Parapseudomma calloplura ( Holt and Tattersall, 1905 )

Wittmann, Karl J., 2023, The genus Parapseudomma from the East Atlantic deep sea, with description of a new species (Mysida: Mysidae), Nauplius (e 2023013) 31, pp. 1-17 : 4-7

Parapseudomma calloplura ( Holt and Tattersall, 1905)

( Figs. 1 , 2 )

Pseudomma affine — Lo Bianco, 1903: 245, 253, 276 (records, Gulf of Naples).

Pseudomma calloplura Holt and Tattersall, 1905: 126 (preliminary diagnosis). — Holt and Tattersall, 1906: 30–32, figs. 1–5 in pl. IV (description, NE- Atlantic records). — Tattersall, 1909: 133, tab. 3, figs. 7–12 in pl. 7 (description, Mediterranean records). — Zimmer, 1909: 106, figs. 211–213 (description, distribution). — Băcesco, 1941: 19–21, fig. 7 (description, W-Mediterranean record). — Tattersall and Tattersall, 1951: 236–238, fig. 53A–G (NE-Atlantic, description, taxonomy). — Murano, 1970: 142, figs. 10–13 (first Pacific records).

Parapseudomma calloplura — Nouvel and Lagardère, 1976: 1311–1317, figs. 206–225 (description, revised generic assignment). — Mauchline, 1986: 814 (biology, NE-Atlantic records). — Băcescu, 1989: 119 (record from Alboran Sea). — Cunha et al., 1997:128, tabs. 5, 9 (Iberian seas, depth range). — Cartes and Sorbe, 1998: 283–285, figs. 5, 7 in tab. VII (feeding). — Cartes et al., 2001: 2226, tabs. 1–5, fig.3 (life history, secondary production). — Meland and Willassen, 2007: tab. 2, fig. 3 (phylogeny, rRNA sequencing). — Petryashov, 2009:tab.1 (biogeographic analysis).— Wittmann et al.,2014:337, fig.54.21(morphology, taxonomy). — San Vicente, 2017: tab 3, fig. 4 (distribution, Iberian Peninsula).— Astthorsson and Brattegard, 2022: 65, fig. 75 (distribution, Iceland). — Mees and Meland, 2022: AphiaID 120165 (accepted). — Ríos et al., 2022: tab. 1 (submarine canyons, Cantabrian Sea).

Material examined. 1 adult male in 2 parts, originally labeled as Pseudomma calloplura (BL about 8 mm), ZMHK 11194 , Celtic Sea , slope from Celtic shelf down to Porcupine Seabight, 144 km SW of Ireland, DD 50.35 -011.00, 625–631 m depth, L. R. 448, coll. E.W.L. Holt Dept. Agricult. Fish. Br. — 5 subadult males (BL 6.1–7.5 mm), 2 subadult females (BL 5.6–6.3 mm), 3 immature females (BL 4.8– 5.7 mm), 1 immature male (BL 5.0 mm), 3 juveniles (BL 3.1–4.0 mm) in vial plus 1 subadult male (BL 7.8 mm) on slides, Bay of Biscay , Le Danois Bank, DD 42.67 -011.74, 500– 496 m depth, ECOMARG 2004 with R / V “Vizconde de Eza”, E04-TS5, 12–30 April 2004, coll. Inmaculada Frutos.

Distribution. Type locality not stated by Holt and Tattersall (1905). A rough estimate by Wittmann (2020) suggests that the type locality is off Ireland in the range of 52– 54°N 12– 13°W, depth 363– 696 m. The present sample from the Celtic Sea was taken near this range by E.W.L. Holt, the first author of the first description. This species is known from the NE-Atlantic and Mediterranean, 35– 58°N 013°W – 014°E, depth 94–1200 m (references listed above); the here presented records are within these ranges. Murano (1970) reported this species as Pseudomma calloplura from the NW-Pacific off Japan, 35– 37°N 137– 140°E, depth 220– 660 m. Records of Parapseudomma calloplura reported by Wittmann (2020) from the Angola Basin are here attributed to the below described Parapseudomma stenurum n. sp.

Revised diagnosis. Based on adults of both sexes. All features within the limits of the genus diagnosis. Carapace without rostrum; disto-lateral edges angular (right-angled to wide-angled). Transverse extension of eye-bar 2.3–3.5 times length of distal segment of antennular trunk. Eyes fused at proximal third, while distally separated by narrow median cleft ( Fig. 2A ). Eyes dorsoventrally flattened by factor of 1.4–2.2 measured at maximum width in dorsal view. Each eye microserrated ( Fig. 2B ) along central third to half of its anterior margin. Disto-mesial lobe dorsally at basal segment of antennular trunk reaching to half-length of median segment. Disto-lateral edge of antennal sympod with tooth-like projection. Antennal scale with small apical segment separated by tiny (in part inconspicuous) suture. Length of scale 3.5–5.0 times maximum width; mesial margin setose;straight lateral margin bare, ending in tooth; distal segment not reaching to tip of this tooth. Scale extending 40–55% its length beyond antennal peduncle and 35–50% beyond antennular trunk. Labrum mid-rostrally slightly prolonged by small acute projection.Mandibles normal, right digitus mobilis smaller than the left one ( Fig. 1C ). Unsegmented carpus of thoracic endopods 3–8 separated from two-segmented propodus by oblique articulation. Male pleopod 4 the largest, penultimate segment of its endopod with large smooth (modified)seta in adults longer than endopod. Exopod of uropods extending beyond endopod; exopod and endopod beyond telson ( Fig. 1A, B ). Endopod with 1 small spine on mesial margin below statocyst. Telson ( Fig. 2E ) with slightly sigmoid, almost straight lateral margins and convex, broadly rounded terminal margin. Telson length1.7–2.9 times maximum width near basis and 4–6 times width at disto-lateral edge. Proximal 29–45% of lateral margins smooth, remaining distal portion of each margin with 10–15 spines distally somewhat discontinuously increasing in size.Terminal margin with minute (often inconspicuous) median spine flanked by 3–4 pairs of large spines; these spines bilaterally armed along their basal to subapical portions with stiff bristles; largest spine 23–34% telson length.

Supplementary notes. Based on adult male and subadults of both sexes. Acute median process from clypeus anteriorly extending shortly beyond eye-bar. Flagellum of thoracic exopod 1 nine-segmented, f lagella 2–8 ten-segmented. Thoracic endopods 1–7 increasing in length and slenderness caudally (endopod 8 not available); endopods 3–7 reach at least to mid of antennular trunk when stretched anteriorly. Endopods 1, 2 with short but strong, weakly curved, smooth nail; nail 1 thrice length of dactylus 1, nail 2 twice length of larger dactylus 2. Endopods 3–7 with slender, needle-like, slightly curved nail increasing in length caudally together with its respective endopod. Juveniles with pair of paramedian sternal processes on thoracomere 2, and single mid-sternal process on each thoracomere 3–8. There are on average fewer such processes ( Fig. 2D ) in immatures of both sexes, versus none in adult male. Statoliths composed of f luorite, diameter 0.15–0.26 mm (n = 4 statoliths from two subadults).

Male sexual characteristics. Size and structure of thoracic exopods are non-dimorphic when comparing equally sized subadults (adult females not available). Exopod of adult and subadult male pleopods 2–4 with short spine-like seta (besides other setae) at penultimate segment; pleopod 5 with group of three small, supernumerary setae in the respective position.

Adult male with BL 8 mm from the Celtic Sea with large, strongly setose appendix masculina about as long as terminal segment of antennular trunk; appendix extending by 3/4 its length beyond this segment. Thoracomeres 2–8 without mid-sternal processes, not counting usual rostral lobe from sternite 1 contributing to caudal closure of mouth area. Penes slightly longer than basal plate of thoracic exopod 8. Spermatozoa visible in efferent ducts. Endopod of pleopods 1–5 with 1, 13, 13, 13, 13 segments, exopod with 12, 14, 13, 13, 13 segments, respectively. Male-specific smooth seta with 1.6 times endopod length arising from penultimate segment of endopod of pleopod 4.

The largest available subadult male with BL 7.8 mm from the Bay of Biscay ( Fig. 1A, B ) with same-sized though less setose appendix masculina and with about same-sized penes ( Fig. 2D ) compared with the adult from the Celtic Sea. Spermatozoa visible in efferent ducts despite certain subadult characters in this specimen, namely thoracic sternum 8 ( Fig. 2D ) with well-developed, hispid, distally blunt, mid-sternal process, sternum 7 with vestigial non-hispid process, while sterna 2–6 without such processes. Endopod of pleopods 1–5 with 1, 13, 12–13, 13, 11 segments, exopod with 11, 14, 12–13, 13, 12segments, respectively; penultimate segment of endopod of pleopod 4 with male-specific seta shorter than small ultimate segment. The respective seta 0.4 times endopod length in a subadult male with BL 7.5 mm. Pleopod 4 of the latter specimen with 12-segmented endopod and 13-segmented exopod. Pleopod 4 with 8-segmented endopod and 8-segmented exopod in subadult with BL 7.3 mm. All pleopods uniramous and unsegmented in immature male with BL 5.0 mm; its penes one third length of basal plate of thoracic exopod 8,no spermatozoa visible; appendix masculina vestigial.

Figures

Figure 1. Parapseudomma calloplura (Holt and Tattersall, 1905), subadult males with BL 7.8 mm (A, B) and 7.5 mm (C) from the Bay of Biscay. A, B, Subadult in toto, dorsal (A) and ventral (B); C, masticatory portion of right (to the left) and left (to the right) mandible with pars incisiva (pi), digitus mobilis (dm), spines of the pars centralis (pc) and pars molaris (pm), caudal. A, B, object artificially separated from background.

Figure 2. Parapseudomma calloplura (Holt and Tattersall, 1905), subadult male with BL 7.8 mm from the Bay of Biscay. A, Eye rudiments, dorsal; B, detail of panel (A) showing serrated portion of anterior margin of right eye rudiment; C, detail of panel (A) showing median eye-cyst; D, thoracic sternite 8 with median process and penis; E, telson.