Heteromysis (Heteromysis) macropsis Pillai, 1961

Daneliya, Mikhail E., 2021, On the Mysid Crustacean Genus Heteromysis (Mysidae: Heteromysinae) of the Tasman Sea, with Notes on the Tribe Heteromysini, Records of the Australian Museum (Rec. Aust. Mus.) 73 (1), pp. 1-50 : 20-26

Heteromysis (Heteromysis) macropsis Pillai, 1961

Figs 9−12

Heteromysis macropsis Pillai, 1961: 32 , plate 6K−S; 1965: 1684, 1726, fig. 96.—O. S. Tattersall: 1967: 169.— Mauchline & Murano, 1977: 59.— Müller, 1993: 225.— Neyt, 2002: 11.— Fukuoka & Murano, 2002: 94.— Wittmann, 2020: 154, 155.

Type material. Two immature specimens, 4−5 mm, off Kollam (former Quilon), State of Kerala, India ( Pillai, 1961). Status unknown .

Type locality. Off Kollam (former Quilon), Kerala State, India ( Pillai, 1961) .

Tasman Sea material. Female (+slide), 4 mm, north east corner of Clark Island, 33°51.85'S 151°14.47'E, 4–5 m, Ecklonia holdfast, 17 Apr 1996, coll. P. A. Hutchings, st. NSW 1244, by hand on SCUBA ( AM P.98707); male, 3.5 mm (pereopod endopods missing), same data as previous ( AM P.98708); 4 females, same data as previous ( AM P.98709); female, 4.5 mm (pereopod endopods missing), same locality and depth, encrustation on outside of bottle, 17 Apr 1996, coll. P. A. Hutchings, st. NSW 1243 ( AM P.98710); female, subadult, juvenile, south of Vaucluse Point, Port Jackson, 33°52'S 151°17'E, 3 m, sponge, 22 Jun 1982, coll. J. K. Lowry, st. NSW 108 ( AM P.98711); female, 5 mm, Clark Island, 7 m, kelp holdfast with sponges, 06 Jun 2001, coll. R. T. Springthorpe ( AM P.98712); female, subadult female, juvenile, Port Jackson, south west of Camp Cove, 33°50'24.65"S 151°16'35.63"E, 11 m, drift algae on sediment covered coarse shell, 19 Feb 2010, coll. RV Baragula, MI NSW 3998, S. J. Keable, by hand on SCUBA ( AM P.98719); female (pereopods absent), 6 mm, Lady Robinsons Beach North (2), Botany Bay, 33°57'30"S 151°09'30"E, 7 m, rock scraping, 29 Oct 1998 ( NSW Fisheries; BB LR2 qual) (P.58590); male, 4.5 mm (pereopods missing), female (pereopods missing), 4.5 mm, Jervis Bay, 05 Jun 1990, coll. Jervis Bay Baseline Study ( CSIRO), site 3, #1 ( AM P.98718); female (in two parts, pereopods missing), 4 mm, same locality and collector, Aug 1989, site 4, #1 ( AM P.98713); 2 specimens (appendages missing), same locality and collector, Aug 1989, site 3, #2 ( AM P.98714); male, 4 mm (pereopods missing; penis illustrated), female, 4.5 mm (appendages missing), same locality and collector, 17 Aug 1989, site 1, #1 ( AM P.98715); female, 3.5 mm (pereopods missing), same locality and collector, 12 Nov 1989, site 1, #4 ( AM P.98716); female, 4.5 mm (pereopods missing), same locality and collector, 05 Jun 1990, coll. same locality and collector, site 3, #1 ( AM P.98717); female, 4 mm, north side of Burrewarra Point, south of Batemans Bay, 35°49.807'S 150°14.014'E, 22 m, 22.5C, rocky reef with vertical faces, under stones, sand bottom, 23 Mar 2004, coll. RV Baragula & RV Sula , st. NSW 2515, P. Berents, K. Attwood, R. Johnson, S. Keable, S. Kiely, K. Monro, A. Murray, R. Springthorpe and J. Watson, airlift on SCUBA ( AM P.98720); 2 subadult specimens, same locality and collectors, 35°49.807'S 150°14.014'E, 17 m, 22.5C, rocky reef with vertical faces, rock with Hydrodendron australe and other encrusting fauna, 23 Mar 2004, st. NSW 2511 ( AM P.98721); subadult, west of Tollgate Island, 35°44.827'S 150°15.42'E, 8.2 m, 22.1C, patches of reef, sand, stones and Ecklonia radiata , under rock, 29 Mar 2004, coll. RV Baragula, NSW 2652, same collectors and gear ( AM P.98723); subadult female, 3 mm, juvenile, south of Batemans Bay, north side of Burrewarra Point, 35°49.776'S 150°13.955'E, 15 m, 22C, rocky reef with sand patches and some large boulders with vertical faces, some patches of Ecklonia , black leathery finger sponge, 24 Mar 2004, coll. RV Baragula, st. NSW 2530, same collectors and gear ( AM P.98722); juvenile, same locality, 35°49.807'S 150°14.014'E, 20.8 m, 22.5C, rocky reef with vertical faces, dead and live bryozoan cf. Triphyllozoon , 23 Mar 2004, coll. RV Baragula, st. NSW 2500, same collectors and gear ( AM P.98724); female, 4.5 mm, male, 4.5 mm, Twofold Bay, Murrumbulga Point, Quarantine Bay side, 37°04'42"S 149°53'06"E, 15 m, subtidal breakwater wall, 17 Sep 1985, coll. P. A. Hutchings & S. J. Keable (P.36619).

Diagnosis. Rostrum ( Fig. 9A ) lateral margins slightly concave, without tubercle, extending to proximal or middle part of antennular peduncle segment 1. Eye cornea ( Fig. 9A,B ) narrower than stalk. Stalk with slight distomedial rim, barely reaching antennular peduncle segment 3. Male sternites ( Fig. 11E ) with smooth processes. Telson (Fig. B−D) 1.2 times as long as last abdominal somite, 1.1−1.4 times as long as wide; its posterior width 0.2−0.3 of anterior width; cleft 0.21−0.27 of telson length, with four to fifteen spinules, occupying anterior 0.37−0.77 of cleft. Telson lateral margins with 11 to 16 spiniform setae, occupying posterior part; outer terminal spiniform setae 0.10−0.13 of telson length and 1.2−2.3 times as long as last posterolateral spiniform setae; inner terminal spiniform setae 0.53−0.73 times as long as outer. Peduncle of antennula ( Fig. 9F ) with two distomedial flagellated setae of about equal length and width. Antennal scale ( Fig. 9G ) longer than middle of antennular peduncle segment 3, reaching distal margin of antennal peduncle, 2.8−3.0 times as long as wide. Pereopod 1 ( Fig. 10F,G ) ischium 1.8−1.9 times as long as wide, merus 2.8−4.1 times as long as wide and 1.7−1.8 times as long as ischium, medially without flagellated setae, but simple long setae, and with distomedial process; carpopropodus segment 1 about as long as merus, 3−4 times as long as wide; its medial margin with non-flagellated spiniform setae, provided medially with smooth long seta; segment 2 without distomedial process, with long paradactylary setae, bearing numerous long setules. Dactylar unguis semilunar, not meandering. Pereopod 2 ( Fig. 10H, I ) carpopropodus 5-segmented. Pereopod 3−6 ( Fig. 11A,B ) carpopropodus 4- to 6-segmented; unguis strong, but not as thick as dactylus, serrated in posterior endopods. Pereopod exopod basal joint without outer acute process. Penis ( Fig. 11F ) with setae. Uropodal endopod 0.9 times as long as exopod, with eight to fifteen spiniform setae along medial margin.

Body length 3.5−6 mm.

Comparison. Heteromysis (Heteromysis) macropsis is rather close to Heteromysis (H.) thailandica , H. (H.) spinosa and H. (H.) minuta . Heteromysis thailandica was described based on an incomplete specimen, lacking most of the pereopods, and differing from H. macropsis by the slightly longer rostrum, extending beyond the middle of the antennular peduncle segment 3 (extending to the proximal or middle part in H. macropsis ), the 4-segmented carpopropodus of the pereopod 2 (5-segmented H. macropsis ), and, possibly, by the structure of the sternal processes, not studied in H. macropsis types. From H. spinosa it differs by the distomedial rim of the eyestalk barely produced beyond the cornea (strongly produced in H. spinosa ), usually larger number of the telson lateral spiniform setae (11 to 16 against 8 to 11 in H. spinosa ), the shorter terminal spiniform setae of the telson (<0.13 against>0.14 of the telson length in H. spinosa ), the longer antennal scale, stretching far beyond the eyes and the middle of the antennular peduncle segment 3 (rather short antennal scale, barely stretching beyond the eye and not reaching the middle of the antennular peduncle segment 3 in H. spinosa ). From H. minuta it differs by the distomedial rim of the eyestalk barely produced beyond the cornea (strongly produced in H. minuta ), the longer antennal scale, stretching beyond the middle of the antennular peduncle segment 3 (not reaching middle of the antennular peduncle segment 3 in H. minuta ), the wider pereopod 1 endopod (rather slender in H. minuta ), and less spiniform setae on the uropodal endopod (8 to 15 against 20−22 in H. minuta ).

Description of Tasman Sea specimens. Rostrum angular, apically blunt or pointed; lateral margins slightly concave, covering half of eyes and half of segment 1 of antenna 1 peduncle. Thoracic sternites of male with triangular smooth processes; largest on sternite 1. Telson 1.2 times as long as last abdominal somite; length 1.2−1.4 its anterior width; posterior width 0.20−0.27 of anterior width; lateral margins with eleven to fifteen spiniform setae, absent in anterior part, with distal wing-like expansions; inner terminal spiniform setae 0.68−0.73 as long as outer; outer 1.2−1.4 times as long as lateral subterminal spiniform seta and 0.10 of entire telson length. Telson cleft 0.24−0.27 of telson full length, with four to fifteen spinules, occupying 0.64−0.73 of cleft length, 0.6–0.7 times as long as last lateral spiniform setae.

Eyes 1.0−1.1 times as long as wide from dorsal view, slightly flattened dorsoventrally. Eye length 0.5−0.6 of anterior head width. Eyestalk with slightly produced distal dorsomedial rim, visible also from lateral view, not extending beyond cornea. Cornea narrower than stalk (0.7−0.8 times as long as stalk) and 0.3−0.4 times as long as eye entire length.

Antennular peduncle, dorsal distomedial corner of segment 3 with two simple setae, directed forward, and two relatively thin and equally long flagellated setae, directed inward and outward, respectively. Antennal scale reaching level of from about half to nearly distal margin of antennular peduncle segment 3, and 3.0 times as long as wide. Mouthparts and maxillipeds typical for the genus. Mandibular palp with flagellated setae; segment 3 is 0.4 times as long as segment 2, with two medial setae. Maxilla 1 outer ramus with four caudal setae.

Thoracopodal exopods with smooth distolateral corner of basal segment. Pereopod 1 endopod, ischium 1.9 times as long as wide, with six short medial setae; merus 4.1 times as long as wide and 1.9 times as long as ischium, with six short and long medial setae and distomedial process. Carpopropodus segment 1 is 3.8 times as long as wide and 1.0 times as long as merus, its medial margin with four single smooth spiniform setae, then distally with a pair of one smooth and one slightly anteriorly serrated (but no excavated) spiniform setae; each single and distal pair of spiniform setae provided medially with smooth long seta; distal pair laterally also with longer seta, distally bearing numerous fine setules; segment 2 without distomedial process, with long paradactylary seta, bearing numerous long setules. Dactylus 0.34 times as long as carpopropodus, semilunar, not meandering. Pereopod 2 endopod, preischium with one seta; ischium 4.1 times as long as wide, with two distomedial setae; merus 1.5 times as long as ischium and 7.1 times as long as wide, with eight medial bunches of one or two setae; carpopropodus 5-segmented, each segment with serrated distolateral seta; serrated setae with strong denticles in proximal part and fine denticles in distal; paradactylary seta proximally serrated; dactylus 0.6 times as long as last carpopropodal segment; unguis rather strong, 1.7 times as long as dactylus. Pereopod 6 exopod 8-segmented. Endopod, ischium rather long and slender, 6.8 times as long as wide, with three lateral setae; merus 0.8 times as long as ischium and 5.8 times as long as wide, with six medial bunches of one or two setae; carpopropodus 5-segmented, last segment with two smooth paradactylary setae; dactylus small, 0.6 the length of last carpopropodal segment; unguis strong, weekly serrated in median part, 2.3 times as long as dactylus.

Penis with rather setose tip: three anterior and three posterior long setae on a lobe. Longest seta of pleopod 5 is 0.8 times as long as ramus. Uropodal endopod 0.88 times as long as exopod, with eight to fifteen spiniform setae along almost entire margin. Uropodal exopod 3.0 times as long as wide.

Variation. The species is considerably variable even within the Tasman Sea, particularly in the length of the antennal scale and armature of the telson. Compared with the original illustrations of Pillai (1961), the Tasman Sea specimens are distinguishable from the Indian Ocean types by the longer rostrum, covering the eyestalk bases and reaching half of the antennular peduncle segment 1 (not covering the stalk and reaching only the proximal part of the antennular peduncle segment 1 in the types), more prominent distomedial rim of the eyestalk (barely established in the types), in the telson outer terminal spiniform setae only slightly (1.2−1.4) longer than the last posterolateral (1.9−2.3 times as long in the types), the paradactylary setae of the pereopod 1 carpopropodus segment 2 shorter than the dactylar unguis (longer than the unguis in the type specimens). The significance of these differences must be confirmed by comparison with actual Indian specimens .

Distribution. Indian Ocean: known here only from the type locality off Kollam in Kerala, India ( Pillai, 1961). Pacific Ocean: in this study collected in the Tasman Sea from the Sydney Harbour and further south along the Australian coast in Botany Bay, Jervis Bay, Batemans Bay and Twofold Bay.

Habitat and life history. Sublittoral species, found at a depth of 3 to 22 m. Originally collected in plankton. In this study it was found in the holdfasts of the brown alga Ecklonia radiata , and may possibly be also associated with sponges. Otherwise, found among and under rocks in the presence of brown algae, bryozoans and hydroids. Female from Burrewarra with two embryos.

Remarks. Heteromysis (Heteromysis) macropsis has not been recorded since its originally description as Heteromysis macropsis Pillai, 1961 , and remained without subgeneric assignment until now. It is clearly a member of the microps - group. Pillai (1961) compared it with H. proxima , belonging to the same group, which, in fact, became rather distant from H. macropsis after the description of more similar H. thailandica , H. spinosa and H. minuta . The revised diagnosis includes characters comparing it with all the species of microps­ group.

Due to considerable variation within Heteromysis macropsis , as well as a similar level difference between H. macropsis , H. minuta , H. spinosa and H. thailandica , all of these species probably represent a complex of closely related taxa, H. macropsis complex. Their geographical relations and actual taxonomic level should be revealed after a more extensive material is studied. I also prefer to provide here a more detailed description of the Tasman Sea specimens.

Figures

Figure 9. Heteromysis (Heteromysis) macropsis, female, 4 mm, AM P.98707. (A) head, dorsal; (B) habitus, lateral; (C) posterior part of body (abdominal somite 6, telson, uropods), dorsal; (D) telson posterior part; (E) uropodal endopod, ventral; (F) distomedial setae of antennular segment 3, dorsal; (G) antenna 2 and interocular process, ventral. Scales (mm): A−C = 1; D, F = 0.25; E, G = 0.5.

Figure 10. Heteromysis (Heteromysis) macropsis, female, 4 mm, AM P.98707. (A) mandibular palp, medial; (B) labrum, ventral; (C) maxilla 1, posterior; (D) maxilla 2, posterior; (E) maxilliped 2 endopod, anterior; (F) pereopod 1 endopod, anterior; (G) distal part of pereopod 1 endopod, anterior; (H) pereopod 2 endopod, anterior; (I) distal part of pereopod 2 endopod, anterior. Scales (mm): A−F, H = 0.5; G, I = 0.25.

Figure 11. Heteromysis (Heteromysis) macropsis. (A−D) female, 4 mm, AM P.98707; (E, F) male, 3.5 mm, AM P.98708. (A) pereopod 6, anterior; (B) distal part of pereopod 6 endopod, anterior; (C) pleopod 2, anterior; (D) pleopod 5, anterior; (E) thoracic sternites with processes, ventral; (F) penis distal part; (i–viii) thoracic sternites numbers. Scales (mm): A, E = 0.5; B−D, F = 0.25.

Figure 12. Heteromysis (Heteromysis) macropsis, female, 6 mm, AM P.58590. (A) head, dorsal; (B) telson; (C) telson posterior part; (D) pleopod 4, right; (E) uropod endopod, ventral. Scales (mm): A, B, D, E = 0.5; C = 0.25.