Platylicoa angela, Bamber, Roger N., 2013

Bamber, Roger N., 2013, Tanaidaceans from Brunei, IV. The Families Kalliapseudidae, Pagurapseudopsidae, Parapseudidae and Apseudidae (Crustacea: Peracarida: Tanaidacea: Apseudomorpha), with descriptions of a new genus and six new species, Zootaxa 3734 (4), pp. 401-441 : 425-432

Platylicoa angela sp. nov.

Figs 13–16

Material: 1 brooding ♀, holotype (BMNH 2013.890), Station B4, 04°51′06"N 114°35′26"E, 20 m depth, sand; March 2009. 1♂, allotype (BMNH 2013.891), Station S14, 04°42′39"N 114°26′24.6"E, 12.7 m depth, sand. 1♀ with oostegites, paratype (BMNH 2013.892), Site DA2; 1♀, paratype (BMNH 2013.893), 1♂ (dissected, not retained), Site DA1; both Station DA, 05°54′28.5"N 114°38′23.3"E, 20 m depth, sand; March 2009. 3♀♀ (1 brooding), paratypes, (BMNH 2013.894–896), Station S14, 04°42′39"N 114°26′24.6"E, 12.7 m depth, sand. 1♀, Station S17, 04°41′13"N 114°27′23"E, 6.5 m depth, sand; March 2009. 3♀♀, 1 juvenile (retained), 05°20′53"N 111°26′51"E, 90 m depth, sand, September 2009.

Description of female: Body ( Fig. 13 A) relatively large for the genus, 6.2 times as long as wide, dorsoventrally flattened, holotype 10.5 mm long (tip of rostrum to posterior of pleotelson). Cephalothorax almost semicircular, 0.8 times as long as wide, with rounded rostrum bearing anterior spine-like apophyses, central apophysis longest; eyelobes distinct, eyes pigmented; single seta behind each eyelobe, fine setules on anterolateral margin of branchial chambers. Pereonites with fine lateral setae on each side, margins of pereonites 2 to 6 expanded into flattened flanges, particularly anteriorly, anterolateral corners rounded. Pereonite 1 with convex lateral margins, laterally extended towards posterior as flanges, 0.4 times as long as cephalothorax; pereonite 2 with uniform margins, 1.4 times as long as pereonite 1, with curved ventral spine on posterolateral corners as found on pereonite 3; pereonite 3 mid-laterally concave above coxal attachment, as long as pereonite 2, with curved ventral spine on posterolateral corners ( Fig. 13 B); pereonite 4 subrectangular, twice as long as long as pereonite 1, narrower above coxal attachments; pereonite 5 similar to but slightly longer than pereonite 4, narrower behind anterolateral flanges; pereonite 6 similar to but only 0.38 times as long as pereonite 5 (all pereonites respectively 3.1, 2.0, 1.9, 1.3, 1.0 and 1.2 times as wide as long). Pleon about one quarter of whole body length; pleonite 1 widely hexagonal, 0.2 times as long as pereonite 6, and about four times as wide as long, with five sparsely plumose setae on each lateral margin just extending onto dorsolateral surface, two simple dorsal setae; pleonites 2 to 4 similar to pleonite one but each with three lateral setae on each side, sparsely plumose on pleonites 2 and 3; pleonite 5 rectangular, 1.5 times as long as pleonite 4, with simple lateral setae and posterolateral margins extended as pointed apophyses. Pleotelson subpentangular, 3.4 times as long as pleonite 5 and 1.7 times as long as wide, with finely setose lateral and distal margins.

Antennule ( Fig. 13 C) proximal peduncle article 3.5 times as long as wide, outer margin with numerous penicillate setae, central and distal simple setae and distal spine, inner margin with central and distal simple setae and central spine. Second article twice as long as wide, half as long as first article, inner and outer margins with central and distal simple setae. Third article 1.3 times as long as wide, half as long as second article, with distal array of simple setae; fourth article half as long as third, with simple mid-distal seta. Main flagellum of 12 segments, single aesthetasc present on tenth segment; accessory flagellum longer than main flagellum, of 15 segments.

Antenna ( Fig. 13 D) proximal peduncle article naked, with rounded inner apophysis. Second article 1.3 times as long as first, with inner seta, elongate squama bearing nine marginal setae. Third article compact, one-third as long as first article, with inner-distal seta. Fourth and fifth articles each as long as first article, fifth article with two fine outer setae. Flagellum of ten segments.

Labrum ( Fig. 14 A) rounded, simple, marginally setose; epistomal apophysis similar in appearance to central apophysis of rostrum. Left mandible ( Fig. 14 B) with four rounded “teeth” on pars incisiva; lacinia mobilis with four rounded “teeth”; setiferous lobe with one trifurcate, two bifurcate and four simple setae; pars molaris stout, distally rugose and marginally extended into slender “teeth”; palp ( Fig. 14 C) of three articles, proximal article with inner tuft of about ten setae, second article with single outer seta, inner margin with comb-like row of spinules in proximal half; third article inner margin with comb-like row of spinules, two slender distal setae. Right mandible as left but with without lacinia mobilis. Labium ( Fig. 14 D) outer corner finely denticulate, palp with inner and outer fine lateral setules and two simple distal setae, conspicuous inner apophysis. Maxillule ( Fig. 14 E) inner endite with subdistal apophysis and four plumose distal setae; outer endite with eleven distal spines and two subdistal setae, outer margin finely setose distally; palp of two articles, distally with five setae. Maxilla ( Fig. 14 F) generally typical of the Pakistanapseudinae , outer margin finely denticulate, moveable endite outer lobe with two subdistal setae and at least three finely-denticulate distal setae, inner lobe with seven simple and two finely-denticulate blunt spines; fixed endite outer lobe with simple, stout and bifurcate distal spines and one bilaterally denticulate spine, inner lobe with three longer setae and rostral row of about 24 setae. Maxilliped basis ad palp ( Fig. 14 G) with simple setae; basis with inner-distal seta but no spine; first palp article with no inner seta, with one outer seta; second palp article with inner margin bearing numerous shorter curled setae largely in two rows, four outer distal setae; third palp article with six recurved inner setae; fourth palp article with five setae around distal margin and one subdistal seta. Maxilliped endite ( Fig. 14 H) distal margin with outer simple setae and inner blunt spines, inner caudodistal seta simple, lanceolate; outer margin expanded, inner margin with nine plumose plump setae and two coupling hooks. Epignath ( Fig. 14 I) large, cup-like, with proximal lobe and setulose spine.

Cheliped ( Fig. 15 A) slender. Basis nearly four times as long as wide, ventrally with four marginal setae, spine in distal half, and two subdistal setae. Exopodite three-articled; article 2 naked, article 3 with four plumose setae. Merus attached to basis subdistally, about half as long as basis, with sparse dorsal setae and numerous ventral setae largely in two groups. Carpus very slender, 6.4 times as long as wide, ventrally with seven marginal and five submarginal setae, six inner setae dorsal of midline, four dorsoproximal and four dorsodistal setae. Chela slender, palm twice as long as wide with three dorsodistal and one distal setae and single ventral seta at base of fixed finger; fixed finger 1.7 times as long as palm, recurved, with four ventral setae, cutting edge without apophyses but with numerous fine setae. Dactylus with three dorsal setae in proximal half, cutting edge naked.

Pereopod 1 ( Fig. 15 B) basis 3.1 times as long as wide, with four ventral spines, one ventrodistal spine and two ventrodistal setae; exopodite three-articled, article 3 with six plumose setae. Ischium with two ventrodistal and four inner-distal setae. Merus half as long as basis, with mid-length and distal tufts of setae, one short, blunt ventrodistal spine with two adjacent setae. Carpus compact, 0.6 times as long as merus, ventrally with distally-tapering marginal setae and one short, blunt distal spine, dorsally with submarginal row of setae, short dorsodistal spine with three adjacent setae, mid-distal margin with three setae. Propodus 1.8 times as long as carpus, ventral margin with distally-tapering setae and two very short spines, one adjacent to dactylus, dorsal margin with row of longer tapering setae in distal half, submarginal row of setae in proximal half, but no spine. Dactylus robust, with five ventral denticulations, unguis distinct, dactylus and unguis together two-thirds as long as propodus.

Pereopod 2 ( Fig. 16 A) basis 3.8 times as long as wide, with three ventral and two ventrodistal setae. Ischium half as long as wide, with four ventrodistal and one dorsodistal setae. Merus 0.3 times as long as basis, with two mid-ventral and two ventrodistal setae and one ventrodistal slender spine, three simple and one penicillate innerdistal setae, and two simple dorsal setae. Carpus 1.5 times as long as merus, with numerous ventral-marginal and dorsal-submarginal setae, one dorsodistal curved spine 0.2 times as long as carpus, and one mid-ventral slender spine. Propodus as long as carpus, with numerous ventral-marginal and dorsal-submarginal setae, one inner subdistal spine and one mid-ventral slender spine, dorsodistally with one slender spine and two setae. Dactylus slender with fine ventral subdistal seta, unguis half as long as dactylus, both together as long as propodus. Pereopod 3 ( Fig. 16 B) similar to pereopod 2, but propodus 0.75 times as long as carpus and dorsodistally with two spines and one seta.

Pereopod 4 ( Fig. 16 C) basis 2.2 times as long as wide with three mid-dorsal and one mid-ventral penicillate setae and one ventrodistal simple seta. Ischium with one dorsal and four ventrodistal setae. Merus one-quarter length of basis, with numerous ventral and three dorsal simple setae. Carpus twice as long as merus, with ventral to distal array of marginal setae interspersed with three slender spines, dorsodistal spine about one-quarter as long as carpus. Propodus 0.6 times as long as carpus, with dorsodistal spine-like apophysis, four ventral setae, three dorsodistal slender spines and dorsoproximal penicillate seta. Dactylus and unguis not clearly distinct, both together shorter than adjacent spines 0.8 times and as long as propodus. Pereopod 5 ( Fig. 16 D) similar to pereopod 4, but propodus 0.75 times as long as carpus and with four dorsodistal spines, dactylus plus unguis longer than adjacent spines.

Pereopod 6 ( Fig. 16 E) basis 2.9 times as long as wide, dorsal and ventral margins each with array of plumose setae, three dorsoproximal penicillate setae, two ventroproximal simple setae, two simple ventrodistal setae; ischium with four ventrodistal simple setae and one dorsal plumose seta; merus one-quarter as long as basis, with six ventral simple setae and two dorsal plumose setae; carpus nearly twice as long as merus, with ventral marginal array of paired shorter and longer setae and two submarginal slender spines, dorsodistal spine and three plumose setae in proximal half, propodus with ventral to dorsal row of about 20 slender, denticulate spines, three dorsodistal slender spines and dorsal penicillate seta. Dactylus and unguis apparently fused, longer than adjacent spines and than propodus.

Pleopods ( Fig. 15 C) alike. Basis with two outer and three inner plumose setae, central inner seta much shorter than other two; rami linguiform, endopod longer than exopod and with 26 plumose setae along outer, inner and distal margins, most proximal inner seta stouter than others and distally trifurcate; exopod with 26 outer, inner and distal marginal plumose setae.

Uropod not recovered.

Male: Generally similar to female. Cheliped as that of female. Antennule not recovered. Antenna ( Fig. 13 E) with secondary segmentation of flagellum, most segments with 10 to 12 aesthetascs; peduncle articles not fused.

Variation: Two specimens from the deeper-water station at 90 m showed variation in the setation of pereopod 6: one had only dorsal plumose setae on the basis, the other had no plumose setae on the basis. One of these specimens had a full array of setae but no spines on the ventral margin of the propodus of pereopod 1.

Etymology. From the Anglo-Saxon angel —a fish-hook (hence the English word—angler), with reference to the unusual posterolateral curved ventral spines on pereonites 2 and 3.

Remarks. The present species has the dense array of plumose setae on pereopod 6 in some specimens, but does not have a row of plumose setae across the dorsum of pleonite 1; in that respect it resembles P. pectinis , but it is without an inner-distal spine on the maxilliped basis (unknown for P. setosa as most mouthparts were unstudied, unfortunately). One of the diagnostic characters of Platylicoa cited by Guţu (2008) was the presence of pointed anterolateral corners on the pereonites: P. angela sp. nov. has rounded corners, but, unlike the other two species, has distinctive posterolateral ventral curved spines on each of pereonites 2 and 3.

In most respects, Platylicoa angela is similar to P. pectinis , the type series of which was from deeper waters off Brunei, but other differences include a shorter dorsodistal spine on pereopods 2 and 3 (less than half as long as the propodus in the present species, much more than half as long as the propodus in P. pectinis ), and distinct setation of the mouthparts and pleopod bases. More conspicuously, with very short ventral spines (when present) on the propodus of pereopod 1, P. angela more-closely resembles P. setosa .

In males with aesthetascs on their antennae, the cheliped of the present species resembles that of the female, as found in the type-series of P. pectinis . Subsequent P. pectinis material collected off Sabah by Bamber & Sheader (2005) had a dimorphic male chela. This may imply a series of moults in the adult males to full maturity; it supports the suggestion by Bamber & Sheader (2003) that fully mature (ultimately mature?) males in the Pakistanapseudinae may all show dimorphism of the cheliped. Unfortunately, chelipeds are rarely retained on fixed specimens of this subfamily unless they are relaxed first, so it may prove difficult to obtain sufficient material to test this hypothesis.

Guţu (2008) placed Platylicoa in his tribe Parapseudini (subsequently raised to subfamily rank by BłaŻewicz- Paszkowycz. & Bamber 2012), presumably based on the wide pleonites and the presumed presence of a “dorsotransversal row of small setae” on pleonite 1 (absent in the generotype and in P. angela ). With the presence of an inner apophysis and two distal spines on the labial palp, and secondary segmentation of the male antennae (features of the “ Pakistanapseudes -group” sensu BłaŻewicz-Paszkowycz. & Bamber 2007), as well as having the pleonites together longer than the carapace in the present species (a diagnostic feature of the “tribe Pakistanapseudini ” sensu Guţu 2008), Platylicoa is transferred to the subfamily Pakistanapseudinae .

Figures

FIGURE 13. Platylicoa angela sp. nov.: A, holotype, dorsal; B, right margin of pereonite 3, ventral (circle represents attachment of coxa); C, antennule of female; D, antenna of female; E, antenna of male (aesthetascs on flagellar segments 4 to 13 shown only by their bases). Scale line = 2 mm for A, 0.5 mm for C to E.

FIGURE 14. Platylicoa angela sp. nov.: A, labrum; B, left mandible; C, mandibular palp; D, labial palp; E, maxillule; F, maxilla; G, maxilliped; H, maxilliped endite; I, epignath. Scale line = 0.2 mm.

FIGURE 15. Platylicoa angela sp. nov.: A, cheliped; B, pereopod 1; C, pleopod (plumose nature of all setae not shown, for clarity). Scale line = 0.5 mm.

FIGURE 16. Platylicoa angela sp. nov.: A, pereopod 2; B, pereopod 3; C, pereopod 4; D, pereopod 5; E, pereopod 6 with detail of marginal propodal spine. Scale line = 0.5 mm.