Heteromysis microps (G. O. Sars, 1877)

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 : 8

Heteromysis microps group

Diagnosis. Eye without distomedial spine (spines) or tubercle. Antennular peduncle segment 3 with two or rarely three, flagellated (but never further modified) spiniform setae, one of them directed anteriorly, another laterally. Merus of pereopod 1 endopod with distomedial process; its medial margin with flagellated spiniform setae in most of species (occasionally absent). Carpopropodus of pereopod 1 rather massive, longer than merus, with medial spiniform setae and long serrated paradactylary setae. Penis slightly widening apically, mostly with setae.

Comparison. Members of the microps -group are clearly distinguished from other species of Heteromysis (Heteromysis) by the structure of the pereopod 1 endopod, particularly by the presence of the distomedial process on the merus, found only in this group. The flagellated spiniform setae on the merus medial margin are almost exclusively found in the microps -group, though absent in certain species. It further differs from other Heteromysis (Heteromysis) by presence of the flagellated distomedial setae on the antennular peduncle segment 3. There is a variety of shapes in these setae in Heteromysis sensu lato, including larger number (up to seven) of the smooth setae, the presence of rather modified structures. The flagellated spiniform setae of the antennular peduncle segment 3 of the microps -group are reminiscent of those found in Heteromysis (Olivemysis) . From Heteromysis (Olivemysis) the microps -group species also differ by the eyestalk lacking the distomedial process (also present in certain members of the subgenus Heteromysis s. str.); the pereopod 1 carpopropodus longer than the merus (predominantly shorter in Olivemysis ), and other unique features mentioned above.

Remarks. The characteristic feature of the microps - group, the distomedial process of the pereopod 1 merus, is also found in the type species of the genus Heteromysis , H. formosa . It has not been previously described or illustrated, but discovered during preparation of this manuscript in detailed examination by Karl Wittmann (personal communication). Further examination of this and other species of Heteromysis will shed light on the taxonomic importance of the microps species group.

Composition. The following 19 species clearly belong to the microps -group, including four from the Tasman Sea (marked with asterisk): Heteromysis (Heteromysis) abednavandii Wittmann, 2020 ; Heteromysis (H.) australica Băcescu et Bruce, 1980 ; Heteromysis (H.) communis *; Heteromysis (H.) dentata Hanamura et Kase, 2001 ; Heteromysis (H.) gracilis Murano, 1988 ; Heteromysis (H.) heronensis Băcescu, 1979 ; Heteromysis (H.) japonica Murano et Hanamura ,