New Tanaidacea (Crustacea: Peracarida) from the Gulf of Guinea

Four new species of deep-sea Tanaidacea taken from the Gulf of Guinea as part of the Ghanaian marine environmental monitoring programme in 2012 are described. One of the species, which was classified to the family Anarthruridae, differed substantially from the other members of the family, and was accommodated to the newly erected genus – Olokun n. gen. Each of the three other species belongs to a different family: Parakanthophoreus guineus n. sp. – Akanthophoreidae, Collettea agnesi n. sp. – Colletteidae, and Araphura studens n. sp. – Tanaellidae. A key for genera of Anarthruridae is given.


Introduction
Studies on the West African Tanaidacea date back to the end of the nineteenth century, when Pseudoleptochelia inermis (Dollfus 1898) was described. Since that time only about 80 species of tanaidaceans were recorded from the Atlantic coast of Africa. The main contributors in the field were Barnard 2009 (Weigmann andGuerrero-Kommritz 2009), and recently described from Lophelia rubble (Jakiel et al. 2015 The collection of benthic samples made as part of the Ghanaian marine environmental monitoring programme  is extremely extensive, and its complete sorting will take a few years. Nevertheless, the completed sorting of the first sets of samples has revealed numerous new species, most of which are apparently represented by single specimens. In this collection, the four species were represented by more than one specimen, and their descriptions are presented in this paper.

Materials and methods
The samples were collected in October and November 2012 in the Gulf of Guinea off Ghana from the RV Dr Fridtjof Nansen (Fig. 1). The cruise was a part of the marine environmental monitoring programme organised in co-operation between the Institute of Marine Research in Bergen (Norway) and the Environmental Protection Agency (Ghana). The sampling programme was supported by the Norwegian Agency for Development Cooperation (NORAD) (Oil for Development Programme -OfD) and the Food and Agriculture Organization of the United Nations (FAO). The project aimed to assess the influence of oil industry on marine benthic fauna in this almost completely unstudied part of the World Ocean. A total of 400 samples were taken on nine transects from the littoral to 1600 m depth, using a 0.2 m 2 van Veen grab. The material was sieved on 0.3 mm mesh size.
Tanaidacean specimens were dissected using chemically sharpened tungsten needles, mounted in glycerin on slides and sealed with nail varnish. Drawings were initially prepared using a microscope combined with a camera lucida and then re-drawn on a digital tablet (as proposed by Coleman 2003). The body length to width ratio was calculated using measurements from the tip of the carapace to the end of the pleotelson, and of the widest part of carapace, while the length and width of articles were measured along their central axes. The morphological terminology follows that proposed by Błażewicz-Paszkowycz et al. (2013). The material is deposited at the University Museum of Bergen (Norway).

Systematics
Suborder Tanaidomorpha  Diagnosis Maxilliped basis with long seta; endites with distinct distal tubercle and single seta. Cheliped carpal shield welldeveloped; propodus covered with microtrichiae; carpus and dactylus without crenulation; fixed finger with four serrated setae on ventral margin. Etymology: species is named after its type locality Gulf of Guinea (adjective).
Description of female holotype: body ( Fig. 2A and B) slender, about eight times as long as wide. Cephalothorax almost 20% of total body length. Pereonite 1 about 0.4 times as long as cephalothorax, about 0.6 times as long as wide, with concave anterior margin; pereonites 2 to 5 subequal, almost as long as wide, wider in the middle part; pereonite 6 shorter than the previous pereonites, about 0.8 times as long as wide. Pleon 20% of total body length. Pleonites subequal, about 0.2 times as long as wide, with simple seta laterally; sterna rounded in lateral profile. Pleotelson about 30% of total length of pleon, tapering distally. Antennule (Fig. 3A) of four articles, proximal article elongate, 2.2 times as long as wide, about 0.7 times as long as distal three articles combined, subdistally with group of six outer setaeone simple, the others penicillate; second article about 1.6 times as long as wide, about 0.5 times as long as proximal article, distally with six setae, three penicillate and two simple outer setae (one broken) and one inner simple seta; third article almost as long as wide, with one long simple seta in middle, inner distal row of spinules, one simple and one penicillate inner distal setae; fourth article about 2.8 times as long as wide, with one aesthetasc and five distal simple setae. Antenna ( Fig. 3B) proximal article naked; second article about 0.7 times as long as wide, with one distal simple seta; third article about 1.7 times as long as wide, with outer distal penicillate seta and row of spinules on distal margin; fourth article longest, about 2.8 times as long as wide, with distal three penicillate and with two long and one short simple setae; fifth article 3.5 times as long as wide, with distal simple seta; sixth article smallest, with four distal simple setae.
Mouthparts. Labrum (Fig. 3C) simple, hood-shaped and setulose. Right mandible (Fig. 3D) incisor flattened distally, two teeth on anterior corner; molar process ( Fig. 3D´)  distally. Maxilliped endite (Fig. 3H´) with outer distal group of microtrichiae one simple inner distal seta and tubercle. Maxilliped palp (Fig. 3H´´) first article naked; second article with two plumose and one simple inner setae and one outer simple seta; third article with distal microtrichiae and four inner setae, two serrated and two simple; fourth article smallest, with microtrichiae, one subdistal seta and group of five distal setae, four of them serrated and one simple. Cheliped (Fig. 3I) basis with rounded posterior part just longer than anterior part, dorsodistally with simple seta; merus about 1.1 times as long as wide, with one ventral seta; carpus about 1.4 times as long as wide, with two ventral simple setae at midlength, two dorsal simple seta, one proximal and one distal, and well-developed carpal shield; propodus robust, palm longer than wide, with four ventral serrated setae, group of three spines near dactylus insertion on inner surface, single distal seta near dactylus insertion on outer surface and numerous microtrichiae; fixed finger with three simple setae and four well calcified teeth on cutting edge.
Pereopod 1 (Fig. 4A) coxa with one seta; basis 2.3 times as long as wide, with one simple ventrodistal seta; ischium with one ventrodistal seta; merus widening distally, about 1.8 times as long as wide, as long as carpus, with two ventrodistal simple setae, one strong and one simple; carpus about 1.7 times as long as wide, with microtrichiae on ventral and distal margins, one ventrodistal serrated seta and one dorsodistal serrated seta; propodus about 2.7 times as long as wide, with paired spinules on ventral and distal margin, one ventrodistal spine, one dorsodistal spine and one subdistal simple seta on dorsal margin; dactylus naked, unguis about 1.2 times as long as dactylus, combined about as long as carpus.
Pereopod 2 (Fig. 4B) coxa with simple seta; basis 2.5 times as long as wide, with two penicillate setae dorsally at midlength; ischium with one ventrodistal simple seta; merus widening distally, about 1.7 times as long as wide, ventrodistally with one serrated seta and one spinule, one simple ventrodistal seta; carpus about 1.6 times as long as wide, with spinules on ventral margin and one ventrodistal simple seta, dorsodistal seta broken; propodus about three times as long as wide, with microtrichiae on ventral margin, serrated spine ventrodistally, dorsal penicillate seta and dorsodistal row of spinules and one simple seta (broken on figure, observed from holotype).
Pereopod 3 (Fig. 4C) basis about 2.8 times as long as wide, with one dorsal penicillate seta proximally; ischium with one ventrodistal simple seta; merus with ventrodistal spinules, one strong serrated and one simple ventrodistal setae; carpus about 1.9 times as long as wide, with ventral microtrichiae, two ventrodistal serrated setae, distal microtrichiae and dorsodistal serrated seta; propodus three times as long as wide, with microtrichiae on ventral margin, ventrodistally with serrated spine, dorsodistally with group of spinules and one simple seta, and dorsally with penicillate seta; dactylus naked, unguis 1.4 times as long as dactylus, combined about as long as carpus.
Pereopod 4 ( Fig. 4D) coxa broken off; basis about 2.3 times as long as wide, naked; ischium with two ventral simple setae; merus with two ventrodistal serrated setae and microtrichiae; carpus three times as long as wide, with microtrichiae on distal margin, one ventrodistal serrated seta and two dorsodistal serrated setae; propodus about 4.2 times as long as wide, with microtrichiae from midlength ventral margin to distal margin, one dorsodistal simple seta and two serrated ventrodistal setae; dactylus with two rows of spinules on ventral margin; unguis about 0.4 times as long as dactylus.
Pereopod 5 (Fig. 4E) coxa with one simple seta; basis about 2.8 times as long as wide, naked; ischium with one simple ventrodistal seta (probably the other broken); merus with one ventrodistal serrated seta and one simple distal seta; carpus 1.3 times as long as wide, with spinules and two simple strong setae on ventral margin and one dorsodistal serrated seta; propodus about 3.1 times as long as wide, with spinules on ventral and distal margins, one ventrodistal strong spine and one dorsal simple seta; dactylus with two rows of spinules, unguis 0.4 times as long as dactylus.
Pereopod 6 ( Fig. 4F) basis 2.4 times as long as wide, slightly wider proximally, naked; ischium with two simple ventrodistal setae; merus 1.25 times as long as wide, with two serrated ventrodistal setae; carpus 2.6 times as long as wide, with ventrodistal and distal microtrichiae, one simple and two serrated setae ventrodistally, and one serrated seta dorsodistally; propodus about 3.6 times as long as wide, with ventral microtrichiae beginning at two-thirds length and two serrated ventrodistal setae and three serrated dorsodistal setae; dactylus with two rows of spinules ventrally; unguis about 0.4 times as long as dactylus.
Pleopods (Fig. 4G, G´) endopod with one seta subdistally on dorsal margin and ten setae distally; exopod with one proximal seta and 17 setae ventrally and distally, all setae plumose. Uropod ( Fig. 4H) biramous, basis naked; exopod of two segments, together about 0.2 times as long as endopod, proximal segment with one distal simple seta, distal segment with one long and one short simple setae distally; endopod of two segments, proximal segment naked, distal segment with five simple distal setae.
Remarks According to the recent re-definition of taxa classified in the Akanthophoreidae (Larsen and Araújo-Silva 2014), Parakanthophoreus guineus n. sp. that lacks spurs on pleonite 5 (ventrally), on the pleotelson (laterally), and on the basis and segment 1 of the endopod of the uropods, but has the basis of pereopods 1-3 of same width as pereopods 4-6, can be classified to the genus Parakanthophoreus Larsen & Araujo-Silva, 2014 or Paraleptognathia Kudinova-Pasternak, 1981. Although the new species has ornamentation on the propodus of the chelaa character proposed as diagnostic for Paraleptognathia, we have decided to classify it in Parakanthophoreus, as it lacks ornamentation on the cheliped fixed finger and the carpus, and lacks proximal denticulation on the fixed finger.
The unique character distinguishing P. guineus from not only other Parakanthophoreus species but also other akanthophoreids is a presence of the four serrated spines on the ventral margin of the fixed finger. Most species of Akanthophoreidae have their fixed finger armed with two setae (e.g. Akanthophoreus phillipsi (Sieg & Dojiri, 1991)) or two spines (e.g. Stenotanais crassiseta Bird & Holdich, 1984) (Sieg and Dojiri 1991;Bird & Holdich 1984), and the only two akanthophoreids with more than two setae/spines on their fixed finger are P. vikingra Błażewicz-Paszkowycz & Bamber, 2011 with three setae and an undescribed species (Błażewicz-Paszkowycz and Bamber 2011), provisionally classified as Chauliopleona armata sensu lato with five serrated spines (Bird 2015).
Etymology: named after Olokun the West African, Yoruban godess of the Ocean. Remarks The row of strong serrated spines presents on the cheliped propodus/fixed finger ventral margin in Olokun n. gen. is a unique character among Anarthruridae and similar to unique multiple meral setation of cheliped in Crenicarpus Drumm &Bird, 2016 (Drumm andBird 2016) adds more morphological diversity. Furthermore, this genus can be distinguished from other genera of this family by the combination of: a conical labrum. A laterally compressed labrum is present in Anisopechys Bird, 2004(Bird 2004, Synarthrura Bird, 2004and Siphonolabrum Lang, 1972(Bird 2004, 2007bLang 1972); a maxillule endite with six spines.  Kudinova-Pasternak 1990;Lang 1968Lang , 1972Sars 1882). the basis of pereopods 4-6 swollen, about 1.5 times as long as wide. The swollen basis of pereopods 4-6 was previously recorded e.g. for Synarthrura (Bird 2004) but never to this extent; the propodus of pereopods 4-6 compact and shorter than the dactylus/unguis combined. In Anarthruridae, the dactylus/unguis of pereopods 4-6 is usually short (compared to with this of pereopods 1-3), thus in most genera of this family the propodus of pereopods 4-6 is longer than the dactylus/unguis combined. Ithyomus, Keska, and Siphonolabrum are the only exceptionas some of their species have the dactylus/unguis as long as propodus or just longer (Bird 2004;Błażewicz-Paszkowycz et al. 2013;Lang 1972); the uropod endopod two-segmented. A uni-segmented uropod is characteristic for Anisopechys, Synarthrura, and Thorkelius (Bird 2004 Description of female holotype: body (Fig. 5A) slender, 8.3 times as long as wide. Cephalothorax about 10% of total body length, about 1.1 times as long as wide, with two simple dorsoproximal setae in distal part of lateral borders. Pereonite 1 about 0.5 times as long as wide, about 0.5 times as long as cephalothorax; pereonite 2 about 0.6 times as long as wide; pereonite 3 about 0.7 times as long as wide; pereonites 4 and 5 longest, about 1.2 times as long as wide; pereonite 6 about 0.9 times as long as wide. Pleon about 25% of total body length. Pleonites 1-4 subequal, about 0.3 times as long as wide; pleonite 5 slightly longer, about 0.4 times as long as wide. All pleonites with simple setae laterally. Pleotelson about 20% of total length of pleon, 0.4 times as long as wide, tapering towards distal part. Antennule (Fig. 5B) of four articles, proximal article naked, proximally broken; second article 0.6 times as long as wide, with two distal simple setae; third article 0.7 times as long as article 2, distally with two simple outer setae (one broken); fourth article about one third as long as proximal three articles combined, distally with group of six simple setae.
Antenna (Fig. 5C) of six articles; first and second article broken; third article 1.1 times as long as wide, distally with simple seta; fourth article elongate, about 3.7 times as long as wide, distally with group of four setae, three simple and one penicillate; fifth article distally with inner simple seta; sixth article with group of five simple setae.
Mouthparts. Labrum (Fig. 5D) simple, rounded, without setae. Mandibles not recovered. Maxillule (Fig. 5E) distally with group of six spines and three setules on inner margin. Maxillipedal palp (Fig. 5F) first article naked; second article about 1.8 times as long as wide, with one midlength seta on inner margin; third article about 1.9 times as long as wide, distally with one simple and three robust setae on inner margin; fourth article with four robust simple setae on distal margin and some spinules on outer margin.
Cheliped (Figs 5G, and 6A-C) basis naked; merus distally with two simple setae; carpus about 2.1 times as long as wide, with large posterior lobe overhanging merus, with one simple, subproximal and distal setae on dorsal margin; propodus with numerous microtrichiae and group of three serrated setae on inner face of palm, near dactylus insertion, one seta on outer face of palm, near dactylus insertion, lateral fold welldeveloped; propodus/fixed finger with six spines on outer margin and some microtrichiae, cutting edge with distal denticles and two robust setae; dactylus crenulate dorsally, with some lateral microtrichiae and one strong serrated seta and some spinules on ventral margin.
Pereopod 1 (Fig. 6D) coxa with single, simple seta; basis about 3.5 times as long as wide, naked; ischium with single simple seta on ventral margin; merus about 1.6 times as long as wide, ventrodistally with two simple setae; carpus about 1.9 times as long as wide, distally with group of three simple setae; propodus about 3.7 times as long as wide, with one ventrodistal simple seta and two dorsodistal simple setae; dactylus about 0.5 times as long as propodus, about 4.6 times as long as wide, proximally with single simple seta and one seta on distal margin; unguis just longer than dactylus.
Pereopod 2 (Fig. 6E) coxa with simple seta; basis about 3.4 times as long as wide, naked; ischium with one ventrodistal seta; merus with two ventrodistal setae; carpus with four distal seta, one short and three long; propodus about 3.3 times as long as wide, with two long distal setae and row of spinules on distal margin; dactylus about 0.7 times as long as propodus, proximally with one simple seta; unguis about 1.4 times as long as dactylus.
Pereopod 4 (Fig. 6G) basis about 1.5 times as long as wide, swollen, naked; ischium with two simple ventrodistal setae; merus about two times as long as wide, distally with two ventral serrated spines; carpus about 1.9 times as long as wide, distally with four serrated spines; propodus short slightly longer than wide with two ventrodistal serrated spines and one short dorsodistal seta; dactylus slightly shorter than propodus, naked; unguis same length as dactylus, with ventral serration.
Pereopod 5 (Fig. 6H) coxa with one seta; basis naked; ischium with one ventral seta; merus about 1.9 times as long as wide, distally with two serrated spines; carpus about 1.7 times as long as wide, distally with four serrated spines and one simple seta; propodus distally with two serrated spines and some spinules; dactylus naked, dactylus and unguis subequal, unguis serrated ventrally.
Etymology: species is dedicated to Agnieszka Janicka-Maj, aunt of the second author, who has always supported that author and had a positive influence on her education.
The description of appendages was done based on a female and only antennule and antenna were taken from a preparatory male (damaged in the female).
Description: body (Fig. 7A, B) slender, about 16 times as long as wide. Cephalothorax 10% of total body length, tapering towards anterior part. Pereonite 1 shortest, one third as Fig. 6 Olokun puellamaritima n. sp. female paratype (ZMBN 116024) A cheliped dorsal view; B basis, merus and carpus of left cheliped lateral view; C cheliped propodus and fixed finger, lateral fold marked with an arrow; D pereopod 1; E pereopod 2; F pereopod 3; G pereopod 4; H pereopod 5; I pereopod 6; J pleopod basis and exopod; J´pleopod endopod; K uropod. Scale bars: 0.1 mm long as cephalothorax; pereonites 2 and 3 subequal in length, about twice as long as pereonite 1; pereonites 4 and 5 subequal in length, about three times as long as pereonite 1; pereonite 6 shorter than pereonites 4 and 5. Pleon about 40% of total body length. Each pleonite longer than pereonite 1; pleonites 1-5 subequal and similar in length to pereonite 6. Pleotelson about 20% of total length of pleon, tapering towards posterior part. Antennule (Fig. 7C) of four articles, proximal article elongate, 4.2 times as long as wide, about 1.3 times as long as distal three articles combined, with row of five outer setae, one simple and four penicillate; second article about 1.7 times as long as wide, about 0.4 times as long as first article, distally with one simple and one penicillate setae; third article shortest, almost as long as wide, distally with one inner and one short outer setae; fourth article about 1.8 times as long as wide, with five distal simple setae and one aesthetasc.
Antenna (Fig. 7D) of six articles. First article missing; second article with simple subdistal dorsal seta; third article naked; fourth article 4.1 times as long as wide, with two setae at midlength and two simple and two penicillate setae distally; fourth article half as long as third article, with simple distal seta; last article minute, with one short and three long simple setae.
Mouthparts. Labrum (Fig. 7E) distally finely setose. Left mandible (Fig. 7F) with pointed incisor, lacinia mobilis stout; molar process broad, with six teeth on distal margin. Right mandible (Fig. 7G) incisor with six denticles. Maxillule (Fig. 7H) with 12 distal spines. Maxillipedal palp (Fig. 7I) first article naked; second article with two strong inner setae; third article with four inner simple setae; fourth article with group of five distal setae (at least three of them serrated) and one outer seta at midlength. Cheliped (Fig. 7J) basis about 1.8 times as long as wide, naked, posterior lobe subequal to anterior mass; merus suboval, with single ventral seta at midlength; carpus about 1.9 times as long as wide, with single ventrodistal seta and single dorsal seta at one-third length; propodus palm longer than wide, with one seta and microtrichiae on inner side near dactylus insertion; fixed finger with single ventral seta and group of three inner simple setae and two triangular teeth on cutting edge; dactylus with one dorsoproximal seta.
Pereopod 1 (Fig. 8A) coxa with single seta; basis slender, about 5.5 times as long as wide, naked; ischium with one ventral seta; merus almost as long as wide, naked; carpus subrectangular, twice as long as wide, with simple ventrodistal seta; propodus tapering distally, about 3.8 times as long as wide, with one ventrodistal spine; dactylus naked, unguis about 0.8 times as long as dactylus, both together about as long as carpus.
Pereopod 2 (Fig. 8B) basis about 2.9 times as long as wide, slightly swollen, with dorsoproximal penicillate seta; ischium with single ventral seta; merus subtriangular, about 1.2 times as long as wide, naked; carpus distally wider, 1.5 times as long as wide, with ventrodistal spine; propodus 3.8 times as long as wide, with spinules on distal margin, one ventrodistal spine and one dorsodistal simple seta; dactylus naked, unguis equal in length to dactylus, with ventral spur.
Pereopod 3 (Fig. 8C) coxa with single seta; basis distally slightly wider, about 2.9 times as long as wide, naked; ischium with single ventral seta; merus as long as wide, naked; carpus as long as wide, with ventrodistal spine and microtrichiae; propodus about 3.1 times as long as wide, with ventral microtrichiae, one ventrodistal spine and one dorsal seta, distal margin with spinules; dactylus naked, unguis equal in length to dactylus, with ventral spur.
Pereopod 4 (Fig. 8D) coxa with single seta, basis distally wider, about twice as long as wide, naked; ischium with single ventral seta; merus about 1.6 times as long as wide, with two distal spines; carpus distally swollen and rounded, about as long as merus, with three serrated spines, one seta and microtrichiae distally; propodus 2.2 times as long as wide, with two serrated ventrodistal spines and two dorsodistal short spines; dactylus ventrally serrated, unguis pointed, slightly shorter than propodus, with ventral serration.
Pereopod 5 (Fig. 8E) similar to pereopod 4, but propodus lacks of one distal simple spine. Uropod (Fig. 8G) biramous, basal article naked; exopod unisegmented not reaching half of endopod first segment, with one long and one short distal setae; endopod of two segments; proximal segment with two penicillate setae distally, distal segment with one penicillate and five simple long setae.
Copulatory male: Antennule (Fig. 9A) first article at least three times as long as wide, with three penicillate setae subdistally and five penicillate setae distally; second article about 0.4 times as long as first article, with one penicillate, two simple and one minute setae distally; third article about 0.6 times as long as second article, with one simple and one minute setae distally; fourth article three times as long as third article, with one aesthetasc and six simple setae.
Antenna (Fig. 9B) first article missing; second article twice as long as wide, with simple distal seta; third article as long as wide, naked; fourth article 5.2 times as long as wide, with one simple and one penicillate setae, one seta broken off; fifth article 0.6 times as long as fourth article, with one simple seta; distal article minute, with four simple setae.
Mouthparts strongly reduced. Maxilliped (Fig. 9C) basis not observed; endite with two simple setae distally; palp first article trapezoidal, naked; second article triangular, with two simple inner setae; third article 2.4 times as long as wide, with two long and two short inner setae; distal article with one simple seta subdistally and three simple and two serrated setae distally. Cheliped (Fig. 9D) basis short, about 1.4 times as long as wide, posterior lobe about as long as anterior mass, naked; merus triangular, with simple ventral seta; carpus 1.4 times as long as wide, with simple ventral and simple dorsodistal setae; propodus 1.8 times as long as wide, with one seta ventrally and one seta near dactylus insertion; fixed finger smooth, with three simple setae on cutting edge; dactylus about as long as fixed finger, with one short seta proximally and two spines on cuting edge.
Pereopod 4 (Fig. 9H) coxa with seta; basis 3.5 times as long as wide, naked; ischium with seta; merus 0.3 times as long as basis, with two ventrodistal short spines; carpus 1.5 times as long as merus, with one seta and one spine dorsodistally and two serrated spines ventrodistally; propodus 1.4 times as long as carpus, with one serrated seta dorsodistally and two ventrodistal serrated spines; dactylus about twice as long as unguis, combined just shorter than propodus.
Pleopods (Fig. 9K) all alike. Basis 1.9 times as long as wide, naked; endopod with one seta subdistally and seven setae distally; exopod just longer than endopod, with nine distal setae. All setae plumose. Uropod (Fig. 9L) basis 1.5 times as long as wide, naked; exopod about 0.4 times as long as endopod, with one seta subdistally and two setae distally; endopod with only one segment, but with fusion line at three quarters of length, with two penicillate setae at fusion line one long seta subdistally, one short and four long setae distally. Remarks The appendages of the female and the preparatory male are similar except pleopods that are present in a reduced form only in the male. The copulatory male differs from the female and the preparatory male in the structure and setation of antennules, cheliped and pereopods, in reduction of mouthparts, and well-developed, setose pleopods. Wi et al. (2015) gave a key to the identification of Collettea species; in this, C. agnesi fails at couplet 4 as pereonites 2-3 are neither shorter or longer than wide. Unlike C. agnesi, the two described species at this point, C. elongata Larsen, 2002 andC. lilliputa Blazewicz-Paszkowycz &Larsen, 2005, both lack a distinct subdistal ventral expansion on the unguis of pereopods 2-3 (Blazewicz-Paszkowycz and Larsen 2005;Larsen 2002). This unguis expansion is also found in C. arnaudi (Shiino, 1978), C. cylindratoides Larsen, 2000, or C. longipleona Błażewicz-Paszkowycz & Larsen, 2005(Blazewicz-Paszkowycz and Larsen 2005Larsen 2000Larsen , 2002Shiino 1978). Moreover, C. agnesi differs from C. elongata by having only single ventral seta on the cheliped fixed finger and from C. lilliputa by having a smooth incisor on the left mandible.
Till this moment, seven species of Collettea were described from the Atlantic Ocean, namely C. bamberi Drumm & Bird 2016, C. cylindrata (Sars, 1882 (Lang, 1971), C. elongata Larsen, 2002, C. minima (Hansen, 1913, C. pegmata Bamber, 2000, C rotundicauda Kudinova-Pasternak, 1983 a n d C . w i l s o n i L a r s e n , 1 9 9 9 ; a n d o n e s p e c i e s (C. vermiformis Lang, 1971) from the Mediterranean Sea.
Collettea agnesi can be differentiated from those species by: a relatively short pleotelson, about as long as the last pleonite. In other Atlantic Collettea species, the pleotelson is at least as long as the last three pleonites combined; a molar with six distinct teeth. Other Atlantic Collettea have molar only with distal serration or spines (Bamber 2000;Drumm and Bird 2016;Hansen 1913;Kudinova-Pasternak 1983;Lang 1971;Larsen 1999Larsen , 2002Sars 1882); the fixed finger with two triangular teeth on the cutting edge. Except C. minima, the remaining species have only serration on the cutting edge of the fixed finger (Bamber 2000;Drumm and Bird 2016;Hansen 1913;Kudinova-Pasternak 1983;Lang 1971;Larsen 1999Larsen , 2002Sars 1882); elongate uropods, distinctly longer than the half of pleotelson. Only in C. elongata, uropods are elongate but only close to the half length of pleotelson (Bamber 2000;Drumm and Bird 2016;Hansen 1913;Kudinova-Pasternak 1983;Lang 1971;Larsen 1999Larsen , 2002Sars 1882).
Collettea agnesi shares those characters with Antarctic C. lilliputa and to some extent also with C. minima, and it is possible that those species can be included in the new colletteid genus as previously suggested by Błażewicz-Paszkowycz and Larsen (2005) and Drumm and Bird (2016). At the moment, this species is classified to the genus Collettea based on: its cylindrical body, antennule of four articles, antenna of six articles, mandibular molar not pointed, pereopods with coxae, pleopods absent in females, uropod endopod of two segments, and exopod with one segment.
Etymology: studens [lat.] = student; the species is described as a part of a student taxonomical project.
Description of female holotype: body (Fig. 10A, B) slender, about ten times as long as wide. Cephalothorax almost 20% of total body length, elongate, with pair minute setae dorsodistally. Pereonite 1 as long as wide, 0.5 times as long as cephalothorax, with pair of simple dorsodistal setae; pereonites 2-4 subequal, about 1.4 times as long as wide, subrectangular; pereonite 5 about 1.1 times as long as wide; pereonite 6 shortest, about 0.8 times as long as wide. Pleon about 20% of total body length. Pleonites subequal, about 0.3 times as long as wide; sterna rounded in lateral profile. Pleotelson almost 20% of total length of pleon, tapering, with four simple distal setae. Antennule (Fig. 11A) of four articles; proximal article 2.6 times as long as wide, 0.8 times as long as three other articles combined, with one simple distal outer seta; second article about 1.8 times as long as wide, with one subdistal outer simple seta; third article about 2.1 times as long as wide, with two distal setae; fourth article about 2.1 times as long as wide, with group of five simple setae and one aesthetasc distally. Antenna (Fig. 11B) of six articles; first article not observed; second and third articles with dorsal seta distally; fourth article elongate, about 4.1 times as long as wide, with penicillate seta in the central part, distally with three penicillate setae and two simple setae; fifth article with distal simple seta; sixth article with five simple distal setae.
Mouthparts. Labrum (Fig. 11C) simple, hood shaped and setulose. Left mandible (Fig. 11D) with bifurcated incisor, lacinia mobilis simple, tapering distally; molar distally acuminate, with four distal teeth. Maxillule (Fig. 11E) with nine  distal setae, four of them serrated and with some small setae. Labium (Fig. 11F) simple, without setae. Maxilliped (Fig. 11G) basis with single seta; each endite with one distal seta, one oval tubercle, and microtrichiae on outer distal margin; palp first article naked; second article with three inner setae, at least one of them serrated and one outer seta; third article with four simple setae, two long and two short; fourth article with one subdistal and five distal setae. Cheliped (Fig. 11H) basis naked, posterior lobe subequal to anterior mass (not shown on figure); merus subtriangular, ventral margin longer that of carpus, with seta; carpus with ventral single simple seta; propodus robust, 1.2 times as long as wide, with one simple seta on inner face, near dactylus insertion; fixed finger with two simple ventral setae, three simple setae and four teeth on cutting edge; dactylus with one proximal seta.
Pereopod 1 (Fig. 12A) coxa with one seta; basis about 3.7 times as long as wide, naked; ischium naked; merus about 1.8 times as long as wide, with ventrodistal strong serrated seta; carpus with one ventrodistal serrated seta, one serrated dorso distal seta and microtrichiae ventrally; propodus with microtrichiae along ventral and distal margins and one ventrodistal serrated seta; dactylus about 0.4 times as long as propodus, with proximal simple seta; unguis broken.
Pereopod 2 (Fig. 12B) basis about 3.2 times as long as wide, with two penicillate setae on dorsal margin; ischium with ventrodistal simple seta; merus about 1.9 times as long as wide, with ventrodistal microtrichiae and one serrated seta; carpus about 1.4 times as long as wide, distally with one dorsal serrated seta, two ventral serrated setae, microtrichiae at midlength of ventral margin; propodus with microtrichiae along ventral margin, row of spinules on distal margin and ventrodistal serrated single seta; dactylus naked; unguis about 1.3 times as long as dactylus, naked.
Pereopod 4 (Fig. 12D) basis about 6.1 times as long as wide, with microtrichiae distally; ischium with one ventral seta; merus with two serrated setae and microtrichiae distally; carpus about 2.2 times as long as wide, with three serrated seta, one simple seta, and microtrichiae distally; propodus with two serrated ventrodistal setae and one simple dorsodistal seta and microtrichiae distally; dactylus naked, unguis about 0.6 times as long as dactylus, naked.
Pereopod 5 (Fig. 12E) as pereopod 4. Pereopod 6 ( Fig. 12F) basis about 2.4 times as long as wide, with two setae (broken) on dorsal margin; ischium with one seta; merus with mictrotrichiae and two serrated setae ventrodistally; carpus about 1.8 times as long as wide, with one simple and four serrated setae distally and ventrodistal microtrichiae; propodus about 2.2 times as long as wide, with one ventrodistal and three dorsodistal serrated setae and ventrodistal microtrichae; dactylus naked; unguis about 0.6 times as long as dactylus, with row of spinules. Pleopod (Fig. 12G, G´) endopod ( Fig. 12G´) just shorter than exopod, with one subdistal and seven distal setae; exopod ( Fig. 12G) with one proximal seta and 16 setae on ventral and distal margins, all setae plumose. Uropod (Fig. 12H) basal process reaching over half of first endopod segment, with three simple setae; endopod two-segmented, first segment article 2.2 times as long as second segment, with four penicillate setae distally; second segment with one subdistal simple seta and one penicillate and three simple setae distally.
Remarks Using the identification key for species classified within genus Araphura ), A. studens n. sp. emerges as A. brevimanus (Lilljeborg, 1864). However, those species can be distinguished by a lack of fusion line on the fourth article of antenna, a presence of outer seta on the second article of maxillipedal palp, as well as pereopods 1-3 merus and pereopods 4-6 ischium with only one seta. Araphura brevimanus has a distinct fusion line on the fourth article of Fig. 12 Araphura studens n. sp. female paratype (ZMBN 116030) A pereopod 1; B pereopod 2; C pereopod 3; D pereopod 4; E pereopod 5; F pereopod 6; G pleopod basis and exopod; G' pleopod endopod; H uropod. Scale bars: 0.1 mm the basal process of uropod reaching over the half of endopod first segment. The short basal process of uropod is characteristic for: A. arvedlundi, A. curticauda, A. extensa, and A. filiformis (Larsen , 2005Lilljeborg 1864). In A. spinitherani, the basal process reaches the half of the first segment ).