Paranesotanais longicephalus, Larsen, Kim & Shimomura, Michitaka, 2008

Larsen, Kim & Shimomura, Michitaka, 2008, Tanaidacea (Crustacea: Peracarida) from Japan. IV. Shallow-water species from Akajima with notes on the recolonization potential of tanaids, Zootaxa 1678, pp. 1-24 : 10-19

Paranesotanais longicephalus n. sp.

( Figs 5–11 )

Material examined. Holotype, non-ovigerous female, body length 2.55 mm ( KMNH IvR 500,221), 6–6.5 meters depth, fine sand, by Majanohama reef, off Akajima (Aka Island), East China Sea, 2–7 June 2007. Allotype, Terminal male ( KMNH IvR 500,222). Paratypes, 2 non-ovigerous female (dissected) ( KMNH IvR 500,223), 1 terminal male (dissected) (( KMNH IvR 500,228), 12 ovigerous females, 121 non-ovigerous females, 8 terminal males, 84 mancae, ( KMNH IvR 500,224), same locality.

Diagnosis. See generic diagnosis.

Etymology. This species is named after dramatically elongated cephalothorax of the terminal male

Description of female (body of holotype, appendages of dissected paratype)

Body ( Fig. 5 A, B). Body length 2.55 mm. 8.25 times as long as broad.

Cephalothorax. Longer than combined length of pereonites 1 and 2. Eye-lobes present, with strong visual pigmentation.

Pereonites. Pereonites 1–3 wider than long. Pereonites 4–5 longer than wide. Pereonite 6 square.

Pleon. Short (less than 25% of total body length). Pleonites all with pleopods, slightly wider than pereonites, with lateral setae. First pleonite slightly larger than others.

Pleotelson. About as long as combined length of last two pleonites.

Antennule ( Fig. 5 C). Shorter than cephalothorax. With three articles; article 1 twice as long as rest of antennule combined, with several simple and broom setae. Article 2 one-quart as long as of article 1, with 1 simple distal seta and two aesthetascs. Article 3 about as long as article 1, with six simple distal setae.

Antenna ( Fig. 5 D). Marginally longer than half of antennule. With six articles (although we consider article 1 as a peduncular process rather than a free article). Article 1 featureless. Article 2 more than twice as long as article 3, with one small rigid dorsal seta and numerous tubercles on a weakly defined dorsal lobe. Article 3 as long as article 1, with one prominent dorsodistal spine. Article 4 longer than other articles, with four distal broom setae. Article 5 about as long as article 3, with one distal seta. Article 6 minute, with five setae.

Mouthparts. Labrum ( Fig. 5 E) slightly widening distally in dorsal view, apex flat and setose. Mandibles ( Fig. 5 F–G) molar broad, longer than incisor, with terminal spines. Left mandible ( Fig. 5 F) lacinia mobilis as big as incisor, with at least five anterior denticles. Incisor with at least seven anterior denticles. Right mandible ( Fig. 5 G) incisor with bifurcate apex and three anterior denticles. Labium ( Fig. 5 H) lobes with a small setose process at outer corners. Maxillule ( Fig. 6 A) with ten spiniform terminal setae, several distal setules on outer margins of endite shaft; palp shorter than endite and with two distal setae. Maxilla ( Fig. 6 B) featureless. Maxilliped ( Fig. 6 C,c1) endites ( Fig. 6 c1) narrower than basis, widening distally, almost completely fused, each with one short and one long simple setae and setules at outer corners. Basis with one seta at palp insertion. Palp article 1 naked. Article 2 with three inner setae and setules. Article 3 with three inner setae; article 4 with four prominent inner, and one small outer seta and distal setules. Distal palp articles with prominent setae ( Fig. 6 c1) with abrupt decrease in width about midlength. Epignath not recovered.

Cheliped ( Fig. 6 D). Basis marginally shorter than carpus, naked, attached via proximally sclerite. Merus with one ventral seta. Carpus longer than propodus including fixed finger, with one ventral and two dorsal setae. Propodus square and with one seta at dactylus insertion, one large seta and several setules on inner margin. Fixed finger with bifurcate apex, with five ventral setae and three setae on inner margin. Dactylus as long as fixed finger, with dorsal crenulation, ventral setules and one inner seta.

Pereopod 1 ( Fig. 7 A). About one-third longer than pereopods 2–6. Coxa with two setae. Basis about as long as rest of appendage, naked. Ischium with one dorsal seta. Merus as long as carpus, with one ventrodistal seta. Carpus longer than half of propodus, with four simple distal setae. Propodus about half as long as basis, with one dorsal and one ventral setae and prominent dorsal spine. Dactylus and unguis combined about as long as propodus and not fused. Unguis longer than dactylus.

Pereopod 2 ( Fig. 7 B). Coxa with one seta. Basis shorter than rest of appendage, with dorsal process, one simple- and two broom setae. Ischium apparently naked. Merus shorter than carpus, with one ventrodistal seta. Carpus longer than half of propodus, with three simple distal setae and cuticular comb scales. Propodus shorter than half of basis, with one simple ventrodistal seta, cuticular comb scales and dorsal spine. Dactylus and unguis combined about as long as propodus and not fused. Unguis longer than dactylus.

Pereopod 3 ( Fig. 7 C). As pereopod 2 except: ischium with one dorsal seta.

Pereopod 4 ( Fig. 7 D). Without coxa. Basis thicker than on pereopods 1–3, with two ventromedial broom setae. Ischium with two dorsal setae. Merus about as long as carpus, widening distally, with one simple- and two prominent spiniform ventrodistal setae. Carpus as long as propodus, with one spatulate (see remarks) and four prominent spiniform distal setae. Propodus shorter than half of basis, with two prominent ventral spiniform setae, one dorsomedial broom seta, one long dorsodistal rigid seta and multiple dorsal spines. Dactylus and unguis fused to a slender bifurcate claw, shorter than propodus.

Pereopod 5 ( Fig. 7 E). As pereopod 4 except: basis with only broom seta. Propodus apparently without dorsal spines.

Pereopod 6 ( Fig. 7 F). As pereopod 4 except: Basis and ischium naked. Propodus with two ventrodistal spiniform setae and three dorsodistal rigid comb setae, without dorsal spines.

Pleopods ( Fig. 6 E). Well developed. Basal article naked. Exopod with 14 outer and one inner plumose setae. Endopod with 24 outer plumose setae. Endites have no gap between proximal seta and other setae but the space between the setae get progressively longer in proximal direction.

Uropods ( Fig. 6 F). Biramous, longer than pleotelson. Basal article naked. Exopod biarticulated, longer than first endopod article; article 1 with one distal seta; article 2 with two distal setae. Endopod biarticulated, article 1 with one distal simple and one broom setae; article 2 with five long simple- and two broom setae distally.

Male (where differing from females)

Body ( Fig. 8 A,B). 8.75 times longer than wide.

Carapace. Much longer than in female, more than one third total body length. Bottle-shaped, as long as 3 first pereonites combined, as long as pereonite 1–5 combined. Eyes present and well developed.

Pereonites. All wider than long.

Pleon. As wide as pereon but not better developed than in female. All pleonites with lateral setae and pleopods.

Antennule ( Fig. 8 C). Much longer and slimmer than in female, particularly article 1. With 4 articles. Article 1 with seven setulated and five simple setae. Article 2–4 of serial repeating appearance. Article 2 with simple setae but apparently without aesthetascs. Article 3–4 with several aesthetasc.

Antenna ( Fig. 8 D). Longer and slimmer than in female but otherwise of same relative proportions. Dorsal seta on article 3 much less spiniform than in female.

Mouthparts ( Fig. 11 A). Reduced in terminal male, only tiny rudiments of maxilliped remains at the proximal end of cephalothorax.

Chelipeds ( Fig. 9 A–C). Elongated and highly modified. Basis and merus proportionally smaller than in female. Merus with ventral bifurcate prolongation ( Fig.11 ). Carpus enlarged, with dorsal process and scattered simple setae. Propodus with row of multiple setae at dactylus attachment. Posterior directed spur reduced to a small shield covering the dactylus attachment. Fixed finger with distal inner process, with multiple setae on inner margin. Dactylus attachment rotated inwards, with proximal and medial inner processes and multiple inner setae.

Pereopods ( Fig. 10 A–F). Identical to those of female, give or take the odd setae. Pleopods ( Fig. 9 D). As in female but exopod.

Uropods ( Fig. 9 E). Basal article somewhat slimmer than in female but uropods otherwise as in female.

MAP 1. Location of collection site.

Figures

FIGURE 5. Paranesotanais longicephalus n. sp. Female (KMNH and IvR 500,223). A, holotype, dorsal view; B same, lateral view, scale bar = 0.5 mm; C, antennule; D, antenna; E, labrum; F, left mandible; G, right mandible; H. labium. Scale bars C – H = 0.25 mm.

FIGURE 6. Paranesotanais longicephalus n. sp. Female (KMNH IvR 500,223). A, maxillule; B, maxilla; C, maxilliped; c 1, same, endites; c 2, maxilliped seta; D, cheliped; E, pleopod; F, uropod. Scale bars = 0.2 mm.

FIGURE 7. Paranesotanais longicephalus n. sp. Female (KMNH IvR 500,223). A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6. Scale bars = 0.25 mm.

FIGURE 8. Paranesotanais longicephalus n. sp. (KMNH IvR 500,222 and IvR 500,225). A, paratype, dorsal view; B same, lateral view, scale bar = 0.5 mm; C, antennule; D, antenna. Scale bars = 0.25 mm.

FIGURE 9. Paranesotanais longicephalus n. sp. Male (KMNH IvR 500,225). A, cheliped, dorsal view; B, propodus of same, outer view; C, propodus of same, inner view. D, pleopod; E, uropod. Scale bars = 0.25 mm.

FIGURE 10. Paranesotanais longicephalus n. sp. Male (KMNH IvR 500,225). A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6. Scale bar = 0.25 mm.

FIGURE 11. Paranesotanais longicephalus n. sp. Male (KMNH IvR 500,222). A, ventral view of cephalothorax and chelipeds. Scale bar = 0.25 mm.