Konarus crassicornis ( Stebbing, 1905 )

Bamber, Roger N & Chatterjee, Tapas, 2010, The new and the old: littoral tanaidomorph Tanaidacea (Crustacea: Peracarida) from the Andaman Islands, Indian Ocean, Zootaxa 2558, pp. 17-32 : 18-22

Konarus crassicornis ( Stebbing, 1905)

Figs 1 , 2

Heterotanais crassicornis Stebbing, 1905 , 4–5; Pl. 1A Konarus crassicornis Bamber, 2008 (synonymy)

?Non- Heterotanais crassicornis Nierstrasz, 1913

Material examined: 1Ƥ ( NMWZ.2010.001.0001), South Andaman: Wandoor (11°40.55’N, 92°45.12’E), Port Blair, Andaman Islands, intertidal sediments among macroalgae ( Padina sp.), December 2005; coll. TC. 1Ƥ, 3 neuters, 1 manca, ( NMWZ.2010.001.0002) Wandoor, Andaman Islands, intertidal sediments among macroalgae ( Halimeda opuntia ), December 2005; coll. TC. 4ƤƤ, 3 neuters ( NMWZ.2010.001.0003), 2ƤƤ (dissected, not retained), intertidal sediments among macroalgae ( Padina sp.), Burmanalla, South Andaman Island (11°33.45’N; 92°43.78’E), December 2005; coll. TC. 1Ƥ from Wandoor kept in second author’s personal collection.

Redescription of female: body ( Fig. 1 A) compact, 2.15 mm long, 5.1 times as long as wide, colour in alcohol translucent white, eyes black. Cephalothorax subrectangular, just longer than wide, nearly three times as long as pereonite 1, with slight rounded rostrum, naked; eyes present, pigmented; dorsal cuticular line distinguishing second thoracomere at posterior of cephalothorax. Six free cylindrical pereonites; pereonite 1 shortest, pereonite 2 slightly longer, pereonites 3 and 6 subequal, 1.3 times as long as pereonite 1, pereonites 4 and 5 subequal, longest, nearly 1.5 times as long as pereonite 1 (all pereonites respectively 2.6, 2.2, 2.1, 1.8, 1.8 and 2.1 times as wide as long). Pleon of five free subequal pleonites bearing pleopods, plus narrower pleotelson; pleonites 6.5 times as wide as long. Pleotelson semicircular, short, 3.5 times as wide as long, distally with four posterolateral and two smaller mid-distal setae.

Antennule ( Fig. 1 B) compact, of three articles, proximal article less than twice as long as wide, with distal and central simple setae and proximal group of penicillate setae on outer margin, inner margin with central simple seta; second article one-quarter as long as first and wider than long, with inner and outer simple distal setae and inner distal penicillate seta; third article just longer than second with six distal setae and single aesthetasc.

Antenna ( Fig. 1 C) of six articles, proximal article compact, naked; second article with dorsodistal seta and flange-like expansion of dorsal margin; third article as long as second, with dorsodistal seta; fourth article longest, 2.5 times as long as third, with four distal simple setae and one simple and one penicillate seta middorsally; fifth article just longer than third, with two distal setae; sixth article minute with one short penicillate and five simple distal setae.

Labrum ( Fig. 1 D) hood-shaped, apically setose. Left mandible ( Fig. 1 G) with wide, crenulate lacinia mobilis, pars incisiva with two crenulations; right mandible ( Fig. 1 H) without lacinia mobilis, pars incisiva marginally crenulate and distally bilobate; pars molaris robust, of grinding type, with parallel rugosities extending as rounded “teeth”. Labium ( Fig. 1 F) bilobed, finely setose distally and laterally, without palp. Maxillule ( Fig. 1 E) with nine distal spines and outer-distal tuft of setae, palp slender with two subequal distal setae. Maxilla simple, subtriangular, naked. Maxilliped ( Fig. 1 J) endites narrow, with setulose outer margin, two linguiform and one ovate distal spines and single subdistal seta; basis with four distal setae, longest pair exceeding distal margin of second palp article; palp first article naked, second article with one outer and three inner setae; third article with crown of six inner and distal setae; fourth article with setae around distal margin. Epignath ( Fig. 1 I) elongate, distally pointed, marginally setulose.

Cheliped ( Fig. 2 A) compact, basis nearly twice as long as wide, with seta mounted on tubercle near subdorsal distal margin; merus triangular, covering less than half ventral margin of carpus, with four shorter and four longer setae in proximal half of ventral margin, longer setae longer than merus; carpus 1.5 times as long as wide, ventrally with three setae in proximal half and two in distal half, distal margin extended as a cuff around base of propodus; propodus 1.4 times as long as wide, narrowing distally at dactylus insertion, with distal seta at base of dactylus; fixed finger two-thirds as long as palm, with lamellate apophyses on cutting edge, paired ventral, one mesial and three dorsal setae, terminal spine distinct; dactylus naked. Sidepiece with small seta.

Pereopod 1 ( Fig. 2 B) longer than other pereopods, coxa simple with seta; basis not slender, 2.5 times as long as wide, with simple seta on raised dorsal margin just proximal of midline; ischium compact with single ventral seta; merus half as long as carpus, with single ventrodistal seta; carpus articulating obliquely on merus, with single dorsal and ventral distal setae and longer subdistal dorsal seta longer than carpus; propodus 1.2 times as long as carpus, with four dorsal subdistal setae and one ventral subdistal seta; dactylus with dorsal seta, distinct, slender unguis 2.2 times as long as dactylus, both together 1.2 times as long as propodus.

Pereopod 2 ( Fig. 2 C) more compact than pereopod 1, ischium with one seta, merus and carpus subequal, carpus without long subdistal seta; propodus 1.4 times as long as carpus, with one shorter dorsodistal seta, and one longer dorsodistal seta longer than propodus; dactylus longer than unguis, both together 0.8 times as long as propodus. Pereopod 3 ( Fig. 2 D) similar to pereopod 2.

Pereopod 4 ( Fig. 2 E) basis robust, 1.8 times as long as wide; iachium with two setae; merus much shorter than carpus, with one slender ventrodistal simple spine on each side; carpus with paired short ventrodistal spines bearing distal setule, and microtrichia along ventral surface; propodus shorter than carpus with ventrodistal molariform spine, longer of two dorsodistal setae as long as claw (these two setae variable in proportion); dactylus and unguis fused into claw, curved, 0.6 times as long as propodus. Pereopod 5 ( Fig. 2 F) as pereopod 4. Pereopod 6 ( Fig. 2 G) as pereopod 4, but propodus with three distal setae.

Pleopods ( Fig. 2 I) all alike, basis with single inner (dorsal) plumose seta only, endopod with single dorsal plumose seta, 14 plumose setae along ventral margin and separated ventroproximal plumose seta; exopod with 16 plumose setae on ventral margin and separated ventroproximal plumose seta.

Uropod ( Fig. 2 H) basis naked, exopod of two segments, proximal segment less than half as long as distal segment; endopod of six segments in adult.

Male unknown.

Remarks. Stebbing (1905) described this species in the genus Heterotanais Sars, 1882 , but Bamber (2008) transferred it to Konarus . The present material agrees entirely with Stebbing’s (1905) description of the Gulf of Mannar material apart from his recording only one ventral seta on the fixed finger of the cheliped and only one seta on the maxillule palp; these are presumed to be errors in the original description: Stebbing (ibid., p.4), in attributing his species to Heterotanais , noted the single maxillule-palp seta was “in accordance with the generic character given by Sars”, whereas Sars (e.g. 1899, p. 14) clearly stated that this palp (in Heterotanais ) had two setae (as in all other leptocheliids where the palp has been recovered). In particular the setation of the cheliped merus, the proportions and segmentation of the uropod, and the proportions of the pereopod 1 articles are consistent.

Konarus crassicornis is very similar to the generotype, K. cheiris Bamber, 2006 , notably in such features as the mandibular structure, the ventral tuft of setae on the cheliped merus, the unusual setose tubercle on the cheliped basis, and the morphology and setation of the antennules, antennae (including the dorsal expansion of the second article), pereopods and uropods. The present species is distinct in the less attenuate body ( K. cheiris being six times as long as wide); in having the distal antennule article only just longer than the subdistal article (1.5 times as long in K. cheiris ); in having only one (as opposed to two) seta on the sidepiece attaching the cheliped; in having one less maxilliped basis seta per side, and less (and differently distributed) setae on the maxilliped palp; in having an ovate distal spine on the maxilliped endite (all three on K. cheiris being linguiform, or “spatulate”), with the distinctly subdistal adjacent seta (unusual for any leptocheliid); and in having proportionately longer chela fingers, inter alia.

Nierstrasz (1913) recorded and described “ Heterotanais ” crassicornis from the Postillon (Sebalana) Islands, Indonesia; however, as he commented, his two specimens had a cephalothorax no longer than wide, and the proximal article of the antennule more than twice as long as wide. In addition, he clearly showed sparse ventral setae on the cheliped merus, and somewhat different proportions of the pereopod 1 articles. Nierstrasz’ material (as Stebbing’s) appears to have been lost, but also appears to represent a distinct species, which can only be confirmed on collection of further material from the Indonesian Archipelago.

Figures

FIGURE 1. Konarus crassicornis (Stebbing, 1905), female, A, habitus, dorsal; B, antennule; C, antenna; D, labrum; E, maxillule and maxilla; F, labium; G, left mandible; H, right mandible; I, epignath; J, maxilliped, with detail of endite. Scale line = 0.6 mm for A, 0.1 mm for B to J.

FIGURE 2. Konarus crassicornis (Stebbing, 1905), female, A, cheliped; B, pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5 (one ischial seta presumed broken); G, pereopod 6; H, uropod; I, pleopod (most setae shown only by their bases). Scale line = 0.2 mm.