Dardanus robustus sp. nov.

(Figs. 8–14, 15 A, 32)

Material examined

Holotype: Ψ, SL 8.0 mm, 1–2 m, Byobu­dani, Chichijima Island, Ogasawara Islands, 6 June 1992, coll. Hiroyuki Tachikawa, CBM­ZC 8702. Paratypes: 1♂, SL 6.1 mm, 149°20’ W, 17°40’ S, stn. 105­57, Tahiti, Society Islands, French Polynesia, 8 Mar. 1957, Smithsonian­Bredin Expedition to the Society and Tuamotu Islands in April and May 1957, leader Waldo L. Schmitt, JF 1057, USNM 1086587; 1Ψ, SL 10.0 mm, 149°50’ W, 17°30’ S, Nuarei Bay, Moorea, opposite to Teanatira, Society Islands, French Polynesia, 11 May 1957, Smithsonian Institution­Bredin Expedition to the Society and Tuamotu Islands in April and May 1957, leader Waldo L. Schmitt, JF 1077a, USNM 1086588; 1♂, SL 9.4 mm, sta. 6592, Marquesas, French Polynesia, 1884, coll. Williams H. Jones (U.S. N.), U.S. S. Schooner Wachusett, JF 0 526, USNM 1086589.

Description

Shield (Fig. 8 A) as long as broad; anterior margin between rostral lobe and lateral projections shallowly concave; lateral margins strongly convex, somewhat irregular, with rows of long setae. Dorsal surface of shield with scattered tufts of setae; weakly­calcified Y­shaped linea present posteriorly; gastric pits distinct. Rostral lobe only weakly produced. Lateral projections large, bluntly triangular, produced. Posterior carapace lateral elements well calcified, unarmed. Branchiostegites unarmed.

Ocular peduncles (Fig. 8 A) 0.7–0.8 length of shield, subcylindrical, only very slightly inflated distally and proximally; corneas only very slightly dilated. Ocular acicles (Fig. 8 A, B) broad; distal margins each with 2–4 spines. Interocular plate (Fig. 8 A) with pair of small protrusions.

Antennular peduncles (Fig. 8 A) slender, when fully extended, distal margins of ultimate segments reaching distal margins of ocular peduncles; ultimate and penultimate segments unarmed; basal segment with ventromesial distal angle bearing small spine.

Antennal peduncles (Fig. 8 A, B), when fully extended, reaching bases of corneas; fifth and fourth segments unarmed; third segment projecting ventrodistally; second segment with dorsomesial distal angle bearing spine, dorsolateral distal angle produced, terminating in strong spine; first segment with ventrolateral distal angle with spine. Antennal acicle (Fig. 8 B) terminating in bifid spine; dorsomesial margin with 5–7 small spines; dorsolateral margin unarmed or 1 subdistal spine. Antennal flagella sparsely setose.

Third maxilliped (Fig. 8 C) with ischium bearing well­developed crista dentata (Fig. 8 D); basis also with 1–3 spines (Fig. 8 D).

Chelipeds vastly unequal, left larger. Left cheliped (Figs. 9, 10) very stout, more elongate in males (Fig. 9) than in females (Fig. 10). Outer faces of dactyl, fixed finger and palm covered with corneous­tipped conical spines and short truncate stiff setae; upper surfaces of dactyl and palm with 1 or 2 irregular rows of prominent conical spines. Dactyl and fixed fingers each terminating in very strong corneous claw, cutting edges each with 5–9 (dactyl) or 5–7 (fixed finger) variously­sized calcareous teeth. Palm and fixed finger with lower portion of outer face deeply concave; lower face and lower portion of inner face with numerous flattened, triangular corneous spines. Carpus with upper margin bearing 1 or 2 irregular rows of weak (male, Fig. 9 A) or prominent (female, Fig. 10 C) corneous­tipped conical spines; outer face varying from few (male, Fig. 9 A) to numerous tubercles (female, Fig. 10 C). Merus with distal margin of lateral face bearing several corneous­tipped spines; dorsal face with 1–5 short transverse rows of corneous­tipped spines; ventrolateral margin with 1–3 spines distally. Ischium unarmed.

Right cheliped moderately slender (Fig. 11 A–C), generally setose. Small corneous spines found on dactyl, fixed finger, palm and carpus flattened, triangular. Dactyl terminating in large corneous claw; cutting edge with broad distal tooth and 6–9 variouslysized calcareous teeth; outer face with numerous small corneous spines; upper margin with 2 or 3 irregular rows of prominent corneous­tipped, conical spines. Fixed finger terminating in large corneous claw; cutting edge with 7–9 variously sized calcareous teeth. Palm and fixed finger with outer face bearing small corneous spines, sometimes forming longitudinal rows; lower face with 2–4 irregular rows of small corneous spines; upper margin of palm with generally 1 but rarely 2 irregular rows of prominent corneous­tipped conical spines. Carpus with upper margin bearing 1 or 2 prominent spines; outer face with few strong spines near upper margin; distal margin of outer face with row of small corneous spines on lower 0.5–0.6. Merus with lateral face bearing several short transverse rows of corneous spines, distal margin with several sharp spines. Ischium unarmed.

Second (Fig. 11 D­G) and right third (Fig. 12) pereopods generally similar, but armament of dactyls and propodi somewhat different between second pair and right third; second pair generally more slender than right third; of second pair, left slightly shorter than right. Small corneous spines on dactyls and propodi flattened, triangular. Dactyls all 1.1–1.2 length of propodi, each terminating in strong corneous claw; dorsal surfaces of second pair with numerous small corneous spines sometimes forming short transverse or oblique rows, particularly, mesially; on right third, dorsal surface with rows of tufts of stiff setae; lateral and mesial faces of both second pair and right third with longitudinal rows of tufts of stiff setae, ventral margins with rows of tufts of stiff setae and each with 1–3 (second) or 4–6 (right third) large spines in distal half. Propodi 1.9–2.1 (second) or 1.5–1.6 (right third) length of carpi; dorsal faces flat and broad, armed with numerous small corneous spines, number of spines much greater in second pair (Fig. 11 G) than right third (Fig. 12 D), dorsodistal margins each armed with row of small corneous spines (second pair, Fig. 11 G) or fringed with stiff setae (right third, Fig. 12 D); lateral and mesial faces with scattered spines near dorsal faces. Carpi 0.4–0.5 (second) or 0.7–0.8 (right third) length of meri; lateral faces flat (second) or moderately convex (right third); dorsal margins each with several, distal large corneous­tipped spines laterally (second), or with large distal corneous­tipped spine accompanied with few small corneous spines laterally (right third). Meri with dorsal and ventral margins bearing rows of stiff setae, ventral margins each with row of several calcareous spines or tubercles. Ischia unarmed.

Left third pereopod (Figs. 13, 14 A–C) generally very stout. Small corneous spines found on mesial face of dactyl and propodus flattened, triangular. Dactyl (Fig. 13) 1.1–1.2 length of propodus, very broad, terminating in strong corneous claw; dorsal margin with series of furrows producing row of lobes, lateral face of each lobe armed distally with 1 or 2 sharp corneous spines (Fig. 13 B­a) and dorsomesial margin of each lobe with 1–3 strong corneous spines and dense setae (Fig. 13 C); lateral face (Fig. 13 B) with dorsal half bearing deep longitudinal concavity (Fig. 13 B­b) with scattered tiny corneous spinules, ventral 0.3–0.4 (Fig. 13 B­c) with numerous, truncate corneous spines or corneous ­tipped spines sometimes in short transverse row along short grooves; ventral margin with series of deep furrows producing row of lobes, lateral face of each lobe with large, truncate corneous spines ventrodistally (Fig. 13 B­c), ventrolateral margin of each lobe with dense stiff setae, ventromesial margin of each lobe armed with 1–4 very large, conical corneous spines (Fig. 13 D); mesial face (Fig. 13 C) strongly convex, with row of tufts of short stiff setae ventrally, 2 or 3 rows of tufts of long stiff setae medially and dorsally and scattered small corneous spines dorsally. Propodus 1.3–1.4 length of carpus, very broad; dorsal margin with series of furrows producing row of lobes, lateral face of each lobe armed dorsodistally with strong corneous spine (Fig. 14 A­a), and dorsomesial surface of each lobe with 1–3 strong spines and dense setae (Fig. 14 B); lateral face (Fig. 14 A) with dorsal half bearing very deep longitudinal concavity (Fig. 14 A­b) with numerous very short, truncate, corneous spines often along short transverse elevation, separated by strong medial longitudinal elevation (Fig. 14 A­c) armed with row of protuberances bearing 1–10 flattened, elongate rectangular corneous spines, from ventral 0.2–0.3 pronouncedly convex (Fig. 14 A­d, e) and just ventral of medial longitudinal elevation with row of protuberances (Fig. 14 A­d) each with marginal flattened, elongate rectangular corneous spines; ventral margin with series of deep furrows producing row of large lobes, ventromesial margin of each lobe (Fig. 14 C) with 1–4 very large, conical corneous spines (Fig. 14 C), each furrow on ventral margin continuing to elongate transverse groove on lateral face (Fig. 14 A­e), producing row of elongate lobes each armed with marginal flattened, elongate rectangular corneous spines and very strong ventrodistal corneous spine; mesial face (Fig. 14 B) strongly convex, with few rows of tufts of long stiff setae and dorsal scattered, small corneous spines, dorsodistal margin of mesial face armed with row of stiff setae and corneous spines. Carpus (Fig. 13 A) 0.8–0.9 length of merus; lateral face with 0–4 large protuberances each armed dorsally or ventrally, or both, with corneous spines. Armament and setation of merus and ischium similar to those of right third.

Sternite of third pereopods with anterior lobe (Fig. 8 F, G) rectangular, with 1 or 2 protrusions each bearing short transverse row of setae.

Fourth pereopod (Fig. 8 E) semichelate; dactyl with 3–5 short corneous spines on lateral face ventrally; propodal rasp well developed; carpus with large dorsodistal spine.

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

Male pleon (Fig. 14 D) with second to fifth left pleopods, fringed with long setae; each with well­developed exopod; single, elongate fleshy membranous protuberance covered with long setae present between fourth and fifth pleopods. Female pleon (Fig. 14 E) with second to fifth left pleopods, fringed with long setae; second to fourth large, triramous; fifth small, endopod vestigial; single, hook­shaped fleshy membranous protuberance covered with long setae present between fourth and fifth pleopods.

Uropods (Fig. 14 D, E) markedly asymmetrical, left larger than right; endopods and exopods with well­developed rasps.

Telson (Fig. 8 H, I) with lateral constrictions; marginal area partially calcified; posterior lobes separated by median cleft, left slightly larger than right, with 4–6 (right) or 5–7 (left) ventral corneous spines near terminal margin, terminal margins fringed with long setae.

Color in life (Fig. 15 A)

Dorsal surface of shield pinkish, with mottled white and red, very dark purplish area, appearing almost black, present mid­anteriorly; bright red area present on either posterolateral side of this dark area. Ocular peduncles pinkish, gradually changed to yellow distally. Chelipeds and ambulatory pereopods generally reddish, or pinkish gray, with mottled white and red, setae black tipped with greenish yellow; chelipeds with carpi and meri bearing bright red splotches; ambulatory pereopods with carpi each bearing very dark purplish area, appearing almost black, propodi and meri each with faint central, transverse red band. Posterior carapace and pleon with red reticulations.

Etymology

From the Latin robustus, meaning strong or stout, in reference to the morphology of the dactyl and the propodus of the left third pereopod in this species, which are very stout among the D. sanguinocarpus species complex.