N. G. Emel’yanova

Reproduction and initial development of manybar goatfish Parupeneus multifasciatus (Mullidae)

Features of reproductive biology and the stages of early ontogeny are described in the mass tropical species manybar goatfish Parupeneus multifasciatus. In general, in the catches represented by mainly sexually mature fishes, females prevail but males prevail in the largest size classes. The females reach their first sexual maturity by approximately 110 mm fork length, and they are characterized by continuous oogenesis and egg deposition in batches. The fish spawn over the entire year with a trend to lower values of the gonadosomatic index (GSI) of the females from June to October. The features of early ontogeny are compared in manybar goatfish and red mullet Mullus barbatus ponticus from the Black Sea.

Morphological criteria of egg quality in marine fishes: Activation and cleavage of eggs of Zebrasoma scopas (Acanthuridae)

Morphological changes of the eggs of Zebrasoma scopas obtained just after ovulation and after the storage of ovulated oocytes in the ovarian cavity of the female (in vivo) or in the external medium (in vitro) are described. The dynamics of cortical reaction is followed in noninseminated oocytes, as well as in inseminated oocytes of various quality. The average proportions of eggs exhibiting normal cleavage in the control series (comprised the eggs inseminated just after ovulation) and in the series stored in vivo for 2 and 4 h at 27°C are 83, 30, and 35%, respectively. The average proportions of eggs with normal cleavage in the control series and in the series stored in vitro for 2 and 4 h at 25°C are 88, 79, and 34%, respectively. The storage of oocytes in vitro at 7°C for 2 h leads to the abrupt decrease of their quality with the proportion of normally cleaved eggs reaching only 15%. The types of abnormal cleavage leading to subsequent degradation of cells of the blastodisc and total mortality of eggs are as follows: (1) mitotic cleavage of nuclei accompanied by incomplete cytotomy, (2) mitotic cleavage of nuclei without cytotomy, (3) a weak adhesion between cells, and (4) desynchronization of cell divisions. The methods for the assessment of egg quality just after ovulation and at initial developmental stages are suggested for marine teleost fishes.

Some data on the structure of the gonads of manybar goatfish Parupeneus multifasciatus (Mullidae) from the Nha Trang Bay, South China Sea

Gonadal differentiation and development of sex cells are described in the tropical representative of the family Mullidae, manybar goatfish Parupeneus multifasciatus, using histological methods and observations of oocytes in vivo. Anatomical differentiation of the gonads is registered by approximately 5 cm fork length (FL) and 1.5 g body weight of the fish, and cytological differentiation (in the females) occurs by approximately 6 cm body length and 2.6 g body weight. In the ovaries of sexually mature females before spawning, oocytes of all phases and periods of development can be found. Based on the gonadal structure and frequency distribution of oocyte diameter, the type of oogenesis is continuous.

Hormonal stimulation of maturation and ovulation, gamete morphology, and raising of larvae in Dascyllus trimaculatus (Pomacentridae)

The experiments on hormonal stimulation of the maturation and ovulation of oocytes of Dascyllus trimaculatus (Pomacentridae) are carried out. Double injections of surfagon (LH-RH-a) (5 + 15 μg/kg of fish body weight) with (or without) the addition of eglonil (5 + 15 mg/kg) are used, and the interval between the injections ranges from 12 to 17 h. Ovulation is registered 33.5–42.0 h after injection I. Morphological changes in oocytes are followed during the process of their maturation. The ultrastructure of spermatozoa and oocyte envelopes is studied. The quality of ovulated oocytes is assessed after their in vitro storage at 25 and 5°C. Preliminary results on the transition of the larvae to exogenous feeding are obtained.

Hormonal stimulation of maturation and ovulation of oocytes in Zebrasoma scopas (Acanthuridae)

The experiments were carried out on hormonal stimulation of oocyte maturation in Zebrasoma scopas from the South China Sea, Vietnam. Three variants of surfagon injections were studied: 1—double injections (5 + 20 μg/kg of fish body weight); 2—double injections (2 + 8 μg/kg); and 3—single injections (20 μg/kg). The time interval between two injections comprised 15–24 h. Ovulation of oocytes in variants 1 and 2 was observed in most (67%) females 33–47 h after the first injection. The increase of the time interval between injections I and II was followed by the decrease of the interval between injection II and ovulation. In variant 3, oocytes ripened but ovulation was absent. The oocytes possessed with the competence for maturation are always present in the ovaries because of a continuous type of oogenesis. The morphological changes in oocytes in the process of maturation were observed. Ovulated oocytes could be stored in the ovary cavity no more than 4 h; the number of embryos with normal cleavage decreased during this time from 90 to 53%.

Gamete ultrastructure in some species of the family Mullidae from the South China Sea

In tropical representatives of the family Mullidae, the ultrastructure of oocyte envelopes (Parupeneus multifasciatus and Upeneus tragula) and spermatozoa (P. multifasciatus and P. barberinoides) is studied. The egg envelopes include the single-layered zona radiata and weakly expressed chorion. The spermatozoa are characterized by the presence of the oval head flattened on a side and deep nuclear fossa reaching approximately 90% of the head length. The centriolar complex and basal part of the flagellum are located inside the nuclear fossa.

The State of the Reproductive System of Several Fish Species from Water Bodies Polluted with Radionuclides during the Chernobyl Catastrophe

The state of the reproductive system in several fish species—offspring of individuals exposed to radiation as a result of the catastrophe at the Chernobyl Nuclear Power Plant (CNPP) was studied. Material was collected in water bodies of Ukraine polluted with radionuclides: water cooler of the CNPP (1992, 2002–2004), Lake Glubokoe (2003–2004), Kiev Reservoir, and Teterev River (1997, 1999–2005). It was shown that the total number and the degree of disturbances in gonads of the studied fish species were positively correlated with the levels of pollution of water bodies: in the cleanest water body, Teterev River, the proportion of fish with gonads without considerable deviations was about 78%; in the Kiev Reservoir, 67%; in the water cooler, 51%; and in Lake Glubokoe, 45%. By the number and pattern of gonad anomalies, species specificity in their response to the radiation background was revealed. A smaller degree of damage of sexual cells and gonads in unisexual (triploid) populations of goldfish Carassius auratus reproducing gynogenetically, as compared to bisexual (diploid) populations, was detected. Among postemergency generations of the studied fish species, in all water bodies the number and degree of gonad disturbances were in F2–4, in Kiev Reservoir and Teterev River, this was most likely accounted for by the phenomenon of prolonged mutagenesis.

Reproduction of freckled goatfish Upeneus tragula (Mullidae) in the coastal zone of Vietnam

Features of reproduction are described in the tropical representative of the family Mullidae freckled goatfish Upeneus tragula from southern Central Vietnam (Nha Trang Bay) and North Vietnam (Ha Long Bay). Sex ratios of the fishes (females: males) in Nha Trang and Ha Long bays are 0.93: 1 and 1.2: 1, respectively. In both bays, the body length-body weight relationship is not substantially different between the females and males. In Nha Trang Bay, the females reach sexual maturity by 10.2 cm fork length (50% of individuals), and the fishes spawn over the entire year. In a part of the population (on average, 23.5% of fishes), the interruptions in spawning not associated with a certain season of the year are registered. In Ha Long Bay, a distinct spawning interruption is observed in all fishes during winter.

Transition to viviparity in the order Scorpaeniformes: Brief review

Among teleost percoid fishes (Percomorpha), the subordes Scorpaenoidei (Scorpaeniformes) and Zoarcoidei (Perciformes) are of particular interest due to the presence of intermediate stages between oviparity and viviparity in several species. We analyze the features of reproductive biology in the fishes of the suborder Scorpaenoidei, including morphology of the urogenital system, gametogenesis, gamete ultrastructure, and embryonic development. The new materials are represented for three tropical coral reef fish species with external insemination from the family Scorpaenidae (Scorpaenopsis possi, Sebastapistes cyanostigma, and Dendrochirus zebra). In particular, a hypertrophied urinary bladder used for storage of mature sperm for insemination of pelagic egg clutch is described in the males. Evolutionary transition to viviparity within the family Sebastidae is discussed. Alternative reproductive strategies are registered in viviparous fishes from the suborders Scorpaenoidei and Zoarcoidei. They are connected with the production of a large number of morphologically weakly developed larvae and a small number of individuals at the juvenile state, respectively.

The state of gonads of resident sockeye salmon Oncorhynchus nerka from the Tolmachev Reservoir

Morphology of gonads and structure of sex cells in females and males of the resident sockeye salmon Oncorhynchus nerka—kokanee—from Tolmachevskoe Reservoir are investigated. Anomalies in structure of sex cells and structure of oocytes are found. Partial or mass resorpbion of cells in the ovaries of males and testes of males is found, leading to sterility of gonads. The relationship between anomalies found in structure of the sex system of kokanee, changes in biological parameters of fish and the increase of the population abundance is discussed.