Paratyphlotanais apletos, 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 : 327-330

Paratyphlotanais apletos sp. nov. Segadilha & Błażewicz

LSID urn:lsid:zoobank.org:act:8DB9BD75-5202-486C-9B64-BD6A3A205E4E

( Figs. 7–10 )

Material examined. Holotype: one female non-ovigerous, length 2.4 mm ( MNRJ 28876 ) Sta PPG1 #2 R3.

Paratypes: one female non-ovigerous, length 3.6 mm ( MNRJ 28877 ) dissected, Sta PPG1 #4 R3; one female ( MNRJ 28878 ) Sta PPG1 #2 R2; one female ( MNRJ 28879 ) Sta PPG1 #2 R3; nine females ( MNRJ 28880 ) Sta PPG1 #3 R1; two females and one manca ( MNRJ 28881 ) Sta PPG1 #3 R2; eight females ( MNRJ 28882 ) Sta PPG1 #3 R3; eight females ( MNRJ 28883 ) Sta PPG1 #4 R1; five females ( MNRJ 28884 ) Sta PPG1 #4 R2; three females ( MNRJ 28885 ) Sta PPG1 #4 R3; one female ( MNRJ 28886 ) Sta PPG1 #5 R1; six females and one manca ( MNRJ 28887 ) Sta PPG1 #5 R3; four females ( MNRJ 28888 ) Sta PPG1 #6 R1; one female ( MNRJ 28889 ) Sta PPG1 #6 R3; six females ( MNRJ 28890 ) Sta PPG1 #7 R1; ten females ( MNRJ 28891 ) Sta PPG1 #7 R2; eleven females ( MNRJ 28892 ) Sta PPG1 #7 R3; fifteen females and two mancae ( MNRJ 29074 ) Sta PPG1 #8 R1; three females ( MNRJ 29075 ) Sta PPG1 #8 R2; three females ( MNRJ 29076 ) Sta PPG1 #8 R3 .

Diagnosis. Body about six times L:W; all pereonites wider than long, with several minute setae on proximal and lateral margins. Large hyposphenium only on pereonite-1 sternite; cephalothorax 1.2 times L:W; cheliped stout, merus with four ventral seta (one long and three short); carpus 1.4 times L:W, with seven ventral setae (two long and five short) and with row of nine minute setae along dorsal margin; propodus almost twice L:W; pereopod-1 coxa with spur; carpus with large serrate spine distally; pereopods 2–6 merus, carpus and propodus with conspicuous serrate spines; exopod uropods shorter than endopod article-1.

Etymology. Apletos (Greek) = immense. The name reflects the conspicuous serrate spines on pereopods 1–6.

Description of female. Paratype dissected, length 3.6 mm ( MNRJ 28877). Body ( Figs. 7A, B ) 5.8 times L: W. Cephalothorax narrowest rostrally, 1.2 times L:W, 3.4 times as long as pereonite-1, longer than pereonites 1–2 combined, naked; eyes absent.

Pereonites 1–6: all rectangular (lateral margins parallel), wider than long, with several minute setae on proximal and lateral margins; 0.4, 0.5, 0.6, 0.7, 0.8, 0.7 times L:W, respectively; large hyposphenium only on pereonite-1 sternite.

Pleon ( Fig. 7A, B ) 0.2 TBL, with five subequal pleonites, each one with lateral seta, together shorter than cephalothorax. Pleotelson rectangular, 0.6 times L:W, with two pairs of lateral and one pair of distal setae.

Antennule ( Fig. 7C ) shorter than cephalothorax (0.6 times L:W), with three articles; article-1 stout, 0.7 TL, 1.7 times L:W, with five simple and two penicillate medial setae, and one long and two penicillate setae distally; article-2 once L:W, 0.2 times as long as article-1, with two distal setae; article-3 5.4 times L:W, 1.7 times as long as article-2, with four simple, one penicillate, one aesthetasc and with apical spur.

Antenna ( Fig. 7D ) of six articles, article-1 broken during dissection; article-2 once L:W, with two distal setae (one simple and one thick); article-3 0.5 times L:W, 0.4 times as long as article-2, with thick seta; article-4 3.1 times L:W, five times as long as article-3, with three simple and two 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. 7E ) rounded, hood-shaped, distally covered by minute setae. Mandibles ( Fig. 7F, G ) with molar broad with irregular edge, without pointed teeth. Left mandible ( Fig. 7F ) incisor simple, lacinia mobilis well developed, with five teeth; right mandible ( Fig. 7G ) incisor distally truncate, without lacinia mobilis. Labium ( Fig. 8A ) with distolateral corner finely setose; outer lobe membranous also with distolateral corner finely setose. Maxillule ( Fig. 8B ) endite with eight terminal spines (one short); palp with two terminal setae. Maxilliped ( Fig. 8C ) basis elongate, with seta reaching distal margin of endites; each endite with seta and two delicate cusps on distal margin and microtrichia on outer corner; palp with four articles; article-1 triangular, naked; article-2 with three inner (at least two weakly serrate) and one outer seta; article-3 with four inner setae (at least three weakly serrate); article-4 with four weakly serrate inner setae and one subdistal outer seta. Maxilla and epignath not recovered.

Cheliped ( Fig. 8D ) stout, basis twice L:W, with posterior lobe partly occluded by the lower part of the cephalo- thorax, and with dorsodistal seta; merus triangular, with 4–5ventral setae (one long and 3–4 short); carpus 1.4 times L:W, with 7–8 ventral setae (two long and 5–6 short) and row of nine/ten minute dorsal setae; propodus as long as carpus, 1.9 times L:W, with two simple setae near dactylus insertion (inner and outer); fixed finger with two ventral setae, cutting edge with small subdistal protrusion and with three setae; dactylus with dorsal seta.

Pereopod-1 ( Fig. 9A ) walking type; slender; coxa with spur and seta; basis four times L:W, with two dorso- proximal and one ventroproximal setae; ischium with two ventral setae (simple and other thick); merus 1.8 times L: W, with dorsodistal seta and ventrodistal spine and seta; carpus about twice L:W, with two dorsodistal setae; ven- trodistal simple and rod-like setae and robust serrate spine distally; propodus 4.3 times L:W, about as long as merus and carpus combined, with mid-dorsal seta, two dorsodistal and one ventrodistal spines; dactylus 0.8 times as long as unguis; dactylus and unguis combined 0.8 times as long as propodus.

Pereopod-2 ( Fig. 9B ) walking type; coxa with seta; basis 3.6 times L:W, with two penicillate mid-dorsal and two simple ventral setae; ischium with two ventral setae (simple and other thick); merus 1.2 times L:W, with dorso- distal seta, and seta and serrate ventrodistal spine; carpus 1.5 times L:W, with dorsodistal and mid-ventral setae and three serrate distal spines; propodus three times L:W, 0.8 times as long as merus and carpus combined, with dorso- distal seta and spine; mid-ventral seta and ventrodistal serrate spine; dactylus 0.6 times as long as unguis; dactylus and unguis combined as long as propodus.

Pereopod-3 ( Fig. 9C ) similar to pereopod-2, except, basis with two dorsoproximal and three ventral setae; dac- tylus 0.8 times as long as unguis; ischium seta not shown.

Pereopod-4 ( Fig. 9D ) walking type; coxa absent; basis 2.6 times L:W, with dorsal simple and two ventral long penicillate setae; ischium with two ventral setae (simple and other thick); merus triangular about 2.4 times L:W, with seta and two ventrodistal serrate spines; carpus 1.9 times L:W, with dorsodistal seta and three distal large ser- rate spines (one longer than others); propodus more than four times L:W, with penicillate mid-dorsal seta, dorsodis- tal seta half of dactylus and two ventrodistal serrate spines; dactylus three times as long as unguis, with microtrichia; dactylus and unguis combined 0.8 times as long as propodus; unguis bifurcate.

Pereopod-5 ( Fig. 9E ) similar to pereopod-4, except, basis 2.3 times L:W; merus twice L:W; carpus 1.5 times L: W; propodus 3.7 times L:W.

Pereopod-6 ( Fig. 9F ) similar to pereopod-5, except basis with dorsal seta; propodus with three dorsodistal setae as long as half unguis.

Pleopod ( Fig. 9G ). All pleopods similar; basal article naked; exopod with nine plumose setae on outer margin and with plumose seta on inner margin; endopod with thirteen plumose setae on outer margin; gap between proximal seta and other ventral setae in both rami.

Uropod ( Fig. 9H ) 1.2 times as long as pleotelson; basis about once L:W, with outer distal seta; exopod one-ar- ticled, eight times L:W, 0.5 times of endopod length, with medial seta, stout and simple distal setae; endopod twoarticled, 8.2 times L:W; article-1 1.4 times as long as exopod, with one long and two penicillate distal setae, article-2 with long subdistal, four simple and two penicillate setae distally.

Distribution. This species is only known from the type-locality southeast of Brazil ( Fig. 10 ), at 100 m depth (continental shelf), occurring on sand. All other locations of the species are very close to the type locality and essentially can be considered the same location.

Remarks. Paratyphlotanais apletos sp. nov. is a member of the genus Paratyphlotanais by the presence of conspicuous large serrate spines on pereopods 2–6 merus and carpus, and with a bifurcate unguis on these pereopods. The new species resembles the other species from Atlantic Ocean, P. pectinatus (from the Hebrides Slope, North-East Atlantic), in having the cheliped carpus with several dorsal and ventral setae and highly serrate pereopodal spines; however, differs from it by (1) stouter body (six times in P. apletos and more than seven times in P. pectinatus ); (2) cephalothorax shorter (1.2 times in P. apletos and twice in P. pectinatus ); (3) antennule article-1 stouter (1.7 times in P. apletos and 2.2 times in P. pectinatus ); (4) cheliped propodus stouter (1.9 times in P. apletos and three times in P. pectinatus ); (4) pereopod-2 without coxal spur; and (5) all pereopods as a whole stouter than in P. pectinatus .

Within the genus, only P. alveolus from Antarctica (Eastern Weddell Sea) has a coxal spur solely on pereopod-1, as in P. apletos . Also, both species have several minute setae on pereonites margins. Nevertheless P. apletos differs from it by (1) stouter body (six times in P. apletos and more than seven times in P. pectinatus ); (2) cephalothorax less triangular (proximal margin 1.6 times larger than distal margin in P. apletos and almost three times in P. alveolus ); (3) cheliped merus with four ventral setae (4) cheliped carpus stouter and setose (1.4 times in P. apletos and 2.2 times in P. alveolus ); and (5) pereopods serrate spines much more developed and conspicuous.

Figures

FIGURE 7. Paratyphlotanais apletos sp. nov. Paratype, female dissected, MNRJ 28877.A. Dorsal view, B. lateral view. Scale = 1 mm. C. Antennule, D. antenna. E. labrum, F. left mandible, G. right mandible. Scale = 0.1 mm.

FIGURE 8. Paratyphlotanais apletos sp. nov. Paratype, female dissected, MNRJ 28877. A. Labium, B. maxilla C. maxilliped, D. cheliped. Scale = 0.1 mm.

FIGURE 9. Paratyphlotanais apletos sp. nov. Paratype, female dissected, MNRJ 28877. A–F. Pereopods 1–6, G. pleopod, H. uropod. Scale = 0.1 mm.

FIGURE 10. Geographic distribution of Paratyphlotanais apletos sp. nov., along the southeastern Brazilian coast. Red point: type-locality (holotype).