Deltamysis lowryi, Daneliya, 2023

Daneliya, Mikhail E., 2023, On the Mysid Crustacean Genus Deltamysis (Mysidae: Heteromysinae), with a New Species and a New Record from Australia, Records of the Australian Museum (Rec. Aust. Mus.) 75 (4), pp. 413-430 : 423-427

Deltamysis lowryi sp. nov.

urn:lsid:zoobank.org:act:079EBE01-C6FE-458F-88DC-DD3ECF81664F

Figs 6–8

Holotype: Male (+slide), 4 mm, Australia, New South Wales, Yamba, off the end of the jetty at the Blue Dolphin Caravan Park , 29 ° 26'S 153 ° 20.5'E, 1 m, Zostera with anoxic mud, st. NSW 316, baited trap, set 15:00, retrieved 08:00–09:00, coll. J. K. Lowry, S. J. Keable, 06–07 Jun 1988, AM P.98699.

Etymology. The species is dedicated to carcinologist James Kenneth (Jim) Lowry, one of the two collectors of the holotype, for his support in various crustacean projects, and for his contributions to zoology.

Diagnosis. Anterior margin of carapace angular, apically rounded ( Fig. 6B ). Cornea narrower than eyestalk (0.7 as wide as stalk). Telson ( Fig. 6C, D ) rather prolonged with nearly parallel lateral margins, 1.4 times as long as wide anteriorly, apically with shallow cleft, 0.05 of telson length, bearing seven spinules, shorter than one third of lateral terminal spiniform setae; its lateral margins with eight spiniform setae; subterminal spiniform setae shorter than preceding lateral and terminal; terminal spiniform setae 0.22–0.23 of telson length. Maxilla 2 ( Fig. 8A ), exopod big, reaching endopod segment 2, without lateral setae, but three apical setae; endopod without lateral setae. Maxilliped 2 with lateral processes on carpus and propodus ( Fig. 8B ). Pereopod dactylus rather thin, about twice as long as wide ( Fig. 8C–G ). Pereopod 3–6 carpopropodus 4- or 5-segmented; segment 1 shorter than other segments combined ( Fig. 8E, F ).

Body length. 4 mm.

Comparison. Deltamysis lowryi sp. nov. is differentiated from all the species of its genus by having seven spinules in the telson cleft (only two, rarely three spinules in other species) and the telson lateral subterminal spiniform setae significantly shorter than the preceding lateral spiniform setae (longer in other species). Additional differences from particular species can be seen in Table 1 .

Description of male holotype. Anterior margin of carapace slightly produced, angular, with rounded apical margin, covering eye stalk bases. Abdomen rather long, more than twice as long as cephalothorax. Abdominal segment 6, posteroventral lobes overlapping. Telson 0.93 of last abdominal segment, rather wide apically, 1.4 times as long as wide and 0.41 times as wide posteriorly (outside of terminal spiniform setae) as anteriorly. Lateral margins almost straight, with eight spiniform setae, gradually increasing in length posteriorly, except for subterminal, half as long as previous lateral and 0.3 of terminal. Terminal spiniform setae 0.22–0.23 times as long as telson and 1.6 times as long as longest posterolateral spiniform setae. Telson apical margin with slight cleft, 0.05 of telson length, bearing seven thin spinules.

Eyes quite large, 0.5 as long as head width, almost globular, 1.2 times as long as wide; stalk anteromedial part slightly produced; cornea lateral, narrower (0.7) than stalk (laterocorneal eyes). Antennular peduncle, segment 3 with one medial and three distomedial plumose setae. Antennal scale reaching about half of antennular peduncle segment 3, slightly longer than antennal peduncle, 2.5–2.6 times as long as wide. Antennal peduncle segment 2 is 1.45 times as long as segment 3. Labrum apically with smoothly rounded marginal plate. Mandible, left incisor and lacinia mobilis with three cusps. Mandibular palp, segment 2 medial margin with two thin median and three distal flagellate setae, lateral margin with one long distal seta; segment 3 is 0.4 times as long as segment 2. Maxilla 1, outer ramus with eight smooth apical spiniform setae. Maxilla 2, exopod oviform, rather big, reaching endopod segment 2, twice as long as wide, with three apical setae and without lateral setae; endopod segment 2 without lateral setae.

Maxilliped 1 exopod 8-segmented. Endopod typical for subfamily; dactylar setae smooth; unguis apically with wing-like expansions. Maxilliped 2 endopod, segments rather strong, with only medial setae (except dactylus). Basis with two plumose setae. Ischium with one plumose seta. Merus 1.6 times as long as wide and 0.8 times as long and about as wide as carpus, with five plumose setae. Carpus 2.2 times as long as wide, with two setae and four distolateral cuticular prominences (or processes). Propodus 1.5 times as long as wide, with five anteriorly finely serrated setae and two lateral prominences. Dactylus 1.7 times as long as wide and 0.7 times as long as carpus, with three lateral setae and lateromedian suture, six distomedial posteriorly serrated setae and thin setae among the latter.

Pereopod 1 endopod with ischium and merus nearly on one line, with slight bending capability in relation to each other; preischium without setae; ischium 4.4 times as long as wide, with three medial setae; merus 4.3 times as long as wide and 0.8 times as long as ischium, with one distomedial bunch of setae; carpopropodus 3-segmented, segment 1 is 1.3 times as long as segments 2 and 3 combined, with two distomedial bunches of one thin seta and one strong anteriorly and posteriorly serrated seta; segment two with distomedial bunch of one thin seta, one stronger seta with anterior and posterior fine serrations and strong seta with robust anterior and posterior serrations; segment 3 with two paradactylary setae, one smooth and one posteriorly finely serrated; dactylus rather thin, about twice as long as wide, half as long as carpopropodus segment 3, with two smooth and equally strong dactylary setae.

Pereopod 4 endopod long and thin, preischium and ischium without setae; ischium 11 times as long as wide; merus 12 times as long as wide and 0.9 of ischium length, with four medial bunches of one or two short setae; carpopropodus 5-segmented, segment 1 being 1.2 times as long as segments 2 and 3 combined. Pereopod 6 exopod 8-segmented, endopod long and thin, preischium and ischium without setae; ischium 12 times as long as wide; merus 8 times as long as wide and 0.6 of ischium length, with three medial bunches of one or two short setae; carpopropodus 4-segmented, segment 1 is 1.5 times as long as segments 2 and 3 combined; paradactylary and dactylary setae smooth; dactylus rather thin, 0.4 times as long as carpopropodus segment 4.

Penis rather long, tubiform, slightly narrowing apically. Pleopods not modified. Pleopod 2 longest apical seta 0.9 of ramus length. Pleopod 4 longest apical seta 0.7 of ramus length. Pleopod 5 longest apical seta 0.4 of ramus length. Uropodal endopod shorter than exopod, without medial spiniform setae.

Distribution. Australia, New South Wales: Clarence River mouth, Yamba.

Habitat. The only male was trapped in the river mouth conditions, on muddy bottom with Zostera , at depth of 1 m.

Figures

Figure 6. Deltamysis lowryi sp. nov., holotype, male, 4 mm, New South Wales,Yamba,AM P.98699. (A) habitus, lateral; (B) head, dorsal; (C) posterior part of body with telson and uropods, dorsal; (D) telson posterior part; (E) posteroventral margin of abdominal segment 6, and uropodal protopod; (F) antennular peduncle distal part, dorsal; (G) antennal peduncle and scale, ventral view. Scales (mm): A = 1; B, C, G = 0.5; D–F = 0.25.

Figure 7. Deltamysis lowryi sp. nov., holotype, male, 4 mm, New South Wales, Yamba, AM P.98699: (A) mandibular palp, anterior; (B) mandibles, ventral; (C) labrum, ventral; (D) maxilla 1 outer ramus, posterior; (E) maxilliped 1, anterior; (F) pleopod 2, anterior; (G) pleopod 4, anterior; (H) pleopod 5, anterior. Scales (mm): A–D, F–H = 0.25; E = 0.5.

Figure 8. Deltamysis lowryi sp. nov., holotype, male, 4 mm, New South Wales,Yamba,AM P.98699:(A) maxilla 2, posterior; (B) maxilliped 2 endopod, anterior; (C) pereopod 1 endopod, posterior; (D) pereopod 1 distal part, posterior; (E) pereopod 4 endopod, anterior; (F) pereopod 6, posterior; (G) pereopod 1 distal part, posterior. Scales (mm): A, D, G = 0.25; B, C, E, F = 0.5.