Heteromysis (Heteromysis) communis Băcescu, 1986

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 : 9-13

Heteromysis (Heteromysis) communis Băcescu, 1986

Figs 1−3

Heteromysis communis Băcescu, 1986: 22 , figs 1M−S, 2A−G.— Hanamura & Kase, 2001a: 18.— Lowry & Stoddart, 2003: 447.

Heteromysis (Heteromysis) communis .— Murano, 1988: 27, 29, 48, fig. 3.— Daneliya, 2012: 135, 146.— San Vicente & Monniot, 2014: 335.— Sawamoto, 2014: 7.

Type specimens. Holotype, female, 4 mm, Australia, Northern Territory, Port Darwin, Channel Island, pool among corals, tide level, 07 Feb 1985, coll. A. J. Bruce, st. A.J.B. 22 ( Museum of Art and Gallery of Northern Territory, Australia [ NTM]). M. Băcescu (1986) also mentioned the allotype male, found from the same locality to be deposited at the “Grigore Antipa” National Museum of Natural History (Bucureşti) ( MGAB) under accession no 711, but this is absent among the MGAB mysid types ( Petrescu & Wittmann, 2009; and Wittmann, personal communication).

Tasman Sea material. Male (+slide), 4 mm, 14 males, 3.5−4 mm, 16 females, 4−4.5 mm, 8 subadults, 31 juveniles, south of Batemans Bay, north side of Burrewarra Point, 35°49.888'S 150°14.112'E, 19.5 m, 22.2C, rocky reef with vertical faces and sediment pockets, honeycomb sponge, 9:57, 27 Mar 2004, coll. RV Baragula and RV Sula , st. NSW 2599, P. Berents, K. Attwood, R. Johnson, S. Keable, S. Kiely, K. Monro, A. Murray, R. Springthorpe, J. Watson, by hand on SCUBA ( AM P.98680); 1 subadult, Batemans Bay, west of Tollgate Islands, 35°44.827'S 150°15.42'E, 7.5 m, 22.1C, patches of reef, sand, stones and Ecklonia radiata , Herdmania grandis (as H. momus ), 29 Mar 2004, coll. RV Baragula & RV Sula , st. NSW 2638, same collectors and gear ( AM P.98681); 3 males, 3.5 mm, 10 females, 3.5−4 mm, 5 juveniles, 1 dried specimen, north side of Burrewarra Point, south of Batemans Bay, 35°49.807'S 150°14.014'E, 20 m, 22.5C, rocky reef with vertical faces, honeycomb sponge, 23 Mar 2004, coll. RV Baragula & RV Sula , st. NSW 2502, same collectors and gear ( AM P.98682); 2 specimens, Jervis Bay, Montagu Roadstead, 35°02'12"S 150°46'E, 12 m, unvegetated sediment, Aug 1989, coll. Jervis Bay Baseline Study ( CSIRO), site 3, #5, hand held corer ( AM P.98683).

Diagnosis. Rostrum ( Fig. 1A ) apically blunt, reaching half of antennular peduncle segment 1; its lateral margins slightly concave, without lateral tubercle, covering eyestalk bases. Eyestalk ( Fig. 1A,B ) with distomedial rim, more or less produced or pointed; cornea narrower than stalk. Eye length 0.56−0.61 of head width. Telson ( Fig. 1C ) 1.1 times length of abdominal somite 6, 1.1−1.2 times as long as wide, 0.30−0.38 times as wide posteriorly as anteriorly. Cleft 0.27−0.31 of telson length, with 15 to 23 spinules, occupying entire cleft and 0.40−0.44 times as long as last posterolateral spiniform setae. Telson lateral margins nearly straight, with six to eleven spiniform setae, including two terminal, occupying posterior part. Inner terminal spiniform setae 0.43−0.56 times as long as outer. Outer spiniform setae 0.10−0.13 times as long as telson and 1.3−2.0 times as long as last posterolateral spiniform setae. Antennular peduncle segment 3 with two almost equally long flagellated spiniform setae ( Fig. 1F ). Antennal scale ( Fig. 1G ) 2.6−2.7 times as long as wide, reaching half of antennular peduncle segment 3 and half of antennal peduncle segment 3. Pereopod 1 ( Fig. 2 E−G) ischium 2.4−2.8 times as long as wide; merus 3.5−3.6 times as long as wide and 1.3−1.5 times as long as ischium, medially with four or five flagellated setae and distomedial process. Pereopod 1 carpopropodus slightly stronger in male; segment 1 is 2.8−3.9 times as long as wide and 0.98−1.1 times as long as merus, its medial margin with four single spiniform setae, then distally with a pair of one regular and one slightly excavate spiniform setae, and two pairs with one slightly excavate and one tooth-like, clearly bifurcate spiniform setae; each single or pair of spiniform setae provided medially with long seta, bearing small number of long proximal setules, and laterally with stronger seta, bearing numerous short setules in thick proximal part and microsetules in thin distal; segment 2 with slight distomedial tubercle, with long paradactylary seta, bearing numerous long setules. Dactylus 0.27−0.40 times as long as carpopropodus, semilunar, not meandering. Pereopod 2−6 ( Fig. 2 H−J, 3A−C) carpopropodus 4-segmented; unguis nearly straight, smooth and nearly as thick as dactylus, becoming thicker in posterior endopods. Pereopod exopod basal joint with outer acute process. Penis ( Fig. 3B ) with one to four distal setae. Uropodal endopod ( Fig. 1C,D ) 0.79−0.84 times as long as exopod, with two to five (mostly three) medial spiniform setae in proximal part; exopod 3.0−3.1 times as long as wide.

Body length. Males 3.5−4 mm (3 mm in the type locality), females 3.5−4.5 mm (4 mm in the type locality).

Comparison. Heteromysis (Heteromysis) communis is a rather distinct species, with its thick and almost straight unguis of pereopods 2−6. Apart from being clearly a member of the microps species group, it is not particularly similar to any species. Among the Tasman Sea species it somewhat resembles H. (H.) keablei sp. nov., but it is readily distinguished from it by a larger number of the telson cleft spinules (15 to 23 against 6 to 10 in H. keablei ), which occupy the entire cleft (only anterior part in H. keablei ), less number of the telson lateral spiniform setae (6 to 11 against 15 to 23 in H. keablei ), which occupy only the posterior part (the entire or almost entire length in H. keablei ), less number of the spiniform setae on the uropodal endopod (2 to 5 against 12 to 27 in H. keablei ), the strong dactylar unguis of the pereopods 2−6 (rather slender in H. keablei ) and other characters.

Description of Tasman Sea specimens. Rostrum angular, apically blunt, reaching half of peduncle segment 1 of antennula; lateral margins slightly concave, covering bases of eyestalks, without lateral tubercles. Telson 1.1 times length of abdominal somite 6, 1.1−1.2 times as long as wide, 0.30−0.38 times as wide posteriorly as anteriorly. Telson cleft 0.27−0.31 times of entire telson length, with 15 to 19 spinules, occupying almost entire cleft length, 0.4−0.7 times as long as last posterolateral spiniform setae; lateral margins nearly straight, with eight or nine spiniform setae, including two apical; inner terminal spiniform setae 0.55−0.56 times as long as outer. Outer spiniform setae 0.10−0.12 times as long as telson and 1.5−2.0 times as long as last posterolateral spiniform setae. Lateral spiniform setae absent in proximal half of telson.

Eyes slightly flattened dorsoventrally, nearly conical from dorsal view; eye length about 1.1−1.2 eye width, and 0.6 times anterior head width. Cornea 0.8 times as wide as stalk and 0.4 times of entire eye length. Eyestalk with distomedial rim, more or less produced. Antennular peduncle segment 3 with two long flagellated setae, one of them directed laterally. Antennal scale 2.6−2.7 times as long as wide, reaching half of antennular peduncle segment 3 and half of antennal peduncle segment 3.

Labrum produced, apically blunt. Mandibular palp, segment 2 with setae along entire posterior margin; segment 3 with two posterior and one medial setae in proximal half. Maxilla 1 outer ramus with serrated apical spiniform setae. Thoracopod exopods 8−10-segmented; basal segment with acute outer process. Maxilliped 2 carpopropodus 0.7 times as long as merus.

Pereopod 1 endopod. Ischium 2.8 times as long as wide, only with short and fine posterior setae. Merus 3.6 times as long as wide and 1.2 times as long as ischium; its medial margin with five strong flagellated setae and distal sharp process. Carpopropodus segment 1 is 2.8 times as long as wide and 1.1 times as long as merus; with four single spiniform setae, then distally with a pair of one regular and one slightly excavate spiniform setae, and two pairs with one slightly excavate and one tooth-like, clearly bifurcate spiniform setae; each single or pair of spiniform setae provided medially with long seta, bearing small number of long proximal setules, and laterally with stronger seta, bearing numerous short setules in thick proximal part and microsetules in thin distal; segment 2 with slight distomedial tubercle, with long paradactylary seta, bearing numerous long setules. Dactylus 0.39−0.40 times as long as carpopropodus, with semilunar unguis.

Pereopod 2−6 endopods rather thin, carpopropodus 4-segmented; unguis nearly straight, smooth and nearly as thick as dactylus, becoming thicker in posterior endopods. Preischium with one seta. Pereopod 2, ischium shorter than merus; both segments with only few setae; carpopropodus rather long, nearly as long as merus; carpopropodal segments prolonged, with short setae; paradactylary setae short and serrated. Pereopod 3−6, ischium slightly longer than merus, with setae along anterior and distal half of posterior margins; merus posterior margin with numerous setae; carpopropodus 0.8 times as long as merus, with four rather short segments and long setae; paradactylary setae rather thin and smooth, longer than unguis.

Penis with four distal setae. Pleopods with seven to ten setae along rather short ramus. Uropodal endopod 0.79−0.84 times as long as exopod, with three to five medial spiniform setae in proximal part; exopod 3.0−3.1 times as long as wide.

Variation. The original description already noted some range of the eye shape variation (Băcescu, 1986). Later Murano (1988) also mentioned that the distomedial corner may be more or less pointed or produced; additionally, the eye shape from dorsal view can vary from nearly rounded to slightly conical. The pereopod 1 carpopropodus in the Tasman Sea specimens is slightly wider in the male, and not as narrow as depicted by Băcescu (1986) from the type specimens, where the carpopropodus length is four times width, rather like mentioned by Murano (1988). The penis is armed with one seta in the holotype, but with two setae in the Murano’s males; yet the Tasman Sea males have four apical setae. The telson cleft is armed by fewer, 15 to 19, spinules (20 to 23 as recorded elsewhere), and the uropod endopod bears two to five spiniform setae (mostly three), compared to three to five, mostly four or five in the Northern Territory specimens. Although Murano (1988) considered the observed variation in his specimens unusual, the Tasman Sea specimens further extend the documented range of variation in the species.

Distribution. Australia: Channel Island at Darwin Harbour (Northern Territory) as the type locality; later also collected from Dudley Point Reef and Fort Hill Wharf of the same Darwin Harbour ( Murano, 1988). First time reported from the eastern Australian coast in this study, namely from Batemans Bay near Burrewarra Point, Tollgate Island, and from Jervis Bay ( Fig. 4 ).

Habitat and life history. Depth 5−12 m; on sponges: honeycomb sponge, and surrounding reefs. Băcescu (1986) found harpactocoids from the stomachs of Heteromysis communis , supposing its predatorial habits.

Remarks. Băcescu (1986), though being the author of the Heteromysis subgeneric system ( Băcescu, 1968), did not attribute this species to any subgenus. That was done by Murano (1988), who assigned it into the nominotypical subgenus. The species was originally distinguished from the other species by the eyestalk with slightly produced anteromedial corner, the telson cleft deep, with more than 20 spinules (in fact, can be from 15), the telson lateral margins with six to nine spiniform setae in the posterior half (in fact, up to eleven) and the pereopod 1 endopods only slightly sexually dimorphic. Murano (1988) also added the rostrum, which was narrowly rounded at the apex, extending to the middle of the antennular peduncle segment 1 and covering the basal parts of the eye stalks; the pereopod 1 merus subequal in length to the carpopropodus, with four (can also be five) small flagellated spiniform setae and the distomedial triangular process; the pereopod 2 endopod with the 4-segmented carpopropodus more slender and hirsute than the posterior endopods, and with the straight unguis (this concerns the ungue of the other pereopods too). The species has many more diagnostic characters documented here after the comparison with the other species of the microps­ group.

Figures

Figure 1. Heteromysis (H.) communis, male, 4 mm, AM P.98680. (A) head, dorsal; (B) head, lateral; (C) posterior part of body, dorsal; (D) uropodal endopod, ventral; (E) posterior margin of abdomen, ventral; (F) distomedial setae of antennular segment 3, dorsal; (G) antenna 2, interocular process and labrum, ventral; (H) mandibular palp, lateral; (I) posterior seta of mandibular palp segment 2. Scales (mm): A−C = 1.0; D, E, G, H = 0.5; F, I = 0.25.

Figure 2. Heteromysis (H.) communis, male, 4 mm,AM P.98680.(A) maxilla 1, anterior; (B) maxilla 2, anterior; (C) maxilliped 1, anterior; (D) maxilliped 2, posterior; (E) pereopod 1 endopod, posterior; (F) distal part of pereopod 1 endopod, anterior; (G) distal part of pereopod 1 endopod, posterior; (H) pereopod 2 endopod, anterior; (I) pereopod 3, posterior; (J) distal part of pereopod 3 endopod, posterior. Scales (mm): A, F, G, J = 0.25; B−E, H, I = 0.5.

Figure 3. Heteromysis (H.) communis, male, 4 mm, AM P.98680. (A) pereopod 5, posterior; (B) pereopod 6 with penis, posterior; (C) distal part of pereopod 6 endopod, posterior; (D−H) pleopods 1−5, anterior. Scales (mm):A, B = 0.5; C−H = 0.25.

Figure 4. Distribution of the Tasman Sea Heteromysis (Heteromysis) species. (A) general distribution of H. (H.) communis and H. (H.) tasmanica (the white signs indicate former records); (B) H. (H.) communis, H. (H.) keablei sp. nov., H. (H.) macropsis and H. (H.) tasmanica in the Tasman Sea.