Deltanthura palpus, Shiraki & Shimomura & Kakui, 2022

Shiraki, Shoki, Shimomura, Michitaka & Kakui, Keiichi, 2022, A new neotenous genus and species, Deltanthura palpus gen. et sp. nov. (Isopoda, Anthuroidea, Paranthuridae) from Japan, with a revised key to the genera in Paranthuridae, Zoosystematics and Evolution 98 (1), pp. 109-115 : 109

publication ID	https://dx.doi.org/10.3897/zse.98.81772
publication LSID	lsid:zoobank.org:pub:CBDFB5FE-1734-4B4A-96AB-C87BDA85E6F2
persistent identifier	https://treatment.plazi.org/id/290406E3-4688-4CC7-8A3F-DC104E7C7BBF
taxon LSID	lsid:zoobank.org:act:290406E3-4688-4CC7-8A3F-DC104E7C7BBF
treatment provided by	Zoosystematics and Evolution by Pensoft
scientific name	Deltanthura palpus
status	sp. nov.

Treatment

Deltanthura palpus sp. nov.

[New Japanese name: Sankaku-ashitarazu-uminanafushi] Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4

Material examined.

Holotype. Japan • 1 female lacking oostegites, body length 7.03 mm, body width 0.91 mm; Mie prefecture, off the southern coast, Shima Spur , Stn. SM-01-(1); 34°00.83'N, 136°53.79'E to 34°01.42'N, 136°51.80'E; depth 805-852 m; 4 Mar. 2008; Tadashi Akiyama leg.; SMBL-V0645, 12 slides and 1 vial. GoogleMaps

Etymology.

The specific name, Deltanthura palpus (Latin: palp), is a singular noun in the nominative case, referring to the presence of a mandibular palp, a unique trait in paranthurid neotenous genera.

Description of holotype female.

Body relatively slender (Figs 1 View Figure 1 , 2A-C View Figure 2 ), length 7.69 times width. Head (Fig. 2A View Figure 2 ) length 1.02 times head width, roughened, irregular dorsally; rostrum protruding as much as anterolateral lobes; eyes dorsolateral, with scattered ommatidia. Pereonites 1-7 (Fig. 2A, B View Figure 2 ) roughened, irregular dorsally, with length ratio 1.00:1.02:1.26:1.19:1.08:0.78:0.18; pereonite 7 (Fig. 2B, C View Figure 2 ) reduced, hidden laterally, lacking pereopod 7. Pleonites 1-5 (Fig. 2B, C View Figure 2 ) fused but with sutures, length 0.06 times body length. Pleonite 6 entirely fused dorsally to telson (Figs 2B, C View Figure 2 , 4H View Figure 4 ); pleotelson triangular, length 1.04 times width, with four dorsal and six apical simple setae.

Antennula (Fig. 2D View Figure 2 ) with three peduncular and six flagellar articles. Peduncular article 1 with one inner and two outer plumose sensory setae; article 2 with inner simple seta; article 3 with three inner and one outer simple setae. Flagellar articles 1 and 2 naked; article 3 with distal aesthetasc and three distal simple setae; article 4 with distal aesthetasc; article 5 with distal aesthetasc and simple seta; article 6 with four distal simple setae.

Antenna (Fig. 2E View Figure 2 ) with five peduncular and nine flagellar articles. Peduncular article 1 with outer simple seta; article 2 with two distal simple setae; article 3 with two inner simple setae; article 4 with two distal plumose sensory setae and three simple setae; article 5 with four distal plumose sensory setae and four inner simple setae. Flagellar articles 1-9 with four, four, seven, four, three, three, two, four and zero distal simple setae, respectively.

Mandible (Fig. 2F View Figure 2 ) with 3-articulate palp. Palp article 1 naked; article 2 with distal simple seta; article 3 with eleven simple setae. Molar absent. Incisor acute.

Maxilla (Fig. 2G View Figure 2 ) slender, with twelve teeth and narrow lamella.

Maxilliped (Fig. 2H View Figure 2 ) with 4-articulate palp. Palp articles 1 and 2 long, 3 and 4 short, with one, four, one, and three simple setae, respectively. Endite present, reaching middle of article 2, with distal simple seta. Epipod oval.

Pereopod 1 (Fig. 3A View Figure 3 ) subchelate, robust. Basis with three dorsal plumose sensory setae and ventrodistal seta (tip broken). Ischium with one outer and one ventrodistal simple setae. Merus with two dorsal, one outer, and one ventral simple setae. Carpus strongly protruding ventrodistally, with three inner mid-ventral spiniform setae and four simple setae. Propodus broad, with two inner proximal spiniform setae, and one outer, four dorsal, and one distal simple setae. Palm with five outer spiniform setae and seven simple setae. Dactylus and unguis fused, with two ventral and five middle simple setae.

Pereopod 2 (Fig. 3B View Figure 3 ) narrow. Basis with two dorsal plumose sensory setae, two simple setae, and dorsal seta (tip broken). Ischium with three simple setae. Merus with two dorsal and two ventrodistal simple setae. Carpus triangular, longer than wide, with three ventrodistal simple setae and ventrodistal seta (tip broken). Propodus with dorsal plumose sensory seta, three ventral spiniform setae, and two dorsal and three ventral simple setae. Dactylus with ventrodistal thick seta and three ventral, three ventrodistal, and four inner distal simple setae. Unguis naked.

Pereopod 3 (Fig. 3C View Figure 3 ) similar to pereopod 2 except in number of setae.

Pereopods 4-6 (Fig. 3D-F View Figure 3 ) narrower than pereopod 2, but similar to it except in number of setae and shape of carpus. Carpus rectangular, with ventrodistal spiniform seta.

Pleopod 1 (Fig. 4A View Figure 4 ) protopod with inner simple seta and outer seta (tip broken). Exopod operculiform, distal margin serrate, with 15 marginal plumose setae and four simple setae on surface. Endopod 0.53 times longer than exopod, with three distal simple setae.

Pleopods 2-5 (Fig. 4B-E View Figure 4 ) similar to one another. Protopod with one or two simple setae. Exopod with five to seven distal plumose setae and outer simple (pleopods 2-4) or plumose (pleopod 5) seta. Endopod with three distal plumose setae.

Uropod (Fig. 4F, G View Figure 4 ) with protopod bearing two outer and one inner plumose setae and outer simple seta. Exopod elongate triangular, tapering, with five (right) and 10 (left) simple setae. Endopod with two distal projections, five outer and three distal plumose sensory setae, and 12 distal simple setae.

Remarks.

Our specimen lacks oostegites and an appendix masculina, but its pereon is expanded ventrally (Fig. 1 View Figure 1 ), leading us to conclude that it is a female prior to spawning, rather than a manca-stage individual. The strongly reduced pereonite 7 also supports this conclusion; this segment is not as reduced as in the mancae of non-neotenous species (cf. Frutos et al. 2011: fig. 2C, D; Wägele 1981: fig. 9M). This is the fifth neotenous genus known in Paranthuridae .

Deltanthura palpus gen. et sp. nov. differs from Califanthura minuta , which may belong in Deltanthura (see Remarks above for the genus), in the following characters (character state of C. minuta in parenthesis): body length 7.03 mm (1.60 mm); carpus of pereopod 1 strongly protruding ventrodistally (not protruding); endopod of pleopod 1 short, about half length of exopod (elongate, slightly shorter than exopod); and uropodal endopod with two distal projections (no projections).