Fageapseudes brachyomos, Bamber, 2007

Bamber, Roger N., 2007, Suborders Apseudomorpha Sieg, 1980 and Neotanaidomorpha Sieg, 1980 *, Zootaxa 1599, pp. 13-40 : 14-19

Fageapseudes brachyomos n.sp.

Figures 1–3

Material examined. Holotype, male (KMNH IvR 500.151), station XR-12, 41º37.67’ – 41º37.08’N 146º54.19’– 146º52.72’E, 5473–5484 metres, 4 m ORE beam trawl, 23 September 2001. Paratypes: 1 female (KMNH IvR 500.152), station TD-8, 39º15.54’– 39º17.01’N 144º45.37’– 144º42.46’E, 5733–5762 metres, 4 m ORE beam trawl, 29 September 2001 (dissected).

Diagnosis. Characteristic of the genus, but second pereonite 1.5 times as wide as long with stout, blunt anterolateral spine-like apophyses, antennule with accessory flagellum of four segments and main flagellum of 13 (female) or 14 (male) segments, first pereopod carpus longer than merus, pleopod basis naked, uropod exopod of nine segments, endopod of about 18 segments.

Etymology. Named derived from the Greek, brachy – short, and omos – shoulder (noun in apposition), referring to the truncated pereonite 2 in comparison with other species of the genus.

Description of male.

Body ( Fig. 1A), dorsoventrally flattened, elongate, holotype 9.6 mm long (anterior tip of cephalon to posterior of pleotelson), 11 times as long as wide, narrower posteriorly.

Cephalothorax. Subrectangular, 1.25 times as long as wide, naked, anterior margin centrally concave without rostrum. Eyes absent; eyelobes modified to prominent spine-like apophyses directed anteriorly and around bases of antennules.

Pereonites. Pereonite 1 shortest, about one-third as long as cephalothorax, lateral margins uniformly convex. Pereonite 2 half as long again as pereonite 1. Pereonites 3 and 6 subequal, twice as long as pereonite 1. Pereonites 4 and 5 equal, 1.2 times as long as pereonite 3 (all pereonites respectively 2.7, 1.5, 1.1, 0.8, 0.8 and 1.0 times as wide as long). Pereonites 2 to 6 with anterolateral spine-like apophyses, blunt on pereonites 2 and 3, and expanded postero-laterally at attachment of coxae. Blunt ventral hyposphenia present on pereonites 1 to 5. Pereonite 6 with mid-ventral penial tubercle.

Pleon. As long as pereonites 2 to 6 together, of five free subequal bell-shaped pleonites bearing pleopods. Pleonites dorsally convex, as wide as long, laterally expanded posteriorly.

Pleotelson long and slender, laterally expanded at attachment of uropods, as long as last three pleonites, three times as long as wide.

Antennule ( Fig. 1B). Peduncle 4-articled. Proximal article elongate, nearly six times as long as wide, setose as figured. Second article 0.3 times as long as article 1, with distal crown of setae. Third article just shorter than article 2, fourth article one-third as long as third article, naked. Main flagellum of 14 segments, articles 2 to 13 bearing 2, 3, 3, 3, 4, 4, 3, 3, 3, 2, 1 and 1 aesthetascs respectively. Accessory flagellum of four segments.

Antenna ( Fig. 1D). Inner process on proximal peduncle article with smooth margin. Article 2 naked, bearing elongate squama with five simple marginal setae. Peduncle article 3 as long as wide, with one seta. Articles 4 and 5 subequal, three times as long as article 3. Flagellum of eight segments.

Mouthparts. Labrum rounded, simple, distally setose; small epistome present. Right mandible ( Fig. 2A) with strong, crenulated pars incisive, setiferous lobe with five, mainly bifurcate setae, pars molaris slender, blunt with fine marginal setae; mandibular palp of three articles, proximal article just longer than wide with single medial seta, article 2 three times as long as article 1 with two denticulate and five simple setae, article 3 half length of article 2 with eight inner setae and two longer distal setae, proximal of which is denticulate. Left mandible ( Fig. 2B) as right but with crenulate lacinia mobilis; article 1 of palp with two setae. Maxillule ( Fig. 2C) inner endite with rounded inner apophysis and finely setose margins, with five variously compound distal setae; outer endite with ten distal spines and two subdistal setae; palp of two articles, distally with five setae. Maxilla ( Fig. 2D) outer lobe of outer endite with two medially setulated setae on outer margin; inner lobe of movable endite with simple setae; outer lobe of inner endite with two simple, one setulated, and five multifurcate spiniform setae; inner lobe of fixed endite with rostral row of 21 setae. Labium ( Fig. 2E) with serrated outer margin and setulose inner margin, palp with fine lateral setules and three simple distal setae. Maxilliped ( Fig. 2F). Basis with small inner distal seta; palp article 1 with small seta on outer margin, long distal seta and field of fine setules on inner margin; palp article 2 longer than wide, with rows of numerous short setae on inner margin; outer margin with two simple setae distally; palp article 3 as long as wide, with two stout and four finer simple setae along inner margin; palp article 4 with five distal setae. Endite with compound (“leaflike”) inner caudo-distal seta. Epignath large, cup-shaped, with inner lobe and laterally setose distal seta ( Fig. 2G).

Cheliped ( Fig. 2H). Slender. Basis 2.4 times as long as wide, dorsally only with small distal seta, ventrally with stout subdistal spine. Exopodite present, 3-articled, second article naked, short, distal article with three plumose setae. Merus elongate with ventrodistal group of setae and small spine. Carpus slender, 3.5 times as long as wide, with four simple setae along ventral margin. Chela slender, ventral margin with two distal setae; three setae near articulation of fixed finger; cutting edge of fixed finger with small, rounded proximal apophysis and row of setules. Dactylus with sparse marginal setae but no apophyses on cutting edge.

Pereopod 1 ( Fig. 3B). With pronounced, setose spine-like apophysis on coxa. Basis stout, 3.8 times as long as wide with small ventrodistal spine. Exopodite present, 3-articled, article 2 naked, article 3 with two distal plumose setae. Ischium with single simple ventrodistal seta. Merus widening distally, with three ventral setae, one stout ventrodistal spine, three subdistal inner setae and four dorsodistal simple setae. Carpus longer than merus, compact, less than twice as long as wide, with dense row of dorsal marginal setae, one dorsodistal blunt spine and two ventral blunt spines interspersed with fine setae. Propodus shorter than merus and 1.4 times as long as wide, with two dorsal spines in distal half and five ventral blunt spines interspersed with single setae. Dactylus stout, with three mid-dorsal fine setae and four ventral denticulations; unguis short.

Pereopod 2 ( Fig. 3C). More slender than pereopod 1. Basis four times as long as wide with three ventrodistal setae. Merus half as long as carpus, widening distally, with tuft of dorsodistal setae and one ventrodistal slender spine. Carpus elongate, with tuft of dorsodistal setae, ventrally with marginal setae and slender subdistal spine. Propodus two-thirds as long as carpus, with three slender spines ventrally and tuft of dorsodistal setae. Dactylus slender with three mid-dorsal fine setae and ventral denticulation; unguis slender, pointed.

Pereopod 3 ( Fig. 3D). Similar to pereopod 2 but merus without spine. Carpus with only one ventral spine.

Pereopod 4 ( Fig. 3E). Similar to pereopod 2 but merus dorso-distally naked. Carpus with distal crown of about 12 setae more than half as long as propodus. Dactylus compact, unguis with four ventral denticulations.

Pereopod 5 ( Fig. 3F). Merus more than half length of carpus. Propodus just shorter than carpus, with ventral row of short leaf-like spines in distal two-thirds. Dactylus and unguis slender, together as long as propodus.

Pereopod 6 ( Fig. 3G). Sparsely setose; propodus distally with row of leaf-like spines surrounding medial and distal part of article. Dactylus and unguis two-thirds as long as propodus.

Pleopods ( Fig. 1E). All alike. Basis elongate, naked. Endopod just shorter than exopod with proximal articulation; both rami slender, respectively with 11 and 13 plumose setae. Outer proximal seta on exopod sub-distally with robust setules, distally naked.

Uropod ( Fig. 1A). biramous, both rami filiform, multi-segmented. Basis with two setae distally. Exopod half as long as endopod, with nine segments. Endopod elongate, as long as fifth pleonite and pleotelson together, with about 18 segments.

Distinctions of female. Generally as male.

Pereonites with sharply pointed hyposphenia.

Antennule ( Fig. 1C) main flagellum of 13 segments with single aesthetascs on segments 9 and 11 only.

Cheliped ( Fig. 3A) proportionately smaller, without proximal apophysis on fixed finger. Pleopods absent.

Remarks. There were two described species of Fageapseudes , F. retusifrons ( Richardson, 1912) from the western Mediterranean, and F. bicornis ( Kudinova-Pasternak, 1973) from the Sea of Okhotsk. The proximity of the latter species (56º10’ to 58º16’N) suggested that the present material may be conspecific. However, there are a large number of morphological differences (vide Bãcescu & Guṭu 1971; Kudinova-Pasternak 1973) which suggest F. brachyomos n.sp. is specifically distinct rather than an example of geographical variation.

Most conspicuously, the anterior pereonites of both of the other species have slender, pointed anterolateral apophyses, those of F. brachyomos being stouter and blunter, and pereonite 2 longer than wide (much wider than long in F. brachyomos ). The antennular and antennal flagella both have more segments in F. brachyomos (main flagellum 13 to 14, accessory flagellum four, antennal flagellum eight) than either F. bicornis (eight, two and six respectively) or F. retusifrons (ten, two and seven respectively). With the additional complement in the male of numerous aesthetascs on the antennule, and the large penial tubercle, this difference might be related to greater maturity of the present specimen: yet both of the other species show more marked dimorphism of the male cheliped, with a stouter and more robust chela bearing a larger tooth-like apophysis proximally on the fixed finger. Both of the previous species have the carpus of pereopod 1 shorter than the merus (longer in F. brachyomos ) and a reduced pleopod in the female (absent in F. brachyomos ). The uropod of the present species also has more segments (exopod nine, endopod 18) than either F. bicornis (5, 8) or F. retusifrons (five, 12). There are also a number of differences in setation between F. brachyomos and F. bicornis , notably in the mouthparts and pleopod basis.

The presence of a compound (“leaf-like”) inner caudo-distal seta on the maxilliped endite ( Fig. 2F) suggests that this genus should be in the Leviapseudinae rather than the Apseudinae , and indeed the morphology of the pleonites and pleotelson are consistent with species of that subfamily.