Paratyphlotanais bessai, Segadilha & Serejo & Błażewicz, 2019

Segadilha, Juliana Lopes, Serejo, Cristiana Silveira & Błażewicz, Magdalena, 2019, New species of Typhlotanaidae (Crustacea, Tanaidacea) from the Brazilian coast genera Hamatipeda, Meromonakantha and Paratyphlotanais, with description of Targaryenella gen. nov., Zootaxa 4661 (2), pp. 309-342 : 332-339

Paratyphlotanais bessai sp. nov. Segadilha & Błażewicz

LSID urn:lsid:zoobank.org:act:06A463F6-15CC-4282-BE72-546D356C6DF6

( Figs. 11–14 )

Material examined. Holotype: female ovigerous (only oostegites remained), length 2.5 mm ( MNRJ 28875 ) Sta #62.

Paratypes: one female non-ovigerous, length 2.2 mm ( MNRJ 20660 ) dissected, Sta #62; one female ( MZUSP 32858 ) Sta HAB 7 A6 R1; one female ( MZUSP 32859 ) Sta HAB 6 CANAC 8 R3; one female ( MZUSP 32893 ) Sta HAB 4 F9 R2; one female ( MZUSP 34408 ) Sta HAB 6 CANAC 8 ; one female ( MZUSP 38959 ) Sta AMB 5 A7 R1; one female ( MNRJ 18307 ) Sta #25; one female ( MNRJ 20788 ) Sta #86; one female ( MNRJ 26494 ) Sta #4 .

Diagnosis. Body about eight times L:W; small hyposphenium only on pereonite-1; cephalothorax shorter than pereonites 1–2 combined; cheliped carpus 2.2 times L:W, with two ventral and one dorsal setae; pereopod 1–3 coxa without spur; pereopods 4–6 carpus with three weakly serrate spines; pereopod-6 dactylus and unguis combined shorter than in pereopods 4–5; uropod exopod 1.3 times longer than endopod article-1.

Etymology. Named in honour of Sérgio Bessa in gratitude for his heroic act in saving the samples during the fire in the Museu Nacional of the Universidade Federal do Rio de Janeiro.

Description of female. Paratype, length 2.2 mm ( MNRJ 20660). Body ( Figs. 11A, B ) about eight times L:W. Cephalothorax triangular, about 1.3 times L:W, 2.1 times as long as pereonite-1, shorter than pereonites 1–2 com- bined, naked; eyes absent.

Pereonites 1–6: lateral margins slightly convex, 0.8, 0.8, 1.0, 1.1, 1.0, and 0.7 times L:W, respectively; small hyposphenium only on pereonite-1.

Pleon ( Fig. 11A, B ) 0.2 TBL, with five subequal pleonites, together shorter than cephalothorax. Pleotelson 0.5 times L:W, with two pairs of terminal setae.

Antennule ( Fig. 11C ) about as long as cephalothorax (0.9 times), with three articles; article-1 0.6 TL, 2.3 times L:W, with simple and four penicillate medial setae, and simple and three penicillate distal setae; article-2 0.7 times L:W, 0.15 times as long as article-1, with two simple and one penicillate distal setae; article-3 5.3 times L:W, 3.4 times as long as article-2, with six simple, one penicillate, one aesthetasc and with apical spur.

Antenna ( Fig. 12A ) of six articles, article-1 broken during dissection; article-2 0.8 times L:W, with one thick seta; article-3 0.7 times L:W, 0.7 times as long as article-2, with thick seta; article-4 3.4 times L:W, 2.6 times as long as article-3, with four simple and one penicillate distal setae; article-5 3.3 times L:W, 0.5 times as long as article-4, with distal seta; article-6 minute with five simple terminal setae.

Labrum ( Fig. 12B ) rounded, hood-shaped, distally covered by minute setae. Left mandible ( Fig. 12C ) molar broad with irregular edge, with one acute tooth, lacinia mobilis well developed, with four teeth; right mandible not recovered. Maxillule ( Fig. 12D ) endite with at least six terminal spines (one short); palp not recovered. Maxilla ( Fig. 12E ) triangular. Labium ( Fig. 12F ) with inner distal and distolateral corners finely setose; outer lobe membranous. Maxilliped ( Fig. 12G ) basis elongate, with seta almost reaching distal margin of endites; endites with one medial seta, two delicate distal cusps and microtrichia on outer corner; palp with four articles; article-1 triangular, naked; article-2 with three inner (two serrate and one simple) and outer setae; article-3 with four serrate inner setae; article- 4 with four serrate inner setae and subdistal outer seta.

Cheliped ( Fig. 12H ) elongated, basis 1.7 times L:W, with posterior lobe partly occluded by the lower part of the cephalothorax and dorsodistal seta; merus triangular, with ventral seta; carpus 2.2 times L:W, with two ventral and two dorsal setae (distal and subproximal); propodus as long as carpus, three times L:W, with two setae near dactylus insertion (inner and outer); fixed finger with two ventral setae, cutting edge poorly calcified, almost simple, with small subdistal protrusion and with three setae; dactylus with proximal inner seta.

Pereopod-1 ( Fig. 13A ) walking type; coxa with seta; basis 6.2 times L:W, with dorsoproximal simple and peni- cillate setae; ischium with ventral thick seta; merus 1.7 times L:W, naked; carpus about twice L:W, with dorsodistal spine and ventrodistal seta; propodus 3.4 times L:W, 1.2 times as long as merus and carpus combined, with two dorsodistal spines and ventrodistal seta; dactylus 0.6 times as long as unguis, with subproximal seta shorter than half of unguis; dactylus and unguis combined as long as propodus.

Pereopod-2 ( Fig. 13B ) walking type; coxa with seta (not figured); basis 4.6 times L:W, naked; ischium with robust ventral seta; merus 1.7 times L:W, with ventrodistal serrate spine; carpus 1.8 times L:W, with two ventrodis- tal serrate spines; propodus three times L:W, 0.9 times as long as merus and carpus combined, with dorsodistal and ventrodistal spines; dactylus half as long as unguis, with subproximal seta shorter than half of unguis; dactylus and unguis combined 0.9 times as long as propodus.

Pereopod-3 ( Fig. 13C ) similar to pereopod-2, except, basis 5.2 times L:W; merus 1.4 times L:W.

Pereopod-4 ( Fig. 13D ) walking type; coxa absent; basis 2.6 times L:W, naked; ischium with ventral thick seta (not seen in draw); merus triangular about 1.7 times L:W, with two ventrodistal weakly serrate spines; carpus 1.4 times L:W, with dorsodistal seta and three distal weakly serrate spines; propodus three times L:W, with dorsodistal seta longer than half of dactylus, two ventrodistal weakly serrate spines; dactylus 2.5 times as long as unguis, with microtrichia; dactylus and unguis combined 0.7 times as long as propodus; unguis bifurcate.

Pereopod-5 ( Fig. 13E ) similar to pereopod-4, except, ischium with ventral thick seta.

Pereopod-6 ( Fig. 13F ) similar to pereopod-5, except, basis 2.8 times L:W; propodus 2.4 times L:W, with three dorsodistal setae longer than half dactylus.

Pleopod ( Fig. 13G ). All pleopods similar; basal article naked; exopod with seven plumose setae on outer margin and with plumose seta on inner margin; endopod with ten plumose setae on outer margin; gap between proximal seta and other ventral setae in both rami.

Uropod ( Fig. 13H ) 1.5 times as long as pleotelson; basis 1.3 times L:W, naked; exopod one-articled, 5.8 times L:W, 0.7 times as long as endopod, with medial seta and stout and simple distal setae; endopod two-articled, 5.7 times L:W; article-1 0.9 times as long as exopod, with simple and two penicillate distal setae, article-2 with one subdistal, four simple and two penicillate setae distally.

Distribution. This species is known from the continental shelf and slope off southeast Brazil ( Fig. 14 ), where it occurs at mud bottom at depths ranging from 390.2 to 1730 m.

Remarks. Paratyphlotanais bessai sp. nov. is a member of the genus Paratyphlotanais by the presence of conspicuous serrate spines on pereopods 4–6 merus and carpus, and a bifurcate unguis on these appendages. Along with this new species, congeners without a coxal spur on pereopods 1–3 are P. armatus , P. colouros , P. japonicus , P. microcheles and P. typicus ( Table 5 ). From these species, the most similar to the P. bessai is the type species P. typicus from the Caribbean Sea by the proportion of body and cephalothorax, and a hyposphenium only on pereonite-1. However, they differ by (1) antennule article-1, that is 2.3 times L:W in P. bessai and about three times in P. typicus ; (2) cheliped carpus, that is 2.2 times L:W and has one dorsal seta in P. bessai and 1.6 times and has two dorsal setae in P. typicus ; (3) cheliped propodus, that is as long as the carpus in P. bessai and little longer than the carpus in P. typicus ; (4) cheliped propodus slender, that is more than three times L:W in P. bessai and 2.3 times in P. typicus ; (4) uropod shorter, 1.5 times L:W in P. bessai and about twice in P. typicus ; and (5) uropod exopod longer than endopod article-1 (1.3 times in P. bessai and 0.6 times in P. typicus ).

The new species is distinct from P. japonicus in having (1) cephalothorax shorter than pereonites 1–2 combined (as long as pereonites 1–3 combined, in P. japonicus ); (2) cheliped merus with one ventral seta in P. bessai but with two in P. japonicus ; and (3) cheliped carpus about twice L:W (2.7 times in P. japonicus ); (4) hyposphenium only on pereonite-1 ( P. japonicus has on pereonites 1–2); and (5) uropod exopod longer than endopod article-1 (0.7 times in P. japonicus ).

Paratyphlotanais bessai differs from P. microcheles by (1) cheliped carpus 2.2 times L:W with one dorsal seta, but 1.8 times and with three dorsal setae in P. microcheles ; (2) cephalothorax shorter than pereonites 1–2 combined; (3) cheliped propodus as long as carpus in P. bessai and little longer than carpus in P. microcheles ; and (4) uropod exopod longer than endopod article-1 (0.7 times in P. microcheles ).

Also, P. bessai is different from P. armatus and P. colouros by (1) a more elongated body (eight times L:W in P. bessai and less than seven in other species); (2) pereonite-1 more than half length of pereonite-2 (but in P. armatus is as long as half and in P. colouros is less than half); and (3) hyposphenium only on pereonite-1 (both P. armatus and P. colouros have on pereonites 1–3).

Figures

FIGURE 11. Paratyphlotanais bessai sp. nov. Holotype, female with oostegites, MNRJ 28875. A. Lateral view; paratype, female dissected, MNRJ 20660. B. dorsal view. Scale = 1 mm. B. Antennule. Scale = 0.1 mm.

FIGURE 12. Paratyphlotanais bessai sp. nov. Paratype, female dissected, MNRJ 20660. A. antenna, B. labrum, C. Left mandible, D. labium, E. maxillule, F. maxilla, G. maxilliped, H. cheliped. Scale = 0.1 mm.

FIGURE 13. Paratyphlotanais bessai sp. nov. Paratype, female dissected, MNRJ 20660. A–F. Pereopods 1–6, G. pleopod, H. uropod. Scale = 0.1 mm.

FIGURE 14. Geographic distribution of Paratyphlotanais bessai sp. nov., along the southeastern Brazilian coast. Red point: type-locality (holotype); yellow points: paratypes.