Zarenkolambrus minutus, Mclay, Colin L., 2009

Mclay, Colin L., 2009, Revision of the crab genus Garthambrus Ng, 1996, with the description of two new genera and discussion of the status of Tutankhamen Rathbun, 1925 (Crustacea: Brachyura: Parthenopidae), Zootaxa 2122, pp. 1-50 : 35-37

Zarenkolambrus minutus sp. nov.

( Figs 18 A, B, 19)

Type material. HOLOTYPE: male 6.2 x 5.1 mm (MNHN-B31883), French Polynesia, Austral Is (Raevavae), SMCB, stn D66, 23°50.54’S 147°42.73’W, 400 m, 3 Dec 1990.

PARATYPE: 1 male 4.1 x 3.5 mm (MNHN-B31884), French Polynesia, Austral Is (Raevavae), SMCB, stn D66, 23°50.54’S, 147°42.73’W, 400 m, 3 Dec 1990.

Description. Carapace wider than long, sub-pentagonal, surface very finely granular. Rostral region broad, median rostral tooth scarcely projecting, deflexed; lateral rostral teeth absent. Frontal region slightly concave, supraorbital region not elevated, no mid-orbital pit. Convex ridge runs length of mesogastric, metagastric, cardiac regions. No projections on central ridge, weak anterior diagonal branchial ridge ends at posterior epibranchial corner. Weak ridge present on posterior branchial, 3 faint pits in branchiocardiac groove, but solitary tubercle is absent. Regions not clearly marked.

Orbital margin finely denticulate, strongly concave to supraorbital suture. Suborbital margin concave to subacute tooth. Hepatic margin not projecting ended by distinct notch. Anterior epibranchial margin armed with 12 or 13 small, blunt teeth, becoming weaker posteriorly. Posterior epibranchial corner blunt, not projecting. Posterior epibranchial margin concave, 3 weak teeth near posterior margin. Blunt tooth present at each end of posterior margin which is convex, granular.

Epistome with shallow central depression, lateral depressions only faintly marked. Subhepatic region not concave, no hepatic fissure. Finely granular ridge runs, without interruption, from corner of buccal frame to sub-branchial region. Pterygostomial region finely granular. Cheliped-blocking mechanism involves proximal spine on posterior margin of merus against prominent sub-branchial spine near base of cheliped. Shallow Vshaped depression on sternites 3, 4. Only sternite 6/7 complete.

Antennular article 1 mobile, 6-sided; article 2 much longer than wide, inserted medially, folded away at an oblique angle; article 3 much longer than wide; articles 3, 4 normally folded in antennular fossa.

Antennal article 1 mobile, wider than long, convex; article 2 trapezoidal, convex, fixed to epistome, suborbital margin; article 3, 4 mobile longer than wide; flagellum as long as articles 3, 4 combined.

Basis-ischium of third maxillipeds with well-marked central longitudinal ridge, medial blade-like margins meet when closed. Surface of merus concave, covered with tubercles of various sizes, lateral corner covers exopod. Palp folded medially, last 2 articles covered by edge of merus.

Inner margin of cheliped merus with 7 tubercles, outer margin with tubercle near base (part of the cheliped-blocking mechanism), faint median tubercle. Carpus finely granular. Inner margin of propodus with 3 evenly spaced, low tubercles; outer flange-like margin, continuous from near carpus, curving towards base of dactylus, without tubercles; dactylus with proximal tubercle on upper margin. Right cheliped (crusher), with 2 or 3 faint teeth on each finger, left cheliped (cutter), with 3 or 4 small interlocking teeth.

Ambulatory legs decrease in length posteriorly. The arrangement of tubercles on legs as follows: P2: merus 4/0; P3: merus 7/0; P4: merus 6/(6 + 0); P5: merus 6/(7 + 6); all other articles of P2 to P5 are devoid of tubercles. Dactyli longer than propodi.

Lateral parts of abdominal segment 3 raised, low central ridge with scattered tubercles on segments 4–6. Segments 3, 4 fused but sutures still evident. No median hooked tubercle on segment 6. Abdominal locking mechanism of tubercles on sternite 5, sockets on segment 6. Male telson slightly wider than long. G1 reaches anterior margin of sternite 5, narrows quickly to straight distal portion, sperm aperture sub-terminal, medially directed. G2 reaches middle portion of sternite 4, slightly longer than G1, tip straight, flagella as long as basal section, twisted. Female unknown.

Distribution. Known from the type locality.

Etymology. The species name is derived from the Latin minutus alluding to the small size of the new species.

Remarks. Zarenkolambrus minutus resembles Z. epibranchialis but differs in the carapace width (CW) to carapace length (CL) ratio, which is 1.2 in Z. minutus but 1.4 in Z. epibranchialis . In addition, the rostrum is much shorter in Z. minutus than in Z. epibranchialis , and the posterior epibranchial corners are not as produced as those in Z. epibranchialis .

Figures

FIGURE 18. Gonopods. Zarenkolambrus minutus sp. nov.: A, B, holotype male 6.2 x 5.1 mm (MNHN), French Polynesia, Austral Is, Raevavae, SMCB, stn D 66, 23 ° 50.54 ʹS 147 ° 42.73 ʹW, 400 m, 3 Dec. 1990 (scale bar = 1 mm). — Zarenkolambrus epibranchialis (Zarenkov, 1990): C, D, male CL 5.0 mm, eastern Pacific Ocean, near Sala y Gómez, Ignolnaya, RV Professor Stockman, stn 2007, 6 – 7 May 1987 (after Zarenkov 1990: fig. 10) (scale bar not available). A left G 1, B, left G 2; C, right G 1; D, right G 2.