Paronesimoides calceolus, Tomikawa & Watanabe & Tanaka & Ohara, 2022

Tomikawa, Ko, Watanabe, Hiromi Kayama, Tanaka, Katsuhiko & Ohara, Yasuhiko, 2022, Discovery of a new species of Paronesimoides (Crustacea: Amphipoda: Tryphosidae) from a cold seep of Mariana Trench, Journal of Natural History 56 (5 - 8), pp. 463-474 : 465-473

publication ID	https://doi.org/ 10.1080/00222933.2022.2074906
publication LSID	lsid:zoobank.org:pub:87787DD8-FEEB-43C1-AEAA-40C37B021768
DOI	https://doi.org/10.5281/zenodo.7015531
persistent identifier	https://treatment.plazi.org/id/03B1E8B1-F086-409B-94AC-CA875ABD3D9A
taxon LSID	lsid:zoobank.org:act:03B1E8B1-F086-409B-94AC-CA875ABD3D9A
treatment provided by	Plazi
scientific name	Paronesimoides calceolus
status	sp. nov.

Treatment

Paronesimoides calceolus sp. nov.

( Figures 2 –6 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 )

Material examined

Holotype. Male (6.8 mm), AMNH _IZC 00361497, the surface of the chimney named ‘Chim 4’ in the CH 3 site in the Shinkai Seep Field ( Okumura et al. 2016) , Mariana Trench (11.656°N, 143.048°E), 5689– 5683 m, collected by H.K. Watanabe, 17 July 2014.

Paratype. Female (3.8 mm), AMNH _ IZC 00361498 About AMNH , data same as for the holotype .

Diagnosis

Lateral cephalic lobe of head rounded distally. Antenna 1 slightly longer than antenna 2. Peduncular article 3 of antenna 2 with strong posteroventral process. Male antennae 1 and 2 with calceoli. Mandibular palp article 3 0.8 times as long as article 2. Propodus of male gnathopod 1 length 1.2 times width, with two uneven-sized nodular robust setae on distal part of palmar margin. Coxa 4 with shallow posteroproximal concavity. Telson with two rows of dorsocentral short setae.

Description

Male [ holotype, AMNH _ IZC 00361497 About AMNH ] . Head ( Figure 2 View Figure 2 ) deeper than long; lateral cephalic lobe large and rounded distally; antennal sinus shallow and rounded; rostrum short; eyes absent. Pereonites 1–7 ( Figure 2 View Figure 2 ) dorsally smooth with fine setae. Pleonites 1–3 ( Figure 2 View Figure 2 ) without dorsal carina, bearing fine setae. Posterior margin of epimeral plates 1 and 2 ( Figure 3a, b View Figure 3 ) rounded, each with a small seta. Posterodistal corner of epimeral plate 3 with small process accompanied by small seta. Urosomites 1–3 ( Figure 2 View Figure 2 ) without dorsolateral flange and notch.

Antenna 1 ( Figure 3d View Figure 3 ) short, 0.3 times as long as body; peduncular articles 1–3 rectangular, in length ratio of 1.0:0.6:0.2; length of peduncular article 1 1.5 times width; primary flagellum 17-articulate with calceoli ( Figure 3e View Figure 3 ); accessory flagellum fivearticulate. Antenna 2 ( Figure 3f View Figure 3 ) 0.9 times as long as antenna 1; posterior part of peduncular article 3 strongly produced; peduncular article 4 slightly longer than article 5; flagellum 15-articulate with calceoli.

Upper lip ( Figure 3g View Figure 3 ) with weakly concave ventral margin, bearing fine setae. Mandible ( Figure 3h, i View Figure 3 ) with small incisor; lacinia mobilis a cuspidate peg; accessory setal row with two short plumose setae; molar with weakly triturative surface, not setose; mandibular palp three-articulate in length ratio of 1.0: 4.9: 3.8, attached opposite molar; palp article 1 bare, articles 2 and 3 with nine and 11 setae, respectively. Lower lip ( Figure 3j View Figure 3 ) with broad outer lobes bearing fine setae, inner lobes indistinct. Maxilla 1 ( Figure 3k View Figure 3 ) with inner plate bearing two setae apically; outer plate ( Figure 3l View Figure 3 ) with 11 robust setae, seven of which obviously serrate; palp two-articulate, article 1 short, article 2 with seven robust setae along apical margin and slender seta on apical submargin. Maxilla 2 ( Figure 3m View Figure 3 ) with narrow inner plate, bearing long plumose setae medially; outer plate slightly longer than inner plate. Maxilliped ( Figure 4a View Figure 4 ) with rectangular inner plate with two nodular and two small robust setae apically ( Figure 4b View Figure 4 ), oblique setal row with nine plumose setae; outer plate ovate with nodular robust setae along apical to medial margin ( Figure 4c View Figure 4 ); palp fourarticulate, article 1 with seta on outer margin, article 2 longest with seta on outer margin and setal row on inner margin, article 3 with setae on inner and outer margins and fine facial setae, article 4 with fine facial setae, nail distinct.

Gnathopod 1 ( Figure 4d View Figure 4 ) subchelate; coxa broad, bearing setae along anterior to ventral margin; basis weakly arched, length 3.3 times width, with setae on anterior and posterior margins; ischium short, length 1.4 times width, with seta on posterior margin, posterodistal corner with pair of setae; merus with five setae on posterior margin; carpus length 1.1 times width; propodus rectangular, length 1.2 times width, posterior margin weakly convex with a few setae, palmar margin ( Figure 4e View Figure 4 ) transverse, waved, with two nodular robust setae distally; dactylus ( Figure 4e View Figure 4 ) slightly exceeding distal part of palm, with seta on anterior margin and three setae on mediodistal surface. Gnathopod 2 ( Figure 4f View Figure 4 ) minutely chelate; coxa subrectangular bearing setae along anterior to ventral margin; basis straight, length 4.3 times width, with setae on anterior and posterior margins; ischium relatively long, length 2.3 times width, with setae on anterior and posterior margins, posterodistal corner with cluster of setae, laterodistal surface with patch of tiny setae; merus with five setae on ventral margin, ventral surface with tiny setae; carpus length 2.6 times width, dorsal and ventral surfaces with tiny setae; propodus length 1.4 times width, surface covered with tiny setae, lateroventral surface with palmate setae, palmar margin ( Figure 4g View Figure 4 ) weakly convex with serration, posterodistal corner of palmar margin with two medial robust setae; dactylus ( Figure 4g View Figure 4 ) short, not reaching posterodistal corner of palmar margin, with seta on anterior margin and four setae on lateral surface.

Pereopod 3 ( Figure 4h View Figure 4 ) with subrectangular coxa bearing setae along anterodistal to ventral margin; lateral surface of merus and carpus with tiny setae; propodus with five robust setae along posterior margin, posterodistal corner with pair of robust setae; dactylus ( Figure 4i View Figure 4 ) slender. Pereopod 4 ( Figure 5a View Figure 5 ) with broad coxa bearing setae along anterodistal to ventral margin, posteroproximal part with wide, shallow concavity; lateral surface of merus and carpus with tiny setae; propodus with five robust setae along posterior margin, posterodistal corner with pair of robust setae; dactylus slender. Pereopod 5 ( Figure 5b View Figure 5 ) with equilobate coxa; basis weakly expanded, length 1.4 times width, with long setae along anterior margin, posterior margin slightly crenate with short setae; merus and carpus without setae on posterior margin, posterodistal corner with robust seta; propodus with five robust setae along anterior margin, anterodistal corner with pair of robust setae; dactylus slender. Pereopod 6 ( Figure 5c View Figure 5 ) with small coxa, anterior lobe reduced, posterior lobe broad; basis length 1.7 times width, with long setae on anterodistal margin, posterior margin slightly crenate with short setae; merus and carpus each with robust seta on posterior margin and posterodistal corner, respectively; propodus with five robust setae along anterior margin, anterodistal corner with pair of robust setae; dactylus slender. Pereopod 7 ( Figure 5d View Figure 5 ) with small coxa, subtriangular; basis expanded posteriorly, length 1.4 times width, with long setae on anterodistal margin, posterior margin slightly crenate with short setae; merus with two robust setae on posterior margin and robust seta on posterodistal corner; carpus with robust seta on posterior margin and posterodistal corner; propodus with four robust setae along anterior margin, anterodistal corner with pair of robust setae; dactylus slender.

Coxal gills on gnathopod 2 and pereopods 3–6 ( Figure 2 View Figure 2 ).

Pleopods 1–3 ( Figure 5e View Figure 5 ) with broad peduncle, with setae along lateral margin, mediodistal margin with paired retinacula ( Figure 5f View Figure 5 ).

Uropod 1 ( Figure 5g, h View Figure 5 ) with peduncle bearing four dorsolateral, one apicolateral, four dorsomedial and one apicomedial robust setae; inner ramus 0.8 times as long as peduncle, with two dorsal robust setae; outer ramus 1.1 times as long as inner ramus, with three dorsal robust setae. Uropod 2 ( Figure 5i View Figure 5 ) with peduncle bearing two dorsolateral, one apicolateral, one apicomedial and one distoventral robust setae; inner ramus 0.8 times as long as peduncle, with dorsal robust seta; outer ramus slightly shorter than inner ramus, with two dorsal robust setae. Uropod 3 ( Figure 5j View Figure 5 ) with peduncle 1.2 times as long as outer ramus, with robust setae distally; inner ramus small, scale-like, 0.1 times as long as outer ramus, with apical seta; outer ramus two-articulate, proximal article marginally bare, with two distal setae, distal article 0.3 times as long as proximal article. Telson ( Figure 5k View Figure 5 ) semicircular, distal margin smooth, length 0.9 times width, with four lateral penicillate setae, two rows of dorsocentral short setae and two distal simple setae.

Female [ paratype, AMNH _ IZC 00361498 About AMNH ] . Antenna 1 ( Figure 6a View Figure 6 ) peduncular articles 1–3 rectangular, in length ratio of 1.0:0.5:0.4; length of peduncular article 1 1.3 times width; primary flagellum nine-articulate without calceoli; accessory flagellum three-articulate. Antenna 2 ( Figure 6b View Figure 6 ) 0.7 times as long as antenna 1; flagellum seven-articulate without calceoli.

Gnathopod 1 ( Figure 6c, d View Figure 6 ) chelate; coxa weakly tapering; propodus length 2.6 times width, mediodistal part of palm with two curved robust setae, palmar margin minutely serrate; dactylus slightly exceeding distal part of palm. Gnathopod 2 ( Figure 6e, f View Figure 6 ) similar to that of male, carpus length 2.0 times width.

Etymology

The new specific name is derived from the presence of calceoli on male antennae 1 and 2.

Remarks

Paronesimoides calceolus sp. nov. differs from its congeners with respect to the following features: from P. lignivorous (features of P. lignivorous in parentheses): the cephalic lobe of the head is rounded (pointed); antenna 2 has the peduncular article 3 with a posteroventral process (lacking a process); mandibular palp article 3 is 0.8 times as long as article 2 (0.6 times); length of propodus of gnathopod 1 is 1.2 times its width (1.6 times); and posteroproximal concavity of coxa 4 is shallow (deep); from P. voightae (features of P. voightae in parentheses), the cephalic lobe of the head is rounded (pointed); antenna 1 is longer than antenna 2 (almost the same length); antennae have calceoli in male (absent); two nodular robust setae on the distal part of the palmar margin of gnathopod 1 are of uneven size (even-sized); coxa 2 does not cover the ventral margin of coxa 1 (most of the posteroventral margin covered by coxa 2); and telson has two rows of dorsocentral short setae (absent).

Distribution

Known only from the type locality.

Key to species of Paronesimoides View in CoL (male)

1. Antenna 2 peduncular article 3 with strong posteroventral process ............................. 2

- Antenna 2 peduncular article 3 without strong posteroventral process ............................ ...................................................................................................................... P. lignivorous Pirlot, 1933

2. Cephalic lobe of head pointed; antennae without calceoli; most of posteroventral margin of coxa 1 covered by coxa 2 .............................................. P. voightae Larsen, 2007 View in CoL

- Cephalic lobe of head rounded; antennae with calceoli; ventral margin of coxa 1 not covered by coxa 2 ............................................. ............................................. P. calceolus sp. nov.