Proliferation of Oogonia and folliculogenesis in the viviparous teleost Ilyodon whitei (Goodeidae)

Oogonial proliferation in fishes is an essential reproductive strategy to generate new ovarian follicles and is the basis for unlimited oogenesis. The reproductive cycle in viviparous teleosts, besides oogenesis, involves development of embryos inside the ovary, that is, intraovarian gestation. Oogonia are located in the germinal epithelium of the ovary. The germinal epithelium is the surface of ovarian lamellae and, therefore, borders the ovarian lumen. However, activity and seasonality of the germinal epithelium have not been described in any viviparous teleost species regarding oogonial proliferation and folliculogenesis. The goal of this study is to identify the histological features of oogonial proliferation and folliculogenesis during the reproductive cycle of the viviparous goodeid Ilyodon whitei. Ovaries during nongestation and early and late gestation were analyzed. Oogonial proliferation and folliculogenesis in I. whitei, where intraovarian gestation follows the maturation and fertilization of oocytes, do not correspond to the late oogenesis, as was observed in oviparous species, but correspond to late gestation. This observation offers an example of ovarian physiology correlated with viviparous reproduction and provides elements for understanding the regulation of the initiation of processes that ultimately result in the origin of the next generation. These processes include oogonia proliferation and development of the next batch of germ cells into the complex process of intraovarian gestation. J. Morphol. 275:1004–1015, 2014. © 2014 Wiley Periodicals, Inc.     

Molecular phylogeny of the livebearing Goodeidae (Cyprinodontiformes)

The Goodeinae is a speciose group of viviparous freshwater fishes endemic to the Mesa Central of Mexico. The current taxonomy of the group is based on morphology associated with viviparity and several of the groupings are questionable. We sequenced part of the mitochondrial cytochrome c oxidase subunit I (COI) gene (627bp) and control region (approximately 430bp aligned) of representatives of 36 species (all genera) of goodeid fishes in order to establish phylogenetic relationships among the taxa. Findings support the monophyly of the Goodeidae, the sister-group relationship of the Empetrichthyinae and Goodeinae, and the relationship of Profundulus to the Goodeidae. All goodeine genera but Xenotoca were recovered as monophyletic. Many of the higher-level relationships within the group contradict the findings of previous studies based upon morphology. The rate of molecular change in COI (0.9% per Myr), calibrated with the fossil record and geological data, suggests an approximate age for the Goodeidae of 16.5Myr. The majority of divergence within the Goodeinae appears to have occurred during the Miocene, with subsequent cladogenesis in the Pliocene and Pleistocene. Most recent speciation appears allopatric. River piracy, particularly involving the Rio Ameca basin, has played a significant role in the diversification of the Goodeinae.     

Reproductive histology of Tomeurus gracilis Eigenmann, 1909 (Teleostei: Atherinomorpha: Poeciliidae) with comments on evolution of viviparity in atherinomorph fishes

Tomeurus gracilis is a species long considered pivotal in understanding the evolution of livebearing in atherinomorph fishes. Tomeurus gracilis is a zygoparous or embryoparous poeciliid: internal fertilization is followed by females laying fertilized eggs singly or retaining fertilized eggs until or near hatching. Tomeurus was hypothesized as the sister group of the viviparous poeciliids until it was proposed as a close relative of a derived viviparous poeciliid, Cnesterodon, hence nested among viviparous taxa rather than near the root of the tree. Here, we describe and compare reproductive morphological characters of the little‐known Tomeurus with those of representative atherinomorphs. In Tomeurus and Cnesterodon, sperm are packaged in naked sperm bundles, or spermatozeugmata, in a configuration considered here diagnostic of viviparous poeciliids. Testes are single and free sperm are stored in the ovary in both taxa in contrast to oviparous atherinomorphs in which testes are paired and sperm are not packaged and not stored in the ovary. Efferent ducts in Cnesterodon testes and other viviparous poeciliids have a PAS‐positive secretion demonstrating presence of a glycoprotein that inactivates sperm or prevents final sperm maturation. No PAS‐positive staining secretion was observed in Tomeurus or oviparous atherinomorphs. Tomeurus shares apomorphic reproductive characters, such as sperm bundle and testis morphology and a gonopodium, with viviparous poeciliids and plesiomorphic characters, such as a thick zona pellucida with filaments, with oviparous taxa. We do not postulate loss or reversal of viviparity in Tomeurus, and we corroborate its phylogenetic position as sister to the viviparous poeciliids. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

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.     

Energy consumption by embryos of a viviparous lizard, Eulamprus tympanum, during development

Energy consumption during development has been measured in many oviparous lizards, but not in viviparous lizards in utero. It has always been assumed that energy consumption by embryos of viviparous lizards during development is similar to that of oviparous species. Estimation of energy consumption of viviparous lizards in vivo are confounded by the possible influence of pregnancy on maternal metabolism. Here we separated maternal and embryonic metabolism in measurements of pregnant Eulamprus tympanum throughout pregnancy. Our data support the hypothesis that the energetic cost of development in viviparous lizards (19.8 kJ g⁻¹) is similar to that in oviparous lizards (mean 16.2 kJ g⁻¹), at least for a species with a simple placenta. An increase in maternal metabolism of 29% above that for non-pregnant E. tympanum goes to maintain pregnancy, and represents an important component of the reproductive effort in E. tympanum.     

Effects of endocrine disruptors on reproduction in viviparous teleosts with intraluminal gestation

Many water systems worldwide are affected by pollutants, including potential endocrine disruptors (EDs). Most studies on the effects of EDs on fish reproduction have focused on oviparous species. However, some important groups of fishes are not oviparous and there is scarce information about how EDs affect species with alternative reproductive modes. Goodeinae is a viviparous matrotrophic subfamily with intraluminal gestation (IG), where transfer of nutrients occurs and embryos develop inside the ovarian cavity. Goodeinae is endemic to the Mexican Central Plateau, an area affected by potential EDs, including 2,4-dichlorophenoxyacetic acid (2,4-D). This review synthesizes the available information about EDs in viviparous teleosts with IG and performs a case study on the effects of 2,4-D on gonadal structure of two Goodeinae species. We hypothesized that individuals exposed to 2,4-D might show altered gonadal structure. The available information included effects on gene expression, sexual differentiation, gametogenesis, secondary sexual characteristics, and sexual behavior. Knowledge gaps persisted on the effects of EDs on viviparous teleosts with IG. Holistic approaches are needed to understand the mechanisms underlying endocrine disruption effects. Field studies are needed to evaluate the consequences of EDs on wild populations. The case study revealed histological alterations in oocytes, spermatogonia, and sperm cysts in fishes exposed to 2,4-D. Ultrastructurally, gonads exhibited alterations in oocyte mitochondrial and nuclear membranes, and in spermatid mitochondria. The observed changes could be related to 2,4-D exposure, which may affect species reproduction in their natural environment. Matrotrophic viviparous teleosts with IG may serve as models to explore endocrine disruption.     

Ultrastructure and protein uptake of the embryonic trophotaeniae of four species of goodeid fishes (Teleostei: Atheriniformes)

Embryos of most species within the viviparous teleost family Goodeidae develop characteristics perianal processes that are considered to be derivatives of the embryonic hindgut. These processes, termed trophotaeniae, are covered with an epithelium that is continuous with the absorptive epithelium lining the hindgut. Gestation is intraovarian, and trophotaeniae mediate the uptake of maternally provided nutrients into the embryo from the ovarian fluid. Ultrastructural examination of the trophotaeniae of four goodeid species reveals substantial diversity in the organization of the epithelium within the family. The trophotaeniae of Alloophorus robustus, Zoogoneticus quitzeoensis, and Ilyodon furcidens have morphological features associated with the endocytosis of macromolecules and can be shown to endocytose the exogenous protein tracer horseradish peroxidase (HRP) rapidly. The trophotaenial epithelia of these species differ from one another with respect to other morphological features such as cell height, organization of the brush border, and the complexity of the intercellular spaces. The trophotaeniae of Goodea atripinnis lack an endocytotic apparatus and do not endocytose HRP. However, the overall organization of G. atripinnis trophotaenial cells suggests a function as a transporting epithelium. The cells have a dense brush border, numerous mitochondria, and many mitochondria that are enveloped by lamellar sheets of intracellular membrane. Post-fixation with osmium and potassium ferrocyanide reveals a marked difference in the complexity of the subepithelial connective tissue. Alloophorus robustus and Z. quitzeoensis exhibit an extremely electron-dense ground substance containing many acellular components. Goodea atripinnis exhibits an electron-lucid ground substance with few acellular components. © 1994 Wiley-Liss, Inc.     

Oogenesis: From Oogonia to Ovulation in the Flagfish,Jordanella floridae Goode and Bean, 1879 (Teleostei: Cyprinodontidae)

We provide histological details of the development of oocytes in the cyprinodontid flagfish, Jordanella floridae. There are six stages of oogenesis: Oogonial proliferation, chromatin nucleolus, primary growth (previtellogenesis [PG]), secondary growth (vitellogenesis), oocyte maturation and ovulation. The ovarian lamellae are lined by a germinal epithelium composed of epithelial cells and scattered oogonia. During primary growth, the development of cortical alveoli and oil droplets, are initiated simultaneously. During secondary growth, yolk globules coalesce into a fluid mass. The full‐grown oocyte contains a large globule of fluid yolk. The germinal vesicle is at the animal pole, and the cortical alveoli and oil droplets are located at the periphery. The disposition of oil droplets at the vegetal pole of the germinal vesicle during late secondary growth stage is a unique characteristic. The follicular cell layer is composed initially of a single layer of squamous cells during early PG which become columnar during early vitellogenesis. During primary and secondary growth stages, filaments develop among the follicular cells and also around the micropyle. The filaments are seen extending from the zona pellucida after ovulation. During ovulation, a space is evident between the oocyte and the zona pellucida. Asynchronous spawning activity is confirmed by the observation that, after ovulation, the ovarian lamellae contain follicles in both primary and secondary growth stages; in contrast, when the seasonal activity of oogenesis and spawning ends, after ovulation, the ovarian lamellae contain only follicles in the primary growth stage. J. Morphol. 277:1339–1354, 2016. © 2016 Wiley Periodicals, Inc.     

Reproductive mode may determine geographic distributions in Australian venomous snakes (Pseudechis,Elapidae)

Summary Why are viviparous squamate reptiles more common in cold climates, and oviparous ones in warmer areas? The usual explanation is that (1) oviparous squamates cannot reproduce successfully in cold areas because soil temperatures are too low for embryonic development; and (2) viviparous squamates experience lower survivorship or reproductive success than oviparous taxa in warmer areas. These hypotheses suggest that the boundaries of geographic distributions of congeneric oviparous and viviparous squamates should be predictable from data on thermal tolerances of embryos, and estimated temperatures of soils and gravid female reptiles throughout the potential geographic range of the taxon. In large venomous Australian snakes of the genus Pseudechis, distributional boundaries of oviparous and viviparous taxa can be accurately predicted from such data. This predictive ability, if substantiated by studies of other reproductively biomodal squamate taxa, would support the putative role of reproductive mode as a direct determinant of reptilian geographic distributions.     

Branchial placenta in the viviparous teleost Ilyodon whitei (Goodeidae)

Intraluminal gestation, as it occurs in viviparous goodeids, allows a wide diversity of embryo‐maternal metabolic exchanges. The branchial placenta occurs in embryos developing in intraluminal gestation when ovarian folds enter through the operculum, into the branchial chamber. The maternal ovarian folds may extend to the embryonic pharyngeal cavity. A branchial placenta has been observed in few viviparous teleosts, and there are not previous histological analyses. This study analysis the histological structure in the goodeid Ilyodon whitei. The moterno ovarian folds extend through the embryonic operculum and reach near the gills, occupying part of the branchial chamber. These folds extend also into the pharyngeal cavity. In some regions, the epithelia of the ovarian folds and embryo were in apposition, developing a placental structure in which, maternal and embryonic capillaries lie in close proximity. The maternal epithelium has desquamated cells which may enter through the branchial chamber to the pharyngeal cavity and the alimentary tract. The complex processes that occur in the ovaries of viviparous teleosts, and its diverse adaptations for viviparity, as the presence of branchial placenta, are relevant in the study of the evolution of vertebrate viviparity. J. Morphol. 275:1406–1417, 2014. © 2014 Wiley Periodicals, Inc.     

MITOCHONDRIAL DNA SEQUENCE-BASED PHYLOGENY AND THE EVOLUTION OF VIVIPARITY IN THE SCELOPORUS SCALARIS GROUP (REPTILIA,SQUAMATA)

The lizard genus Sceloporus contains both oviparous and viviparous species. The scalaris complex is the only monophyletic group within the genus that includes both reproductive modes, thus it is particularly well suited for studies of the evolution of viviparity. Approximately 874 nucleotides of mtDNA sequence data, collected from 38 specimens, comprising 25 populations of all five recognized species within the group, were used in a phylogenetic analysis of the origin of viviparity. Viviparity appears to have evolved twice in this group: once in S. goldmani, included in a clade formed by a northern group consisting of S. scalaris, S. chaneyi, and S. goldmani, and one more time in S. bicanthalis, included in the southern group formed by S. bicanthalis and S. aeneus. An oviparous population of S. bicanthalis nested within that viviparous clade, indicates that reversal from viviparity to oviparity may be possible. Degree of sequence divergence among several S. bicanthalis individuals pertaining to a population in which both parity modes occur, was no larger between oviparous and viviparous lizards than among viviparous lizards. This suggests that this population is a single species, and it may represent a transition from oviparity to viviparity or vice-versa.     

Polarized distribution of binding sites for concanavalin A and wheat-germ agglutinin in the zona pellucida of goodeid oocytes (teleostei)

Summary Zonae pellucidae of the viviparous goodeid teleosts Girardinichthys viviparus, Xenoophorus captivus, and Xenotoca eiseni were investigated ultrastructurally, and binding sites for ConA and WGA were localized on cross-sections using a colloidal gold technique. In late stages of development, the oocytes are surrounded by a three-zonated acellular matrix multiply perforated by pore canals allowing long microvilli of the oocyte to penetrate interstices of the follicle epithelium. Together, the surface of the microvilli and zona pellucida is coated by a thin layer of homogeneous slightly electron-dense material. In early oogenesis, the thin acellular layer is entirely packed with binding sites for WGA, whereas those for ConA occur only sparsely. Three-zonated zonae pellucidae amply contain both WGA and ConA receptors. The asymmetric labelling pattern obtained with both lectin protein gold preparations indicates a polarized organization of the different glycoconjugates. WGA receptors are concentrated within the outer region of the zona pellucida. Labelling with ConA-HRP-Au complexes produced heavy deposits of marker beads within the inner two thirds of the zona pellucida and weak labelling of the superficial coat. After prolonged digestion with neuraminidase, WGA binding sites were no longer detectable.Supported by the Deutsche Forschungsgemeinschaft (Schi 268/1-1)     

Description of different stages of oogenesis in Ophidion barbatum (Pisces,Ophidiidae)

Ophidion barbatum is an oviparous fish species, with external fertilization. In females, a single-lobed ovary is followed by a short oviduct that opens directly out through the genital opening. Ovarian development is asynchronous. In a mature ovary and during the breeding season, oocytes in various stages of development can be observed simultaneously. Six stages are described in the oogenesis from the oogonia to the mature egg, using different histological techniques and based on differences of staining, of size and on the nucleus and cytoplasm structure, as viewed through a light microscope. Three of them correspond to the previtellogenic phase and the other three to the vitellogenic phase. Atretic degeneration of eggs is also described.     

Comparative study on ovarian structures in scorpaenids: possible evolutional process of reproductive mode

The reproductive modes of the Scorpaenidae are extremely varied: oviparity, viviparity, and even spawning of internally fertilized eggs or embryos (zygoparity or embryoparity), as in Helicolenus, are known. The ovarian structure of this family is divided into two types by the arrangement of the stroma and the ovarian cavity. One type is the ovary in which the lamella-like stroma develops from the ovarian hilus located on the dorsal side and where the ovarian cavity is located on the ventral side of ovary, classified as “cystovarian type II-1” by Takano (1989). In the other type, the stroma in the ovary develops radially around the blood circulatory system that traverses the center of the ovary, and then the ovarian cavity surrounds all the ovary, classified as “cystovarian type II-3” by Takano (1989). In the present analysis, previous reports about ovarian structure and the relationship to the reproductive mode of scorpaenids were described, and the ovarian structure of eight genera of Scorpaenidae was examined. The ovary of cystovarian type II-1 is seen only in viviparous genera and is not seen in oviparous genera. However, the cystovarian type II-1 is a general structure in other families of Scorpaeniformes, and this structure could be considered a primitive type of ovary rather than that acquired by the process of evolution from oviparity to viviparity. The ovary of cystovarian type II-3 is seen in all six oviparous genera and the one zygoparous genus examined. The ovary of this type is not found in any other family of teleosts, so it could be a structure originally divided in Scorpaenidae. In the genera having the cystovarian type II-3 ovary, there is a common feature of spawning: a floating egg mass encompassed by the gelatinous material. We postulate that the evolution of reproductive mode in the scorpaenid fishes is as follows: Sebastes and Sebastiscus have a primitive ovary in which viviparity has developed, whereas the genera that spawn a floating egg mass evolved the ovarian structure from primitive type to cystovarian type II-3, and further zygoparity, such as in Helicolenus, evolved from them.     

Ovary cord structure and oogenesis in Hirudo medicinalis and Haemopis sanguisuga (Clitellata, Annelida): remarks on different ovaries organization in Hirudinea

In Hirudo medicinalis and Haemopis sanguisuga, two convoluted ovary cords are found within each ovary. Each ovary cord is a polarized structure composed of germ cells (oogonia, developing oocytes, nurse cells) and somatic cells (apical cell, follicular cells). One end of the ovary cord is club-shaped and comprises one huge apical cell, numerous oogonia, and small cysts (clusters) of interconnected germ cells. The main part of the cord contains fully developed cysts composed of numerous nurse cells connected via intercellular bridges with the cytophore, which in turn is connected by a cytoplasmic bridge with the growing oocyte. The opposite end of the cord degenerates. Cord integrity is ensured by flattened follicular cells enveloping the cord; moreover, inside the cord, some follicular cells (internal follicular cells) are distributed among germ cells. As oogenesis progresses, the growing oocytes gradually protrude into the ovary lumen; as a result, fully developed oocytes arrested in meiotic metaphase I float freely in the ovary lumen. This paper describes the successive stages of oogenesis of H. medicinalis in detail. Ovary organization in Hirudinea was classified within four different types: non-polarized ovary cords were found in glossiphoniids, egg follicles were described in piscicolids, ovarian bodies were found characteristic for erpobdellids, and polarized ovary cords in hirudiniforms. Ovaries with polarized structures equipped with apical cell (i.e. polarized ovary cords and ovarian bodies) (as found in arhynchobdellids) are considered as primary for Hirudinea while non-polarized ovary cords and the occurrence of egg follicles (rhynchobdellids) represent derived condition.     

The ovaries of aphids (Hemiptera,Sternorrhyncha, Aphidoidea): morphology and phylogenetic implications

The ovaries of aphids belonging to the families Eriosomatidae, Anoeciidae, Drepanosiphidae, Thelaxidae, Aphididae, and Lachnidae were examined at the ultrastructural level. The ovaries of these aphids are composed of several telotrophic ovarioles. The individual ovariole is differentiated into a terminal filament, tropharium, vitellarium, and pedicel (ovariolar stalk). Terminal filaments of all ovarioles join together into the suspensory ligament, which attaches the ovary to the lobe of the fat body. The tropharium houses individual trophocytes and early previtellogenic oocytes termed arrested oocytes. Trophocytes are connected with the central part of the tropharium, the trophic core, by means of broad cytoplasmic processes. One or more oocytes develop in the vitellarium. Oocytes are surrounded by a single layer of follicular cells, which do not diversify into distinct subpopulations. The general organization of the ovaries in oviparous females is similar to that of the ovaries in viviparous females, but there are significant differences in their functioning: (1) in viviparous females, all ovarioles develop, whereas in oviparous females, some of them degenerate; (2) the number of germ cells per ovariole is usually greater in females of the oviparous generation than in females of viviparous generations; (3) in oviparous females, oocytes in the vitellarium develop through three stages (previtellogenesis, vitellogenesis, and choriogenesis), whereas in viviparous females, the development of oocytes stops after previtellogenesis; and (4) in the oocyte cytoplasm of oviparous females, lipid droplets and yolk granules accumulate, whereas in viviparous females, oocytes accrue only lipid droplets. Our results indicate that a large number of germ cells per ovariole represent the ancestral state within aphids. This trait may be helpful in inferring the phylogeny of Aphidoidea.     

Intraspecific Phylogeography of Lacerta vivipara and the Evolution of Viviparity

The lacertid lizard Lacerta vivipara is one of the few squamate species with two reproductive modes. We present the intraspecific phylogeny obtained from neighbor-joining and maximum-parsimony analyses of the mtDNA cytochrome b sequences for 15 individuals from Slovenian oviparous populations, 34 individuals from western oviparous populations of southern France and northern Spain, 92 specimens from European and Russian viviparous populations, and 3 specimens of the viviparous subspecies L. v. pannonica. The phylogeny indicates that the evolutionary transition from oviparity to viviparity probably occurred once in L. vivipara. The western oviparous group from Spain and southern France is phylogenetically most closely related to the viviparous clade. However, the biarmed W chromosome characterizing the western viviparous populations is an apomorphic character, whereas the uniarmed W chromosome, existing both in the western oviparous populations and in the geographically distant eastern viviparous populations, is a plesiomorphic character. This suggests an eastern origin of viviparity. Various estimates suggest that the oviparous and viviparous clades of L. vivipara split during the Pleistocene. Our results are discussed in the framework of general evolutionary models: the concept of an oviparity–viviparity continuum in squamates, the cold climate model of selection for viviparity in squamates, and the contraction–expansion of ranges in the Pleistocene resulting in allopatric differentiation.     

Description of oviparous females and alate males of Macrosiphum dzhibladzeae Barjadze, 2010 (Hemiptera: Aphididae) from Georgia

The hitherto unknown oviparous females and alate males of M. dzhibladzeae Barjadze, 2010, living on Euphorbia macroceras Fish. & Mey. and Euphorbia sp. (Euphorbiaceae), are described from resort Bakhmaro (Chokhatauri district, Guria region, Western Georgia). The life cycle of this species is established. Apterous and alate viviparous females and oviparous females of M. dzhibladzeae are compared to the same morphs of morphologically similar M. meixneri Börner, 1950. A key is provided to Euphorbia-feeding Macrosiphum spp. based on males.     

Reproductive biology of the viviparous scorpion,Liocheles australasiae (Fabricius) (Arachnida,Scorpiones, Ischnuridae) III. Structural types and functional phases of the adult ovary

Summary

Five structural types of the adult ovary were distinguished in a parthenogenetic viviparous scorpion Liocheles australasiae based on the presence or absence of swollen ovarian diverticula (SD) containing embryos and/or empty ones (ED) as remnants of past pregnancies. These structural types seem to correspond to the following ovarian functional phases: the ovary (1) with SD and without ED corresponds to the first pregnancy; (2) without SD and with ED to after the first parturition; (3) with SD and ED to the second pregnancy; (4) without SD and with old and new ED to after the second parturition; and (5) with SD and old and new ED to the third pregnancy. Such correspondence indicates that a female can repeat pregnancies at least three times. Some possible cases in which the present structural types correspond to other functional phases were also discussed.     

The occurrence of spermatozoa in the ovary of the gynogenetic viviparous teleost Poecilia formosa (POECILIIDAE)

The reproductive mode of the female viviparous teleost Poecilia formosa (Poeciliidae) represents the phenomenon known as gynogenesis; that is, parthenogenetic development is initiated by spermatozoa which are needed for physiological activation of the egg and the initiation of gestation, but spermatozoa are prevented from contributing to the genome of the embryo. For the reason that no previous histological analyses of the ovary of this species during the reproductive cycle has been published the present study has been conducted. This study examined the histology of the ovary of P. formosa during nongestation and gestation phases and identified the presence of spermatozoa inside the ovary. Spermatozoa were observed in folds of the ovarian epithelium of P. formosa during both the nongestation and gestation phases. Sperm storage as documented in this study is a very important trait for the gynogenetic viviparous fish P. formosa contributing to the understanding of this species reproduction. J. Morphol. 277:341–350, 2016. © 2015 Wiley Periodicals, Inc.