Heteromysis (Heteromysis) tasmanica W. M. Tattersall, 1927

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 : 26-30

Heteromysis (Heteromysis) tasmanica W. M. Tattersall, 1927

Figs 13−15

Heteromysis tasmanica W. M. Tattersall, 1927a: 255 .— Hale, 1929: 363.— Illig, 1930: 600.— Gordan, 1957: 353.—O. S. Tattersall, 1962: 234, 237, 238; 1967: 165−167, 211.— Pillai, 1968: 49.— Mauchline & Murano, 1977: 60.— Mauchline, 1980: 341.— Murano, 1988: 27, 48.— Daneliya, 2012: 136.

Heteromysis (Heteromysis) tasmanica . — Fenton, 1986: 15, 145, 169, 183, 186, 372−377, figs 2.52E, 3.7, 3.8.— Lowry & Stoddart, 2003: 448.

Type specimens. Syntypes: 3 males, Australia, Tasmania, D’Entrecasteaux Channel , 10 Aug 2014, coll. W. M. Tattersall (Natural History Museum, London, 1946.11.26.81−82). Deposited under the name Heteromysis tasmaniae , and labeled as “types” .

Type locality. Tasman Sea: Australia, Tasmania, D’Entrecasteaux Channel (W. M. Tattersall, 1927a) .

Tasman Sea material. Female (+slide), 6 mm, Twofold Bay, Munganno Point , 37°06'12"S 149°55'42"E, 15 m, subtidal wharf pile, 27 Jun 1985, coll. S. J. Keable & A. L. Reid, site M8 (P.36618); female, 5.5 mm, same locality, 0−7 m, subtidal rock platform, 10 Oct 1984, coll. P. A. Hutchings, site M3 (P.36617) .

Diagnosis. Rostrum ( Fig. 13B ) reaching half of antennular peduncle segment 1; its lateral margins without lateral tubercle. Eyestalk without distomedial rim. Telson ( Fig. 13C,D ) сleft 0.14−0.15 of telson length, with 6 to 24 spinules, occupying entire cleft length. Telson lateral margins straight, with 13 to 20 spiniform setae, occupying posterior part, including two terminal. Inner terminal spiniform setae 0.5−0.7 times as long as outer. Outer spiniform setae 0.07−0.09 times as long as telson and 1.4−2.0 times as long as last posterolateral spiniform setae. Pereonite 3 of males with allantoid sternal process, extended backwards between pereopodal bases. Antennal scale ( Fig. 13B ) 2.5−2.9 times as long as wide, extending beyond middle of antennular peduncle segment 3. Pereopod 1 ( Fig. 14 H−J) merus 2.7−3.1 times as long as wide, medially with thin setae or without them, but without flagellated spiniform setae. Pereopod 1 carpopropodus segment 1 is 2.4−2.5 times as long as wide and 0.89−0.94 times as long as merus, its medial margin with eight or nine spiniform setae, two distal of them also stronger and apically bifurcated, with additional smooth spiniform seta medially to them; each spiniform seta medially provided with long seta; segment 2 without distomedial process, with long paradactylary seta on each side, about as long as unguis, bearing dense serrations. Dactylus 0.36−0.42 times as long as carpopropodus. Pereopod 2−6 ( Fig. 15 A−E) carpopropodus 6−7-segmented; unguis strong, but not as thick as dactylus. Pereopod exopod basal joint without outer acute process. Uropodal endopod ( Fig. 13C,E ) 0.79−0.88 times as long as exopod, with 8 to 16 medial spiniform setae along entire margin, though not reaching endopodal apex.

Body length 5.5−12 mm.

Comparison. Heteromysis (Heteromysis) tasmanica has the shallowest telson cleft in relation to the telson length (0.14−0.15) in the group. It is not particularly related to any species, though has a similarity to the species of the H. macropsis complex, from which it is distinguished, in addition, by the complete absence of the distomedial rim on the eyestalk, the cleft spinules, occupying the entire cleft length (0.17−0.77 of cleft length in the H. macropsis complex), shorter outer terminal spiniform setae of the telson in relation to the telson length (0.07−0.09 against 0.10−0.33 the H. macropsis complex), the presence of the bifurcated spiniform setae on the pereopod 1 carpopropodus segment 1 (absent in the H. macropsis complex).

Description of Tasman Sea specimens. Anterior margin of carapace angular, apically smoothly rounded, covering half of eyes and half of segment 1 of antenna 1 peduncle; lateral margins slightly concave. Telson 1.1 times as long as last abdominal somite; length 1.3 its anterior width; posterior width 0.3 of anterior width; lateral margins with 18 and 19 spiniform setae, including two terminal, absent in anterior part: inner 0.5 as long as outer; outer 1.4 times as long as lateral subterminal spiniform seta. Telson cleft rather shallow, 0.15 of telson full length, with 16 spinules, shorter than lateral spiniform setae.

Eyes nearly globular from dorsal view, 0.9−1.0 times as long as wide and slightly flattened dorsoventrally. Cornea narrower than stalk (0.8 times as long as stalk) and 0.3−0.4 times as long as eye entire length. Antennular peduncle segment 3 with two nearly equally long flagellate spiniform setae. Antennal scale reaching level of about half of antennular peduncle segment 3 or extending slightly beyond that, and 2.5 times as long as wide. Mouthparts and maxillipeds typical for the genus. Maxilla 1 outer ramus with six caudal setae. Exopod of thoracopods, basal segment outer margin apically rounded.

Pereopod 1 endopod, preischium with one seta; ischium with six short medial setae; merus with 12 short medial setae and distomedial process. Carpopropodus about as long and as wide as merus; segment 1 is 2.4−2.5 times as long as wide, its medial margin with seven spiniform setae, finely serrated anteriorly, among which two distal rather strong, with accessory subterminal spine (bifurcated); in addition a smooth spiniform seta present medially to them; pair of thin setae at base of each spiniform seta, one of each pair with posterodistal serration; segment 2 with strong paradactylary seta, serrated in median part. Dactylus length 0.36 of carpopropodus length; unguis semilunar, not meandering, smooth. Pereopod 2 exopod 10-segmented. Endopod, preischium with one seta; ischium 6.4 times as long as wide, with a distomedial bunch and two distolateral setae; merus 1.4 times as long as ischium and 7.2 times as long as wide, with eight medial setae; carpopropodus 6-segmented, each segment with serrated distolateral seta; dactylus 0.5 times as long as last carpopropodal segment; unguis rather strong, 1.7 times as long as dactylus. Pereopod 4 exopod 10-segmented. Pereopod 6 exopod 9-segmented. Endopod, preischium with one seta; ischium rather long and slender, 6.0 times as long as wide, with five lateral and three distomedial setae; merus 0.7 times as long as ischium and 5.0 time as long as wide, with 10 medial bunches of one or two setae; carpopropodus 6-segmented, last segment with four smooth paradactylary setae; dactylus small, 0.5 the length of last carpopropodal segment; unguis strong, weakly serrated in median part, 2.0 times as long as dactylus. Carpopropodus of pereopods 2, 3 and 6 (others missing) is 6-segmented. Uropodal endopod shorter than exopod, with 11 spiniform setae along entire margin.

Variation. The female specimens from the Twofold Bay are distinguished from the males from the type locality in Tasmania (as illustrated by W. M. Tattersall, 1927a) by the rostrum being apically rounded with straight lateral margins (apically pointed, with concave margins in the types) ; the eyes being about as long as wide, with the cornea narrower than the eyestalk (eyes longer than wide, with the cornea wider or about as wide as the stalk in the types); the telson being 1.03−1.06 times as long as the abdominal somite 6 (1.25−1.3 in the types); the telson lateral margins bearing 17 to 20 spiniform setae (13 to 15 in the types); the antennal scale barely extending beyond the half of the antennular peduncle segment 3 (nearly reaching the peduncle distal margin in the types); the pereopod 1 merus bearing distomedial triangular process (absent in the male type specimens); the pereopod 2−6 carpopropodus 6-segmented (7-segmented in the types). There is still a chance that the observed differences are due to sexual dimorphism, since no females are known from the original description and no males were available for this study from New South Wales. I will leave this question open .

Distribution. Except for the type locality in Tasmania, D’Entrecasteaux Channel, it was also originally recorded in the South Australian coast, Gulf of St. Vincent (W. M. Tattersall, 1927a), and later in several localities of the Bass Strait ( Fenton, 1986). In this study the species was collected from Twofold Bay, New South Wales ( Fig. 4 ).

Habitat. Sublittoral species, found at depths of 0−79 m (W. M. Tattersall, 1927a; Fenton, 1986; this study), at the bottom with coarse shell, muddy shell-grit, muddy fine shell, fine, very fine sand and rocks ( Fenton, 1986; this study). The species has not been recorded yet in association with any invertebrates. It is the southernmost species of the group, found in cooler waters of the southern and southeastern coast of Australia.

Remarks. W. M. Tattersall (1927a) made a rather detailed description of Heteromysis tasmanica , comparing it only with Heteromysis waitei W. M. Tattersall, 1927 , which belongs to the subgenus Olivemysis . Here I provide a diagnosis of the species in comparison with other species of the microps -group. The allantoid sternal process on the pereonite 3 is so far known only in the males from the southern Australian populations. The status of the South Australian populations requires clarification. Particularly, as expressed by W. M. Tattersall (1927a), their telson cleft bears six spinules compared to 24 in Tasmania and 16 or 17 in New South Wales, and the uropodal endopod has eight spiniform setae against 16 and 9 to 12, respectively. More material is necessary to check the importance of these characters.

Figures

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.

Figure 13. Heteromysis (Heteromysis) tasmanica, female, 6 mm, AM P.36618. (A) habitus, lateral; (B), head, dorsal; (C) posterior part of body (abdominal somite 6, telson, uropods), dorsal; (D) telson posterior part; (E) uropodal endopod, ventral. Scales (mm): A−C = 1; D = 0.25; E = 0.5.

Figure 14. Heteromysis (Heteromysis) tasmanica, female, 6 mm, AM P.36618. (A) mandibular palp, medial; (B) labrum, ventral; (C) mandible, left; (D) maxilla 1, anterior; (E) maxilla 2, anterior; (F) maxilliped 1 endopod, posterior; (G) maxilliped 2 endopod, anterior; (H) pereopod 1 endopod, anterior; (I) distal seta of pereopod 1 carpopropodus segment 2; (J) distal cuspidate setae of pereopod 1 carpopropodus segment 1. Scales (mm): A, E−H = 0.5; B−D, I = 0.25; J = 0.1.

Figure 15. Heteromysis (Heteromysis) tasmanica, female, 6 mm, AM P.36618. (A) pereopod 2, posterior; (B) distal part of pereopod 2 endopod, posterior; (C) pereopod 6 endopod, posterior; (D) distal part of pereopod 6 endopod, posterior;(E) pereopod 6 exopod, posterior; (F) pleopod 5, anterior. Scales (mm): A = 1; B, D, F = 0.25; C, E = 0.5.