Typhlotanais longiseta, Segadilha & Serejo, 2022

Segadilha, Juliana L. & Serejo, Cristiana S., 2022, New insights gained from museum collections: new deep-sea species of Typhlotanais (Tanaidacea, Typhlotanaidae) from Brazil, European Journal of Taxonomy 820, pp. 1-54 : 15-21

Typhlotanais longiseta sp. nov.

urn:lsid:zoobank.org:act:E69B1440-9838-44DA-8CF0-D3600AF99FD8

Figs 5–7 , 21

Diagnosis

Cheliped basis with ventral transversal grooves; propodus 1.7 × L:W, calcified on cutting edge; pereopod-1 coxa with very long seta reaching half-length of basis; basis with many small penicillate dorsal setae; pereopods 2–3 propodus with many small penicillate ventral setae; uropod as long as pleotelson, endopod two-articled, exopod one-articled, as long as endopod article-1.

Etymology

From the Latin ‘ longus ’, meaning ‘long’ and referring to the long seta on pereopod-1 coxa that reaches half-length of basis. It is a compound Latin noun in the nominative case used in apposition.

Material examined

Holotype

BRAZIL – Espírito Santo State • neuter, length 1.3 mm; Espírito Santo Basin , stn AMB 5 A7 R1 ; 21.0793° S, 40.0752° W; depth 1294 m; 31 Dec. 2011; MZUSP 38969 .

Paratypes

BRAZIL – Rio de Janeiro State • 5 neuters (1 dissected), length 2.3 mm; Campos Basin , stn HAB 9 CANAC 7 R2; 21.7907° S, 40.0320° W; depth 780 m; 6 Feb. 2009; MZUSP 38015 • 2 neuters; Campos Basin , stn HAB 7 I 7 R2 ; 21.1842° S, 40.2053° W;depth 790.2 m; 5 Jul. 2008; MZUSP 22851 . – Espírito Santo State • 1 neuter; Espírito Santo Basin , stn AMB 12 E7 R3 ; 19.7841° S, 39.0533° W; depth 1242 m; 26 Jun. 2013; MZUSP 38960 • 1 neuter; Espírito Santo Basin , stn AMB 11 C6 R1 ; 20.2598° S, 39.7713° W; depth 1040 m; 9 Jan. 2012; MZUSP 38964 .

Additional material (lost in the fire)

BRAZIL – Rio de Janeiro State • 4 neuters; Campos Basin , stn HAB 6 CANAC 7 R1 ; 21.7908° S, 40.0370° W; depth 758.2 m; 28 Jun. 2008; MZUSP 22850 • 1 neuter; Campos Basin , stn HAB 6 A7 R2 ; 23.6557° S, 41.3078° W; depth 693.7 m; 23 Jun. 2008; MZUSP 22852 • 3 neuters; Campos Basin , stn HAB 6 C7 R1 ; 22.9977° S, 40.7952° W; depth 710.1 m; 24 Jun. 2008; MZUSP 32840 • 1 neuter, 4 juveniles; Campos Basin , stn HAB 6 A7 R1 ; 23.6557° S, 41.3078° W; depth 693.7 m; 23 Jun. 2008; MZUSP 32847 • 2 neuters; Campos Basin , stn HAB 4 G9 R 3; 22.1214° S, 39.8177° W; depth 1299.8 m; 28 May 2008; MZUSP 32856 • 2 juveniles; Campos Basin , stn HAB 6 I 9 R2 ; 21.1843° S, 40.2049° W; depth 807 m; 29 Jun. 2008; MZUSP 32866 • 16 neuters; Campos Basin , stn HAB 6 A7 R2 ; 23.6557° S, 41.3078° W; depth 693.7 m; 23 Jun. 2008; MZUSP 38016 • 1 neuter; Campos Basin , stn AC #24 ; 22.0578° S, 39.7520° W; depth 1730 m; 8 May 2002; MNRJ 26500 • 1 neuter; Campos Basin , stn OP #49 ; 22.0758° S, 39.9032° W; depth 750 m; 30 Jun. 2003; MNRJ 27375 .

Description

Paratype (MZUSP 38015 dissected)

BODY ( Fig. 5A–B ). Slender, 7.3 × L:W. Cephalothorax 1.3× L:W, 2.8× as long as pereonite-1, naked; eyes absent.

PEREONITES 1–6. All pereonites rectangular, wider than long; pereonite-1 shortest, 0.5× L:W; pereonite-2 0.6 × L:W; pereonite-3 0.8 × L:W; pereonite-4 0.9× L:W; pereonite-5 0.9× L:W; pereonite-6 0.7× L:W; pereonites 1–3 with setae on proximal margin, pereonites 4–6 with lateral setae.

PLEON ( Fig. 5A–B ). 0.3× TBL, with five subequal pleonites, pleonite-5 with lateral seta. Pleotelson trapezoidal, with three pairs of setae distally.

ANTENNULE ( Fig. 5C ). 0.8 × as long as cephalothorax, with three articles; article-1 0.6× TL, about 2.7× L:W, with two simple and six penicillate middle setae, and one simple and three penicillate distal setae; article-2 0.7 × L:W, 0.2× as long as article-1, with two simple and penicillate distal setae; article-3 3.1× L:W, 2.9 × as long as article-2, with five simple and one penicillate terminal setae.

ANTENNA ( Fig. 5D ). Of six articles, article-1 naked, fused with body; article-2 about 1.2× L:W, naked; article-3 about 1.2× L:W, 0.7× as long as article-2, naked; article-4 5.1× L:W, 2.7× as long as article-3, with two simple and two penicillate distal setae; article-5 3.8 × L:W, 0.6× as long as article-4, with distal seta; article-6 minute with four simple terminal setae.

LABRUM ( Fig. 6A ). Rounded, hood-shaped, distally covered by minute setae. Mandible ( Fig. 6B–C ) molar broad with prominent irregular nodules on distal margin. Left mandible ( Fig. 6B ) incisor with two lobe, lacinia mobilis well developed, not crenulated; right mandible broken during dissection, incisor almost smooth ( Fig. 6C ), without lacinia mobilis. Maxillule ( Fig. 6D ) endite with seven to eight terminal spines and microtrichia; palp seta broken during dissection. Maxilla ( Fig. 6E ) semitriangular (drop form). Labium ( Fig. 6F ) with distolateral corner finely setose; outer lobe membranous. Epignath ( Fig. 6G ) elongate, linguiform, naked. Maxilliped ( Fig. 6H ) sparsely setose; basis with seta almost reaching distal margin of endites; endites with subdistal seta, two small gustatory cusps and seta on distal margin and microtrichia on outer corner; palp with four articles; article-1 triangular, naked; article-2 with two serrated and one simple inner setae; article-3 with three serrated and one simple long inner setae; article-4 with five inner setae (at least four serrated) and subdistal outer seta.

CHELIPED ( Fig. 6I ). Basis elongate, distally rounded, 2.5× L:W, with dorsodistal seta and ventral grooves; merus subtriangular, with ventral seta; carpus stout 1.5 × L:W, with two ventral setae and one dorsodistal seta; propodus stout, as long as carpus, 1.7 × L:W, with two setae near dactylus insertion (one on inner and one on outer side); fixed finger with two ventral setae; cutting edge very calcified, with subdistal protrusions and three setae; dactylus slightly curved, as long as fixed finger, with dorsoproximal seta.

PEREOPOD-1 ( Fig. 7A ). Walking type; slender; coxa with long seta reaching half of basis; basis elongate, almost 3.0× L:W, with ventral seta and one simple and many penicillate dorsal setae; ischium with ventral seta; merus 1.7× L:W, about as long as carpus, with two dorsodistal and one ventrodistal setae; carpus 1.9× L:W, with three dorsodistal and two ventrodistal setae; propodus 3.9 × L:W, 1.3× as long carpus, with three simple dorsodistal and one ventrodistal setae; dactylus just 0.4× as long as unguis; dactylus and unguis together 0.6× as long as propodus.

PEREOPOD-2 ( Fig. 7B ). Walking type; coxa broken during dissection; basis elongate 2.8× L:W, with ventral seta; ischium with ventral seta; merus 1.6× L:W, as long as carpus, with two ventrodistal setae; carpus 1.4× L:W, with three distal setae; propodus about 2.7× L:W, 0.8× as long as merus and carpus combined, with two dorsodistal setae and four penicillate ventral setae; dactylus 0.5× as long as unguis, with dorsoproximal seta shorter than unguis.

PEREOPOD-3 ( Fig. 7C ). Similar to pereopod-2, except basis 2.0 × as long as wide; merus with ventrodistal seta; propodus with six penicillate ventral setae; dactylus 0.5 × as long as unguis.

PEREOPOD-4 ( Fig. 7D ). Clinging type; coxa absent; basis 2.2× L:W, naked; ischium with two setae; merus triangular about 1.3× L:W, with ventrodistal spine and microtrichia; carpus 1.7× L:W, with dorsodistal seta, distal spine and ventral prickly tubercles almost as long as carpus; propodus 5.3× L:W, with penicillate middorsal seta and dorsodistal seta shorter than dactylus; dactylus 2.5× as long as unguis, both combined 0.8 × as long as propodus.

PEREOPOD-5 ( Fig. 7E ). Similar to pereopod-4, except basis 1.8× L:W, with ventral seta; merus 1.6× L:W; carpus 1.4 × L:W; propodus 4.6 L:W.

PEREOPOD-6 ( Fig. 7F ). Similar to pereopod-5, except basis naked; propodus with three dorsodistal setae shorter than dactylus.

PLEOPOD ( Fig. 7G ). All pleopods similar; basal article naked; exopod with nine plumose setae on outer margin and with plumose seta on inner margin; endopod with fourteen plumose setae on outer margin; gap between proximal seta and others in both rami.

UROPOD ( Fig. 7H ). Stout, as long as pleotelson; basis about as long as wide, naked; exopod one-articled, as long as endopod article-1, with stout and simple setae distally; endopod two-articled; 4.1× L:W, first article with penicillate medial seta; second article with simple and two penicillate setae medially, one stout, one simple and three penicillate setae distally.

Distribution

Brazil: Campos Basin, Rio de Janeiro and Espírito Santo Basin, Espírito Santo. Occurring on the middle and lower slope, from the depth range 692 to 1730 m ( Fig. 21 ).

Remarks

The main unique and conspicuous characters of Typhlotanais longiseta sp. nov. are the pereopod-1 coxa with very long seta reaching half of basis length, distal part of cheliped basis (basal lobe) long and basis with several small penicillate dorsal setae. The first character is found only in Paratyphlotanais armatus (Vanhöffen, 1914) , Typhlotanais greenwichensis and T. plebejus Hansen, 1913 . The new species can be distinguished from T. greenwichensis by its (1) body stout, 6.0× L:W (versus almost 7.0× L:W in T. greenwichensis ); (2) cheliped carpus dorsal margin with seta (versus seven minute setae in T. greenwichensis ); (3) pereopods 1–3 coxa without spur; (4) pereopods 4–6 carpus prickly tubercles not surrounded by spines; (5) uropod endopod two-articled.

Typhlotanais longiseta sp. nov. resembles T. plebejus in habitus and cheliped basis with ventral grooves. However, the new species can be distinguished by (1) pereonite-4 form ( T. longiseta 0.7 × L:W and T. plebejus as long as wide); (2) pereopod-1 basis with several small penicillate ventral setae; and (3) pereopods 2–3 propodus with several small penicillate ventral setae.

“ cornutus ” group

Species included

Typhlotanais adipatus Tzareva, 1982 ; T. andeepae Błażewicz-Paszkowycz, 2007 a ; T. (= Paratanais ) cornutus (Sars, 1879) ; T. crassus Dojiri & Sieg, 1997 ; T. bolarticulus sp. nov.

Figures

Fig. 5. Typhlotanais longiseta sp. nov., paratype (MZUSP 38015), ♀, dissected. A. Dorsal view. B. Lateral view. C. Antennule. D. Antenna. Scale bars: A–B = 1 mm; C–D = 0.1 mm.

Fig. 6. Typhlotanais longiseta sp. nov., paratype (MZUSP 38015), ♀, dissected. A. Labrum. B. Left mandible. C. Right mandible. D. Maxillule. E. Maxilla. F. Epignath. G. Labium. H. Maxilliped. I. Cheliped. Scale bar = 0.1 mm.

Fig. 7. Typhlotanais longiseta sp. nov., paratype (MZUSP 38015), ♀, dissected. A–F. Pereopods 1–6. G. Pleopod. H. Uropod. Scale bar = 0.1 mm.

Fig. 21. Bathymetric range of species of Typhlotanais along the Brazilian coast (19° S–24° S) based on samples listed in Table 1.