Discovery of a new micro-pagurid fauna (Crustacea: Decapoda: Paguridae) in the Lesser Antilles, Caribbean Sea Author Lemaitre, Rafael Author Felder, Darryl L. Author Poupin, Joseph text Zoosystema 2017 2017-06-30 39 2 151 195 http://dx.doi.org/10.5252/z2017n2a1 journal article 10.5252/z2017n2a1 1638-9387 5391902 urn:lsid:zoobank.org:pub:5C83606A-10C1-449A-B5AC-AF88BE563671 Paguruncio parvulus n. sp. ( Figs 18-20 ; Table 1 ) TYPE MATERIAL . — Holotype . ♀ 0.4 mm , Curaçao , ARMS 17, 224 m , BCURA 0952 , USNM 1297508 . Paratypes . Curaçao : 1♂ 0.6 mm (missing left chelipeds, ambulatory legs and pleon), ARMS 23, 91.4 m , BCURA 1557, USNM 1297613. ETYMOLOGY. — The specific name is from the Latin parvulus , meaning small, tiny, and refers to the very small size of individuals of this new species. DISTRIBUTION. — So far known only from Curaçao , where it was collected on ARMS. Depth: 91.4- 224 m . DESCRIPTION Shield ( Fig. 18A ) Weakly subtriangular or nearly ovate, glabrous except for few setae near rostrum, about 1.2 times as long as broad; anterior margin between rostrum and lateral projections weakly concave; anterolateral margins sloping; posterior margin roundly truncate. Rostrum bluntly and broadly subtriangular, reaching slightly beyond level of lateral projections. Lateral projections subtriangular, each terminating in sharp spine. Ocular peduncles About 0.7 length of shield, glabrous; corneas weakly dilated. Ocular acicles subtriangular, dorsal surface flat; terminating in strong spine. Antennular peduncles Exceeding distal margins of cornea when fully extended by about 0.5 length of ultimate segment. Ultimate, penultimate and basal segments naked; basal segment with blunt ventromesial angle, and small spine on lateral face. Antennal peduncles exceeding distal margins of corneas when fully extended by about 0.5 length of fifth segment. Fifth and fourth segments unarmed except for scattered short setae. Third segment with small spine on ventrodistal angle. Second segment with dorsolateral distal angle produced into spine-like process reaching to about distal margin of third segment; dorsomesial distal angle with small spine. First segment unarmed. Antennal acicle not exceeding distal margin of cornea, broadly curving outward and terminating in strong spine, mesial margin with few distal setae. Flagella long, slightly exceeding tip of right cheliped, with few short setae <1 flagellar article in length. Mouthparts Not dissected. Third maxilliped ischium with crista dentata consisting of row of about 12 small teeth, and one accessory tooth. Right cheliped ( Fig. 19A, B ) Chelipeds nearly equal in length, right largest but not massive. Right cheliped with scattered setae. Chela ovate, with dorsal and ventral surfaces smooth, lacking armature. Fingers each terminating in sharp corneous claw slightly overlapping when closed. Dactyl subequal in length to palm, cutting edge with two large calcareous teeth on proximal half, and row of fused small teeth distally; mesial margin rounded or weakly defined; ventral face convex, smooth. Fixed finger similar to dactyl except for cutting edge having one large calcareous tooth; dorsolateral margin defined by weak ridge of minute tubercles continued posteriorly for about 0.7 of palm; ventromesial face convex, smooth. Palm about as long as broad, dorsal surface convex, unarmed except for scattered short setae, and dorsolateral ridge extending from fixed finger; mesial face rounded; ventral surface convex. Carpus about 1.8 times as long as broad, subequal to merus in length; dorsal surface weakly convex or somewhat flattened, unarmed except for row of dorsomesial small blunt or sharp spines; lateral face rounded, mesial face flat, nearly vertical; ventral surface glabrous. Merus subtriangular in cross-section; ventral face smooth, ventrolateral and ventromesial margins with distal row of sharp spines. Ischium glabrous. Coxa with row of setae on ventromesial distal angle. Left cheliped ( Fig. 19C, D ) Elongate, glabrous or at most with scattered short setae; dactyl and fixed finger each terminating in sharp corneous claw, slightly overlapping when closed, cutting edge of dactyl consisting of row of mostly fused minute corneous teeth, cutting edge of fixed finger with minute calcareous teeth interspersed with fused corneous teeth. Dactyl about 1.2 times as long as palm; dorsal, mesial, and ventral surfaces rounded. Palm dorsal surface with weakly raised longitudinal median row of small tubercles or spines; ventral surface convex, smooth. Carpus about as long as merus; dorsal surface somewhat flat, with a few long bristles, dorsodistal margin with two or three small spines; dorsolateral and dorsomesial margins each with row of two or three small spines; ventral surface convex. Merus subtriangular in cross-section; ventrolateral and ventromesial margins each with row of small sharp spines. Ischium glabrous. Coxa with row of setae on ventromesial distal angle. Ambulatory legs ( Fig. 20 A-D) Exceeding tip of chelipeds by about 0.2 length of dactyls when fully extended, sparsely setose. Dactyl broadly curved, about 1.2 times as long as propodus, terminating in sharp corneous claw; with ventromesial row of four or five slender corneous spinules arranged in acute angle to dactyl margin. Propodus nearly straight; with few setae on dorsal and ventral margins, lateral and mesial faces glabrous. Carpus with blunt dorsodistal angle, and few setae on dorsal margin. Merus somewhat laterally compressed, lateral and mesial faces glabrous, dorsal margin with few setae; ventral margin with row of several long, well spaced setae. Ischium unarmed. Anterior lobe of sternite XI (of pereopods 3; Fig. 18B ) subrectangular, with fringe of setae on distal margin. FIG. 18. — Paguruncio parvulus n. gen., n. sp. : A -D , holotype ♀ 0.4 mm, Curaçao, ARMS 17, USNM 1297508; E , paratype ♂ 0.6 mm, ARMS 23, USNM 1297613. A , shield and cephalic appendages, dorsal view; B , sternite XI and coxae of third pereopods, ventral view; C , propodus and dactyl of right pereopod 4, lateral view; D , telson, dorsal view. Scale bar: 0.5 mm. Fourth pereopod 4 ( Fig. 18C ) Semichelate. Dactyl weakly curved, terminating in short, inwardly directed 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 0.7 length of propodus. Uropods and telson ( Fig. 18D ) Uropods markedly asymmetrical, left largest. Telson nearly symmetrical, slightly longer than broad, with distinct lateral indentations; anterior shorter than posterior lobes; posterior lobes with chitinous lateral margins, lobes separated by narrow U-shaped median cleft, terminal margins oblique, each armed with four or five spines, lateral most strongest and somewhat curved ventrolaterally. FIG. 19. — Paguruncio parvulus n. gen., n. sp. , holotype ♀ 0.4 mm, Curaçao, ARMS 17, USNM 1297508: A , right cheliped, dorsal view; B , same, lateral view; C , left cheliped, dorsal view; D , same lateral view. Scale bar: 0.5 mm. Sexual tubes ( Fig. 18E ) and pleopods Males with coxae of pereopods 5 somewhat asymmetrical, right largest, slightly extending posteriorly and each with very short, membranous slender sexual tube directed posteriorly and curving dorsally; pleopod condition unknown (single known male paratype missing pleon). Females with paired gonopores; pleopod condition undetermined except for presence of left pleopod 5 (single known female holotype missing other pleopods). Genetic data See Table 1 . Colour Unknown REMARKS As previously mentioned under the genus Remarks, Paguruncio parvulus n. gen., n. sp. and Paguriscus robustus n. gen., n. sp. have paired subequal sexual tubes and the same total number of gills, but the morphology of the tubes and branchial formulas are markedly different. The sexual tubes in Paguruncio parvulus n. gen., n. sp. consist of slightly expanded coxae each with a short, slender, membranous extension ( Fig. 18E ), whereas in Paguriscus robustus n. gen., n. sp. the coxae are considerably expanded and lack any membranous extensions. In other features, these two species also differ markedly, most notably in the shape and armature of the dactyls of pereopods 2 and 3, as well as the telson shape and armature (compare Figs 16C, F with Figs 18D ; 20B, D ). The gill formula in Paguruncio parvulus n. gen., n. sp. is 0 gill on third maxilliped, one arthrobranch on the cheliped, two arthrobranchs on pereopod 2, two arthrobranchs on pereopod 3, and three gills (one pleurobranch, two arthrobranchs) on pereopod 4; whereas in Paguriscus robustus n. gen., n. sp. there are two arthrobranchs on third maxilliped, cheliped and pereopod 2, and one arthrobranch on each of pereopods 3 and 4.