Comparison of Olfactory Sensilla Structure in Littoral and Deep-water Amphipods from the Baikal Region

The structure of olfactory sensilla was compared in amphipods from the Baikal region, namely in nine Baikal species (Ommatogammarus carneolus melanophthalmus Bazikalova, 1945; O. flavus (Dybowsky, 1874); O. albinus (Dybowsky, 1874); Eulimnogammarus verrucosus (Gerstfeldt, 1858); E. vittatus (Dybowsky, 1874); E. cyaneus (Dybowsky, 1874); Acanthogammarus godlewskii (Dybowsky, 1874); Pallasea cancelloides (Gerstfeldt, 1858); and Gmelinoides fasciatus (Stebbing, 1899)) and a Holarctic species, Gammarus lacustris Sars, 1863. The results of the study demonstrate the comparison of aesthetasc lengths and numbers, as well as SEM images of the aesthetascs for Baikal amphipods for the first time. Our results confirm and complement the previously obtained data on the number of aesthetascs per segment for three deep-water Baikal amphipod species of the genus Ommatogammarus. Within the studied deep-water amphipods with different habitat depth ranges, Ommatogammarus albinus (Dybowsky, 1874), inhabiting maximum habitat depths, have the highest number of aesthetascs. The size and number of aesthetascs did not differ between males and females of the littoral Eulimnogammarus verrucosus (Gerstfeldt, 1858) and deep-water species. The littoral amphipods were shown to have more antennae I equipped with mechanoreceptors than deep-water amphipods.