Deltamysis (Daneliya, 2021)

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 : 419

Key to the species of the genus Deltamysis

1 Anterior margin of carapace triangular, apically pointed or blunt. Telson apical spinules as long as or longer than lateral terminal spiniform setae. Pereopod 3–6 carpopropodus, segment 1 longer, as long as or slightly shorter than other segments combined ........................................ D. songkhlaensis (Yolanda, Sawamoto & Lheknim, 2019)

—— Anterior margin of carapace apically rounded ( Figs 2B , 6B ). Telson apical spinules clearly shorter than lateral terminal spiniform setae ( Figs 2C, D , 6C, D ). Pereopod 3–6 carpopropodus, segment 1 shorter than other segments combined ( Figs 5B–E , 8E, F ) .................................................................................................... 2

2 Telson rather narrow, 1.5–1.6 times as long as wide anteriorly; terminal spiniform setae 0.12 of telson length. Maxilla 2, exopod and endopod segment 2 with lateral setae ............................................ D. nana ( Murano, 1998)

—— Telson rather wide ( Figs 2C , 6C ), 1.1–1.4 times as long as wide anteriorly; terminal spiniform setae 0.2–0.4 of telson length. Maxilla 2, exopod and endopod segment 2 without lateral setae ( Figs 3E , 8A ) .................................................................................................................... 3

3 Telson apically without cleft ( Fig. 2C, D ), armed with two (rarely three) spinules; lateral subterminal spiniform setae not shorter than preceding lateral spiniform setae. Maxilla 2 exopod rather small, barely reaching half of endopod segment 1 ( Fig. 3E ). Pereopod dactylus rather thick, nearly as long as wide ( Figs 4C, D , 5A–E ) ....................................................................... D. holmquistae Bowman & Orsi, 1992

—— Telson with cleft ( Fig. 6C, D ), armed with seven spinules; lateral subterminal spiniform setae significantly shorter than preceding lateral spiniform setae. Maxilla 2 exopod rather big, nearly reaching endopod segment 2 ( Fig. 8A ). Pereopod dactylus rather thin, about twice as long as wide ( Fig. 8C–G ) ..................................................................................................... D. lowryi sp. nov.

Figures

Figure 2. Deltamysis holmquistae Bowman & Orsi, 1992, female, 4 mm, New South Wales, Yamba, AM P.98703: (A) habitus, lateral; (B) head, dorsal; (C) posterior part of body with telson and uropods, dorsal; (D) telson posterior part; (E) posterolateral lobe of abdominal segment 6; (F) posteroventral margin of abdominal segment 6, and uropodal protopod. Scales (mm): A = 1; B, C, E = 0.5; D, F = 0.25.

Figure 3. Deltamysis holmquistaeBowman & Orsi, 1992, female, 4 mm, New South Wales, Yamba,AM P.98703:(A) antennular peduncle distal part, dorsal; (B) antennal peduncle and scale, ventral view; (C) mandibular palp, posterior; (D) labrum, ventral; (E) maxilla 2, posterior; (F) pleopod 3, anterior; (G) pleopod 5, anterior. Scales (mm): A, B, F, G = 0.5; C–E = 0.25.

Figure 4. Deltamysis holmquistae Bowman & Orsi, 1992, female, 4 mm, New South Wales, Yamba, AM P.98703: (A) maxilliped 1 endopod, anterior; (B) maxilliped 2 endopod, anterior; (C) pereopod 1 endopod, anterior; (D) pereopod 1 endopod distal part, anterior. Scales (mm): A, B, D = 0.25; C = 1.

Figure 5. Deltamysis holmquistaeBowman & Orsi, 1992, female, 4 mm, New South Wales,Yamba,AM P.98703:(A) pereopod 2 endopod, anterior; (B) pereopod 3 endopod, anterior; (C) pereopod 4, anterior; (D) pereopod 5 endopod, anterior; (E) pereopod 6, anterior; (F) pereopod 6 basis distal part, anterior. Scales (mm): A–E = 0.5; F = 0.25.

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 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.