Mendamanus ailurostoma Bamber, 1998

Bamber, Roger N, Chatterjee, Tapas & Marshall, David J, 2012, Inshore apseudomorph tanaidaceans (Crustacea: Peracarida) from Brunei: new records and new species, Zootaxa 3520, pp. 71-88 : 79-85

Mendamanus ailurostoma Bamber, 1998

Mendamanus ailurostoma Bamber, 1998: 176 –181, figs 5–7.

Material examined: 13, Brunei Darussalam, 0 4°40.5ʹN 114°26.5ʹE, sand, 2–8 m depth, March 2009.

Remarks. The type, and only previous, collection of this species, including both males and females, was taken at 60 m depth off the Brunei coast, on shelly fine sand with silt. As the fifth pereopod was described but not figured in the original description, the opportunity is taken to confirm the lack of a row of lanceolate spines on the propodus of that appendage (a significant feature of classification within the Apseudinae ).

Family Parapseudidae Gu ţ u, 1981

Genus Aponychos gen nov.

Diagnosis. Parapseudid without apophysis on pereopod 1 coxa, without dorsal row of setae on pleonite 1. Body glabrous, eyes present but eyelobes not demarcated from carapace; rostrum present, rounded or pointed. Pereon and pleon taper towards posterior, pleonites more than half as long as pereonite 6, pleotelson longer than wide, naked. Flagella of antennule of few segments; peduncle of antenna of only four articles, first article without apophysis, squama present, setose. Mandibular palp with sparse setation on all articles; labial palp with three distal spines but no apophyses; maxillule inner endite with outer apophysis; maxilliped basis with distal seta, proximal palp article without inner setae or spines; endite with caudo-distal inner seta finely-denticulate. Cheliped with midventral spine on basis, with exopodite, carpus slender; pereopods without plumose setae, pereopod 1 with exopodite, each pereopod dactylus with ventrodistal seta-like apophysis longer than minute unguis; dactylus and unguis of pereopod 4 as developed as those of other pereopods. Five pairs of biramous pleopods present; uropods biramous, multisegmented.

Antennules of male with more-numerous aesthetascs than those of female; antennae of male with aesthetascs on proximal flagellar segments; cheliped of male more robust than tat of female, with conspicuous tooth-like proximal apophysis on fixed-finger cutting-edge.

Etymology. from the Greek apo —separate, divide, and onychos —a claw, pertaining to the cloven appearance (although not reality) of the unguis of all pereopods (masculine).

Type species: Aponychos hyperaesthesia sp. nov. by monotypy.

Remarks. The relatively simple gross morphology of the species described below, without apophyses, spines nor setae on its somites, nor particular distinction of the pleonites from the pereonites, shows affinity only to such genera as Saltipedis Guţu, 1995 sensu lato and Pakistanapseudes Bäcescu, 1978 sensu lato, and these are also the parapseudid genera which display elaborate aesthetasc armament on the antenna of the male. Other similarities with Pakistanapseudes sensu lato include the apparent bifurcation of the claws, such species as P. toloensis (Bamber, 1997) , P. tenuicorporeus ( Shiino, 1963) and P. goofi Bamber & Sheader, 2003 having this feature on a number (but not all) of pereopods, and the dimorphic chela with tooth-like apophysis in mature males (in those few species of Pakistanapseudes in which mature males with chelipeds are known) ( Bamber & Sheader 2003; Błażewicz-Paszkowycz & Bamber 2007). Unlike Aponychos , both of these genera are characterized by an apophysis and only two distal spines on the labial palp, numerous segments in the antennular flagella (e.g. seven or more segments in the accessory flagella, where known), and secondary segmentation of the male antennae and antennules, while species of Saltipedis have a dorsal row of setae on the first pleonite.

The reduction to only four articles in the antennal peduncle is unusual in the Parapseudidae (although distinction of the peduncle from the flagellum can be unclear in Pakistanapseudes species); such reduction does occur in other families, for example in some kalliapseudids and metapseudids.

Aponychos hyperaesthesia sp. nov. ( Figs 5–7 )

Material: Brooding Ƥ holotype ( BMNH.2012.1072), 3 allotype ( BMNH.2012.1073), 433, 4Ƥ (1 brooding, 1 with oostegites), paratypes ( BMNH.2012.1074–1081), 1Ƥ with oostegites, dissected, Brunei Darussalam, 0 4°40.5ʹN 114°26.5ʹE, sand, 2–8 m depth, March 2009.

13,1Ƥ, 1 brooding Ƥ, paratypes ( BMNH.2012.1082–1084), 1 paratype 3, dissected, Sungai Besar, Sungai Brunei Estuary and Bay, Brunei Darussalam, 4º56'N, 115º1'E, mud flat and algae covering the pneumatophores of Avicennia marina , coll T Chatterjee and David J Marshall, 10 March 2011.

Description of female: Body ( Fig. 5 A) tapering towards posterior, holotype 2.5 mm long, 5.6 times as long as wide. Cephalothorax subrectangular, glabrous, 1.25 times as long as wide, twice as long as pereonite 3, with rounded or triangular rostrum ( Fig. 1 B); eyelobes not demarcated from carapace, eyes present, pigmented. Pereonites naked, with convex lateral margins, wider than long. Pereonite 1 shortest, pereonites 2 and 6 subequal in length, 1.1 times as long as pereonite 1; pereonites 3, 4 and 5 subequal in length, 1.3 times as long as pereonite 1 (all pereonites respectively 2.4, 2.1, 1.7, 1.6, 1.6 and 1.8 times as wide as long). Pleonites naked, about 2.7 times as wide as long, without extended epimera. Pleotelson subrectangular, twice as long as each pleonite, 1.2 times as long as wide, naked.

Antennule ( Fig. 5 C) about as long as cephalothorax, proximal peduncle article 2.7 times as long as wide without marginal tuberculation, inner margin with four simple setae, outer margin with two simple setae; second article twice as long as wide, 0.6 times as long as first article, with two inner and one longer outer simple setae; third article one-third length of second, with two inner and one outer simple distal setae; distal peduncle article half as long as third article, naked. Main flagellum of four segments, single aesthetasc on segment 4; accessory (inner) flagellum of two segments.

Antenna ( Fig. 5 D) with only four apparent peduncular articles; proximal peduncle article without apophysis, 1.6 times as wide as long, bearing small outer marginal seta; second article 1.3 times as long as first, with single inner and outer simple setae, squama a narrow oval bearing five distal simple setae; third peduncle article short, naked; fourth article (possibly a fusion of original fourth and fifth articles) twice as long as second, with single inner and outer distal setae. Flagellum of five segments, without aesthetascs.

Labrum ( Fig. 5 E) apically rounded, setose. Left mandible ( Fig. 5 F) with four rounded teeth on pars incisiva, lacinia mobilis elongate with four rounded distal teeth, spiniferous lobe bearing one denticulate and two bidentate spines; right mandible ( Fig. 5 G) similar but without lacinia mobilis, spiniferous lobe bearing three denticulate spines; pars molaris robust with strong distal margin; first article of mandibular palp bearing one inner distal seta; second article about twice as long as first, with one or two distal setae; third article about as long as first, with three distal setae. Labium ( Fig. 5 H) distally naked, outer-distal margin with fine denticulations, palp without apophyses, marginally setose and with three distal spines. Maxillule ( Fig. 5 I) outer endite with ten distal spines and two subdistal setae, inner endite (not figured) with five finely-plumose distal setae and outer subdistal apophysis; palp of two articles, distally with three setae. Maxilla (not figured) with three denticulations on outer margin; outer lobe of moveable endite with two subdistal simple setae and five distally-widened and denticulate distal setae; inner lobe of moveable endite with six denticulate setae; outer lobe of inner endite apparently with five simple outer distal setae; inner lobe of fixed endite with rostral row of 13 setae guarding two longer finely denticulate setae. Maxilliped ( Fig. 5 J) basis with one long seta almost reaching distal margin of second palp article; endites with two coupling hooks, four outer fusiform setae, distal margin with a mixture of five spatulate spines and fine setae, caudo-distal inner seta finely-denticulate, slender; palp first article with fine outer-distal spine; second article with outer distal spine, inner margin with about nine shorter curved setae in two rows and three longer straight setae; third article with six inner submarginal short, curved setae and four inner marginal longer curved setae; fourth article with one subdistal and five distal setae. Epignath ( Fig. 5 K) ovoid, lobate, margins and distal spine finely setulose.

Cheliped ( Fig. 6 A) slender, basis twice as long as wide, ventrally with two subdistal simple setae and one spine at mid-length; exopodite with four plumose setae on distal article; merus subrectangular, with inner subdistal seta and tuft of four setae on ventrodistal “shoulder”; carpus 4.2 times as long as wide, with one dorsoproximal seta, two dorsodistal setae, ventrally with four marginal setae in proximal half and two subdistal setae; propodus 1.4 times as long as wide, dorsally with single proximal and distal setae and two setae in junction of fingers; fixed finger anaxial, as long as palm of propodus, with three distal setae and row of fine setules along cutting edge, terminal spine distinct; dactylus with three distal setae and fine spinules along cutting edge; neither cutting edge with denticulations or apophyses.

Pereopod 1 ( Fig. 6 B) coxa without apophysis, bearing one seta; basis three times as long as wide, with two ventral subdistal setae; exopodite with five plumose setae on distal article; ischium compact with one ventrodistal setae; merus 0.6 times as long as basis, with seven ventral marginal setae, two dorsodistal setae, and single ventrodistal spine; carpus 0.7 times as long as merus, with two ventral spines interspersed with simple setae, one dorsodistal spine amongst marginal row of setae; propodus just longer than carpus, ventrally with three spines interspersed with simple setae, dorsally with two curved spines in distal half and six marginal setae; dactylus as long as propodus, with mid-ventral denticulation, ventrodistal seta-like apophysis; unguis minute.

Pereopod 2 ( Fig. 6 C) coxa with seta; basis 2.5 times as long as wide, with ventroproximal penicillate seta and two ventrodistal setae; ischium with two ventrodistal setae; merus 0.3 times as long as basis, with one ventrodistal slender spine and four ventrodistal setae; carpus 1.5 times as long as merus, ventrally with two slender spines interspersed by simple setae, row of five setae across distal margin; propodus just shorter than carpus, ventrally with three slender spines and one simple seta, dorsally with four distal setae; dactylus 1.4 times as long as propodus, with ventrodistal seta-like apophysis; unguis minute. Pereopod 3 ( Fig. 6 D) similar to pereopod 2, but carpus with two spines and two setae dorsodistally, propodus with three dorsodistal setae.

Pereopod 4 ( Fig. 6 E) basis 2.4 times as long as wide, with single dorsal and ventral penicillate seta and one ventrodistal seta; ischium with two ventrodistal setae; merus one-quarter as long as basis, with four ventrodistal setae; carpus 2.2 times as long as merus, with two setae and six slender spines in pairs along ventral and onto distal margin, dorsodistally with one seta and two slender spines; propodus about half as long as carpus, with eight distal stout setae and dorsal penicillate seta; dactylus and unguis as those of pereopod 3, 1.3 times as long as propodus. Pereopod 5 ( Fig. 6 F) similar to pereopod 4, but basis without penicillate setae, merus with two setae and one spine ventrodistally, carpus 2.5 times as long as merus and without dorsodistal spines or setae, propodus with only single ventrodistal and dorsodistal spines.

Pereopod 6 ( Fig. 6 G) similar to pereopod 5, but basis naked; merus with one spine and three setae ventrodistally; carpus with dorsodistal seta; propodus with four dorsodistal setae and distal row of six bidenticulate spines.

Pleopods ( Fig. 6 H) all alike, basis with three inner plumose marginal setae; endopod with thirteen plumose marginal setae in distal half; exopod two-thirds as long as endopod, with eleven marginal plumose setae distally and along outer margin.

Uropod ( Fig. 5 A) basis with small inner and outer distal setae; exopod of four segments; endopod elongate, about as long as pleon, with about 14 segments.

Description of male: Generally as female, pereonites 3 to 5 proportionately slightly shorter ( Fig. 5 B), rostrum either triangular or rounded. Dimorphism shown by antennule, antenna and cheliped. Antennule ( Fig. 7 A) main flagellum of five segments, first segment with three proximal and three distal aesthetascs, segments 2 to 5 with three, four, zero and two aesthetascs respectively. Antenna ( Fig. 7 B) peduncle similar to that of female, flagellum of seven segments, proximal four segments with four, five, six and four aesthetascs respectively.

Cheliped of smaller male ( Fig. 7 C) stouter than that of female, basis 1.7 times as long as wide, without midventral spine but with paired ventrodistal spines; carpus 1.8 times as long as wide, with expanded inner margin bearing five setae, one dorsodistal and no dorsoproximal seta; propodus more elongate than that of female, without dorsoproximal seta; fixed finger with large tooth-like apophysis at proximal end, distal end of cutting edge with rounded crenulations each bearing fine seta; dactylus over-reaching fixed finger. Cheliped of larger male ( Fig. 7 D) with midventral basis spine, inner-marginal expansion of carpus extended as a flange, with inner row of setae in proximal half; apophysis and cutting-edge crenulations on fixed finger, and over-reaching dactylus all more developed.

Etymology. Hyperaesthesia is an abnormal extension of the senses (from the Greek hyper —very, over, and aesthesis —feeling), pertaining to the elaborate aesthetascs on the antenna of the male, in addition to those on the antennule (noun in apposition).

Remarks. The variation in form of the rostrum, either pointed ( Fig. 5 A) or rounded ( Fig. 5 B), occurring in both males and females, is unusual in the Parapseudidae , this feature often being a valuable character for species distinction (e.g. Bamber & Sheader 2003). The different degrees of development of the male cheliped shown in Figure 7 may either reflect two moults of adult males (unlikely), or simply the variation resulting from the extreme degree of change in morphology from juvenile to adult leading to imprecision in the final form, a character also found in such genera as Leptochelia (see Lang 1973).

The preponderance of male chelae with large inner tooth-like apophyses in Brunei species is interesting but probably not significant, being found in Aponychos hyperaesthesia sp. nov., the unrelated parapseudids Pakistanapseudes pectinis Bamber, 1998 and Hainanius nigrifrons ( Shiino, 1963) (see Bamber 1998), and the even more distantly related apseudid Apseudopsis opisthoskolops (see above).

Family Pagurapseudopsidae Gu ţ u, 2006

Figures

FIGURE 1. Apseudopsis opisthoskolops sp. nov., female: A, holotype, dorsal; B, anterior margin of cephalothorax; C, pleotelson and proximal part of uropods; D, antennule; E, antenna; F, labrum; G, left mandible; H, right mandible; I, labium; J, maxilla. Scale line = 1.0 mm for A, 0.3 mm for B – E, 0.2 mm for F to J.

FIGURE 5. Aponychos hyperaesthesia gen. et sp. nov., A, female, dorsal; B, male, dorsal; C, female antennule; D, female antenna; E, labrum; F, left mandible; G, right mandible; H, labium; I, maxillule (inner endite not shown); J, maxilliped with endite; K, epignath. Scale line = 1 mm for A – B, 0.2 mm for C – K.

FIGURE 6. Aponychos hyperaesthesia gen. et sp. nov., female: A, cheliped; B – G, pereopods 1 to 6 respectively; H, pleopod (plumose nature of all setae not shown). Scale line = 0.2 mm.

FIGURE 7. Aponychos hyperaesthesia gen. et sp. nov., male: A, antennule; B, antenna; C, right cheliped of smaller male (exopodite not shown); D, left cheliped of larger male. Scale line = 0.2 mm.