Comparative character of the deep-water and inshore cottoid fishes endemic to Lake Baikal

Lake Baikal's 29 endemic species of cottoid fishes form three groups: shallow-water species in depths to 350 m; eurybathic species from 50 to 1300 m; and abyssal species from 400 to 1600 m. These groups differ in their abilities to withstand high hydrostatic pressure. As in marine deep-water fishes, abyssal cottoids in Baikal have few or no cones in the retina, and some have tubular eyes. Their seismosensory systems predominate, based chiefly on free neuromasts. The proportion of species with canal systems decreases with depth. Diversity of the predominantly gammarid foods also decreases from 45 species in shallow water to five species in deep water, and the lateral line system plays the dominant role in food detection at all depths. Two abyssal cottoids have become secondary pelagic, achieving close to neutral buoyancy through high lipid levels and reduced skeletal mineralization. These forms take advantage of the abundant pelagic planktonic amphipod populations. The adaptations of abyssal forms parallel those seen in deep-water marine fishes.     

Resource density regulates the foraging investment in higher termite species

1. Resource density can regulate the area that animals use. At low resource density, there is a conflict in terms of balance between costs of foraging and benefits acquired. The foraging of the higher termite Nasutitermes aff. coxipoensis consists of searching throughout trails and a building galleries phase. 2. In this study, a manipulative field experiment was used to test the hypothesis that colonies of N. aff. coxipoensis forage towards a more profitable balance between the establishment of trails and gallery construction at low resource density. 3. The experiment was conducted in north‐eastern Brazil. Seven experimental plots were established with a continuous increase in resource density (sugarcane baits). Entire colonies of N. aff. coxipoensis were transplanted from their original sites to the experimental plot, totalling 35 nests. The number, branches and total length of trails and galleries were quantified. 4. The results show that N. aff. coxipoensis optimises its foraging output, intensifying the establishment of trails at the cost of gallery construction when resource density is low. The number of trails, the number of trail branches and the total length of trails decreased with increasing resource density. Interestingly, at low resource density, the search effort was concentrated on forming longer and a greater number of trails, a small proportion of which were converted into galleries. The opposite relationship was observed at high resource density. 5. These results suggest an optimisation of search efforts during foraging depending on resource density, a mechanism that may help researchers to understand the use of space by higher termite species.     

Morphological and mtDNA sequence studies on three crucian carps (Carassius: Cyprinidae) including a new stock from the Ob River system, Kazakhstan

Three morphologically and genetically distinct forms of the genus Carassius were collected from the Ob River system, Kazakhstan, Central Asia; Carassius carassius , Carassius gibelio gibelio and an unknown stock tentatively referred to as Carassius gibelio sub-species M. The last mentioned had 33–41 gill rakers, being intermediate between the other two forms (23–27 in C. carassius and 44–49 in C. g. gibelio ), and five scales in the upper transverse series, less than in the others. It also had a relatively larger erythrocyte suggesting triploidy and an mtDNA haplotype distinct from all other known crucian carps. Comparative mtDNA phylogenetic analysis suggested that C. gibelio gibelio in the Ob River system was introduced from China and the Amur River, the same possibly being true for European C. gibelio gibelio based on published haplotypes. C. gibelio sub-species M is thought to be more widely distributed in central Asia, probably extending as far west as European Russia.     

Communities of the cottoid fish (Cottoidei) in the areas of hydrothermal vents and cold seeps of the abyssal zone of Baikal Lake

The hydrothermal vent in Frolikha Bay and the methane cold seep “Saint Petersburg” in Baikal Lake are characterized by the highly productive communities of the aquatic invertebrates and cottoid fish (Cottoidei). The benthic and pelagic ichthyofauna of the vent comprises twelve key species belonging to eight genera, while that of the seep comprise eight species (six genera belonging to three families). The only one obligate hydrothermal species, N. thermalis, has been found; it dominated by abundance (91.6% of total abundance) in Frolikha Bay. N. werestschagini dominated in the cold seep community (39.5%). The spatial distribution of the fish around the hydrothermal vents and the cold seeps was patchy. The largest schoolings has been observed in two biotopes, in the areas of the silty bottom sediments and at the areas covered by the bacterial mats, as well as in the near-bottom water layer.     

A new species of sculpin Cottus kolymensis sp. nova (Scorpaeniformes, Cottidae) from Rivers of Kolyma

Sculpin from the Kolyma, Dukcha, and Glukhaya rivers is described as a new species Cottus kolymensis from the species group ??Cottus poecilopus??. This species differs from the remaining species of the group (C. altaicus, C. szanaga, C. kuznetzovi, C. koreanus, and C. volki) in the combination of several characteristics: very short internal ray of ventral fin averaging 1/5 of the long ray; comparatively wide interorbital space equal or slightly smaller than longitudinal eye diameter, presence of teeth on palatine bones; as a rule, paired fifth pore of the preoperculo-mandibular canal; and an incomplete lateral canal terminating in two to three autonomous segments and opening by (13 + 2 + 2)-(23 + 2 + 2 + 2) pores.     

Trophic relationships between macroinvertebrates and fish in St. Petersburg methane seep community in abyssal zone of Lake Baikal

Trophic relationships were examined for macroinvertebrates and fish inhabiting the St. Petersburg methane seep (central part of Lake Baikal, ~1400 m depth). The analyses of the values of carbon and nitrogen stable isotopes showed that all animals associated with the seep were heterotrophs with different feeding strategies; symbiotrophes were absent. Seep animals consumed combined food with different portion of methanederived carbon ranged from 2.7 to 89%. The average δ¹³С values varied in the range of–26.2‰ (in benthopelagic amphipods) to–64.5‰ (in gastropods). The trophic food web in the methane seep consists of filter feeders (pelagic amphipods, trophic position (TP) is 1.9), detritophages (gastropods, TP of 2.2, and burrowing amphipods, TP of 2.1), polyphages and necrophages (nectobenthic and benthopelagic amphipods of TP 2.8–3.2), and predators (planarians of TP 3.6–4.2 and cottoid fish of TP 3.0–3.8). Animals occupying similar trophic positions significantly differed in the δ¹³С values and have partially overlapping components of food.