Cruranthura viridis, Shiraki & Kakui, 2024

Shiraki, Shoki & Kakui, Keiichi, 2024, Description of a New Cruranthura Species from the Miyako Islands, Japan, with Its DNA Barcode (Isopoda: Anthuroidea: Paranthuridae), Species Diversity 29 (1), pp. 65-72 : 66-71

publication ID	https://doi.org/ 10.12782/specdiv.29.65
publication LSID	lsid:zoobank.org:pub:AF1BB6CA-3549-4C4B-B7B4-9CFAC36197CE
persistent identifier	https://treatment.plazi.org/id/D9E7F1B5-2F7E-4985-AB5A-54F1FE212CDE
taxon LSID	lsid:zoobank.org:act:D9E7F1B5-2F7E-4985-AB5A-54F1FE212CDE
treatment provided by	Felipe
scientific name	Cruranthura viridis
status	sp. nov.

Treatment

Cruranthura viridis sp. nov.

[New Japanese name: Kappa-ashitarazu-uminanafushi] ( Figs 1–5 View Fig View Fig View Fig View Fig View Fig )

Diagnosis. Body small (length 2.53–3.38 mm) and moss green in color. Eyes present. Pleonite 1 longer than pleonite 2. Telson length 2.06–2.33 times telson width. Propodus of pereopod 1 with 6–10 spiniform setae. Endopods of pleopods 2–5 uniarticulate, with plumose setae.

Etymology. The specific name is from the Latin adjective viridis (green), referring to the moss green body color.

Material examined. Holotype: ovigerous female ( ICHUM8565 View Materials , 8 View Materials slides and 1 vial), body length 3.08 mm; coral rubble, 10–20 m depth, Irabu Island (24°51′57.7″N 125°09′41.9″E), Miyako Islands, Okinawa, southwestern Japan, 25 April 2022, collected by Shoki Shiraki. GoogleMaps Paratypes: two ovigerous females, ICHUM 8566 (body length 3.38 mm; 12 slides and 1 vial) and ICHUM 8567 (body length 2.80 mm; 1 slide and 1 vial), and one female lacking oostegites, ICHUM 8568 (body length 2.53 mm; 2 slides and 1 vial); collection data for paratypes as for holotype.

Sequence. Partial COI sequence (658 bp, encoding 219 amino acids) from holotype ( INSD accession number LC775393 ) .

Description of female based primarily on holotype. Body ( Figs 1A–D View Fig , 2A, B View Fig ) color moss green, length 11.54 times body width, slender. Head ( Fig. 2C View Fig ) length 1.35 times head width; rostrum not extending past anterolateral lobes; eyes dorsolateral, small, black; eye length 0.13 times head length. Pereonites 1–7 ( Fig. 2A View Fig ) with length ratios 1. 18: 1.07: 1.19: 1.25: 1.22: 0.78: 0.15 relative to head length; pereonite 7 ( Figs 2A, B View Fig , 5C, D View Fig ) reduced, not hidden laterally but rarely visible, lacking pereopod 7 in adults. Pleonite 1 free; pleonites 2–5 articulated laterally but fused dorsally and indicated by folds ( Figs 2A, B View Fig , 5C, D View Fig ); pleonite 1 1.72 times as long as pleonite 2. Pleonite 6 delineated dorsally, 0.53 times as long as combined length of pleonites 1–5, delineated dorsally from telson. Telson ( Fig. 4H View Fig ) oval, length from basal narrowest point to the tip 2.12 times width, with six dorsal simple setae and twelve distal simple setae.

Antennula ( Fig. 2D View Fig ) with three peduncular articles and one flagellar article. Peduncular article 1 longest, with two outer plumose sensory setae; article 2 with two distal plumose sensory setae and distal simple seta; article 3 with distal plumose sensory seta and three distal simple setae. Flagellar article with four distal aesthetascs and three distal simple setae.

Antenna ( Fig. 2E View Fig ) with five peduncular articles and one flagellar article. Peduncular article 1 naked; article 2 longest, with two distal simple setae and distal seta (tip broken); article 3 with two distal simple setae; article 4 with two distal plumose sensory setae and two simple setae; article 5 with outer plumose sensory seta, seven simple setae, and distal seta (tip broken). Flagellar article with numerous distal simple setae.

Mandible ( Fig. 5A, B View Fig ) not articulated with head, without palp.

Maxilla ( Fig. 2F View Fig ) slender, with 14 teeth and narrow lamella.

Maxilliped (from paratype ICHUM8566; Figs 2G View Fig , 5A, B View Fig ) biarticulate; article 1 (presumably corresponding to basis and palp, except for terminal palp article) with seven simple setae; article 2 minute, with four simple setae. Epipod ( Fig. 5A, B View Fig ) oval.

Pereopod 1 ( Fig. 3A View Fig ) subchelate. Basis with dorsal plumose sensory seta and one dorsal and one ventrodistal simple setae. Ischium with ventrodistal simple seta. Merus with two dorsal and two ventrodistal simple setae. Carpus triangular, with five ventral simple setae. Propodus broad, with 10 inner spiniform setae and one outer and two dorsodistal simple setae. Palm with proximal trapezoidal projection and 10 simple setae. Dactylus with three ventral and four inner simple setae. Unguis naked, length about 0.4 times dactylus length.

Pereopod 2 ( Fig. 3B View Fig ) subchelate, narrower than pereopod 1. Basis with two dorsal plumose sensory setae, four simple setae, and dorsal seta (tip broken). Ischium with two ventral simple setae. Merus with two dorsal and three ventral simple setae. Carpus triangular, with three ventrodistal simple setae. Propodus oval, with dorsodistal plumose sensory seta and two dorsodistal simple setae. Palm with five spiniform setae with sensory bristle sensu Negoescu (1994) and three simple setae. Dactylus with two ventral, three ventrodistal, and four inner simple setae. Unguis naked, length about one-third dactylus length.

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

Pereopod 4 ( Fig. 3D View Fig ) narrow. Basis with three dorsal plumose sensory setae and three simple setae. Ischium with two ventral simple setae. Merus with two dorsal and two ventrodistal simple setae. Carpus trapezoidal, with two ventral spiniform setae with sensory bristle, dorsal plumose sensory seta, and one dorsal and two ventrodistal simple setae. Propodus with two ventral spiniform setae with sensory bristle, dorsodistal plumose sensory seta, and two dorsodistal and three ventral simple setae. Dactylus with one ventral, three ventrodistal, and three outer simple setae. Unguis naked, length about one-third dactylus length.

Pereopod 5 ( Fig. 3E View Fig ) similar to pereopod 4 except in number of plumose sensory setae and simple setae on basis.

Pereopod 6 ( Fig. 3F View Fig ) similar to pereopod 4 except in number of plumose sensory setae on basis and simple setae on merus and propodus. Propodus with two dorsodistal trifurcate spiniform setae.

Pleopod 1 ( Fig. 4A View Fig ) protopod with three inner hooks. Exopod operculiform, with sinuate outer distal margin and 13 plumose setae (possibly 14; one pore observed); three simple setae on surface. Endopod with six plumose setae.

Pleopod 2 ( Fig. 4B View Fig ) protopod with two inner hooks. Exopod with five plumose setae and outer simple seta. Endopod uniarticulate, with three plumose setae.

Pleopods 3–5 ( Fig. 4C–E View Fig ) similar. Protopods with one or two simple setae. Exopods with four plumose setae and outer simple seta. Endopods uniarticulate, with three plumose setae.

Uropod ( Fig. 4F, G View Fig ) with triangular-prism-shaped protopod bearing dorsodistal simple seta, and three inner ventral and four outer ventral plumose setae. Exopod ( Fig. 4F View Fig ) broad, oval, with 24 plumose setae (possibly 25; one pore observed), seven simple setae, and two setae (tip broken). Endopod ( Fig. 4G View Fig ) with eight plumose sensory setae, three plumose setae, 11 simple setae, and five setae (tip broken).

Variation. Table 1 indicates differences in length measurements and ratios among the four specimens examined. All specimens shared the following characters: (1) the body color was moss green; (2) eyes were present; and (3) pleonite 1 was longer than pleonite 2. The ratio of telson length to telson width ranged from 2.06 to 2.33 among three specimens (it could not be measured for ICHUM8567 View Materials , which was used for SEM observation) . The number of spiniform setae on the propodus of pereopod 1 ranged from 6 to 10 among seven pereopods of four specimens (it was not counted for right pereopod 1 of the holotype, which was used for DNA extraction).

Genetic information. In BLAST searches ( Altschul et al. 1990), the COI sequence most similar to the holotype COI sequence was from the insect “ Cecidomyiidae sp.” (INSD accession number OM561009; identity score 80.66%, query cover 99%; Bukowski et al. 2022) rather than from a paranthurid, though there are several paranthurid COI sequences in the database. In a BLAST search with the “Organism” option set to “Anthuridea”, the sequence most similar to ours was from Colanthura pigmentata Kensley, 1980 (KR095339; identity score 81.03%, query cover 88%; Song and Min 2015).

Remarks. Cruranthura viridis sp. nov. differs from congeners in the suite of characters listed in Table 2. This paper is the first report of Cruranthura from Japan.

All paranthurid isopods have piercing-type mouthparts specialized for sucking ( Poore 2001), but the degree of specialization differs among genera. We can roughly divide them into two groups: a moderately specialized group ( Deltanthura Shiraki, Shimomura, and Kakui, 2022 , Paranthura Bate and Westwood, 1866 , and Pseudanthura Richardson, 1911 ); and a highly specialized group ( Califanthura Schultz, 1977 , Colanthura Richardson, 1902 , Cruranthura , and Cruregens Chilton, 1882 ). The mouthparts in the former group retain the mandibular palp, the articulation between the mandible and head, and the articulation between the maxilhead length; HW, head width; EL, eye length; P1L–P7L, lengths of pereonites 1–7; p1L–p6L, lengths of pleonites 1–6.

Aggregated length of pleonites 1–5.

Scattered, darkly pigmented patches present on head, but information on body color lacking ( Thomson 1946). b) Counted from Mezhov (1976: fig. 4).

lipedal basis and palp (cf. Shiraki and Kakui 2022: fig. 1B). The mouthparts in the latter group lack these three structures (cf. Fig. 5A, B View Fig ; Annisaqois and Wägele 2021: fig. 31). A piercing apparatus that is fixed on the head and lacks joints and unnecessary structures (such as the mandibular palp) will have higher stability and strength, which may enable species in the latter group to pierce more strongly and may have increased the range of possible prey in the group. Poore (2001) suggested that genera in the moderately specialized group (information on the phylogenetic position of Deltanthura in Paranthuridae is unavailable) are more basal within Paranthuridae than genera in the highly specialized group. If this is true, the specialization of piercing mouthparts may have steadily increased in the evolution of Paranthuridae . Molecular phylogeny can test this hypothesis.