Filitanais elongatus Segadilha & Dos Santos & Serejo 2017, sp. nov.

Filitanais elongatus sp. nov.

urn:lsid:zoobank.org:act: 2BB6 BAF 1-E2AC-4EA3-8EED-BC62C46F296A

Figs 1–3

Diagnosis (based on females)

Body about 13 times longer than wide; pereonite 2 four times longer than pereonite 1; pereopod 1–3 carpus with three spiniform setae distally and propodus with one spiniform ventral seta; pereopod 1–6 ischium without seta; pleon about 0.6 times as long as pereon; pleotelson square, as long as wide; uropod as long as pleotelson; uropod exopod longer than first article of endopod.

Etymology

The specific epithet refers to the long second pereonite, about four times longer than the first pereonite in species of Filitanais.

Material examined

Holotype

ANTARCTICA: ♀, dissected, adult non-ovigerous, length 1.9 mm, Bransfield Strait, station #2, 62º17′33.4″ S, 58º18′12.6″ W, 1.147 m deep, 6 Dec. 2008 (MNRJ 24443).

Paratype

ANTARCTICA: 1 ♀, adult non-ovigerous, length 1.8 mm, other data as for the holotype (MNRJ 26238).

Description

BODY (Fig. 2). About 13 times as long as wide. Cephalothorax oval, 1.6 times as long as wide; eyelobes absent. Pereonites 2–6 longer than wide. All pereonites with lateral setae. Pereonite 1 shortest, about 0.6 times longer than wide. Pereonite 2 longest, about 1.8 times as long as wide. Pereonite 3 as long as pereonite 4, about 1.4 times as long as wide. Pereonite 5 slightly longer than pereonite 6, both about 1.3 times as long as wide. Pleon (Fig. 2) long, about 30% of body length. All pleonites sub-equal in size, with first two pleonites slightly longer than others (0.7 and 0.6 times longer than wide). Pleonite 5 with lateral simple seta. Pleotelson square, about as long as wide, with dorsal plate not covering uropods; one pair of lateral and one pair of terminal simple setae. Apex pointed.

ANTENNULE (Fig. 2). With four articles, slightly shorter than cephalothorax. Article 1 longest, about 2.3 times as long as wide, with one simple and four penicillate outer setae. Article 2 about 1.4 times as long as wide, one inner distal penicillate seta and one simple and two penicillate outer setae. Article 3 stout, as long as wide, with two simple and one penicillate distal setae. Article 4 slender, about 2.0 times as long as wide, with five simple terminal setae and one aesthetasc.

ANTENNA (Fig. 2). With five articles. Article 1 short and fused to the cephalothorax, naked. Article 2 as long as wide, with one simple long outer seta. Article 3 longest, about 2.9 times as long as wide, with two simple and one penicillate inner distal setae and two outer distal penicillate setae. Article 4 narrow, 2.9 times as long as wide, with one distal simple seta. Article 5 minute, with six simple terminal setae.

MOUTHPARTS. Labrum (Fig. 2) rounded and setulose. Mandible molar process longer than incisor and narrow, distal part with three small spines. Left mandible (Fig. 2) lacinia mobilis in the shape of a single blunt spine, shorter than incisor; incisor with pointed distal margin. Right mandible (Fig. 2) incisor crenulated dorsally and pointed distally. Labium (Fig. 2) simple, with naked lobes. Maxillule (Fig. 3) endite with ten distal spiniform setae. Palp not recovered. Maxilla (Fig. 3) with oval shape elongated. Maxilliped (Fig. 3) basis wider than endite, rectangular and partly fused. Endites not fused, with one distal tubercular process each. Palp article 1 smooth; article 2 with three inner and one outer seta; article 3 with three inner setae; article 4 with five inner setae (one short, four long). Epignath not recovered.

CHELIPED (Fig. 3). Basis unequally divided by long prominent sclerite, longer than carpus, proximal part narrow, distal part wide, attached to cephalothorax via large sclerite. Merus triangular, with one simple seta ventrally. Carpus about 1.8 times as long as wide, no carpal shield, with two ventral and one dorsal simple setae. Propodus about 1.8 times as long as wide, with three simple setae on inner view. Fixed finger with four simple setae on cutting edge and two simple ventral setae. Dactylus slightly curved and smooth, as long as fixed finger.

PEREOPOD 1 (Fig. 3). Coxa present with one simple seta. Basis stout and naked, about 2.2 times as long as wide. Ischium naked. Merus about 1.4 times as long as wide, with one simple and one long spiniform distoventral setae. Carpus longer than merus, with three spiniform setae distally. Propodus shorter than merus and carpus combined, with one minute distodorsal and one spiniform distoventral setae. Dactylus 0.6 times as long as unguis. Dactylus and unguis combined longer than propodus.

PEREOPOD 2 (Fig. 3). Similar to pereopod 1, except coxa naked; carpus with one distodorsal and two distoventral spiniform setae; propodus with one spiniform distoventral seta.

PEREOPOD 3 (Fig. 3). Similar to pereopod 2, except, dactylus and unguis combined as long as propodus.

PEREOPOD 4 (Fig. 3). More slender than pereopod 1–3. Coxa absent. Basis about 3.1 times as long as wide, naked. Ischium, with one simple seta. Merus about 1.7 times as long as wide, with two spiniform distoventral setae. Carpus longer than merus, with one simple and three spiniform setae distally. Propodus shorter than merus and carpus combined, with one minute and one spiniform distodorsal setae, and two spiniform distoventral setae. Dactylus 1.3 times as long as unguis. Dactylus and unguis combined longer than propodus.

PEREOPOD 5 (Fig. 3). Similar to pereopod 4, except ischium with two ventral setae.

PEREOPOD 6 (Fig. 3). Similar to pereopod 4, except carpus with one simple and four spiniform distal setae. Propodus with four distal spiniform setae. Dactylus 0.8 times shorter than unguis.

PLEOPODS. Absent.

UROPOD (Fig. 3). As long as pleotelson. Basal article long and naked, about 1.1 times as long as wide. Exopod uniarticulate, longer than endopod first article, with one simple medial and two long simple setae apically. Endopod biarticulate, first article longer than second, with one simple subdistal seta; second article with one simple medial seta, and one penicillate and five simple terminal setae.

Remarks

The diagnostic characters used to identify species of Filitanais are the shape of the pleotelson and the pleonites as well as the length of the uropodal exopod. The mouthparts and the articulation of the uropodal exopod are not reliable characters for species separation (Larsen 2005). The main differences between the six species of Filitanais are shown in Table 1. Filitanais elongatus sp. nov. resembles F. moskalevi in habitus, but it can be distinguished by the pleonites and the pleotelson with lateral margins parallel, the merus of pereopod 1 with two setae and the uropod exopod longer than half of the first article of the endopod.

Filitanais elongatus sp. nov. differs from F. filiformis in having:

(i) antennules slightly shorter than the cephalothorax (instead of equally long); (ii) pereonite 1 wider than long (instead of equally long);

(iii) the pleonites combined about 0.6 times as long as pereonites length (instead of as long as or longer); (iv) the uropod exopod longer than half of the first article of endopod (instead of as long as).

The new species differs from F. vulgaris by:

(i) the length of pleotelson (as long as wide in F. elongatus sp. nov. and 1.5 times longer than wide in F. vulgaris);

(ii) the slender uropod, as long as the length of the pleotelson, instead of shorter than half of the pleotelson;

(iii) the seta of pereopod 1 merus longer than the distal margin of the carpus.

Filitanais elongatus sp. nov. is distinct from both Antarctic species (F. rebainsi and F. curticaudus) in: (i) pereonite 2 four times longer than pereonite 1, instead of sub-equal in length;

(ii) the uropod exopod longer than the first article of the endopod, instead of shorter;

(iii) the pleotelson as long as wide (instead of 1.3 and 1.5 times longer than wide, respectively).

Distribution

Bransfield Strait, Antarctica, 1.147 m.