Dardanus balhibuon, Celia & Machel & Malay & Chan, 2018

Malay, Maria Celia (Machel) D., Rahayu, Dwi Listyo & Chan, Tin-Yam, 2018, Hermit crabs of the genera Calcinus Dana, Clibanarius Dana, and Dardanus Paul’son from the PANGLAO 2004 Expedition, with description of a new species and a checklist of the hermit crabs of the Philippines (Crustacea: Anomura: Paguroidea), Raffles Bulletin of Zoology 66, pp. 23-65 : 44-50

Dardanus balhibuon , new species

( Figs. 4B , 5D , 6–8 )

Material examined. Female, holotype SL 14.3 mm ( NMCR 40109 ), stn R38, Pamilacan I., Bohol Prov., 9°29.4′N, 123°56.0′E, 6–37 m, 11.vi.2004 .

Description. Shield ( Fig. 6A ) 0.9 times longer than wide; anterior margin between rostrum and lateral projections shallowly concave; lateral margins slightly convex, slightly irregular, with dense tufts of long setae. Posterior margin rounded. Dorsal surface of shield somewhat inflated, with tufts of long setae, strongly calcified; Y-shaped line present posteriorly. Rostral lobe weakly produced. Lateral projections large, bluntly triangular, produced. Posterior carapace lateral elements well calcified, unarmed. Branchiostegites unarmed.

Ocular peduncles ( Fig. 6A ) 0.8 times length of shield, subcylindrical, somewhat inflated distally, diameter of corneas slightly less than 0.2 of ocular peduncles length. Ocular acicles ( Fig. 6B ) broad, distal margins each with 3 spines, with fringe of setae along distal margins. Interocular plate ( Fig. 6B ) with pair of protrusions.

Antennular peduncles ( Fig. 6A ) slender, when fully extended, ultimate segments reaching middle of corneas; ultimate and penultimate segments unarmed, basal segment distal margin with fringe of long setae.

Antennal peduncles ( Fig. 6A, C ), when fully extended reaching 0.6 length of ocular peduncles; fifth segment unarmed, with 3–4 scattered setae on dorsal and ventral surfaces; fourth segment with tufts of setae on mesiodistal margin; third segment with tufts of long setae on ventral surface; second segment with dorsolateral distal angle produced, terminating in strong simple or bifid spine, lateral margin unarmed, dorsomesial distal angle unarmed or bearing 1 spine, mesial margin, lateral margin, and dorsolateral distal angle with dense tufts of setae; first segment with ventrolateral distal angle with 2 spines, ventromesial distal angle produced, rounded. Antennal acicle ( Fig. 6C ) terminating in strong bifid spine; dorsomesial margin with 3 spines, dorsolateral margin unarmed or with single small spine. Antennal flagella bearing minute seta on each articulation.

Third maxilliped with well developed crista dentata; basis with 1 or 2 small corneous spines, spines concealed by dense tufts of long setae.

Chelipeds vastly unequal, left larger than right. Left cheliped ( Fig. 7A, B ) very stout, 1.7 times longer than wide. Outer face of palm, dactyl, and fixed finger ( Fig. 7A ) convex; bearing irregular rows of corneous-tipped conical spines; and covered with tufts of mixed short and long setae, setae not arising singly but rather in dense tufts of 3 or more. Dactyl and fixed finger each terminating in strong corneous claw, cutting edges each with 5 (dactyl) or 7 (fixed finger) low, molar-like calcareous teeth. Upper face of palm and dactyl with 2 or 3 irregular rows of corneous-tipped conical spines, spines larger and more hooked in upper proximal angle; lower margin bearing row of conical corneous tipped spines. Inner face of palm, dactyl, and fixed finger ( Fig. 7B ) slightly convex; fixed finger and disto-lateral corner of palm with 3–4 irregular rows of low corneous-tipped spines; inner face with scattered tufts of setae particularly on upper and lower margins. Carpus with upper margin bearing 4 prominent corneous-tipped spines; outer face slightly convex with irregular rows of corneous-tipped spines, lower outer margin with 4 small corneous-tipped spines; inner face with scattered tufts of setae particularly on inner distal margin. Merus with disto-dorsal and disto-ventral margins of lateral face each bearing 4–5 corneous-tipped spines; entire lateral face with tufts of long setae; ventromesial margin crested with 7 calcareous teeth, proximal larger. Ischium with 4 teeth on ventromesial margin.

Right cheliped ( Fig. 7C, D ) more slender than left, 1.7 times longer than wide. Outer face of palm, dactyl, and fixed finger ( Fig. 7C ) bearing irregular rows of corneous-tipped spines, spines absent from lower proximal area of palm; covered with dense tufts of long setae, setae not arising singly, but rather in dense tufts of 3 or more. Dactyl terminating in strong corneous claw; cutting edge with 6 low molar-like calcareous teeth; upper margin with 3 irregular rows of strong corneous-tipped conical spines. Fixed finger terminating in strong corneous claw; cutting edge with 6 low molar-like calcareous teeth; outer, lower, and inner faces with irregular rows of low corneous-tipped spines. Inner face of palm, dactyl, and fixed finger ( Fig. 7D ) slightly convex; fixed finger and disto-lateral corner of palm with low corneoustipped spines; inner face of palm with scattered tufts of long setae. Carpus with upper margin bearing 3 strong corneous-tipped conical spines; outer face with few strong spines; distal margin of outer face with 2 strong corneoustipped corneous spines near midline; outer face covered with tufts of long setae. Merus with distal margin bearing 3 corneous-tipped spines, two of which prominent and located at dorso-distal and ventro-distal angles; upper margin with 1 corneous-tipped spine sub-distally; outer face covered with tufts of long setae; ventromesial margin crested with 3 large calcareous teeth proximally. Ischium with 5 calcareous teeth on ventromesial margin.

Second pereopods ( Fig. 8A ) and right third pereopod generally similar, but setation and armament slightly different between second pair and right third; second pair more slender than right third; of second pair, left slightly shorter than right. Dactyls all 1.3–1.4 length of propodi; each terminating in strong corneous claw; subcylindrical; ventral margins each with 5–10 small corneous spines distally; dactyls otherwise unarmed but densely covered with dense tufts of setae, setae especially dense on dorsal surfaces. Propodi 1.4 length of carpi; lateral faces convex, unarmed, and uniformly covered with dense tufts of setae (second) or setae absent from the lower 0.6 of lateral face (right third); mesial face flattened, smooth, unarmed, with sparse (second) or moderate (right third) tufts of setae. Carpi 0.7–0.8 length of meri; lateral faces flat with tufts of setae on dorsal and ventral margins; dorsal faces flat, covered with tufts of long setae, bearing one prominent corneous-tipped conical spine on the disto-mesial angle and 8–13 small to moderate corneous-tipped spines on distal 0.3. Meri lateral faces flat (second) or slightly convex (right third), with tufts of setae on dorsal and ventral margins; ventrolateral distal angle bearing 1 strong corneous-tipped spine (second) or unarmed (right third); ventral margins crested with row of tubercles bearing dense tufts of long setae and 0–2 calcareous teeth distally. Ischia unarmed.

Left third pereopod ( Fig. 5D ) stout. Dactyl 1.4 length of propodus, terminating in large corneous claw; lateral face flattened and covered with tufts of short and long setae, setae especially dense along dorsal and ventral margins and not arising singly but rather in dense tufts of 3 or more; dorsal and ventral areas of lateral face with 1 (dorsal) or 2–3 (ventral) rows of sharp corneous spines on proximal 0.5; ventral margin with 5 small corneous spines distally; mesial face convex, with tufts of long setae along median line. Propodus ( Fig. 8B ) 1.4 length of carpus, very broad, 2.1 as long as broad; lateral face flattened, with nearly indistinct longitudinal lobe along midline (not visible in figure), covered with tufts of short and long setae, setae especially dense along dorsal and ventral margins; dorsal margin of lateral face with 2 irregular rows of sharp corneous spines; subventral 0.3 of lateral face with irregular rows of sharp corneous spines; distal margin of lateral face with 3 small corneous spines; mesial face convex, smooth, bearing 5 small corneous spines on ventral half of distal margin, with sparse tufts of long setae forming 3 longitudinal rows (2 rows on dorsal half, 1 row subventrally). Carpus 0.8 length of merus; lateral face flat; dorsal margin with row of corneous-tipped spines; dorsolateral angle with several strong corneous-tipped spines covered by dense tufts of long setae; dorsal, distal, and ventral margins covered by dense tufts of setae; mesial face slightly convex, smooth, unarmed, distal margin bearing tufts of long setae. Merus lateral face strongly convex, with tufts of long setae on the dorsal, ventral, and subdistal margins; mesial face flattened with tufts of setae on subdorsal margin; ventral margin crested with row of tubercles bearing dense tufts of long setae and 2 calcareous teeth distally. Ischium unarmed.

Sternite of third pereopods ( Fig. 6D ) with anterior lobe rectangular, with 2 protrusions each bearing tuft of long setae anteriorly.

Fourth pereopods semichelate; dactyls each with 5 corneous ventral spines on lateral face; propodal rasps well developed; carpi each with sharp dorsodistal spine covered by dense tuft of long setae (spine missing/broken in right fourth pereopod).

Fifth pereopods chelate; rasps of dactyl and propodus well developed.

Female pleon with second to fifth left pleopods fringed with long setae; second to fourth triramous; fifth damaged; single, very large, elongate, triangular fleshy membrane fringed with long setae present between fourth and fifth pleopods.

Uropods strongly asymmetrical, left larger than right; endopods and exopods with well developed rasps.

Telson ( Fig. 6E, F ) with lateral constrictions; marginal area partially calcified; posterior lobes separated by median cleft, left much larger than right, each with 7 (left) or 6 (right) ventral corneous spines near terminal margin, terminal margins fringed with long setae; anterior lobes with long setae on lateral margins.

Colour. In life unknown, but the specimen was initially mistakenly identified as D. lagopodes and therefore live colouration must resemble D. lagopodes or the closely related D. sanguinolentus . Colour in preservative ( Fig. 4B ): shield, ocular acicles, and antennae orange with white spots; ocular peduncles pale brown; antennules and antennal flagellae pale yellow; chelipeds and ambulatory legs orange with white spots and mottlings overall; ambulatory legs with a wide deep orange-red ring on the subdistal dorsal face of the propodus; chelipeds and ambulatory legs with bright orange patches on outer faces of carpi and meri.

Habitat. Subtidal, 6–37 m deep, on reef slope.

Etymology. From the Boholano/Cebuano word, “balhibuon”, meaning hairy, referring to the exceptionally setose condition of the species.

Remarks. A single specimen was found that closely resembles D. lagopodes and D. sanguinolentus in morphology and overall colouration after preservation in alcohol, and yet differs in some important respects: this new species is larger (14.3 mm SL) than typical D. lagopodes and D. sanguinolentus , and is exceedingly setose, with numerous (3 or more) long setae arising in tufts from the same spot. The excessively setose condition of the entire body is one of the most distinct features of the new species, a condition which is not mentioned in the original descriptions nor observed in the type specimens of D. lagopodes , D. sanguinolentus , or any of their junior synonyms. Another easy way to see the differences between these three species is from the shape of left third pereopod. In D. lagopodes the lateral face of dactyl and propodus of the left third pereopod is convex or slightly flattened, in D. sanguinolentus those lateral surfaces are flattened with a longitudinal concavity medially, while in D. balhibuon n. sp. they are flattened with indistinct longitudinal lobe along the midline ( Table 2 , Figs. 5 , 8B ; indistinct longitudinal lobe in D. balhibuon not shown in line figures). While it is allied to D. lagopodes and D. sanguinolentus, COI sequence data show that D. balhibuon n. sp. is genetically very distinct from other members of the D. lagopodes complex ( Fig. 9 ). Dardanus balhibuon is presently only known from Pamilacan Island, the Philippines.

Figures

Fig. 4. A, Dardanus sanguinolentus (Quoy & Gaimard, 1824). Female ovig. SL 6.3 mm, stn R6; B, Dardanus balhibuon, n. sp. Holotype female SL 14.3 mm, stn R38, NMCR 40109, preserved colouration; C, Dardanus megistos (Herbst, 1804). Male SL 11.0 mm, stn M8; D, Dardanus pedunculatus (Herbst, 1804). Male SL 13.4 mm, stn N3; E, Dardanus scutellatus. Male SL 9.8 mm, stn D12; F, Dardanus woodmasoni (Alcock, 1905). Male SL 5.8 mm, stn R76.

Fig. 5. Lateral view of left third pereopod. A, Dardanus lagopodes (Forskål, 1775). Male SL 9.8 mm, stn N2, ZRC 2015.0489; B, Dardanus lagopodes (Forskål, 1775). Female SL 7.6 mm, stn R1, ZRC 2015.0488; C, Dardanus sanguinolentus (Quoy & Gaimard, 1824). Male SL 7.8 mm, stn R38, ZRC 2015.0491; D, Dardanus balhibuon, new species, holotype. Female SL 14.3 mm, stn R38, NMCR 40109. Scale bars = 1 mm.

Fig. 6. Dardanus balhibuon, new species, holotype. Female SL 14.3 mm, stn R38, NMCR 40109. A, Shield and cephalic appendages; B, Interocular plate and right ocular acicle; C, Right antennal peduncle; D, Anterior lobe of sternite of third pereopods; E, Telson, dorsal view; F, Posterior lobes of telson, ventral view. Scale bars = 1 mm.

Fig. 7. Dardanus balhibuon, new species, holotype. Female SL 14.3 mm, stn R38, NMCR 40109. A, Left cheliped, outer view; B, Left cheliped, inner view; C, Right cheliped, outer view; D, Right cheliped, inner view. Scale bars = 1 mm.

Fig. 8. Dardanus balhibuon, new species, holotype. Female SL 14.3 mm, stn R38, NMCR 40109. A, Left second pereopod, lateral view; B, Propodus of left third pereopod, lateral view. Scale bars = 1 mm.

Fig. 9. Maximum likelihood phylogram based on COI mitochondrial DNA sequences. Branch support for the major clades are indicated above (= likelihood bootstrap values) and below (= Bayesian posterior probabilities) the branches. Bootstrap values <70% were not reported.