Voprosy ihtiologii

The piranha Serrasalmus hollandi was described in 1915 by Eigenmann based on a single specimen from the upper Madeira River basin in the southwestern Amazon and the holotype was later lost. Because morphological variation is absent from the description, species identification is somewhat difficult. Misidentification with S. eigenmanni, another poorly known but morphologically similar species, may have been common in ichthyological inventories. This last species was described in 1929 by Norman, based on a single specimen collected from the Essequibo River, which drains the Guyana Shield, northeast of the Amazon Basin. The present study redescribes S. hollandi, a species commonly known in the Iténez basin of Bolivia as piraña dulce, based on morphological and genetic (mtDNA-COI) information. A neotype was designated from the Paraguá River, a tributary of the Itenéz River which is close to the type locality. A diagnosis to differentiate among S. hollandi and species reported in the Bolivian Amazon and La Plata basins, and S. eigenmanni is presented.

Рассмотрены пластические и меристические признаки, особенности расположения зубов на челюстях и окраска двурогого бычка Enophrys diceraus из Тауйской губы Охотского моря. Впервые приведены данные об аллометрической изменчивости пластических признаков вида. Установлено, что бо́льшая часть рассмотренных признаков двурогого бычка подвержена положительной аллометрической изменчивости (пропорции головы, размеры плавников), отрицательная аллометрия наблюдается лишь по нескольким признакам (длина головы, длина верхнего предкрышечного шипа, наибольшая высота затылочного гребня). Выявлен ряд признаков, не подверженных аллометрии – диаметр орбиты, расстояние от заднего края орбиты до края затылочного гребня, предорсальное расстояние, длина основания грудного плавника, длина хвостового стебля. Выделены таксономически значимые признаки – длина верхнего предкрышечного шипа, межглазничное расстояние, форма и положение выростов lacrimale.

Being a group of popular model organisms in eco-evolutionary biology, genetic, and genomic research studies, the genus Pungitius with 12 species is the most species-rich genus in the stickleback family Gasterosteidae including the Caspian nine-spine stickleback, Pungitius platygaster (Kessler, 1859), the only known species from southern Caspian Sea basin. Here, the new data based on morphological and molecular characters of the mtDNA COI barcode region, and current distribution range of P. platygaster is presented. These data confirm the validity of P. platygaster among its congeners, being sister clade to P. hellenicus from Greece. Morphologically, it is distinguished from the other congeneric species by complete pelvic girdle, 8−11 dorsal spines, and presence of large lateral scutes. The Caspian nine-spine stickleback is found in several closely placed freshwater and brackish waterbodies in the southern Caspian Sea.

Small freshwater (resident) populations of the European river lamprey Lampetra fluviatilis from an isolated from the sea upper part of a river system with numerous lakes (the upper reaches of tributaries of the Daugava River and Lake Peipus, Pskov Oblast, Russia) have been studied. Adult individuals of the lamprey have been attributed to common and large size groups; adults are similar to other resident lamprey from the Baltic Sea basin. The presence of larvae of different size and age groups indicates regular spawning of the European river lamprey in the studied watersheds. Analysis of the modern and historical (before the isolation) distribution of lamprey revealed a reduction in habitats and a decrease in the number of individuals. Dam-associated disruption of migration routes led to the disappearance of anadromous form, and consequently, disappearance of resident lamprey from most of the studied waterbodies. We attribute the decrease in the number of rivers inhabited by lamprey and abundance of the lamprey both to anthropogenic factors (direct blocking of an access of anadromous form of the lamprey to spawning grounds by hydraulic construction) and to the characteristics of the studied area. The richness of the river system with lentic waterbodies makes it suitable for lamprey inhabitation with an influx of large anadromous individuals capable of crossing such reservoirs in search of spawning sites.

The results of the study of growth, ossification sequence and peculiarities of the development of skeletal elements, body proportions and meristic characters of laboratory-reared larvae and fry of two dwarf forms of Arctic charr Salvelinus alpinus сomplex spawning at the shore slope (Lake Tokko) and in the profundal zone (Lake Bol’shoe Leprindo) (Transbaikalia) are presented. Charr from Lake Bol’shoe Leprindo demonstrated slower rates of growth and morphogenesis, retardation of the ossification of their predorsal bones series with its displacement from larval to juvenile period of the ontogeny, but the acceleration of the development of the vertebral column. High mortality of pre-larvae of charr from this lake connected with the transfer to exogenous feeding was observed. For the first time the problem of the reorganization of early ontogeny of charr of the genus Salvelinus in connection with the colonization of deepwater habitat is discussed. In larvae of charr from Lake Tokko, the ossification of vertebral centra was often accompanied by the formation of anomalous bony structures in the notochord. The phenomenon of the penetration of skeletogenic cells into the notochord, which has been described in hybrids of sympatric charr forms, was found in a pure charr form for the first time. The development of characteristic morphological features of the two charr forms in the ontogeny was traced. Differences in body proportions between their fry corresponding to those between adult fish were revealed.

Cyprinodon eremus is endemic to the Sonoyta River system, where wild populations comprise two conservation management units, one in Quitobaquito Springs, Arizona, and another small segment of the Sonoyta River, Sonora. Declining habitat from overmining of groundwater threatens both populations. Because of concern for the Sonoyta River population, refuges were built in Sonora and stocked with individuals from the river. Using seven microsatellite loci, we evaluated the genetic diversity of the wild population and three refuge populations. Comparison with earlier results for the wild population suggests that diversity changed little over the 12 years between collections. Two refuge populations established in 2007–2008 had levels of diversity comparable to that of the wild population. This reflects the relatively recent origins and exchange with the wild population. Notably lower measures of diversity occurred in an older refuge population that was established in 1988 and has no history of exchange with other populations. Suggestions for a program of genetic exchange are presented to inform future management.

The balance between phenotypic plasticity and adaptive specialization in response to environmental pressures remains a hot topic in evolutionary biology. In fish, one of the strongest impact factors is the chemical pollution of habitats. In an attempt to assess the consequences of heavy pollution of fresh waters for resident fishes, we studied Kamchatkan charr, which undergo paedomorphosis in the case of isolation in streams of volcanic areas contaminated with heavy metals. Experiments were carried out on the resistance of charr to metal mixtures during normal development and in six experimental groups with therapeutically altered intensity of metabolism and the secretory activity of thyroid gland. Water from volcanically contaminated streams was found to be lethally toxic for embryos and early juveniles of unadapted charr. The success of acclimation to toxic exposure was correlated with an increase in thyroid status. In experiments, the group with significantly elevated thyroid status showed a significant decrease in mortality and attenuation of oxidative stress in solutions of heavy metals. Under natural conditions, hyperthyroidism provokes a redistribution of the charr’s organism resources from somatic growth and morphological differentiation to stress counteracting and accelerated maturation, which is necessary for the long-term survival of the population under conditions of increased risk of individual mortality. Our experiments highlight the role of thyroid hormones in the rapid response to habitat pollution and the subsequent adaptation of fish populations to chronic deterioration.

The study of the effect of thyroid hormones on the development of the pigment pattern, including the expression of sexual dichromatism, contributes to our understanding of the role of endocrine signaling in the evolution of cichlid fishes, one of the most diverse groups of teleosts. This work shows the effect of reduced thyroid hormone signaling on the development of reversed sexual dichromatism in Amatitlania nigrofasciata, a Neotropical cichlid in which females, unlike males, have carotenoid coloration. In hypothyroid fishes, there was a slowdown in the rate of metamorphic transformations of the pigment pattern and an increase in phenotypic variability. The adult pattern based on carotenoids began to develop in females only after the completion of treatment of thiourea, which suppresses the synthesis of endogenous thyroid hormones. The data obtained indicate a potentially important role of thyroid hormone-mediated developmental plasticity in the diversification of carotenoid coloration in Neotropical cichlids.

The present study reports the deformities in two different species of stingrays Maculabatis bineeshi and Neotrygon kuhlii along the Rameswaram Island. The structural deformity was observed in M. bineeshi species that were collected from Pamban–Therkuvadi fish landing centre, which was the first to be recorded along the Indian coasts with rostral irregularity of the aperture from the anterior margin of the snout around the right margin of the disc from the first gill opening. In addition to the first record, vertebral column deformity was observed in N. kuhlii, which was collected from Kunthukal fish landing centre. The external morphological characteristics showed a curved tail that had vertebral column deformities with severe scoliosis–kyphosis–lordosis starting from the pectoral girdle to the tail region

Two specimens of Baltic herring Clupea harengus membras with anatomically different signs of synchronous hermaphroditism, discovered for the first time in the eastern part of the Gulf of Finland, are described. Individuals with abnormal gonads did not differ from ordinary representatives of the species in other biological characteristics and external morphology. Possible causes of disturbances in the reproductive functions of herring in the studied region are discussed.