Atlantapseudes nigrichela Băcescu, 1978

Matsushima, Yoshinobu, Bâlcu, Maxim-Jean & Kakui, Keiichi, 2025, Atlantapseudes tridens sp. nov. (Tanaidacea: Apseudidae) from the Okinawa Trough, Japan, with a note on the taxonomic status of Atlantapseudes curvatus, Zootaxa 5679 (4), pp. 484-500 : 487-490

Atlantapseudes nigrichela Băcescu, 1978

( Figs 2 , 3 )

Atlantapseudes nigrichela Băcescu, 1978 , 317–322 [in part], fig. 1B–D, K.

Atlantapseudes curvatus Esquete & Cunha, 2017 , 61, 65–72, 87, figs 2–6

Atlantapseudes curvatus : García-Herrero et al. 2021a, 66; García-Herrero et al. 2021b, suppl. 2, 3. Material examined. Holotype: ovigerous female (393/30686, Muzeul Național de Istorie Naturală “Grigore Antipa,” TBL = 5.85 mm), Stn 396, Atlantic Ocean, western Portugal (41°17'4"N, 09°15'7"W), 900 m depth, silty or sandy-silty bottom, cruise “Thalassa,” September 1972. Paratypes: three females (TAN 032-1–3, TBL = 5.60 mm, 5.20 mm, 4.20 mm, respectively, Muzeul Național de Istorie Naturală “Grigore Antipa”), Atlantic Ocean, western Portugal, without other data; three males (49217-1–3, TBL = 4.50 mm, 3.75 mm, 4.10 mm, respectively, Muzeul Național de Istorie Naturală “Grigore Antipa”), Stn 407, Atlantic Ocean, western Portugal (40°33'5"N, 09°24'0"W), 740 m depth, silty or sandy-silty bottom, cruise “Thalassa,” 1 September 1972.

Amended diagnosis. Rostrum tridentate. Pereonite-1 lateral margin with posterior spine but without anterior spines. Lateral margin of pereonites 2 and 3 with one anterior spine and one posterior spine. Lateral margin of pereonites 4–6 with anterior spine but without posterior spines. Squama more than 2.5 times longer than antennal article-3. Labial palp with three spiniform setae. Maxillipedal palp article-2 with two outer distal setae. Cheliped with carpus bearing two ventral long setae.

Supplemental description of holotype. The holotype was strongly deformed and had lost several parts, but we observed the following character states: tridentate rostrum (left part partly broken) ( Fig. 2A ), a spine present on mid-lateral margin of cephalothorax ( Fig. 2B ), each eye lobe with anterior spine ( Fig. 2A ), pereonite-1 with spine on posterolateral margin, a spine present on anterolateral and posterolateral margin of pereonites 2 and 3 ( Fig. 2C–F ), a spine present on subanterior lateral margin of pereonites 4–6 ( Fig. 2F–H ), the squama about 3.3 times longer than antennal article-3 ( Fig. 2I ) and the cheliped with basis and merus each bearing ventro-subdistal spine and carpus bearing two long ventral simple setae ( Fig. 2B ).

Supplemental description of paratypes. Cephalothorax and pereonites 1–6 ( Fig. 3A–D ) similar to those in holotype; squama about 3.1 times longer than antennal article-3; labial palp with three spiniform setae ( Fig. 3E ); maxillipedal palp article-2 with two outer distal setae ( Fig. 3F ); pereopod-3 coxa with spine ( Fig. 3D ) (see also Supplementary File S1).

Remarks. The holotype of A. nigrichela had (1) a tridentate rostrum; (2) pereonite-1 with a posterolateral spine; and (3) pereonites 2 and 3 with one anterolateral spine and one posterolateral spine. All three states were also found in three female and three male paratypes. We did not detect states (2) and (3) in the monodentate individuals of “ A. nigrichela ” ( Băcescu 1978, fig. 1A; Błażewicz-Paszkowycz et al. 2011, fig. 6), but did find them in A. curvatus , which has a tridentate rostrum ( Esquete & Cunha 2017, fig. 2A). Those character states were summarized in Table 1. The type locality of A. nigrichela is near the area where A. curvatus has been reported ( Fig. 1B ). The holotype of A. nigrichela was collected at 900 m depth, within the known depth range of A. curvatus (497–1001 m) (Supplementary Table S1). Based on these morphological and distributional similarities, we concluded that A. curvatus is a junior synonym of A. nigrichela .

We found that the specimen designated as the allotype and one designated paratype had a monodentate rostrum. Based on this morphology, we identified them as Atlantapseudes sp. (see below). One female designated as a paratype ( TAN 032-4 ) was badly deteriorated and could not be identified to species level .

Figures

FIGURE 1. Map showing the distributions of Atlantapseudes species. A. Global distributions of Atlantapseudes species. B. Atlantapseudes records in the northeastern Atlantic. C. Sampling sites for A. tridens sp. nov. off the Ryukyu Islands, Japan. Circles with black outline indicate type localities. The maps were generated with GMT6 software (Wessel et al. 2019).

FIGURE 2. Atlantapseudes nigrichela, holotype ovigerous female 393/30686, Muzeul Național de Istorie Naturală “Grigore Antipa,” photomicrographs, dorsal view. A. Anterior region of cephalothorax (black arrowheads = spines of rostrum; white arrowheads = anterior spines on eye lobes). B. Cephalothorax (left) and left cheliped (grey arrowhead = mid-lateral spine on cephalothorax; black arrows = ventral spines on chelipedal basis and merus; white arrows = ventral simple setae on chelipedal carpus). C. Cephalothorax (posterior), pereonites 1–4, and pereonite-5 (anterior). D. Left region of pereonite-2. E. Pereonite- 2 (right) and pereonite-3 (right anterior). F. Pereonite-2 (left posterior), pereonite-3 (left), and pereonite-4 (left anterior). G. Pereonite-4 (posterior), pereonite-5, and pereonite-6 (anterior). H. Pereonite-5 (posterior), pereonite-6, and pleon (anterior). C–H: black circles = anterolateral spines on pereonites; white circles = posterolateral spines on pereonites. I. Right antenna. Scales not available.

FIGURE 3. Atlantapseudes nigrichela, paratype female TAN 032-1, Muzeul Național de Istorie Naturală “Grigore Antipa,” photomicrographs.A. Cephalothorax, dorsal view (black arrowheads = spines of rostrum; white arrowheads = anterior spines on eye lobes; grey arrowheads = mid-lateral spines on cephalothorax).B. Cephalothorax (posterior), pereonites 1–3, and pereonite-4 (anterior), dorsal view. C. Pereonite-1 (posterior), pereonite-2, and pereonite-3 (anterior), dorsal view. D. Pereonite-2 (posterior), pereonite-3, and pereonite-4 (anterior), dorsal view. B–D: black circles = anterolateral spines on pereonites; white circles = posterolateral spines on pereonites; grey circles = spines on pereopodal coxae. E. Labial palp (black arrows = spiniform setae on labium palp). F. Maxillipedal palp (white arrows = outer distal setae on maxilliped-palp article-2). Scales not available.