rows of ovate corneous scales. Carpus unarmed except for few setae dorsally. Merus unarmed except for dorsodistal tuft of long setae.

Pereopod 5 chelate. Propodal rasp dorsally extending for about 0.3 length of propodal surface. Coxae of males asymmetrical, left larger than right and with gonopore covered by dense short setae directed mesially; right gonopore also having setae but distinctly shorter and less dense than on right gonopore. Coxa a females symmetrical.

Uropods ( Fig. 1C ) markedly asymmetrical, left largest, exopods each with row of long setae dorsally; ventral margin of left exopod with distinct fringe of long corneous bristles, ventral margin of right exopod naked. Telson ( Fig. 1C ) nearly symmetrical, longer than broad, with distinct lateral indentations; posterior lobes with corneous lateral margins, lobes separated by U-shaped median cleft, terminal margins weakly oblique, each armed with row of 3 small spines in addition to acute laterodistal angle.

Males with paired gonopores, lacking sexual tubes ( Fig. 1B ); with unpaired left biramous pleopods 3–5. Females with paired gonopores; with unpaired left pleopods 2–5 (pleopod 5 non-ovigerous); only available ovigerous female (shield length = 1.6 mm, UF 031910) carrying relatively few (21) large eggs ~0.6. mm in diameter.

Color ( Fig. 4 ). Shield with unevenly light yellow and brown portions. Ocular peduncles whitish with brown stripes dorsolaterally and dorsomesially; corneas white with reddish blotches. Antennular and antennal peduncles semitransparent distally, light brown proximally; antennal flagella dark red with about 8 short white bands. Right cheliped reddish, with chela somewhat faded. Left cheliped brownish, with spines on chela faded red. Pereopods 2 and 3 (ambulatory legs) brownish similar to left cheliped, with short white portions nearer articulations of mericarpi and distal portion of propodi; dactyls faded brownish.

Etymology. The specific name is derived from the Greek asteriskos, meaning small star, and refers to the characteristic minute star-like tubercles that adorn the dorsal surface of the right chela of this new species.

Distribution. Caribbean Sea, known so far from St. Martin, French Antilles, and Bocas del Toro Province, Panama. Depth: 1.5– 18 m.

Remarks. Anisopagurus asteriscus sp. nov. and A. pygmaeus are the only species of Anisopagurus having multispinose ocular acicles and a fringe of long bristle-like setae on the posterior margin of the exopod of the left uropod. In other respects, however, these two species differ significantly. In the new species the right chela ( Fig. 2 A–C) is markedly operculate in shape, with the dorsal surface of the palm crowned with strong, corneous-tipped marginal spines directed upwardly, and the surface is covered with numerous well-spaced star-like tubercles; whereas in A. pygmaeus , the right chela is not operculate, and is armed dorsally with only simple often strong spines. Furthermore, males of the new species have asymmetrical coxae, the left being larger and with a gonopore covered by more dense and longer setae directed mesially, whereas the coxae and setation are symmetrical in A. pygmaeus . The presence in males of this new species of asymmetrical coxae of the fifth pereopods might suggest a relationship with another species in the Pylopagurus group of genera, Pylopaguridium markhami McLaughlin & Lemaitre, 2001 . Asymmetrical coxae of the fifth pereopods is considered a generic character of Pylopaguridium . However, A. asteriscus sp. nov. and P. markhami differ in other generic as well as species characters. Particularly distinct in these two species are color differences in pereopods 2 and 3 (ambulatory legs), in the former the segments being brownish with short white portions near the articulations of the meri, carpi and propodi, and light brown dactyls ( Fig. 4 ), whereas in the latter the segments are tricolored orange-white-blue (in two tones) and bicolored orange-white dactyls (see Poupin 2018: 161, fig. 164).

Anisopagurus asteriscus sp. nov. differs most distinctly from the other five species of Anisopagurus by the armature of the chelipeds, in particular the right cheliped. In A. asteriscus sp. nov., the dorsal surface of the right chela bears numerous low star-like tubercles, whereas these type of tubercles are absent in other congeners.

The armature of the dorsal surface of the right chela in A. asteriscus sp. nov. might, at first examination, be confused with that exhibited by Rhodochirus rosaceus (A. Milne-Edwards & Bouvier, 1893) , a species belonging in another of the “ Pylopagurus ” group of genera ( Lemaitre & McLaughlin 2003). In Anisopagurus asteriscus sp. nov., however, the dorsal surface of the right chela is in part covered with numerous flat-topped, well-spaced low star-like tubercles, whereas in species of Rhodochirus the same surface is covered with tightly clustered or even partially fused sharp to blunt tubercles or spines with rosette-like bases ( Fig. 2D ; McLaughlin 1981). Further differentiating these two species is that in Anisopagurus asteriscus sp. nov. the dorsal surface of the left chela bears only spines and lacks any tubercles similar to those on the right chela, whereas in Rhodochirus species, the left chela has a similar rosette-like armature to that of the right chela.

Figures

FIGURE 1. Anisopagurus asteriscus sp. nov., holotype male 3.7 mm, St. Martin, French Antilles, Caribbean Sea (UF 032279): A, shield and cephalic appendages, dorsal; B, sternum and coxae of pereopods 1–5, ventral; C, uropods and telson, dorsal. Scale: 0.5 mm.

FIGURE 2. A–C, E, F, Anisopagurus asteriscus sp. nov., holotype male 3.7 mm, St. Martin, French Antilles, Caribbean Sea (UF 032279); D, Rhodochirus rosaceus (A. Milne-Edwards & Bouvier, 1893), SE Caribbean Sea, R/V Pillsbury, sta P-479, 11°19’42”N, 62°01’12”W, 121–131 m, 3 Aug 1966 (USNM 267504).A, right chela, dorsal; B, right cheliped, lateral; C, portion of dorsal surface of palm showing star-like tubercles; D, portion of dorsal surface of palm showing rosette-like tubercles; E, left cheliped, lateral; F, chela of same dorsomesial. Scales: 0.5 mm.

FIGURE 3. Anisopagurus asteriscus sp. nov., holotype male 3.7 mm, St. Martin, French Antilles, Caribbean Sea (UF 032279): A, right pereopod 2, lateral; B, dactyl of same, mesial; C, right pereopod 3, lateral; D, dactyl of same, mesial; E, propodus and dactyl of pereopod 4, lateral; F, dactyl of same, lateral. Scales: 0.5 mm (A–E), 0.25 mm (F).

FIGURE 4. Anisopagurus asteriscus sp. nov., Bocas del Toro Province, Panama, Caribbean Sea: A, B, female (in shell) 2.1 mm (UF 044440); C, male 1.8 mm, removed from shell (UF 044486); D, same male in shell (UF 044312). Scales: 2.0 mm. (Photographs: G. Paulay).