Poligarida keriakis, Bamber & Marshall, 2013

Bamber, Roger N. & Marshall, David J., 2013, Tanaidaceans from Brunei III. A New Genus and Two New Species of Shallow-water Sphyrapodids (Crustacea: Peracarida: Tanaidacea) from the South China Sea, Species Diversity 18, pp. 255-267 : 262-266

Poligarida keriakis sp. nov.

( Figs 5–8 )

Material examined. Holotype: ♀ ( BMNH 2013.213 ), 05°21′56″N 111°27′22″E, 90 m depth, sand . Allotype: ♂ ( BMNH 2013.214 ), same data as holotype . Paratype: 1♀ with oostegites ( BMNH 2013.215), microslide preparation, 05°22′10″N 111°27′00″E, 67 m depth, sand.

Description. Female (based predominantly on the holotype, appendages of paratype): body ( Fig. 5A ) glabrous, dorsoventrally flattened, holotype 1.6 mm long, 4.5 times as long as wide, narrower posteriorly. Cephalothorax onion-shaped, 0.8 times as long as wide, anterior margin with conspicuous extended rostrum without distal tubercles. Eyes absent; eyelobes conspicuous. Pereonite 1 not fused to cephalothorax, 0.4 times as long as cephalothorax, laterally rounded; pereonite 2 as long as but narrower than pereonite 1; pereonite 3 as wide as pereonite 2, 1.3 times as long as pereonite 1, posteriorly expanded at coxal attachment, with slight anterolateral apophyses (“shoulders”); pereonite 4 almost as long as but just narrower than pereonite 3, 1.2 times as long as pereonite 1, with slight anterolateral apophyses; pereonite 5 as long as pereonite 4, without apophyses; pereonite 6 shorter, 0.7 times as long as pereonite 1 (pereonites respectively 3.1, 2.8, 2.0, 2.1, 2.0 and 3.3 times as wide as long). Pleon 0.3 times as long as whole body; pleonites four times as wide as long, epimera held closely to body laterally, extended into posterior spine-like apophyses (as in Poligarida beni , Fig. 1D ). Pleotelson semicircular but distally extended, 0.3 times length of whole pleon, 0.6 times as long as wide, with paired simple setae caudodistally.

Antennule ( Fig. 6A ) with proximal peduncular article robust, 3.5 times as long as wide, with three outer and three inner simple setae, outer margin with two proximal penicillate setae and conspicuous subdistal spine-like apophysis; second article 0.3 times as long as first article, with two outer and inner simple setae, outer margin with small distal spine-like apophysis; third article one-quarter as long as second, with inner distal seta; fourth article very short, with inner distal seta. Accessory flagellum of two segments, distal segment shorter than proximal segment. Main flagellum of three segments, first and second segments subequal in length, each bearing an aesthetasc; distal segment shortest.

Antenna ( Fig. 6B ) with four-articled peduncle, squama absent; proximal article with inner expansion with smooth margin; article 2 nearly four times as long as wide, naked; article 3 short, naked; article 4 elongate, 1.5 times as long as article 2, with fine simple medial and distal setae and three outer penicillate setae. Flagellum of three segments.

Labrum ( Fig. 6C ) rounded, marginally setose. Left mandible ( Fig. 6D ) with pars incisiva and lacinia mobilis each bearing five rounded distal “teeth”, setiferous lobe bearing three slender, simple setae and one bifurcate seta, and pars molaris wide, flattened, distally bearing four slender setae interspersed with fine setules; palp absent. Right mandible ( Fig. 6E ) with pars incisiva bearing five rounded marginal teeth, and setiferous lobe bearing three slender setae and lanceolate spine resembling a lacinia mobilis. Maxillule ( Fig. 6F ) inner endite with three simple distal setae; outer endite with nine longer distal spines (no inner spines seen), palp absent. Maxilla (not figured) apparently similar to that of P. beni . Labium ( Fig. 6G ) with smooth outer margin, inner margins setulose, palp sparsely setose with one distal barbed spine. Maxilliped ( Fig. 6H ) basis apparently naked; palp article 1 with single short seta on outer margin and longer subdistal seta on inner margin; second palp article longer than wide, with three inner setae and single shorter outer distal spine; third palp article with six distally-tapering setae along expanded inner margin; fourth palp article with six distal and one subdistal setae. Maxilliped endite ( Fig. 6I ) with three outer plumose stout setae, two inner coupling hooks, and five simple distal spines. Epignath ( Fig. 6J ) large, semicircular, with long, naked distal seta.

Cheliped ( Fig. 7A ) malleolate. Basis rounded, 1.5 times as long as wide, naked. Exopodite 3-articled, distal article with three plumose setae. Merus subrectangular but extending distally along ventral margin of carpus, with single midventral seta. Carpus 2.3 times as long as wide, with one longer proximal and one shorter subdistal simple setae on ventral margin, one dorsal subdistal seta. Propodus massive, proximally overhanging carpus, 1.25 times as long as wide, with two mid-distal setae near base of dactylus; fixed finger 1.25 times as long as palm, ventral margin with two setae, cutting edge with irregular “teeth” and three submarginal setae; dactylus with sinuous cutting edge bearing one fine spinule, three medial setae also present.

Pereopod 1 ( Fig. 7B ) much larger than remaining pereopods (overall length ∼ 1 mm), all spines with fine distal denticulations. Coxa naked; basis relatively stout, three times as long as wide, with single ventrodistal seta; exopodite present, 3-articled, distal article with three distal plumose setae. Ischium compact, naked. Merus 0.6 times as long as basis, with one midventral and three distal setae and one ventrodistal spine. Carpus 0.65 times as long as merus, with two proximal setae along ventral margin, four dorsal submarginal setae, and one dorsodistal and two ventrodistal spines. Propodus as long as carpus, dorsal margin with three setae and two spines, ventral margin with four spines. Dactylus slender, with two ventral denticulations, unguis 0.4 times as long as dactylus, both together 1.1 times as long as propodus.

Pereopod 2 ( Fig. 7C ) 0.6 times as long as pereopod 1; basis 5.4 times as long as wide with fine, simple ventrodistal seta. Ischium with one ventral seta. Merus 0.4 times as long as basis, with one subdistal ventral seta. Carpus just shorter than merus, with three dorsal and three ventral marginal setae. Propodus 1.2 times as long as carpus, with three ventral and four dorsal setae. Dactylus slender, with ventrodistal spine-like apophysis, unguis short, both together 0.9 times as long as propodus. Pereopod 3 ( Fig. 7D ) similar to pereopod 2, but merus with one ventral seta, carpus with four ventral and no dorsal setae, propodus with two dorsal setae.

Pereopod 4 damaged in preparation, propodus ( Fig. 7E ) with seven finely-denticulate curved setae and mid-dorsal penicillate seta. Pereopod 5 ( Fig. 7F ) relatively simple, basis 6.7 times as long as wide; merus 0.2 times as long as basis, with two ventrodistal setae; carpus 1.5 times as long as merus, with single ventral and longer distal setae; propodus as long as carpus, with two ventral and one dorsal setae; dactylus slender, with ventrodistal apophysis, together with unguis 1.4 times as long as propodus. Pereopod 6 ( Fig. 7G ) similar to but smaller than pereopod 5, propodus with two distal setae.

Pleopods ( Fig. 7H ) all alike. Basis elongate, naked. Endopod as long as exopod, with one outer and four distal plumose setae; exopod of two segments, proximal segment with outer-distal plumose seta; distal segment with five distal plumose setae.

Uropod ( Fig. 7I ) biramous. Basis naked. Exopod of three segments, reaching past distal end of second endopod segment, distal segment longer than two proximal segments together, with two distal setae. Endopod elongate, almost as long as whole pleon, with ten segments, alternate segments with simple setae as figured.

Distinctions of male (allotype): Generally as female but larger (1.8 mm long), body ( Fig. 5B ) more slender, invaginations between pereonites three to five more conspicuous than those of female; pleotelson caudally extended. Pereopod 1 ( Fig. 5B ) proportionately larger than that of female. Dimorphism shown by antennule and cheliped. Antennule ( Fig. 8A ) with proximal peduncle article stout, twice as long as wide, articles 2 to 4 all shorter than wide; main flagellum with five segments, proximal two segments shorter than wide, and each furnished distally with dense row of about 16 aesthetascs. Cheliped ( Fig. 8B ) basis more slender than that of female, 2.2 times as long as wide, carpus 2.9 times as long as wide, propodus 1.8 times as long as wide with three distal setae; fixed finger truncated, only 0.3 times as long as propo- 5 Antennal peduncle article 2 about as long as article 3; pereopod bases with hook-like apophyses ....................... .......................................................................... Ansphyrapus Antennal peduncle article 2 at least four times as long as article 3; pereopod bases without hook-like apophyses......................................................................................... 6

6 Carapace longer than wide; mandible with palp ............. ................................................................... Pseudosphyrapus Carapace wider than long; mandible without palp ......... ............................................................................... Poligarida dus; dactylus three times as long as fixed finger.

Etymology. Derived from the Greek keraia — a feeler or antenna and akis — a barb (f.), with reference to the unusual spine-like outer-distal apophyses on the antennular peduncle articles (noun in apposition).

Remarks. Poligarida keriakis sp. nov. shows the unusual structure of the mandibles and maxillules diagnostic of this genus, with an almost identical morphology to those of P. beni , as well as having the carapace shorter than wide and generally simple setation of the pereopods. It is distinguished from P. beni in particular by the subdistal spinelike apophysis on the proximal antennular peduncle article, while it lacks the anterolateral apophyses on pereonite 3 found in that species. Pereopod 1 of the present species has one more spine on the propodus, while the rostrum is distally simple and the pleopod basis is naked. The antennulae and chelipeds of the male show a greater degree of sexual dimorphism in P. keriakis than in P. beni .

Poligarida keriakis was taken in deeper water (67–90 m) than was P. beni .

Figures

Fig. 5. Poligarida keriakis sp. nov., A, female holotype; B, male allotype. Scale: 1mm.

Fig. 6. Poligarida keriakis sp. nov., paratype female, A, antennule; B, antenna; C, labrum; D, left mandible; E, right mandible; F, maxillule; G, labium; H, maxilliped; I, maxilliped endite; J, epignath. Scale: 0.2mm.

Fig. 7. Poligarida keriakis sp. nov., paratype female, A, right cheliped; B, pereopod 1; C, pereopod 2; D, pereopod 3; E, distal articles of pereopod 4; F, pereopod 5; G, pereopod 6; H, pleopod (plumosity of all setae omitted); I, uropod. Scale: 0.2mm.

Fig. 8. Poligarida keriakis sp. nov., allotype male, A, antennule; B, left cheliped. Scale: 0.2mm.

Fig. 1. Poligarida beni sp. nov., A, female holotype; B, male allotype; C, variations in rostra, including (i) holotype and (ii) allotype; D, pleonal epimere. Scale: 1mm for A and B.