Typhlotanais spinibasis, 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 : 41-49

Typhlotanais spinibasis sp. nov.

urn:lsid:zoobank.org:act:BE1ACEFF-02E4-476E-B2E4-067F04C607CA

Figs. 17–21

Diagnosis

Pereonites 1–3 elongated, longer than wide; carapace 1.2× as long as pereonite-1; antenna article-2 and 3 without ventral hooks; pereopods 1–3 ischium with long seta extending beyond merus distal margin; merus with long ventrodistal seta extending beyond carpus distal margin; pereopods 2–3 carpus with long ventral seta reaching half length of propodus; pereopods 2–3 propodus with two simple dorsodistal (one longer than unguis) dorsodistally and spine ventrodistally; pereopods 2–3 dactylus with seta longer than dactylus and unguis combined; and pereopods 4–6 basis with large and conspicuous spines.

Etymology

Named after the conspicuous and strong spines on pereopods 4–6 basis.

Material examined

Holotype

BRAZIL – Espírito Santo State • neuter, length 2.4 mm; Espírito Santo Basin , stn AMB 5 A7 R3 ; 21.0793° S, 40.0752° W; depth 1294 m; 31 Dec. 2011; MZUSP 37680 .

Paratypes

BRAZIL – Rio de Janeiro State • 1 neuter (dissected, length 2.1 mm), 1 juvenile; Campos Basin , stn HAB 4 F9 R3 ; 22.4289° S, 39.901° W; depth 1288.5 m; 29 May 2008; MZUSP 32893 • 6 neuters; Campos Basin , stn HAB 9 CANAC 7 R 2; 21.7907° S, 40.0320° W; depth 780 m; 6 Feb. 2009; MZUSP 32902 . – Espírito Santo State • 1 neuter; Espírito Santo Basin , stn AMB 5 A7 R3 ; 21.0793° S, 40.0752° W; depth 1294 m; 31 Dec. 2011; MZUSP 38955 • 2 neuters; Espírito Santo Basin , stn AMB 11 C6 R1 ; 20.2598° S, 39.7713° W; depth 1040 m; 9 Jan. 2012; MZUSP 38957 • 1 neuter; Espírito Santo Basin , stn AMB 5 B5 R2 ; 20.5873° S, 39.8966° W; depth 406 m; 8 Jan. 2012; MZUSP 38958 • 2 neuters; 1 juvenile; Espírito Santo Basin , stn AMB 11 B6 R 2; 20.6000° S, 39.8596° W; depth 998 m; 8 Jan 2012; MZUSP 38961 • 1 neuter; Espírito Santo Basin , stn AMB 5 C6 R2 ; 20.2595° S, 39.7707° W; depth 1041 m; 9 Jan. 2012; MZUSP 38974 .

Additional material (lost in the fire)

BRAZIL – Rio de Janeiro State • 3 neuters; Campos Basin , stn HAB 4 CANG 7 R2 ; 21.9367° S, 39.9625° W; depth 720 m; 7 Feb. 2009; MZUSP 32851 • 1 juvenile; Campos Basin , stn HAB 6 CANAC 6 R3 ; 21.8327° S, 40.1056° W; depth 466.8 m; 28 Jun. 2008; MZUSP 34414 • 1 neuter; Campos Basin , stn HAB 3 C8 ; 23.0257° S, 40.7565° W; depth 975 m; 10 May 2008; MZUSP 34473 • 2 neuters; Campos Basin , stn HAB 6 CANAC 7 R1 ; 21.7908° S, 40.0370° W; depth 758.2 m; 28 Jun. 2008; MZUSP 38012 • 1 neuter; Campos Basin , stn HAB 9 H8 R3 ; 21.6713° S, 39.9684° W; depth 1005.8 m; 6 Feb. 2009; MZUSP 38013 • 1 neuter; Campos Basin , stn HAB 9 CANAC 8 R 1; 21.7652° S, 39.9909° W; depth 1030 m; 2 Jun. 2009; MNRJ 25238 .

Description

Paratypes (MZUSP 34473; MZUSP 32893 dissected)

BODY ( Fig. 17A–B ). Slender, 8.5× L:W. Cephalothorax 1.4 × L:W, 1.2 × as long as pereonite-1, naked; eyes absent.

PEREONITES 1–6. All pereonites rectangular, with lateral margins parallels; pereonites 1–3 longer than wide, with setae on proximal margin, pereonites 4–6 with lateral setae; pereonite-1 1.2× L:W; pereonite-2 1.5 × L:W; pereonite-3 1.2× L:W; pereonite-4 once L:W; pereonite-5 0.9× L:W; pereonite-6 shortest, 0.6× L:W.

PLEON ( Fig. 17A–B ). 0.14 × TBL, with five subequal pleonites, together almost as long as carapace, with lateral setae. Pleotelson distally gently rounded, with a pair of setae distally.

ANTENNULE ( Fig. 17C ). 0.7 × as long as cephalothorax, with three articles; article-1 0.6 × TL, 2.1× L:W, with two simple middle setae and seven (or more) penicillate setae (broken), and with one simple and three penicillate setae distally; article-2 about as long as wide, 0.2× as long as article-1, with two simple and one penicillate distal setae; article-3 3.5 × L:W, 2.5 × as long as article-2, with five simple terminal setae and aestethasc.

ANTENNA ( Fig. 17D ). Of six articles, article-1 with two distal setae, fused with body; article-2 1.2× L:W, naked; article-3 1.2 × L:W, about as long as article-2, naked; article-4 4.2 × L:W, about 2.6× as long as article-3, with two simple and one penicillate setae distally; article-5 2.4× L:W, 0.4× as long as article-4, with distal seta; article-6 minute with five terminal setae.

LABRUM ( Fig. 17E ). Covered by minute setae (view from the top). Mandible ( Fig. 17F–G ) molar broad with prominent nodules. Left mandible ( Fig. 17F ) incisor with two lobe, lacinia mobilis well developed, gently crenulated; right mandible ( Fig. 17G ) as left, but without lacinia mobilis. Maxillule ( Fig. 18A ) endite with seven to eight terminal spines and microtrichia on outer and inner margins; palp with two distal setae. Maxilla ( Fig. 18B ) triangular. Labium ( Fig. 18C ) with distolateral corner finely setose; outer lobe membranous, finely setose. Maxilliped ( Fig. 18D ) sparsely setose; basis with simple seta not reaching distal margin of endites; endites unfused, with simple seta, two large gustatory cusps on distal edge and microtrichia on outer corner; palp with four articles; article-1 triangular, naked; article-2 with two serrated and one rod on inner margin and simple setae on outer margin; article-3 with three serrated and one simple inner setae; article-4 with five serrated inner setae and simple subdistal outer seta. Epignath not observed.

CHELIPED ( Fig. 18E ). Stout, basis distally rounded, 1.8× L:W, with minute seta dorsally; merus subtriangular, with ventral seta; carpus stout 1.3× L:W, with two ventral setae; one middle and one dorsodistal simple setae; propodus 1.4 × as long as carpus, 1.9× L:W, with two setae near dactylus insertion (one on inner and one on outer side); fixed finger with two simple setae ventrally; cutting edge with three setae; dactylus slightly curved, as long as fixed finger, with one dorsoproximal and two midventral simple setae.

PEREOPOD-1 ( Fig. 19A ). Walking type; slender; coxa with seta; basis elongate 5.9 × L:W, naked; ischium with long ventral seta (extending beyond merus distal margin); merus twice L:W, slightly shorter than carpus, with long ventrodistal seta (almost reaching carpus distal margin; article folded upwards); carpus 2.5 × L:W, with four simple setae distally; propodus 4.5× L:W, 1.6× as long carpus, with two robust and one simple dorsodistal setae, and minute ventral seta; dactylus just half as long as unguis, with seta shorter than unguis; dactylus and unguis together half as long as propodus.

PEREOPOD-2 ( Fig. 19B ). Walking type; coxa with seta; basis elongate 5.7 × L:W, naked; ischium with long ventral seta (extending beyond merus distal margin); merus 1.8× L:W, subequal to carpus, with one short and one long ventrodistal setae (extending beyond carpus distal margin); carpus 1.9 × L:W, with two long (one half as long as propodus and one almost reaching propodus distal margin) and one short setae; propodus 4.1× L:W, 0.9 × as long as merus and carpus combined, with two simple dorsodistal (one longer than unguis) and one ventrodistal minute setae; dactylus with seta longer than unguis.

PEREOPOD-3 ( Fig. 19C ). Similar to pereopod-2, except carpus with long ventrodistal seta (almost reaching propodus distal margin); propodus 3.6 × L:W; dactylus 0.5 × as long as unguis; dactylus and unguis together 0.3 × as long as propodus.

PEREOPOD-4 ( FIG. 19D ). Clinging type; coxa absent; basis robust 1.9 × L:W, with six big and strong spines dorsally; simple and two long penicillate setae and big and strong spine ventrally; ischium short, with seta; merus triangular about 1.4× L:W, with spine and seta ventrodistally and microtrichia; carpus 1.3× L:W, with simple seta and robust spine dorsodistally, and prickly tubercles almost as long as carpus; propodus 4.4× L:W, with penicillate middorsal seta, long dorsodistal seta (twice as long as dactylus and unguis combined), subdistal ventral spine and numerous microtrichia; dactylus with small microtrichia dorsally; dactylus 3.2× as long as unguis, both combined 0.6× as long as propodus.

PEREOPOD-5 ( Fig. 19E ). Similar to pereopod-4, except basis 1.4× L:W, with seven big and strong spines dorsally; simple and long penicillate setae and big and strong spine ventrally; propodus 4.4× L:W, with long dorsodistal seta and subdistal ventral spine.

PEREOPOD-6 ( Fig. 19F ). Similar to pereopod-4, except basis with nine big and strong spines and long penicillate seta dorsally; merus triangular 1.1× L:W, with two spine ventrodistally; carpus once L:W; propodus 3.9× L:W, with two serrate and one long dorsodistal setae (longer than dactylus and unguis combined).

PLEOPOD ( Fig. 19G ). All pleopods similar; basal article naked; exopod with six plumose setae on outer margin and with plumose seta on inner margin; endopod with eleven plumose setae on outer margin. Large gap between proximal seta and others in both rami.

UROPOD ( Fig. 19H ). Stout, 0.7× as long as pleotelson; basis 1.2× L:W, naked; exopod one-articled, 0.8× as long as endopod, with simple medial seta and tipped by stout and simple setae; endopod one-articled; 3.4 × L:W, with two penicillate setae medially, tipped by five simple and two penicillate setae.

Morphological variation

Based on paratype MZUSP 38011

CHELIPED ( Fig. 20A ). More slender, basis twice L:W; merus with two ventral setae; carpus 1.6× L:W.

PEREOPOD-1 ( Fig. 20B ). Basis with two dorsal and two ventral setae; merus as long as carpus, with long ventrodistal seta (extending beyond carpus distal margin); carpus with two simple setae distally (one almost reaching half length of propodus); propodus 3.9× L:W, with two simple and one serrate dorsodistal setae, and ventral spine.

PEREOPOD-2 ( Fig. 20C ). Basis elongate 6.6× L:W, with two dorsal and two ventral setae; carpus with one dorsodistal and one ventrodistal long setae (one extending beyond half length of propodus and one almost reaching propodus distal margin); propodus 3.5× L:W, with spine ventrodistally.

PEREOPOD-3 ( Fig. 20D ). Basis with simple and penicillate dorsal setae; propodus 2.8 × L:W.

PEREOPOD-4 ( Fig. 20E ) basis slender, about 2.8 × L:W, with four spines distally; ischium with seta; merus with spine ventrodistally; propodus 5.4 × L:W; dactylus with small microtrichia dorsally.

PEREOPOD-5 ( Fig. 20F ). Basis robust with several spines along the article and penicillate dorsal seta; propodus with two subdistal ventral spines and numerous microtrichia; dactylus over 4.0× as long as unguis.

PEREOPOD-6 ( Fig. 20G ). Carpus with two setae dorsodistally; propodus with middorsal seta, two serrate and one long dorsodistal setae (less than twice as long as dactylus and unguis combined).

Distribution

Brazil: Campos Basin, Rio de Janeiro and Espírito Santo Basin, Espírito Santo. Occurring on the upper and middle slope, from the depth range 406 to 1299.3 m ( Fig. 21 ).

Remarks

We classified Typhlotanais spinibasis sp. nov. in the ‘ trispinosus ’ group based on the presence of very long seta on pereopods 1–3 ischium ( Table 5 ). The new species resembles T. spatulasetosus , but can be distinguished from it by having (1) antenna article-3 without ventral hooks; (2) cheliped carpus with two ventral seta (instead of three); (3) pereopods 2–3 merus with long ventral seta reaching distal margin of carpus; (4) pereopods 2–3 carpus with long setae reaching half length of propodus; (5) pereopods 2–3 propodus with seta longer than dactylus and unguis combined; and (6) pereopods 4–6 basis with large and conspicuous spines. Typhlotanais spinibasis sp. nov. also lacks ventral hooks on antenna article 2 as seen in other species of Typhlotanais .

Typhlotanais spinibasis sp. nov. differs from both T. tenuicornis and T. trispinosus by having (1) antenna article-2 and 3 without ventral hooks; (2) pereopods 2–3 carpus with long ventral seta reaching half length of propodus; and (3) pereopods 4–6 basis with large and conspicuous spines. Also, the new species is distinguished from these three ‘ trispinosus ’ group species by having slender pereonites 1–3, all longer than wide, and pereonite-1 slightly shorter than carapace.

As already mentioned, only Typhlotanais plicatus , T. spinipes and T. bolarticulus sp. nov. have pereopods 4–6 and/or pereopods 2–3 bases with spines. Typhlotanais spinibasis sp. nov. is distinguished from T. plicatus by pereonites 1–3 not been corrugated, T. bolarticulus sp. nov. by pereopods 1–3 ischium with seta shorter than merus, and from T. spinipes by (1) body long, 8.5× L:W (5.2 × in T. spinipes ); and (2) uropods rami one-articled (two-articled in T. spinipes ).

The most abundant intraspecific variation found was the type with bigger spines on the pereopods 4–6 basis. These two morphological variations are probably two different species, however as the material was destroyed during the fire and the new type material designated for T. spinibasis sp. nov. was from the intraspecific variation with bigger spines on the pereopods 4–6 basis, the authors decided to treat them as the same species for the moment.

Figures

Fig. 17. Typhlotanais spinibasis sp. nov. A–B. Additional material, ♀ (MZUSP 34473). A. Dorsal view. B. Lateral view. C–G. Paratype (MZUSP 32893), ♀, dissected. C. Antennule. D. Antenna. E. Labrum. F. Left mandible. G. Right mandible. Scale bars: A–B = 1 mm; C–D = 0.1 mm.

Fig. 18. Typhlotanais spinibasis sp. nov., paratype (MZUSP 32893), ♀, dissected. A. Maxillule. B. Maxilla. C. Labium. D. Maxilliped. E. Cheliped. Scale bar = 0.1 mm.

Fig. 19. Typhlotanais spinibasis sp. nov., paratype (MZUSP 32893), ♀, dissected. A–F. Pereopods 1–6. G. Pleopod. H. Uropod. Scale bar = 0.1 mm.

Fig. 20. Typhlotanais spinibasis sp. nov., paratype (MZUSP 38011), ♀, dissected. A. Cheliped. B–G. Pereopods 1–6. 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.