Typhlotanais froufesae, Larsen, Kim, 2011

Larsen, Kim, 2011, The tanaidacean assemblage from the Central Pacific Manganese Nodule Province. II. The genera Stenotanais and Typhlotanais (Crustacea), Zootaxa 3088, pp. 39-53 : 44-49

Typhlotanais froufesae n. sp.

( Figs 3–5 )

Material examined. Holotype, non-ovigerous female, dissected, (MNHN-Ta1034). CAROT-B, no 24, 04/06- 2004. 14˚02.96’N, 130°08.18’W, 4909 m.

Diagnosis. Antennule as long as carapace. Antenna article 1–3 with multiple setules; article 4 long (about five times the length of article 3). Pereopod 1 coxa with anterior process. Cheliped carpus without row of small dorsal setae. Pereopods 1–3 basis without multiple setules. Pereopods 2–3 merus and carpus with scales at distal margin. Pereopods 4–6 prickly tubercle comparably small (smaller than half of carpus) and surrounded by spines. Uropod endopod biarticulated; exopod uniarticulated.

Etymology. The species is named after Dr. Elsa Froufe who conducts the genetic analysis of the Tanaidacea at CIIMAR.

Description. Female (body and appendages of holotype). Body length 1.8 mm

Body ( Fig. 3 A) long (12 times as long as wide). Cephalothorax longer than wide, with slightly rounded lateral margins. Pereonites all wider than long; pereonite1 shortest, almost twice as wide as long, half as long as pereonite 2; pereonites 2–4 subequal. Pereonite 5 shorter than pereonite 4. Pereonite 6 marginally longer than pereonite 1. Pleon 25% total body length. Pleonites 1–5 subequal. Pleotelson as long as combined length of last two pleonites, with rounded apex.

Antennule ( Fig. 3 B) as long as cephalothorax. Article 1 thick (just over twice as long as wide, with several proximal and medial setulated setae; distally with one simples and three setulated setae. Article 2 shorter than wide, with two simple distal setae. Article 3 long (more than three times as long as article 2), with apical spur-like process, two aesthestascs, four simple and one setulose distal setae.

Antenna ( Fig. 3 C) about 75% as long as antennule. Article 1 with scattered short thin setae. Article 2 with multiple setules, more than twice as long as article 3. Article 3 about as long as article 1, with few setules. Article 4 more than twice as long as article 5, with two simple and multiple setulated distal setae. Article 5 marginally longer than article 2, with one simple distal seta. Article 6 minute, with three terminal setae and one aesthetasc.

Mouthparts. Labrum ( Fig. 3 D) with rounded and setulose apex, without spines. Mandibles (Figs E–F) molar well developed, longer than incisor with clearly demarcated terminal spines. Left mandible ( Fig. 3 F) incisor bluntly bifurcate; lacinia mobilis well developed and longer than incisor, with blunt apex. Right mandible ( Fig. 3 E) incisor weakly bifid, with outer crenulations. Labium ( Fig. 3 G) with flat, sparsely setulose distal corners. Maxillule ( Fig. 3 H) endite with eight spiniform distal setae, palp as long as endite, with two apical setae Maxilla ( Fig. 3 H) ovoid and featureless. Maxilliped ( Fig. 5 A): basis fused medially, with long (as long as endite) distal seta near palp insertion; endite with one simple seta and serrated outer distal corners, with inner articulated tubercle outer projection and setules on corners; palp article1 with multiple setules or scales; article 2, with three bipinnate distal setae on inner margin and proximal setulations, with one smaller seta on outer margin; article 3 with four bipinnate setae on inner margin; article 4, with one simple seta outer and five bipinnate distal inner setae. Epignath ( Fig. 3 I) naked tapering into a pointed apex.

Cheliped ( Fig. 4 A) basis attached via small triangular sclerite, distal part larger than proximal part, shorter than carpus, with one sub-dorsomedial seta near carpus connection. Merus less than half as long as carpus, with one ventral seta. Carpus almost three times longer than wide, with two simple ventromedial seta, one small stout ventrodistal seta, and one short dorsoproximal seta, with proximal scales. Propodus (including fixed finger) slender, marginally shorter than carpus, with one seta at dactylus insertion. Fixed finger with two ventral and three inner setae, inner margin smooth. Dactylus with dorsoproximal seta.

Pereopod 1 ( Fig. 4 B) coxa with anterior directed process with one seta. Basis longer than three succeeding articles combined, with one simple and one setulose dorsoproximal setae. Ischium with one ventral seta. Merus elongated, shorter than carpus, with one simple ventrodistal seta. Carpus only marginally shorter than propodus, with five distal setae, one thicker than others. Propodus only marginally longer than dactylus and unguis combined, with two dorso-subdistal setae, one distal seta, apical spine and one short ventrodistal spiniform seta. Dactylus less than half as long as unguis; both naked.

Pereopod 2 ( Fig. 4 C) coxa projection much smaller than on pereopod 1, apparently naked. Basis naked. Ischium with one ventral seta. Merus shorter than carpus, with prominent scales on distal margin, with three distal setae of which one is thicker than the others. Carpus with prominent scales on distal margin, with three dorsodistal setae of which one is thicker than the others, with one short ventrodistal spiniform seta. Propodus more than twice as long as dactylus and unguis combined, with two dorso-subdistal setae, apical spine and one short ventrodistal spiniform seta. Dactylus with one proximal seta, less than half as long as unguis.

Pereopod 3 ( Fig. 4 D) shorter than, but similar to pereopod 2 except: coxa projection with seta. Basis with dorsoproximal setulated seta. Dactylus with proximal seta.

Pereopod 4 ( Fig. 4 E) basis more robust than on pereopod 1–3, about 2.5 times longer than wide, apparently naked. Ischium with one ventral seta. Merus with scattered scales and two spiniform distal setae. Carpus apparently with one bone-shaped and one dorsodistal spiniform setae and with clearly defined prickly tubercle surrounded by row of minute spines. Propodus with two ventro-subdistal spiniform and one robust distal setae. Dactylus three times as long as unguis; both combined shorter than propodus, with row of small ventral spines.

Pereopod 5 ( Fig. 4 F) similar to pereopod 4 except: basis with one ventro-subdistal setulated seta. Ischium with two ventral setae. Propodus with ventral setules and scales and dorsomedial setulated seta.

Pereopod 6 ( Fig. 4 G) similar to as pereopod 5 except propodus with four distal and one subdistal spiniform setae but without dorsomedial setulated seta.

Pleopods ( Fig. 5 B) no differences between the five pairs were observed (although most were in a bad condition). Basal article elongated and naked; exopod with one plumose seta on inner margin and ten plumose setae on outer margin, pronounced gap between proximal and other setae; endopod with 15 plumose setae on outer margin, pronounced gap between proximal and other setae.

Uropod ( Fig. 3 J) basal article almost square. Exopod slender, 75% as long as endopod, uniarticulated with one small proximal seta; distally with two dissimilar length distal setae of which one is longer than exopod. Endopod slender, article 1 almost twice as long as article 2, with two simple and three setulated distal setae, article 2 with two short setulated and four simple distal setae of which two are longer than endopod.

Remarks. The groupings by Błażewicz-Paszkowycz (2007) of typhlotanaid species, while not taxonomic entities, are very helpful for narrowing down identifications. The coxa projection of the pereopod 1 and the long maxilliped basis setae indicate that this species may belong to the ‘ greenwichensis’ group. However, the ‘ greenwichensis ’ group is also defined ( Błażewicz-Paszkowycz 2007) by a suite of other characters: 1) Lack of gap between the cheliped basis and pereonite 1. 2) Row of short setae on the cheliped carpus. The new species clearly demonstrates a gap between the cheliped basis and pereonite 1, but it has no row of short seta on the cheliped carpus. Since another species, T. mimosis , also displays a coxal projection on pereopods 1–3 but nevertheless is assigned to the ‘ mixtus ’ group ( Błażewicz-Paszkowycz 2007), the distinctions between these groups are not clear. Therefore comparisons are made with the species from both these ‘groups’ while abstaining from assigning the new species to a specific group.

The ‘ greenwichensis’ group currently consists of only two named species ( T. greenwichensis and T. messinensis ). The new species differs from T. greenwichensis by the much shorter antenna article 4, by lacking the row of small dorsal setae on the chelipeds carpus. T. greenwichensis is also recorded from a much more shallow-water habitat of 79 meters ( Shiino, 1970). Typhlotanais froufesae n.sp. differs from T. messinensis by the antennule being as long as the carapace and by lacking the row of small dorsal setae on the chelipeds carpus. The third ‘species’ in the greenwichensis’ group (‘? T. greenwichensis ‘ [sic] sensu Błażewicz-Paszkowycz, 2007:107 ) might well be a separate, cryptic species rather than the ‘true’ T. greenwichensis but can be separated from T. froufesae on the same characters as the original T. greenwichensis .

The ‘ mixtus’ group, also constitutes of only two named species ( T. mixtus Hansen, 1913 and T. mimosis Błażewicz-Paszkowycz, 2007 ). From T. mixtus , the new species differs by the pereopod coxa projection and from T. mimosis by lacking the long dorsal setae on the first pereonite. Also, the comparatively small prickly tubercles are not in concord with the ‘ mixtus’ group definition. However, the ‘ mixtus’ group definition contains other conflicting characters, such as the pereopods 4–5 dactylus and unguis combined being almost as long as propodus while it is later stated that these are actually longer than the propodus ( Błażewicz-Paszkowycz 2007:108). These conflicts suggest that many of these typhlotanaid ‘groups’ at present do not represent monophyletic lines.

Figures

FIGURE 3. Typhlotanais froufesae, female. Holotype. A, lateral view, scale bar 0.5 mm. B, antennule. C, antenna. D, labrum. E, right mandible. F, left mandible. G, labium. H, maxillule and maxilla. I, epignath. J, uropod. Scale bars 0.1 mm.

FIGURE 4. Typhlotanais froufesae, female. Holotype. A, cheliped. B, pereopod 1. C, pereopod 2. D, pereopod 3. E, Pereopod 4. F, pereopod 5. G, pereopod 6. Scale bar 0.1 mm.

FIGURE 5. Typhlotanais froufesae, female. Holotype. A, maxilliped. B, pleopod. Scale bar 0.1 mm.