Pusillopagurus polulus, Lemaitre & Felder & Poupin, 2017

Lemaitre, Rafael, Felder, Darryl L. & Poupin, Joseph, 2017, Discovery of a new micro-pagurid fauna (Crustacea: Decapoda: Paguridae) in the Lesser Antilles, Caribbean Sea, Zoosystema 39 (2), pp. 151-195 : 187-190

Pusillopagurus polulus n. sp.

( Figs 25-28 ; Table 1)

TYPE MATERIAL. — Holotype. ovig ♀ 0.9 mm, Curaçao, ARMS 16 , 91 m, 15.IX.2015, BCURA 0779 , USNM 1297496 .

Paratypes. Curaçao: 1 ♀ (incomplete) 0.7 mm, ARMS 13, 115.8 m, 15.IX.2015, BCURA 0632 , USNM 1291925 ; 1 ♂ 0.7 mm, ARMS 20 , 15.2 m, 15.IX.2015, BCURA 1278 , USNM 1291924 ; 1 ovig ♀ 0.7 mm, ARMS 23 , 91 m, 15.IX.2015, BCURA 1556 , USNM 1291923 .

ETYMOLOGY. — The specific name is from the Latin polulus , meaning small, and refers to the very small size of individuals of this new species.

DISTRIBUTION. — Known exclusively from Curaçao, where it has been found so far only on ARMS. Depth 15.2-115.8 m.

HABITAT. — Found in gastropod shells, and living in ARMS.

DESCRIPTION

Shield ( Fig. 25A )

Subtriangular, glabrous except for scattered short setae, about as long as broad; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; posterior margin roundly truncate. Rostrum bluntly and broadly subtriangular, reaching to about same level of lateral projections. Lateral projections subtriangular, each terminating in sharp spine.

Ocular peduncles

About 0.8 length of shield, mostly glabrous or scattered short setae; corneas weakly dilated. Ocular acicles subtriangular, dorsal surface flat; terminating in bifid spine.

Antennular peduncles

Long, exceeding distal margins of cornea when fully extended by about 0.5 to 0.7 length of ultimate segment. Ultimate, penultimate and basal segments naked except for long dorsodistal seta on ultimate segment; basal segment with blunt ventromesial angle, and small spine on lateral face.

Antennal peduncles

Not exceeding distal margins of corneas when fully extended. Fifth and fourth segments unarmed except for scattered short setae. Third segment with spine on ventrodistal angle. Second segment with dorsolateral distal angle produced into spine-like process reaching slightly beyond distal margin of third segment; dorsomesial distal angle with small spine. First segment unarmed. Antennal acicles each reaching at most to about midlevel of cornea, broadly curving outward and terminating in strong spine, mesial margin with few distal setae. Flagella long, slightly exceeding tip of chelipeds, with few short setae <1 flagellar article in length.

Mouthparts

Not dissected.Third maxilliped ischium ( Fig. 25B ) with crista dentata consisting of slightly projecting edge medially having three small teeth, no accessory tooth.

Right cheliped ( Fig. 26A, B )

Chelipeds relatively slender, subequal in length, right not much larger. Right cheliped with moderate number of short setae or bristles. Chela elongate, ovate; fingers each terminating in sharp corneous claw overlapping when closed. Dactyl 0.7 as long as palm, lacking armature; cutting edge with two large calcareous teeth on proximal half, and uneven ridge distally; mesial margin rounded; ventral face convex, smooth. Fixed finger similar to dactyl except for cutting edge consisting of several unequal large teeth proximally, and ridge with smaller teeth distally; dorsolateral margin weakly defined; ventral face convex, smooth. Palm long, about 1.5 times as long as broad, dorsal surface convex, with dorsomesial row of sharp, slen- der spines; lateral face rounded; mesial face rounded; ventral surface convex, smooth. Carpus about 1.8 times as long as broad, shorter than merus in length; dorsal surface convex, with dorsomesial row of two or three small sharp spines; lateral face rounded, mesial face flat, nearly vertical; ventral surface smooth. Merus subtriangular in cross-section; ventral face smooth, ventrolateral and ventromesial margins with distal row of two or three small spines. Ischium glabrous. Coxa with row of setae on ventromesial distal angle.

Left cheliped ( Fig. 26C, D )

With moderate number of short setae or bristles. Chela elongate; fingers each terminating in sharp corneous claw slightly overlapping when closed, cutting edge of dactyl consisting of row of fused minute corneous teeth, cutting edge of fixed finger with minute calcareous teeth interspersed with fused corneous teeth. Dactyl about 1.1 times as long as palm; dorsal, mesial and ventral surfaces rounded. Palm unarmed except for dorsolateral row of small, sharp spines, mesial face rounded; ventral surface convex, smooth. Carpus about as long as merus; dorsal surface convex, with 2 or 3 minute spine or tubercles dorsomesially on distal half, and few long bristles on dorsomesial face; dorsodistal margin with 2 small spines; ventral surface convex, smooth. Merus subtriangular in cross-section; ventrolateral and ventromesial margins each with row of sharp spines. Ischium glabrous. Coxa with row of setae on ventromesial distal angle.

Ambulatory legs ( Fig. 27 A-D)

Exceeding tip of chelipeds when fully extended by 0.3 length of dactyls, sparsely setose.Dactyl broadly curved, about 1.6 longer than propodus, terminating in sharp, slender corneous claw; ventromesial margin unarmed or with obscure row of 2-7 very slender spinules. Propodus nearly straight; with few setae on dorsal and ventral margins, lateral and mesial faces glabrous. Carpus with small spine on dorsodistal angle, and few setae on dorsal margin. Merus somewhat laterally compressed, lateral and mesial faces glabrous, dorsal margin naked or with few setae; ventral margin with few long setae. Ischium unarmed. Anterior lobe of sternite XI (of pereopods 3; Fig. 25C ) subrectangular or bilobed, distal margin with small blunt spines and fringe of setae.

Fourth pereopods ( Fig. 27E )

Semichelate. Dactyl weakly curved, terminating in corneous claw, lacking preungual process; propodal rasp with single row of ovate corneous scales. Carpus unarmed except for few short setae dorsally. Merus unarmed except for with dorsodistal tuft of long setae.

Fifth pereopods

Chelate. Propodal rasp extending on dorsal surface for about 0.5 length of propodus.

Uropods and telson ( Fig. 25D )

Uropods markedly asymmetrical, left largest. Telson weakly asymmetrical, about 1.5 longer than broad; posterior lobes with distinct, thin, chitinous lateral margins, separated by broad, deep, U-shaped median cleft, terminal margins weakly oblique, setose, each armed with 2often bifid spines, and blunt laterodistal angle.

Sexual tubes ( Fig. 25E ) and pleopods

Males with coxae of pereopods symmetrical, right coxa with long, coiled and distally filamentous sexual tube, left coxa with short, slender, membranous sexual tube directed slightly laterally ( Fig. 25E ); with unpaired left pleopods 3-5. Females with paired gonopores; with unpaired left pleopods 2-5; eggs few (8 in single ovigerous female known), large, about 0.6 mm in maximum width.

Genetic data

See Table 1.

Colour ( Fig. 28 )

Shield, cephalic appendages, and chelipeds mostly white, mottled with small brown or orangish parts, cheliped fingers nearly translucid. Ambulatory legs with translucid dactyls, and weak bands of white and maroon on propodi, carpi and meri. REMARKS

Aside from the generic characters, this new species can be characterized by the terminal bifid ocular acicles ( Fig. 25A ); subequal chelipeds ( Fig. 26 A-D) with the right relatively slender and carpus and palm armed with dorsomesial row of sharp spines; ambulatory legs ( Fig. 27 A-D) with dactyls obscurely or armed with very slender spinules on ventromesial margin; anterior lobe of sternite XI (of pereopods 3; Fig. 25C ) bilobed and armed distally with small blunt spines; and telson ( Fig. 25D ) with relatively broad, thin, chitinous lateral margins, and terminal margins divided by broad, deep U-shaped cleft.

Figures

FIG. 25. — Pusillopagurus polulus n. gen., n. sp., Curaçao: A-D, holotype ovig ♀ 0.9 mm, ARMS 16, USNM 1297496; E, paratype ♂ 0.7 mm, ARMS 20, USNM 1291924: A, shield and cephalic appendages, dorsal view; B, ischium of left third maxilliped, internal view; C, sternite XI and coxae of third pereopods, ventral view; D, telson, dorsal view; E, sternite XIII and coxae of fifth pereopods with sexual tubes, ventral view. Scale bars: A-C, E, 0.5 mm; D, 0.1 mm.

FIG. 26. — Pusillopagurus polulus n. gen., n. sp., holotype ovig ♀ 0.9 mm, Curaçao, ARMS 16, USNM 1297496: A, right cheliped, dorsal view; B, same, lateral view; C, left cheliped, dorsal; D, same lateral view. Scale bar: 0.5 mm.

FIG. 27. — Pusillopagurus polulus n. gen., n. sp., holotype ovig ♀ 0.9 mm, Curaçao, ARMS 16, USNM 1297496:A, left pereopod 2, lateral view; B, dactyl of same, mesial view; C, left pereopod 3, lateral view; D, dactyl of same, mesial view; E, propodus and dactyl of left pereopod 4, lateral view. Scale bars: A-D, 0.5 mm; E, 0.1 mm.

FIG. 28. — Pusillopagurus polulus n. gen., n. sp., Curaçao,ovig ♀ (in shell) 0.7 mm, ARMS 23, USNM 1291923: A, dorsal view; B, left lateral view; C, frontal view.