The life histories of Dolly Varden Salvelinus malma, white-spotted char S. leucomaenis, and their hybrids from the Utkholok River, northwestern Kamchatka, were retrospectively reconstructed using X-ray fluorescence spectrometric data on Sr2+ and Ca2+ concentrations in otoliths. The fish exhibited a complex, clearly species-specific pattern of migration and spatial distribution. Sr2+ and Ca2+ accumulation patterns in the otoliths indicate spatial segregation of chars during the marine feeding period. In Dolly Varden, migratory polymorphism is manifested in the coexistence of individuals undertaking long marine migrations (the typical anadromous type) and short coastal migrations (the coastal-anadromous type). In white-spotted char, only one migratory type was detected—the so-called shuttle type of migration, in which fish repeatedly and regularly move from the estuary to the sea and back during the summer. Hybrids showed a semi-anadromous migration pattern, with feeding confined to the low-salinity estuary. The parental species and hybrids occupied distinct habitats within marine areas. Differences in migration strategy may indicate that hybrids have become established in the fish community of the Utkholok River and therefore reflect the development of adaptations to exploit available habitat space. The observed spatial segregation of Dolly Varden, white-spotted char, and their hybrids may serve as a clear example of niche formation in these hybrids and as evidence of successful reticulate speciation. These results broaden current understanding of reticulate speciation and the natural hybrid zone of chars of the genus Salvelinus in rivers of northwestern Kamchatka.
A new species, Paraliparis sodalitas sp. nov., is described based on three specimens caught in the Commonwealth Sea off the coast of East Antarctica at a depth of 808 m. It belongs to a group of species with multi-row teeth and gill opening not pore-like. The new species shows no obvious affinity to any of the previously described species of the region and is characterized by a complex of meristic features (69–71 vertebrae, 62–64 rays in the dorsal fin, 21–23 in the pectoral fin, 7 in the caudal fin), unsegmented rays of the vertical fins, and chin pores not closely paired. The upper ray of the pectoral fin is located below the level of the eye, and three or four elongated rays of its lower lobe are separated almost to the base. The end of the caudal part of the body is noticeably thinned. The body is light, pinkish–brown, the abdomen is dark, and the peritoneum is black.
The level of monoamines (dopamine, serotonin, norepinephrine) and that of a number of their metabolites were studied in common roach (Rutilus rutilus) larvae from the coastal area of Lake Glubokoe. For the first time, early larvae, inhabiting lentic water, had significantly different biochemical parameters, allowing attributing the fish to the two groups, characterized by high and low levels of monoamines and their metabolites, respectively. These differences suggest active migration of larvae with high hormone levels from their resident (coastal) biotope to migratory (pelagic) habitat.
The taste attractiveness of 24 carboxylic acids, two of their salts, ascorbic acid (vitamin C), and boric acid, all tested at 0.1 M, was determined for juvenile barramundi Lates calcarifer. Of the carboxylic acids examined, 13 acids, including citric, lactic, and malic acids, showed attractive taste properties and stimulated consumption of agar–agar pellets, whereas three were taste-aversive and eight were taste-indifferent. All acids with aversive taste properties and most acids with attractive taste properties were monocarboxylic acids, whereas most dicarboxylic acids, as well as ascorbic acid, did not affect pellet consumption. No significant relationship was found between the taste attractiveness of carboxylic acids and either their molecular mass or pH. The presence of functional groups (–OH and –NH2) in the molecule, but not of double bonds, altered the taste properties of the acids. The sodium salts of taste-attractive citric and malic acids were taste-aversive and reduced pellet consumption by a factor of 8–10. In most cases, the taste attractiveness of carboxylic acids in barramundi did not correlate significantly with that reported for other fish species. During orosensory testing, barramundi feeding behavior involved repeated grasps of pellets, especially those containing acids with indifferent or weak taste properties. In more than half of the cases, pellets were destroyed by the fish. The more attractive the taste of the pellets and the more likely they were to be consumed, the longer they were retained in the oral cavity.
The results of a detailed comparative study of the phenotype of two geographically isolated populations of the Amur sculpin Mesocottus haitej (Dybowski) are presented. The broad range and sedentary lifestyle of this species imply population differentiation. Analysis of covariance performed on equal-sized individuals from the Ussuri and Tugur river basins revealed numerous reliable differences, the most pronounced of which concerned caudal-peduncle length and depth and pectoral-fin-base height; together, these differences indicate a deeper-bodied phenotype. Most characters in individuals of the two populations substantially overlap in their values. Differences were found in prickle shape and in the extent of prickle distribution on the ventral side of the body. Differences in the number of pores in the postorbital canal of the seismosensory system are discrete. Prickle morphology was used for a preliminary assessment of morphological homogeneity among populations within the Amur River basin. The specimens from the upper Ussuri appear to represent the morphologically least modified population among those examined.
