Paranesotanais incisus, Tzeng & Wei & Ma & Li, 2023

Tzeng, You-Wei, Wei, Chih-Lin, Ma, Lin & Li, Xinzheng, 2023, Three new species of Paratanaoidea (Crustacea, Tanaidacea) from the South China Sea, Zootaxa 5375 (1), pp. 1-30 : 20-27

Paranesotanais incisus sp. nov.

Figs 10–14

Material examined. Holotype: non-ovigerous female ( NMNS8568-05 ), body length 2.8 mm, completely dissected and body parts preserved in 75% alcohol, Dongsha Atoll (20°36’53.4”N, 116°46’02.4”E), the South China Sea, from bottom sand of a patch of coral reef at a depth of 5 m, 31 March 2016.

Allotype: male ( NMNS8568-06 ), body length 2.8 mm, completely dissected and body parts preserved in 75% alcohol, same collection data as holotype.

Paratypes: male ( NMNS8568-07 ), body length 2.9 mm, same collection data as holotype ; non-ovigerous female ( NMNS8568-08 ), body length 3.0 mm, same collection data as holotype ; male ( NMNS8568-09 ), body length 2.5 mm, same collection data as holotype ; non-ovigerous female ( NMNS8568-10 ), body length 2.8 mm, same collection data as holotype ; non-ovigerous female ( NMNS8568-11 ), body length 2.1 mm, same collection data as holotype .

Other material: female ( NMNS8568-12 ), Dongsha Atoll (20°36’46.7”N, 116°47’32.0”E), the South China Sea, from bottom sand of a patch of coral reef at a depth of 5 m, 2 April 2017 ; female ( NMNS8568-13 ), Dongsha Atoll (20°36’53.4”N, 116°46’02.4”E), the South China Sea, from bottom sand of a patch of coral reef at a depth of 10 m, 31 March 2016 ; 1 female and 1 male ( NMNS8568-14 ), same collection data as NMNS8568-13; 7 females ( NMNS8568-15 ), same collection data as NMNS8568-13; 2 females ( NMNS8568-16 ), same collection data as holotype; 5 females ( NMNS8568-17 ), same collection data as holotype; 6 females and 1 male ( NMNS8568-18 ), same collection data as holotype; female ( NMNS8568-19 ), Dongsha Atoll (20°41’22.4”N, 116°42’48.2”E), the South China Sea, from bottom sand of a patch of coral reef at a depth of 5 m, 8 April 2017 ; male ( NMNS8568-20 ), same collection data as NMNS8568-19; 2 females ( NMNS8568-21 ), Dongsha Atoll (20°41’22.4”N, 116°42’48.2”E), the South China Sea, from bottom sand of a patch of coral reef at a depth of 5 m, 12 September 2017 .

Diagnosis. Female: Antennule article-3 with two proximal and one distal aesthetascs. Antenna article-3 dorsodistal seta not spiniform; article-6 with one aesthetasc. Cheliped propodus with one robust inner seta. Male: Antennule article-3 with two distal aesthetascs; article-4 with one distal aesthetasc. Cheliped merus with one small hook-like apophysis; carpus with one long and conspicuous notch extending from outer surface to ventrodistal corner.

Description (some characters stated in genus or species diagnosis not included). Non-ovigerous female (holotype): Habitus ( Fig. 10A , 11A ) dorsoventrally flattened, 2.8 mm long, 7.8 times longer than wide. Carapace long sub elliptical, 0.2 times as long as body 1.7 times longer than wide; lateral margin with one pair of anterior setae near eye lobe. Eye lobe with developed visual elements, remaining red-colored in alcohol. Pereon slightly more than half as long as body; pereonite-1 shortest, half as long as wide, with one pair of dorsal setae on anterior margin, and one pair of anterolateral setae; pereonites 2–6 0.7, 0.8, 1.0, 1.1, 1.0 times as long as wide, respectively, each with one pair of anterolateral setae. Pleon about 0.8 times as long as carapace; each pleonite with similar length and width, half as long as wide; pleonite-1 with one pair of dorsolateral setae and two pairs of lateral setae; pleonites 2–4 with two pairs of lateral setae; pleonite-5 with one pair of dorsolateral setae and one pair of lateral setae. Pleotelson semicircular, 0.6 times as long as wide, with two pairs of setae on posterolateral margin, and one pair of setae on posterior tip.

Antennule ( Fig. 11C ) three-articled; article-1 3.8 times longer than wide, inner margin with one middle and one distal setae, outer margin with a subproximal cluster of three broom setae, a middle cluster of two broom setae and one long seta, a subdistal cluster of two broom setae and one long seta; article-2 0.2 times as long as article-1, with one broom setae and two subdistal setae; article-3 1.3 times longer than wide, with two subproximal aesthetascs, one distal aesthetasc, and six distal setae.

Antenna ( Fig. 11E ) six-articled; article-1 naked, without clear articulation line between carapace; article-2 1.6 times longer than wide, with one subdistal seta; article-3 short, 0.4 times as long as article-2, with one subdistal seta; article-4 long and curved, 1.6 times longer than article-2, with five distal broom setae; article-5 0.4 times as long as article-2, with one distal seta; article-6 very short, with five setae and one aesthetasc.

Labrum ( Fig. 11G ) typical, covered with setules. Left mandible ( Fig. 12A ) lacinia mobilis with five anterior denticles; incisor with seven anterior denticles; molar typical. Right mandible ( Fig. 12B, C ) incisor bifurcate, with several small denticles; molar typical. Labium ( Fig. 12D ) typical, antero-outer corner covered with denser setules. Maxillule ( Fig. 12E ) endite outer margin covered with setules, with ten distal spiniform setae; palp not examined. Maxilliped ( Fig. 12F ) basis with a pair of short subdistal setae; endite ( Fig. 12G ) with one pair of short subdistal setae and one pair of long inner setae, outer distal margin covered with setules; palp article-1 naked, article-2 inner margin with two subdistal setae and one short and robust distal seta, article-3 inner margin with three robust setae and covered with setules, dorsal surface with one short seta, article-4 outer margin with one short seta, distal margin covered with setules, with one short seta and four robust setae.

Cheliped ( Fig. 12I ) coxal sclerite crescent, naked; basis 1.5 times longer than wide, with one outer seta; merus with one ventral seta; carpus slightly longer than basis 1.8 times longer than wide, dorsal margin with one subdistal seta and one seta on proximal half, ventral margin with two middle setae; propodus ( Fig. 12J ) palm and fixed finger combined slightly shorter than basis twice as long as wide, palm with a row of ten inner setae and one robust inner seta near dactylus articulation, inner surface partially covered with setules, fixed finger ventral margin with five setae, incisive margin with one seta on proximal half, a cluster of three setae on distal half, and one distal apophysis, together with unguis bifurcate; dactylus ( Fig. 12J ) slightly curved, 2.6 times longer than wide, outer margin conspicuously crenulate, inner surface with one seta, ventral half partially covered with setules.

Pereopod-1 ( Fig. 13A ) coxa with one seta; basis long, 5.9 times longer than wide, dorsal margin with one seta one proximal half; ischium with one ventral seta; merus 0.3 times as long as basis 1.6 times longer than wide, naked; carpus 1.3 times longer than merus 2.6 times longer than wide, dorsal margin with one subdistal seta, ventral margin with two subdistal setae; propodus 1.3 times longer than carpus 4.4 times longer than wide, dorsal margin with one small distal denticle, ventral margin with one subdistal seta; dactylus and unguis not fused, combined slightly longer than propodus, unguis 0.6 times as long as dactylus.

Pereopod-2 ( Fig. 13B ) coxa with one seta; basis four times longer than wide, dorsal margin with one seta and two broom setae on proximal half; ischium with one ventral seta; merus 0.3 times as long as basis 1.6 times longer than wide, with one ventrodistal seta; carpus 1.5 times longer than merus 2.5 times longer than wide, dorsal margin with one subdistal seta, ventral margin with two subdistal setae; propodus slightly longer than carpus 3.6 times longer than wide, dorsal margin with several very small denticles and one small distal denticle, ventral margin with one subdistal seta, outer surface partially covered with setules; dactylus and unguis not fused, combined slightly shorter than propodus.

Pereopod-3 ( Fig. 13C ) very similar to pereopod-2 but basis dorsal margin with one seta and one broom seta; carpus relatively shorter, 1.2 times longer than merus.

Pereopod-4 ( Fig. 13D ) coxa absent; basis thick, 2.4 times longer than wide, ventral margin with two middle broom setae; ischium with two ventrodistal setae; merus half as long as basis twice as long as wide, ventral margin with one subdistal seta and two subdistal spiniform setae; carpus as long as merus 2.3 times longer than wide, dorsal margin with one subdistal seta, distal margin with two outer and two inner spiniform setae; propodus slightly shorter than carpus 3.1 times longer than wide, dorsal margin with one middle broom seta, one small distal denticle and one long and strong distal serrated seta, longer than dactylus and unguis combined, ventral margin with two distal spiniform setae.

Pereopod-5 ( Fig. 13E ) very similar to pereopod-4 but basis ventral margin with one middle broom seta; merus ventral margin with two subdistal spiniform setae without simple seta.

Pereopod-6 ( Fig. 13F ) very similar to pereopod-5 but basis naked; propodus dorsal margin without broom seta, with three distal serrated setae, shorter than dactylus and unguis combined.

Pleopod-1 ( Fig. 13G ; all setae circumplumose, setules omitted in figure) peduncle naked; exopod with 21 outer circumplumose setae; endopod with twelve outer circumplumose setae, inner margin with one subdistal circumplumose seta.

Uropod ( Fig. 13H ) peduncle naked; exopod two-articled, article-1 with one long distal seta, article-2 with two long distal setae; endopod two-articled, article-1 long, 0.9 times as long as exopod, with one subdistal seta and one distal broom seta, article-2 with two distal broom setae and five distal setae.

Male (allotype): Habitus ( Fig. 10B, C , 11B ) dorsoventrally flattened, 2.8 mm long, eight times longer than wide. Carapace 2.7 times longer than wide; lateral margin with one pair of setae near eye lobe. Eye lobe with strong visual elements, remaining red-colored preserved in alcohol. Pereon half as long as body; pereonites 1–5 0.4, 0.7, 0.8, 1.0, 1.1, 1.0 times as long as wide, respectively, each with one pair of anterolateral setae. Pleon half as long as carapace; each pleonite with similar length and width, 0.4 times as long as wide, setal pattern similar to that of female. Pleotelson semicircular, 0.7 times as long as wide, setal pattern similar to that of female.

Antennule ( Fig. 11D ) four-articled; article-1 elongate, 0.6 times as long as carapace 6.9 times longer than wide, setal pattern similar to that of female; article-2 0.1 times as long as article-1, setal pattern similar to that of female; article-3 0.9 times as long as article-2, with two distal aesthetascs; article-4 0.9 times as long as article-3, with five distal setae, one distal broom seta, and one distal aesthetasc.

Antenna ( Fig. 11F ) six-articled; articles 1–3 similar to that of female; article-4 straight and elongate, 2.4 times longer than article-2, with one broom seta on distal half and five distal broom setae; article-5 with one distal seta; article-6 very short, with six setae.

Maxillule not examined. Maxilliped ( Fig. 12H ) basis completely fused, firmly attached to carapace, with one pair of setae near palp; palp articles 1–3 naked, article-4 very short, with one distal lamellar seta.

Cheliped ( Fig. 14A ) coxal sclerite crescent, naked; basis relatively short, 1.5 times longer than wide, with one outer seta; merus with ventral margin with one seta and one small hook-like apophysis; carpus 1.5 times longer than basis twice as long as wide, with one dorsal seta on proximal half, two outer setae on ventral half, and one long and conspicuous notch extending from outer surface to ventrodistal corner; propodus palm and fixed finger combined 1.3 times longer than carpus 3.2 times longer than wide, palm with a row of 18 inner setae near articulation of dactylus ( Fig. 14B ), fixed finger curved, distally steeply down curved, with one outer middle seta and nine setae along incisive margin; dactylus ( Fig. 14B ) incisive margin with one proximal, one middle large apophysis and six setae.

Pereopod-1 ( Fig. 14C ) very similar to that of female but merus with one ventrodistal seta.

Pereopod-2 ( Fig. 14D ) very similar to that of female but basis with one seta and one broom seta.

Pereopod-3 ( Fig. 14E ) very similar to that of female but basis with one seta and two broom setae.

Pereopod-4 ( Fig. 14F ) very similar to that of female but basis with one broom seta.

Pereopods 5–6 ( Fig. 14G, H ) very similar to those of female.

Pleopods and uropod very similar to those of female.

Etymology. The name is from the Latin incisus (incised), referring to the long and conspicuous notch on the carpus of the male cheliped.

Type locality. Dongsha Atoll, the South China Sea.

Distribution. It is only known from the South China Sea.

Remarks. The female of P. incisus sp. nov. closely resembles that of P. longicephalus Larsen & Shimomura, 2008 , with the exception of differences in the antennule and cheliped. In the female P. incisus , the antennule possesses two subproximal and one distal aesthetascs on article-3, which is a noticeable contrast to the female P. longicephalus , having two distal aesthetascs on article-2 but lacking an aesthetasc on article-3. The antennule as described in the partial redescription of P. longicephalus by Kakui & Yamasaki (2013) shares more, though not entirely identical, features with that of the new species, displaying three proximal and one distal aesthetascs on article-3. Additionally, the propodus palm of the cheliped in the female P. incisus holds one robust inner seta, a feature that is not present in P. longicephalus ( Larsen & Shimomura 2008: 11, figs 6D; Kakui & Yamasaki 2013: 252, fig 6C; Figs 11C , 12I, J ).

The male of P. incisus can be distinguished from that of P. longicephalus by having: 1) two distal aesthetascs on antennule article-3 (three in P. longicephalus ); and 2) one long and conspicuous notch extending from the outer surface to the ventrodistal corner of the cheliped carpus (absent in P. longicephalus ) ( Larsen & Shimomura 2008: 12, 14, figs 8C, 11A; Kakui & Yamasaki 2013: 252, fig 6D; Figs 11D , 14A, B ).

Figures

FIGURE 10. Paranesotanais incisus sp. nov. specimens (ethanol-preserved), photo by You-Wei Tzeng. Paratype (NMNS8568- 11), female: A, dorsal view. Allotype (NMNS8568-06), male: B, dorsal view; C, lateral view.

FIGURE 11. Paranesotanais incisus sp. nov. Holotype (NMNS8568-05), female: A, body dorsal view; C, right antennule; E, right antenna (outer view); G, labrum. Allotype (NMNS8568-06), male: B, body dorsal view; D, right antennule; F, right antenna (outer view).

FIGURE 12. Paranesotanais incisus sp. nov. Holotype (NMNS8568-05), female: A, left mandible; B, right mandible; C, right mandible incisor; D, labium; E, maxillule endite; F, maxilliped; G, maxilliped endite; I, right cheliped; J, right cheliped propodus and dactylus inner view. Allotype (NMNS8568-06), male: H, maxilliped.

FIGURE 13. Paranesotanais incisus sp. nov. Holotype (NMNS8568-05), female:A–B, right pereopods 1–2; C, left pereopod-3; D, right pereopod-4; E–F, left pereopods 5–6; G, right pleopod-1 (all setae circumplumose, setules omitted); H, right uropod.

FIGURE 14. Paranesotanais incisus sp. nov. Allotype (NMNS8568-06), male: A, right cheliped; B, right cheliped ventral view; C–H, right pereopods 1–6.