Akanthinotanais pedecerritulus, Tzeng & Hsueh, 2021

Tzeng, You-Wei & Hsueh, Pan-Wen, 2021, Additions of new species to the Paratanaoidea (Crustacea, Tanaidacea) of Taiwan, Zootaxa 4949 (1), pp. 131-148 : 142-147

Akanthinotanais pedecerritulus sp. nov.

Figs 6–7

Material examined. Holotype:non-ovigerous female( NMNS8288-18 ),body length 1.2mm,Jialulan (22°48’10.2”N, 121°11’57.0”E), eastern Taiwan, intertidal, washing from red algae Asparagopsis taxiformis (Delile) Trevisan de Saint-Léon, 1845 , collected by You-Wei Tzeng, 23 July 2013.

Paratypes: non-ovigerous female ( NMNS 8288-19 ), body length 1.1 mm, Shitiping (23°28’57.4”N, 121°30’46.9”E), eastern Taiwan, intertidal, washing from red algae A. glomerata , collected by You-Wei Tzeng, 21 April 2012 .

Diagnosis. Female: Body about 5.4 times longer than wide. Antennule article-3 with one distal aesthetasc. Antenna articles 4–6 with strong setae. Cheliped carpus 1.4 times longer than wide, dorsal margin with one subdistal wide notch, fixed finger and dactylus slender and smooth. Pereopod 2–3 merus with one ventrodistal spine, carpus with one ventrodistal bayonet spine (up to 0.7 times as long as carpus) and one shorter ventrodistal spine, propodus with one ventrodistal spine, dactylus plus unguis approximately sigmoid. Pereopods 4–5 merus and carpus with two ventrodistal bayonet spines, propodus with one ventrodistal spine. Pereopod-6 merus with three ventrodistal spines, carpus with three ventrodistal bayonet spines, propodus with one ventrodistal spine. Uropod exopod 0.8 times as long as endopod.

Description (some characters stated in generic or species diagnosis not included). Female: Habitus ( Fig. 6A , figure and description based on NMNS 8288-19, 1.1 mm) dorsoventrally flattened. Carapace subtriangular, 1.1 times longer than wide, eye lobe distinct. Pereon about 0.6 times as long as body; pereonite-1 very short, 0.2 times as long as wide; pereonite-2 slightly longer than pereonite-1, 0.2 times as long as wide; pereonite-3 two times longer than pereonite-2, 0.4 times as long as wide; pereonite-4 almost two times longer than pereonite-3, 0.7 times as long as wide; pereonite-5 longest, 1.2 times longer than pereonite-4, 0.8 times as long as wide; pereonite-6 0.7 times as long as pereonite-5, 0.6 times as long as wide. Pleon 0.2 times as long as body; all pleonites about the same length, with one lateral seta. Pleotelson with one seta on each lateral margin and two setae on posterior margin.

Antennule ( Fig. 6B ) three-articled, as long as carapace; article-1 longest, about 0.5 times as long as total length, outer margin with one subproximal seta, one distal long seta and three distal broom setae, inner margin with one medial seta; article-2 0.4 times as long as article-1, with two distal setae and one distal broom seta; article-3 1.5 times longer than article-2.

Antenna ( Fig. 6C ) six-articled, 0.9 times as long as antennule; article-1 naked; article-2 dorsal margin with one subdistal spine; article-3 dorsal margin with one subdistal spine, ventral margin with one small distal seta; article-4 longest, about 0.5 times as long as total length, with one mid-dorsal broom seta, four distal broom setae and three strong distal setae; article-5 with one strong distal seta; article-6 extremely short, with four setae and one strong seta.

Labrum not observed. Left mandible ( Fig. 6D ) lacinia mobilis large, subtriangular, distal margin crenulate; incisor with blunt acuminate apex, distal margin with one small protrusion; molar slender, distally bent and pointed. Right mandible ( Fig. 6E ) incisor with bifid apex and subtly crenulated distal margin ( Fig. 6F ); molar slender, distally bent and pointed. Labium ( Fig. 6G ) naked. Maxillule ( Fig. 6H ) palp not observed; endite with eight distal spines. Maxilla not observed. Maxilliped ( Fig. 6I ) basis completely fused, with one distal seta; endite ( Fig. 6J ) almost fused, with one inner seta, distal margin covered with setules; palp article-1 naked, articles 2 and 3 inner margin with three setae, article-4 with six distal setae.

Cheliped ( Fig. 7A ) attached to cephalothorax via sclerite; basis stout, 1.3 times longer than wide, naked; merus subtriangular, without seta; carpus about as long as basis, dorsal margin with one subdistal wide angle process and one seta on it, ventral margin with two setae; propodus palm 1.1 times longer than carpus, 1.7 times longer than wide, with one ventral seta and one seta near dactylus articulation, fixed finger 2.8 times longer than wide, distally pointed, incisive margin smooth, with two setae, unguis short; dactylus curved and slender, 4.5 times longer than wide, unguis short.

Pereopod-1 ( Fig. 7B , figure and description based on NMNS 8288-19) coxa with one seta; basis curved, 4.5 times longer than wide, with one dorsal seta; ischium naked; merus 0.45 times as long as basis, two times longer than wide, without seta; carpus 1.3 times longer than merus, 2.4 times longer than wide, with one dorsodistal seta; propodus long and slender, 1.7 times longer than carpus, over 4.5 times longer than wide, with one subventral seta; dactylus combined unguis 0.7 times as long as propodus, unguis longer than dactylus.

Pereopod-2 ( Fig. 7C ) coxa with one seta; basis naked, four times longer than wide; ischium with two ventral setae; merus 0.3 times as long as basis, two times longer than wide; carpus long and distally wider, 1.4 times longer than merus, 2.4 times longer than wide, distal margin with one dorsal seta, one ventral spine and one ventral bayonet spine, which nearly 0.7 times as long as carpus; propodus long and slender, 1.1 times longer than carpus, over four times longer than wide, dorsal margin with one small distal spinule, ventral margin with one distal spine; dactylus plus unguis ( Fig. 7D ) approximately sigmoid, unguis longer than dactylus, duckbill-like.

Pereopod-3 ( Fig. 7E, F ) very similar to pereopod-2.

Pereopod-4 ( Fig. 7G , figure and description based on NMNS 8288-19) coxa with one seta; basis naked, 2.4 times longer than wide; ischium with two ventral setae; merus 0.5 times as long as basis, 2.3 times longer than wide, with two ventrodistal bayonet spines of different lengths; carpus about as long as merus, distally wider, 2.2 times longer than wide, with one dorsodistal seta and two ventrodistal bayonet spines; propodus long and slender, 1.5 times longer than carpus, 4.7 times longer than wide, dorsal margin with one small distal spinule and one strong seta, ventral margin with one distal spine; dactylus claw-like, with unguis.

Pereopod-5 ( Fig. 7H ) very similar to pereopod-4 but with sub-equal ventrodistal bayonet spines on merus.

Pereopod-6 ( Fig. 7I ) coxa with one seta; basis over 3.5 times longer than wide, without seta; ischium with two ventral setae; merus short, 0.2 times as long as basis, 1.1 times longer than wide, with one ventrodistal seta and three ventrodistal spines; carpus 1.6 times longer than merus, 2.2 times longer than wide, with one dorsodistal seta and three ventrodistal bayonet spines; propodus long and slender, 1.5 times longer than carpus, over four times longer than wide, dorsal margin with one small distal spinule and three long distal setae, ventral margin with one distal spine; dactylus claw-like, unguis separated.

Pleopod-5 ( Fig. 7J ) peduncle naked; exopod distal margin with ten long plumose setae and one shorter circumplumose seta; endopod with four distal plumose setae and one short circumplumose seta.

Uropod ( Fig. 7K ) peduncle naked; exopod two-articled, article-1 with one distal seta, article-2 with two distal setae and one distal broom seta; endopod two-articled, article-1 with one distal seta, article-2 with four distal setae and three distal broom setae.

Male unknown.

Etymology. The name is derived from the Latin “ pede ” (foot) and “ cerritulus ” (weird), referring to the sigmoid dactylus of pereopod-2 and 3.

Type locality. Jialulan, Taitung County, eastern Taiwan.

Distribution. It is only known from Shitiping, Jialulan and Jihuei, eastern Taiwan.

Remarks. The present species, A. pedecerritulus sp. nov., can be readily distinguished from all other Akanthinotanais by having an unusual sigmoid dactylus (including unguis) in pereopods 2 and 3, and the tip of unguis is also uncommonly blunt, duckbill-like. Moreover, A. pedecerritulus differs from its congeners by the number of spines on the merus, carpus and propodus of pereopods 2–6, that vary among Akanthinotanais species. Fig. 7C–I and Table 2 show that the number of spines on pereopods 2–6 in A. pedecerritulus is unique in Akanthinotanais .

Figures

FIGURE 6. Akanthinotanais pedecerritulus sp. nov. Paratype (NMNS 8288-19), female: A, body dorsal view. Holotype (NMNS 8288-18), female: B, right antennule; C, right antenna; D, left mandible; E, right mandible; F, right mandible incisor; G, labium; H, maxillule endite; I, maxilliped; J, maxilliped endite. Scale: A–J, 0.1 mm.

FIGURE 7. Akanthinotanais pedecerritulus sp. nov. Holotype (NMNS 8288-18), female:A, right cheliped; C, left pereopod-2; D, left pereopod-2 dactylus; E, right pereopod-3; F, right pereopod-3 dactylus; H–I, right pereopods 5–6; J, left pleopod-5; K, right uropod. Paratype (NMNS 8288-19), female: B, right pereopod-1; G, right pereopod-4. Scale: A–K, 0.1 mm.