Two new species of Colletteidae ( Crustacea : Tanaidacea : Tanaidomorpha ) from Bransfield Strait , Antarctica

Abstract. Samples from deep benthic areas in the Bransfield Strait, Antarctica, revealed the presence of two new species of Colletteidae: Filitanais elongatus sp. nov. and Macrinella lavradoae sp. nov. Filitanais elongatus sp. nov. resembles F. moskalevi in its habitus; it can, however, be distinguished by characters such as the pleonites and pleotelson with lateral margins parallel and the uropod exopod being longer than half of the first endopod article. Macrinella lavradoae sp. nov. differs from the other species of Macrinella in the shape of the uropod and the pleotelson, with the uropod exopod shorter than the first article of the endopod, the uropod about as long as the pleotelson and the pleotelson with a rounded tip. The number of species of Tanaidacea recorded from Antarctica increases to 162, while the colletteids are now represented by 16 species. Moreover, the diagnosis of the genus Filitanais is herein modified.

The family Colletteidae currently contains 52 species in 16 genera (Anderson 2013;Błażewicz-Paszkowycz 2007;Morales-Núñez et al. 2016).It has a great morphological disparity and heterogeneity and is often well represented in deep-sea samples (Bird 2007).The two genera covered herein have a similar taxonomic history.Both Filitanais Kudinova-Pasternak, 1973 andMacrinella Lang, 1971 were described in the family Paratanaidae Lang, 1949, transferred to Leptognathiidae Sieg, 1976 and later moved to Anarthruridae Lang, 1971 by Sieg (1986) (Anderson 2013).More recently, both genera were transferred to the family Colletteidae based on a morphological phylogenetic analysis (Larsen & Wilson 2002).
In Antartica, colletteids occur from depths of 90 m to 7100 m, representing the majority of deep-sea species (Błażewicz-Paszkowycz 2014).The material was collected at a depth of 1100 m in the Bransfield Strait (South Shetland Islands, Antarctica; Fig. 1) in 2008 and 2009.The sediment was collected with a box corer, washed in a mesh size of 0.5 mm, fixed in 4% borax buffered formalin and subsequently preserved in 70% alcohol.
All specimens were examined and drawings of the habitus and appendages were made from one dissected specimen of each species.Dissections were made in glycerin using chemically-sharpened tungsten wire needles.All material examined is deposited in the Crustacean Collection of the Museu Nacional, Universidade Federal do Rio de Janeiro, Brazil (MNRJ).
The body length was measured from the tip of the cephalothorax to the apex of the pleotelson.All measurements were made between the largest distances of the articles (length and width).The terminology follows Larsen (2003)

Female
Body almost nearly cylindrical and filiform.Carapace longer than wide.Eye-lobes and visual elements absent.Pleon long, at least 0.4 times the length of pereon, without lateral edges of dorsal shield.Pleonites and pleotelson not fused.Pleotelson with dorsal plate not covering uropods.Antennule with four articles.Antenna with 5-6 articles.Mandibles with pointed molar.Maxillipedal endites without distal setae; palp article 2 without multifurcate seta.Chelipeds attached via lateral sclerite.Pereopods slender, with coxae, dactylus and unguis not fused to a hook.Pleopods absent in female.Uropods long (about 0.5 times as long as pleotelson), biramous; endopod with two articles; exopod with 1-2 articles.Larsen (2005) proposed a diagnosis of the genus and considered the "pleonites long, almost as long as the pereonites and pleotelson".According to Larsen (2005), Filitanais vulgaris, even with a long pleon, was classified within the genus Collettea because of its broad mandibular molar.Larsen (2005) also wrote that F. curticaudus might not belong to Filitanais because of its short pleon, about 0.4 times the length of the pereon.

Remarks
On the other hand, Błażewicz-Paszkowycz (2005: key) characterized Filitanais as having a pleon longer than half the length of the pereon, and the pleotelson clearly longer than wide.Our examination of the six species of the genus, however, revealed that the pleon of F. moskalevi is only 0.4 times the length of the pereon, which casts doubt on the inclusion of this species within the genus.Alternatively, we propose to change the diagnosis of Filitanais as having a pleon at least 0.4 times the length of the pereon.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.

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.
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.

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.(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).

Etymology
The new species is named in honour of Dr Helena Passeri Lavrado (IB/UFRJ) in recognition of her incentive and encouragement to the first author to initiate taxonomic studies on tanaidaceans.Moreover, she coordinates the subproject MABIREH and is a member of the committee board of the Instituto Nacional de Ciência e Tecnologia Antártico de Pesquisas Ambientais (INCT-APA).

Fig. 1. A. Antarctic
SEGADILHA J.L. et al., Two new species of Colletteidae from Antarctica Continent.B. South Shetland Islands, King George Island (Admiralty Bay) and Bransfield Strait highlighted.C. Sampling sites in Bransfield Strait.(Source: Google Earth.)