Pagurus abditus, 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 : 182-187

Pagurus abditus n. sp.

( Figs 21-24 ; Table 1)

TYPE MATERIAL. — Holotype. ♀ 0.8 mm, Curaçao, ARMS 16 , 91 m, 15.IX.2015, BCURA 0924 , USNM 1297485 .

Paratypes. Curaçao: 1♂ 0.8 mm, ARMS 13, 115.8 m, 15.IX.2015, BCURA 0605 , USNM 1297441 ( ULLZ 16885 ) ; 1 ♀ 0.7 mm, ARMS 16 , 91 m, 15.IX.2015, BCURA 0780 , USNM 1297489 ; 1 ovig ♀ 0.9 mm, ARMS 31 , 91.4 m, 16.X.2016, BCURA 2555 , USNM 1292078 ; 1 ovig ♀ 0.8 mm, ARMS 33, 225.5 m, 16.X.2016, BCURA 2754 , USNM 1292079 .

ETYMOLOGY. — The specific name is derived from the Latin abditus , meaning hidden, concealed, and refers to the cryptic nature of this new species that contributed to hide its discovery until now.

DISTRIBUTION. — Known so far only from deep reefs in Curaçao, where it has been found living in ARMS. Depth: 91-115.8 m.

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

DESCRIPTION

Gills and shield ( Fig. 21A )

Eight pairs of biserial phyllobranch gills (no pleurobranch on thoracomere above pereopod 4). Shield glabrous, about as long as broad; anterior margin between rostrum and lateral projections weakly concave; anterolateral margins sloping; posterior margin roundly truncate. Rostrum broadly triangular or nearly obsolete, reaching distally to about same level of lateral projections. Lateral projections subtriangular, terminating in small sharp spine.

Ocular peduncles

Relatively long, about 0.8 length of shield; dorsal surfaces naked or with scattered short setae; corneas weakly dilated. Ocular acicles subtriangular, terminating in strong, simple spine.

Antennular peduncles

At most slightly exceeding distal margins of cornea when fully extended. Segments naked or with scattered short setae; basal segment with blunt ventromesial distal angle, and small spine on lateral face.

Antennal peduncles

Not exceeding distal margins of corneas when fully extended, reaching to about proximal margins of cornea. 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; dorsomesial distal angle with small spine. First segment with small lateral spine. Antennal acicles not reaching proximal margins of corneas, broadly curving outward, terminating in strong spine, mesial margin with few setae distally. Flagellum short, not exceeding extended right cheliped, with setae 1 to 2 flagellar articles in length.

Mouthparts

Not dissected. Third maxilliped ischium with crista dentata consisting of about 15 small, subequal teeth, and strong accessory tooth.

Right cheliped ( Fig. 22A, B )

Chelipeds unequal in strength, short and stout, right distinctly stronger than left, with sparse setae. Right cheliped ( Fig. 22A, B ) with chela about 1.3 times as long as broad, dactyl and fixed finger each terminating in small, inwardly curved corneous claw slightly overlapping when closed; chela ventral surface glabrous. Dactyl about as long as palm, dorsally with short median row of spines, mesial margin with row of small spines; cutting edge with two or three unequal, rounded calcareous teeth, and row of fused small teeth distally. Fixed finger with short irregular row of small blunt spines dorsally; dorsolateral margin well defined by row of small spines continued for half or more of palm; cutting edge with one large rounded calcareous tooth medially, and row of small corneous teeth distally. Palm approximately as long as carpus, dorsally convex; dorsal surface with irregular short, longitudinal rows of small spines; dorsolateral margin well defined by row of small spines; dorsomesial margin with row of small spines; ventral surface convex, shiny and lacking spines. Carpus dorsal surface weakly convex; dorsodistal margin unarmed; dorsomesial margin with row of five spines; lateral and mesial faces nearly flat, vertical; ventral surface weakly convex. Merus subtriangular in cross-section, dorsodistal margin unarmed except for short setae; ventrolateral margin with row of small spines distally, ventromesial margin unarmed or with one or two small spines. Ischium unarmed. Coxa with row of setae on ventromesial distal angle.

Left cheliped ( Fig. 22C, D )

Relatively strong; carpus and chela about half as wide as same segments of right cheliped, sparsely setose, ventral surfaces glabrous; dactyl and fixed finger each terminating in sharp corneous claw slightly overlapping when closed, cutting edges consisting of fused row of minute teeth. Dactyl about 0.5 as long as palm; dorsal and ventral surfaces rounded, unarmed. Palm dorsal surface with distinctly raised longitudinal median ridge armed with double row of small spines continued on fixed finger; mesial face sloping, unarmed or with few small tubercles; ventral surface unarmed. Carpus slightly longer than merus; dorsodistal margin with two or three small spines medially; with dorsolateral and dorsomesial row of small spines; lateral and mesial faces sloping; ventrolateral margins with small blunt spines distally; ventral surface unarmed. Merus subtriangular in cross-section, unarmed except for row of setae on dorsal margin; ventrolateral margin with row of sharp spines distally. Ischium unarmed. Coxa with row of setae on ventromesial distal angle.

Ambulatory legs ( Fig. 23 A-E)

Sparsely setose, subequal left from right, except for right pereopod 3 with slightly shorter and higher propodus and dactyl, and different spination on ventral margins of dactyl and propodus. Right pereopod 3 with dactyl about 5.3 times longer than high (vs 6.4 in other ambulatory legs), propodus about 2.8 longer than high (vs 4.1 in other ambulatory legs); ventral margin of dactyl and ventrodistal margin of propodus with row of microscopic, short corneous spinules in addition to six long, slender corneous spinules ( Fig. 23B ). Dactyls of other ambulatory legs about 1.1 times as long as propodus, broadly curved, terminating in sharp corneous claw, ventromesial margin with row of usually six corneous spinules. Propodus nearly straight or broadly curved, about 1.2 times as long as carpus, lacking spines except for slender corneous spinule on ventrodistal angle. Carpus with small dorsodistal spine. Merus unarmed or with 1-3 small spines on ventrodistal margin. Ischium unarmed. Anterior lobe of sternite XI (of pereopods 3; Fig. 21B ) subrectangular, naked distally.

Fourth pereopods ( Fig. 21C )

Semichelate. Dactyl nearly straight, slender, terminating in short, inwardly directed corneous claw, lacking preungual process, with distal row of small blunt teeth; 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 dorsally extending for about 0.3 length of propodal surface.

Uropods and telson ( Fig. 21D )

Uropods markedly asymmetrical, left largest, exopods each with row of long setae dorso- and ventrodistally. Telson weakly symmetrical, about as long as broad, with distinct lateral indentations; posterior lobes separated by U-shaped median cleft, terminal margins weakly oblique, each armed with row of 2 small spines in addition to laterodistal spine, latter distinctly stronger and outwardly curved on left lobe.

Gonopores and pleopods ( Fig. 21B )

Males with paired gonopores and no sexual tubes; with unpaired left pleopods 3-5. Females with unpaired left pleopods 2-5 (ovigerous females unknown).

Genetic data

See Table 1.

Colour ( Fig. 24 )

Shield mottled with whitish and orange patches. Ocular peduncles transparent to pale blue translucent with light orange stripes; corneas white. Antennules and antennal peduncles lavender to translucent blue. Chelipeds mostly orange except for whitish distal portions of fingers, dorsomesial margin of right palm, spines on meri, carpi and chelae, and distal portion meri. Ambulatory legs colored on meri and propodi with broad band of light maroon to rust orange proximally and broad band of white distally.

REMARKS

Pagurus abditus n. sp. falls under the current broad definition of Pagurus Fabricius, 1775 , although it does not fit in any of the 11 informal groups defined to accommodate many, but not all, of the species currently assigned to this genus (e.g., McLaughlin 1974; Nucci & Melo 2003; Lemaitre & Cruz Castaño 2004; Olguín & Mantelatto 2013; Komai & Rahayu 2014). In particular, the peculiar morphology of the propodus and dactyl ( Fig. 23B ) of the right pereopod 3 in this new species is unique among western Atlantic congeners, and suggests that P. abditus n. sp. might represent a different clade from those presumably represented by the 11 informal groups of Pagurus . Curiously, P. abditus n. sp. is the second species of Pagurus recently discovered in the southern Caribbean that exhibits a unique, albeit different, morphology of the propodus and dactyl of pereopod 3. The other species, P. scopaopsis Lima & Lemaitre, 2016 , can be distinguished from all other tropical western Atlantic congeners by the presence of dense brush-like setation on the ventromesial margin of the dactyl of left pereopod 3.

Figures

FIG. 21. — Pagurus abditus n. sp., Curaçao:A, C, D, holotype ♀ 0.8 mm,ARMS 16, USNM 1297485;B, paratypes ♂ 0.8 mm, ARMS 13,USNM 1297441; A, shield and cephalic appendages, dorsal view; B, sternites IX-XIII,and coxae of chelipeds and pereopods 2-5, ventral view; C, propodus and dactyl of right pereopod 4, lateral view; D, telson, dorsal view. Scale bars: A-C, 0.25 mm; D, 0.1 mm.

FIG. 22. — Pagurus abditus n. sp., holotype ♀ 0.8 mm, Curaçao,ARMS 16, USNM 1297485:A, B, right cheliped,dorsal view (A), carpus and chela of same,lateral (B); C, D, left cheliped, dorsal (C); lateral (D). Scale bar: 0.25 mm.

FIG. 23. — Pagurus abditus n. sp., holotype ♀ 0.8 mm, Curaçao, ARMS 16, USNM 1297485: A, right pereopod 2, lateral; B, dactyl of right pereopod 3, lateral view; C, right pereopod 3, lateral view; D, left pereopod 2, lateral view; E, left pereopod 3, lateral view. Scale bar: A, C-E, 0.25 mm; B, 0.1 mm.

FIG. 24. — Pagurus abditus n. sp., Curaçao: A, paratype ♂ 0.8 mm (dismembered), ARMS 13, USNM 1297441 (ULLZ 16885), dorsal view; B, paratype ovig ♀ 0.9 mm, ARMS 31, USNM 1292078.