Pylopaguropsis mollymullerae, Lemaitre, Rafael, 2017

Lemaitre, Rafael, 2017, Discovery of a new species of hermit crab of the genus Pylopaguropsis Alcock, 1905 from the Caribbean: " den commensal " or " cleaner "? (Crustacea, Anomura, Paguridae), ZooKeys 646, pp. 139-158 : 141-149

Pylopaguropsis mollymullerae sp. n. Figs 1, 2, 3, 4, 5, 6, Table 1, Suppl. materials 1, 2, 3 (color photographs, video)

Type material.

Holotype: male 2.4 mm, "Something Special", central W coast of Bonaire, 12°09'46.0"N, 68°17'08.6"W, 11.6 m, 17 December 2015, sand/rubble under coral ledge, night dive, coll. E Muller (USNM 1291987).

Paratypes (all same locality, habitat, and collector, as holotype): 1 male 1.8 mm (USNM 1291989), 1 male 2.2 mm (USNM 1291988), 13.7 m; 1 male 0.9 mm, 1 female 1.5 mm, 27 January 2016 (USNM 1292072); 1 ovigerous female 1.9 mm, 28 January 2016 (USNM 1292073).

Non-type specimens (not collected) photographed in situ.

5 sex undertermined (Fig. 6C, E, and Suppl. material 3), "Something Special", 12°09'46.0"N, 68°17'08.6"W, ~10 m, night dive; 1 ovigerous female, 1 sex undetermined (color photos in Suppl. materials 1-2), "Front Porch", E Muller night dives 4125 095a and 4125 156z2, central W coast of Bonaire, 12°09'55.2"N, 68°17'12.0"W, night dive, 12.2 m, 17 September 2016.

Description.

Shield (Fig. 1A) about as long as broad, weakly convex, well calcified, smooth except for weak depression behind each lateral projection; naked except for few short rows or tufts of fine setae. Rostrum acutely triangular, ending in small, sharp spine, and extending well beyond distal level of lateral projections. Anterior margins between rostrum and lateral projections concave. Lateral projections broadly triangular, ending in small, sharp spine. Anterolateral margins sloping. Accessory portions narrow, well calcified, fused to shield. Branchiostegite membranous; anterior margin rounded, setose.

Ocular peduncles moderately long, about 0.8 as long as shield, slightly inflated basally and tapering to base of corneas, with dorsodistal row of long setae; corneas weakly dilated. Ocular acicles subtriangular, with strong terminal spine; separated basally by less than basal width of one acicle.

Antennules (Fig. 1A) exceeding distal margins of corneas by 0.5-0.6 length of ultimate segment. Ultimate segment with few long dorsodistal setae. Penultimate and basal segments naked or with scattered short setae. Basal segment with laterodistal spine. Ventral flagellum with five or six articles.

Antennal peduncles (Fig. 1A) exceeding distal margins of corneas by 0.2 length of fifth segment. Fifth and fourth segments unarmed except for sparse setae. Third seg ment with strong ventromesial spine. Second segment naked or with scattered short setae; dorsolateral distal angle strongly produced, ending in small spine at tip; dorsomesial distal angle with small spine. First segment with small spine on lateral face distally. Acicle broadly curved outward, slightly exceeding distal margin of cornea, terminating in strong spine; with dorsomesial row of long setae. Flagellum (Fig. 1B) slightly exceeding extended right cheliped, densely setose, with setae>1 - 8 flagellar articles in length.

Mandible (Fig. 2A) with edge of incisor process armed with three blunt calcareous teeth. Maxillule (Fig. 2B) with endopod slender, internal lobe with one long bristle. Maxilla (Fig. 2C) with endopodite slightly exceeding distal end of scaphognathite. First maxilliped (Fig. 2D) with endopodite not exceeding distal endite. Second maxilliped (Fig. 2E) without distinguishing characters. Third maxilliped (Fig. 2F) with merus armed with small blunt, dorsodistal spine; ischium with crista dentata consisting of about 13 small, subequal corneous teeth, two larger basal teeth, and one accessory tooth; basis with two sharp teeth on mesial margin; coxa with small distomesial spine. Sternite IX (of third maxillipeds) with small, sharp spine on each side of midline.

Chelipeds markedly asymmetrical. Right cheliped (Fig. 3A, B, 4 A–E) massive, nearly naked, with chela operculate, ovate; fingers curving ventrally, broad basally and terminating in small, inwardly curved, corneous claw; cutting edges (Fig. Fig. 3B) uneven, minutely and sharply denticulate, fixed finger with large subtriangular tooth medially. Dactyl 0.8 times as long as palm, set very obliquely relative to longitudinal axis of chela; dorsoventrally flattened; dorsal surface weakly convex, unarmed except for scattered short setae; dorsomesial margin sharp, plate-like; ventral surface moderately concave, with longitudinal ridge parallel to mesial margin. Palm and fixed finger weakly convex, nearly naked or with scattered short setae; dorsal surfaces with scattered small, low tubercles on lateral half, smooth except for shallow longitudinal groove on mesial half; lateral margin sharply defined by minute denticles; mesial face strongly produced ventrally, ventromesial margin rounded; ventral surface smooth, deeply excavated, mesial face and lateral margin forming distinct, semi-cylindrical scoop-like surface. Carpus subtrapezoidal, naked; dorsal surface with dorsolateral and dorsomesial ridges marked by minute, sharp spines; lateral face sloping; ventrolateral margin unarmed; mesial face strongly sloping, distomesial margin with row of minute spines; ventral surface convex, smooth. Merus subtriangular, smooth; ventromesial margin minutely spinulose proximally except for row of moderately strong spines distally; ventrolateral margin unarmed. Ischium unarmed except for ventromesial row of setae.

Left cheliped (Fig. 3 C–E) slender, reaching nearly to base of dactyl of right cheliped. Fingers each terminating in short, inwardly curved corneous claw; dactyl shorter than palm, cutting edge with row of closely set, minute corneous spinules, mesial face with few tufts of long setae; fixed finger with tufts of setae on lateral face, cutting edge with row of small, well-spaced calcareous teeth interspersed with fused corneous spinules. Palm smooth, naked except for tufts of long setae mostly on dorsomesial face. Carpus subtriangular; dorsal margin with row of tufts of setae, lacking spines. Merus nearly naked except for scattered tufts of setae; ventrolateral margin with row of few well-spaced spines usually on distal half; ventromesial margin unarmed. Ischium unarmed except for ventromesial row of setae.

Ambulatory legs or pereopods 2 and 3 (Fig. 5 A–F) not significantly different left from right; meri to dactyls with lateral faces evenly convex, with long setae or tufts of setae on dorsal margins. Dactyl nearly straight, about 1.8 times as long as propodi, terminating in sharp corneous claw; dorsomesial margin with row of minute corneous spinules on distal half; ventromesial margin with row of 6-8 corneous spinules. Propodus slightly arched. Carpi each with small dorsodistal spine. Merus unarmed. Ischium with row of setae on ventral margins.

Sternite XII (of pereopod 3; Fig. 1D) with anterior lobe weakly rounded, setose.

Pereopod 4 (Fig. 1C) semichelate. Dactyl subtriangular, terminating in sharp, corneous claw, lacking preungual process; with ventrolateral row of minute, fused corneous teeth. Propodal rasp consisting of one distal row of lanceolate scales.

Pereopod 5 chelate. Propodal rasp occupying nearly half of lateral face of propodus.

Sternite XIV (pereopod 5) subdivided anteriorly into two subrectangular, setose lobes (Fig. 1D).

Uropods strongly asymmetrical. Telson (Fig. 1E) with distinct lateral indentations separating anterior and posterior lobes; posterior lobes subtriangular, nearly symmetrical, separated by deep, narrow median cleft, distal margins armed with row of small, sharp spines and blunt laterodistal angle.

Male with paired gonopores (Fig. 1D), and unpaired left pleopods 2-5. Female with paired pleopods 1 modified as gonopods, and unpaired left pleopods 2-5 (pleopod 5 not ovigerous).

Coloration

(Fig. 6A, B, Suppl. materials 1-3). General background color white with bright red stripes. Shield white with two pairs of oblique red stripes on each side of anterior half. Ocular peduncles white with two red stripes uniting across corneas. Corneas transparent, with black colored core. Antennular peduncle white with red dorsal stripe. Antennal peduncles white with red dorsal and ventral red stripe; antennal acicle white with red dorsal stripe; flagellum light red. Right cheliped with dorsal surfaces of chela, carpus and merus light red, and mesial faces with continuous red stripe; lateral faces of carpus and merus white with continuous red stripe. Left cheliped white with dorsal, lateral, and mesial red stripes. Ambulatory legs or pereopods 2 and 3, with dactyl white with red lateral and mesial stripes; merus to propodus with dorsal, lateral and mesial red stripes; ischium white with red dorsal stripe.

Distribution.

So far known only from the island of Bonaire, Lesser Antilles, southern Caribbean Sea; depth: 11.6-13.7 m.

Etymology.

The name of this new species is given to acknowledge the efforts of the collector, photographer and environmentalist, Ms Ellen Muller, who when informed of the intended honor, preferred that the name of her granddaughter, Ms Molly Muller, be used, in hopes to inspire her to continue the tradition of protecting the amazing and fragile diversity of marine life in Bonaire.

Common name.

"Candy striped hermit crab", in reference to the bright white and red striped color pattern that is similar to that of traditional candy cane.

Affinities.

Pylopaguropsis mollymullerae sp. n. is remarkably similar in morphology to Pylopaguropsis teevana , a species distributed in the tropical eastern Pacific from Colombia to Ecuador, including the Galapagos Islands. There is such minimal differentiation between the two species that they can be considered geminate. They are unique among congeners and even among other Paguridae , in the unusual structure of the right chela, with a ventral surface deeply excavated, forming a semi-cylindrical scoop-like surface (Fig. 4A, D, E). Both species also have antennal flagella with long, dense setae. The condition of the antennal flagella was not mentioned by McLaughlin and Haig (1989) in their redescription of Pylopaguropsis teevana , although in her description Boone (1932: fig. 4, as Galapagurus teevanus ) did illustrate this setal condition, noting that the flagella have "long radiating setae". The only differences detected between these two species are minor, as follows: the antennal acicles slightly exceed the corneas, whereas the acicles do not reach the distal margin of the cornea in Pylopaguropsis teevana ; the dorsal surfaces of the right chela is smooth (dactyl) or with only scattered minute tubercles on the lateral half (palm), whereas the same surfaces have numerous albeit well-spaced small tubercles in Pylopaguropsis teevana ; and the lateral face of the dactyl of right pereopod 3 is evenly convex, whereas the lateral surface is slightly flattened in Pylopaguropsis teevana . Although coloration was only briefly described by McLaughlin and Haig (1989: 159, based on AJ Provenzano, Jr’s color notes) for Pylopaguropsis teevana , it appears that at least the striped pattern of that eastern Pacific species is similar to that of the Caribbean Pylopaguropsis mollymullerae sp. n. In this new species, however, the stripes are bright red over white, whereas in Pylopaguropsis teevana the stripes are brown over light cream.

Given that the dactyls of the left and right pereopods 3 in Pylopaguropsis mollymullerae sp. n. are similar, this new species belongs in the teevana group of species of this genus as defined by McLaughlin and Haig (1989).

Habitat and behavior.

As previously mentioned, Pylopaguropsis mollymullerae sp. n. was first photographed fortuitously, but not collected, while observing the "flaming reef lobster" Enoplometopus antillensis . Five of the six specimens collected of Pylopaguropsis mollymullerae sp. n. were found living in gastropod shells, and obtained during dives in late afternoon or at night inside a crevice under a large coral ledge about 3.6 m wide by 1.5 m high at the site "Something Special" (Fig. 6D). The sixth specimen was collected a short distance north of that ledge, at a slightly shallower depth. Specimens were photographed, but not collected, in a crevice where a large "broad banded moray" Channomuraena vittata , has been known to divers to live for many years (Fig. 6C, E). An "ocellate swimming crab", Achelous sebae (H. Milne Edwards, 1834), was also observed at this crevice (Fig. 6E). It appears that this new species is reclusive, and prefers to hide in the deep, dark recesses of crevices under coral ledges where divers (E Muller, pers. comm.) occasionally have also observed two other species of moray eels, the "spotted moray" Gymnothorax moringa (Cuvier, 1829), and the "green moray" Gymnothorax funebris Ranzani, 1839. After the discovery of specimens of Pylopaguropsis mollymullerae sp. n., additional photographs were taken at the site "Front Porch", and a video at the site "Something Special", in order to document any particular behavior (see Suppl. materials 1-3). Frequently, one or more individuals of this this new hermit crab species were seen in close proximity of a moray eel, and in one instance clearly on its body (Fig. 6E).