Ultrastructural correlates of acoustic sensitivity in Baikal coregonid fishes

Ultrastructural correlates of acoustic sensitivity in Baikal coregonid fishes

Sapozhnikova, Yulia P.; Belous, Anastasia A.; Makarov, Mikhail M.; Glyzina, Olga Y.; Klimenkov, Igor V.; Yakhnenko, Vera M.; Sukhanova, Lyubov V.

We investigated the ultrastructure of the sensory saccular and lagenar epithelia of the coregonid fishes: pelagic planktophage Baikal omul (Coregonus migratorius), benthophage lacustrine-riverine whitefish, or Baikal pidschian (C. pidschian), a typical inhabitant of the shallow water of the lake, and their hybrids of the first generation (F1). We made a few suggestions on the possible adaptive significance of ultrastructural specializations to acoustic sensitivity in different species of coregonid fishes. Unlike the shallow-water pidschian, both the pelagic omul and F1 hybrids possess higher morphological diversity of sensory cells. However, sensory cells of pidschian are characterised by sensory bundles with shorter stereocilia that presumably could perceive higher frequency sound oscillations. The saccular orientations are different from the earlier described ones in other whitefishes. The predominance of any direction in the morphological polarization of the sensory macula of different fish species is expected to be attributed to their ecology. READY

Ultrastructure of saccular epithelium sensory cells of four sculpin fish species (Cottoidei) of Lake Baikal in relation to their way of life

Various structural elements of the apical region of hair cells and their location in the saccular macula of four sculpin fish species (Cottoidei) of Lake Baikal—two oilfish species (big golomyanka Comephorus baicalensis and small golomyanka C. dybowski), Severobaikalsk yellowfin Cottocomephorus alexandrae, and stone sculpin Paracottus knerii—were studied by scanning electron microscopy. In stone sculpin Paracottus knerii, which inhabits the coastal areas and leads a benthic lifestyle, the diversity of hair cells (in terms of the height of kinocilium and stereocilia) is big than that in the secondary pelagic species big and small golomyankas and in Severobaikalsk yellowfin, which inhabits the near-slope areas. Stereocilia of hair cells of stone sculpin and Severobaikalsk yellowfin are shorter than in the other species studied. The presence of such cells in the macula can ensure the sensitivity to more high-frequency acoustic signals and facilitate their perception by fish against the background of low-frequency noises characteristic of the coastal zone of the lake. READY

Gut microbiome of juvenile coregonid fishes: comparison of sympatric species and their F1 hybrids

Authors: Belkova, Natalia L.Sidorova, Tuyana V.Glyzina, Olga Y.Yakchnenko, Veronika M.Sapozhnikova, Yulia P.Bukin, Yurij S.Baturina, Olga A.Sukhanova, Lyubov V.

Gut prokaryotic communities of coregonid fishes reared in the aquaria of the Baikal Museum (Listvyanka sttl., Lake Baikal, Russia) for two years were identified using next generation sequencing of 16 S rDNA. We compared pelagic planctophage Baikal omul, Coregonus migratorius Georgi, bathypelagic bentophage lacustrine Baikal whitefish, Coregonus baicalensis Dyb. and their first generation hybrid crosses (♀ omul × ♂ whitefish and vice versa). The closest prokaryotic communities were determined in the omul and ♀ omul × ♂ whitefish hybrid, which differ from whitefish and the ♀ whitefish × ♂ omul hybrid. Most of the bacteria were Proteobacteria, Bacteroidetes, Firmicutes or Actinobacteria. The number of bacterial operational taxonomic units (OTUs) was 624 and declined from the omul to hybrids and to whitefish. The dominant bacterial OTU in all examined fish was closely related to the genus Serratia of the Enterobacteriaceae family. In total, 34 OTUs were detected in all studied fishes, consisting of 91.4% of the total number of sequences. The highest diversity of microorganisms was found in omul, where 197 unique OTUs were detected belonging to Chlamydiae, Chloroflexi, Deinococcus-Thermus, Fusobacteria, Spirochaetes, Synergistetes, Verrucomicrobia and Candidatus Saccharibacteria. The effect of respective ecotypes on the gut microbiome diversity is discussed. READY