Species Of Viviparous Fishes Research Articles

Differential effects of parental and developmental temperatures on larval thermal adaptation in oviparous and viviparous model fish species

Phenotypic plasticity has been identified as a major mechanism of response to changing temperatures. Parental effects are potentially important drivers of ecological and evolutionary dynamics, while developmental plasticity also plays a key role in generating phenotypic variation. However, little is known of the interaction between parental effects and developmental plasticity on the thermal phenotypes of fishes with different reproductive modes (i.e. oviparous vs. viviparous). To understand the contributions of inter- and intra-generational plasticity of thermal phenotypes (preferred temperature, avoidance temperatures, critical thermal thresholds) in fishes with different reproductive modes, we carried out a factorial experiment in which both breeding parents and offspring were exposed to lower (22 °C) or higher (28 °C) temperatures, using zebrafish (Danio rerio) and guppies (Poecilia reticulata) as representative oviparous and viviparous species. We found that offspring thermal preference and avoidance of both species were significantly influenced by parental effects and developmental plasticity, with higher thermal preference and avoidance consistent with higher background (parental) temperature treatments. However, parental effects were only found to impose significant effect on the thermal tolerances of guppies. The findings suggest that phenotypic plasticity, both within and across generations, may be an important mechanism to adapt to rapid climate changes, and that future temperature fluctuations may impose more profound effects on viviparous fish species in general.

Gonad Ontogeny and Sex Differentiation in a Poeciliid, Gambusia holbrooki: Transition from a Bi- to a Mono-Lobed Organ.

Despite their uniqueness, the ontogeny and differentiation of the single-lobed gonads in the poeciliids are very poorly understood. To address this, we employed both cellular and molecular approaches to systematically map the development of the testes and ovary in Gambusia holbrooki from pre-parturition to adulthood, encompassing well over 19 developmental stages. The results show that putative gonads form prior to the completion of somitogenesis in this species, a comparatively early occurrence among teleosts. Remarkably, the species recapitulates the typical bi-lobed origin of the gonads during early development that later undergoes steric metamorphosis to form a single-lobed organ. Thereafter, the germ cells undergo mitotic proliferation in a sex-dependent manner before the acquisition of the sexual phenotype. The differentiation of the ovary preceded that of the testes, which occurred before parturition, where the genetic females developed meiotic primary oocytes stage I, indicating ovarian differentiation. However, genetic males showed gonial stem cells in nests with slow mitotic proliferation at the same developmental stage. Indeed, the first signs of male differentiation were obvious only post-parturition. The expression pattern of the gonadosoma markers foxl2, cyp19a1a, amh and dmrt1 in pre- and post-natal developmental stages were consistent with morphological changes in early gonad; they were activated during embryogenesis, followed by the onset of gonad formation, and a sex-dimorphic expression pattern concurrent with sex differentiation of the ovary (foxl2, cyp19a1a) and testes (amh and dmrt1). In conclusion, this study documents for the first time the underlying events of gonad formation in G. holbrooki and shows that this occurs relatively earlier than those previously described for ovi- and viviparous fish species, which may contribute to its reproductive and invasive prowess.

Maternal nutrients and 15N Leucine tracing in Sebastes schlegelii

Sebastes schlegelii is a commercially important fishery resource that is also a representative viviparous fish species in the Northeast Asian Sea. The mode of nutritional supply of embryos fertilized and developed in vivo is not clear. To screen biomarkers for nutrient transfer between mother and embryo, we studied the composition of and changes in maternal plasma at different developmental stages. The results showed that the plasma of S. schlegelii was rich in nutrients, including 16 hydrolysed amino acids, 20 fatty acids, glucose and fructose. The contents of amino acids in the plasma reached 3.44-4.58 g/100 g, which is approximately 3-5 times that of fatty acids and 44-155 times that of sugar. Thirteen amino acids, 15 fatty acids and glucose showed an increasing trend in the early stage of embryonic development and a decreasing trend in the later stage. The contents of leucine, as an essential amino acid in early development, changed significantly in maternal blood and was therefore selected as a biomarker. The results of isotope labelling showed that 15N leucine was not detected in the eggs, gastrula embryos or organogenesis embryos, but a high abundance of 14N leucine was detected in the eggs and embryos of the control and experimental groups, indicating that leucine, an essential amino acid for aquatic animals, plays an important role in gamete and embryo development. An abundance in 15N-labelled leucine was detected in the embryonic blood and ovarian villi but not in the embryos, which indicates that the ample free naturally abundant leucine in maternal blood during the middle and late developmental stages of the eggs and embryos was not absorbed or utilized. These results showed that eggs and embryos had certain autonomy and selectivity when absorbing nutrients and gave priority to the active transport of certain complex macromolecular nutrients that could meet their needs for a variety of nutrients at the same time.

Insemination, intrafollicular fertilization and development of the fertilization plug during gestation in Heterandria formosa (Poeciliidae).

The viviparous teleost Heterandria formosa is a remarkable species for its reproductive characters including: (a) the smallest oocyte in viviparous fish species; (b) a high level of matrotrophy with a complex placenta; and (c) the highest level of superfetation. Superfetation involves (d) the continuous development of oocytes and fertilization at the same time with embryos in gestation. The sequential fertilization of oocytes requires (e) storage of spermatozoa in the ovary. Among these characteristics, fertilization is of fundamental interest, specifically the intrafollicular fertilization of poeciliids, species that do not present micropyle, and the consequent formation of the fertilization plug, a structure developed at the periphery of the follicle where the entrance of spermatozoa occurs. Both processes intrafollicular fertilization and formation of the fertilization plug have been rarely described. There is only one study illustrating, the fertilization plug of H. formosa with a drawing. In the context of reproductive aspects of H. formosa, the goal of this study is to describe the morphology of the ovary during insemination, intrafollicular fertilization and development of the fertilization plug. After insemination, spermatozoa enter the ovary and occupy folds of the lamella near follicles of all stages of oogenesis, the delle, where the germinal epithelium establishes contact with the follicular epithelium. The results of the present study provide evidence that both epithelia open at the distal end of the delle, this morphological change allow that the spermatozoa to make contact with the zona pellucida of the oocyte. After fertilization, the delle becomes blocked by proliferation of cells of the germinal epithelium, to form the fertilization plug that persists throughout gestation. Abundant reticular fibers and blood vessels are seen around the fertilization plug. Persistence of the fertilization plug suggests that it could be the site where the juvenile will gain entrance to the ovarian lumen during birth.

Accumulation of cells expressing macrophage colony-stimulating factor receptor gene in the ovary of a pregnant viviparous fish, Neoditrema ransonnetii (Perciformes, Embiotocidae).

Macrophage colony-stimulating factor receptor (M-CSFR), a member of the group of type III protein tyrosine kinase receptors, is expressed primarily by monocyte/macrophage lineage cells. In order to describe the distribution of macrophages at the maternal-fetal interface in Neoditrema ransonnetii, a viviparous fish species, M-CSFR cDNA was sequenced. Two sequences were obtained: NrM-CSFR1 (4381 bp, encoding 980 amino acids), and NrM-CSFR2 (3573 bp, encoding 1016 amino acids). Both the genes were expressed in the ovary of pregnant females. In situ hybridization revealed that a number of cells that were positive for NrM-CSFR1 and/or NrM-CSFR2 populated the ovigerous lamellae of the ovary during pregnancy. Following parturition, M-CSFR-positive cells disappeared from the subepithelial region of ovigerous lamellae, and were localized in perivascular tissues. These results suggest the role of M-CSFR-positive cells, which appear to be macrophages, in N. ransonnetii during pregnancy.

Have superfetation and matrotrophy facilitated the evolution of larger offspring in poeciliid fishes?

Superfetation is the ability of females to simultaneously carry multiple broods of embryos, with each brood at a different developmental stage. Matrotrophy is the post-fertilization maternal provisioning of nutrients to developing embryos throughout gestation. Several studies have demonstrated that, in viviparous fishes, superfetation and matrotrophy have evolved in a correlated way, such that species capable of bearing several simultaneous broods also exhibit advanced degrees of post-fertilization provisioning. The adaptive value of the concurrent presence of both reproductive modes may be associated with the production of larger newborns, which in turn may result in enhanced offspring fitness. In this study, we tested two hypotheses: (1) species with superfetation and moderate or extensive matrotrophy give birth to larger offspring compared to species without superfetation or matrotrophy; (2) species with higher degrees of superfetation and matrotrophy (i.e. more simultaneous broods and increased amounts of post-fertilization provisioning) give birth to larger offspring compared to species with relatively low degrees of superfetation and matrotrophy (i.e. fewer simultaneous broods and lesser amounts of post-fertilization provisioning). Using different phylogenetic comparative methods and data on 44 species of viviparous fishes of the family Poeciliidae, we found a lack of association between offspring size and the combination of superfetation and matrotrophy. Therefore, the concurrent presence of superfetation and moderate or extensive matrotrophy has not facilitated the evolution of larger offspring. In fact, these traits have evolved differently. Superfetation and matrotrophy have accumulated gradual changes that largely can be explained by Brownian motion, whereas offspring size has evolved fluidly, experiencing changes that likely resulted from selective responses to the local conditions.

Spatial and temporal variation in superfoetation and related life history traits of two viviparous fishes: Poeciliopsis gracilis and P. infans.

Superfoetation is the ability of females to simultaneously bear multiple broods of embryos at different developmental stages. Most studies on the phylogenetic distribution of superfoetation and on the factors that potentially promote superfoetation ignore variation within species. Here, we studied 11 populations of two species of viviparous fishes of the family Poeciliidae (Poeciliopsis gracilis and Poeciliopsis infans) and document wide variation in superfoetation and in three related life history traits: brood size, individual embryo mass and total reproductive allotment. We found significant differences in the average number of simultaneous broods among populations of P. gracilis but not among populations of P. infans. In addition, we found even greater variation between months within populations for both species, although no specific pattern of temporal variation was evident. Instead of the expected consistency of seasonal differences in superfoetation across populations, we found that large variation among months within seasons and the amount and direction of this monthly variation differed widely between populations. Our results emphasize the importance of including intraspecific variation in superfoetation and other life history traits in studies that aimed at finding general explanations of life history trait evolution.

Reproductive Impairment of a Viviparous Fish Species Inhabiting a Freshwater System with Anthropogenic Impact

The potential threat to animal reproduction by contaminated freshwater systems posed the necessity to identify and develop bioindicators and biomarkers to be used for screening and evaluation of the effects in organisms. The main goal of this work was to determine, through histological analyses and changes in gonopodium morphology, whether a freshwater system polluted by anthropogenic activities-sewage, agricultural, and industrial-could cause alterations at the organ level. We also propose the live-bearing fish, Jenynsia multidentata, as a species suitable to study the effects of contaminated aquatic environments. We compared male fish sampled at two different stations in Suquía River basin (Córdoba, Argentina), both differing in degree of pollution, through liver and testis histology and gonopodial morphometric parameters. The water quality, based on the physicochemical characteristics of the studied stations, varied markedly with a decrease in water quality at the downstream site (station 2). At the highest polluted area, detrimental effects on liver and testis were evidenced on histological analysis. Male individuals from station 2 also presented noticeable structural changes of the anal fin, such as a straight gonopodium and abnormal tip area. The present results demonstrate that a freshwater system polluted by the impacts of anthropogenic activities has detrimental effects to J. multidentata. The alterations registered in individuals from the polluted station indicate an impairment of male reproductive performance and imply a risk for other live-bearing species as well as the entire biodiversity. We consider J. multidentata a sentinel species that is useful to evaluate the potential risk present in the studied basin not only to itself but to other species as well.

Endohelminth parasites of the freshwater fish Zoogoneticus purhepechus (Cyprinodontiformes: Goodeidae) from two springs in the Lower Lerma River, Mexico

In order to establish the helminthological record of the viviparous fish species Zoogoneticus purhepechus, 72 individuals were collected from 2 localities, La Luz spring (n= 45) and Los Negritos spring (n= 27), both in the lower Lerma River, in Michoacan state, Mexico. Twelve helminth taxa were recovered, 5 adults (the digeneans Margotrema bravoae and Phyllodistomum sp., the cestode Bothriocephalus acheilognathi, the nematode Rhabdochona lichtenfelsi and the acanthocephalan Pomphorhynchus cf. bulbocolli), and 7 larvae (the metacercariae of Clinostomum complanatum, the cysticercoid of Cyclophyllidea, the nematodes Rhabdochona sp., Eustrongylides sp., Contracaecum sp. and Spiroxys sp., and the cysthacanth of Polymorphus brevis). Of these, R. lichtenfelsi was the most prevalent and abundant species at La Luz spring with 15.6% and 0.33 individuals per analyzed host. The remaining species were relatively more rare and infrequent. The helminth parasite community of Z. purhepechus at Los Negritos spring was remarkably poor and abundance was very low. The omnivorous feeding habits, the position of the host species in the food web, and the environmental characteristics of each locality are suggested as the main factors determining the helminth parasite communities in this freshwater fish.

Culture of embryos from viviparous fishes of the genusXiphophorus

A procedure is described for the in vitro culture ofXiphophorus embryos. The method permits the raising of embryos of viviparous fish species from an early stage of embryo-genesis (first somite formation) beyond the stage of birth and into fertile adults.

Induction of hepatic tumors with 7,12-dimethylbenz[ a]anthracene in two species of viviparous fishes (genus Poeciliopsis)

Liver neoplasms were induced in two species of viviparous fishes, Poeciliopsis lucida and P. monacha, by repeated short-term exposures to an aqueous suspension of 5 ppm 7,12-dimethylbenz[ a]anthracene (DMBA). Predominantly hepatocellular neoplasms developed in 47 out of 106 fish surviving the period allowed for tumor development, 6–9 months after initial exposure to DMBA. The use of short-term exposure periods of 6 hr in young fish and up to 20 hr in adults reduced stress and mortalities caused by the toxicity of DMBA at 5 ppm. A lower concentration of DMBA, 0.25 ppm, failed to induce tumors in any of the surviving 230 of 295 young fish administered repeated 20-hr exposures. This study shows for the first time that DMBA is carcinogenic to fish.

REPRODUCTIVE ADAPTATIONS AMONG VIVIPAROUS FISHES (CYPRINODONTIFORMES: POECILIIDAE).

Adaptations for placing a maximum number of mature offspring in the next generation fall between the two adaptive extremes of having either high reproductive rates and low survival rates or low reproductive rates and high survival rates. Among the fishes, both extremes have been realized; for example, the ling, Molva molva may produce 20-30 X 106 eggs at a single spawning (Blaxter, 1969), whereas some species of viviparous fishes have only one to four well-developed young at a time. Among the variable reproductive adaptations in teleosts, a remarkable array is found within a single family of viviparous fishes, the Poeciliidae. All but one of the 150 species of poeciliids known (Rosen and Bailey, 1963; Bussing, 1963, 1966; Hubbs and Peden, 1969; Miller, 1975; Miller and Minckley, 1970; Rivas, 1969; Rivas and Fink, 1970; Rosen and Kallman, 1969) are viviparous. Brood sizes within the family range from a few to 315 young at a time (Krumholz, 1948). Production of small numbers of young which are born in an advanced state of development clearly places poeciliids at one end of the array of reproductive adaptations. Although poeciliids seemingly have sacrificed quantity for quality, they have not done so to the same degree nor by the same mechanism; thus a fairly wide range of productivity levels persists within the family. Once internal fertilization evolved, various modifications in the reproductive system were possible. For example, adjust-