Cyprinodont Fish Research Articles

Diet of the killifish Rivulus marmoratus collected from land crab burrows, with further ecological notes

One-hundred eleven specimens of the cyprinodont fish Rivulus marmoratus were trapped from burrows of the great land crab Cardisoma guanhumi in east central Florida and the entire alimentary tract removed for analysis of food items. Three categories of burrows (inactive, active and sealed) were sampled to examine possible relationships between burrow type and presence of R. marmoratus. Forty percent of the guts examined contained no food items, while the remaining 60% contained items of both terrestrial and aquatic origin. Capture rates among burrow categories did not vary significantly, and most collections consisted of 1 or 2 individuals per burrow. Mean standard length of fish within a burrow declined when more than 3 specimens were captured from a burrow. Supplemental observations on reproductive status and burrow water temperature are noted.

The establishment of the North-American mosquito fish,Gambasia holbrooki, in Syrian inland waters)

Abstract The North-American mosquito fish, Gambusia holbrooki (Girard, 1859), came to Syria in 1929 but only recently spread over large parts of the country. Between 1977 and 1979 Gambusia was studied in various water bodies throughout Syria. The conditions For its successful establishment and its effect on populations of the indigenous cyprinodont fish Aphanius mento (Heckel, 1843) were surveyed. Out of 31 localities where Gambusia and/or Aphanius occurred 17 were inhabited by both species, 11 only by Aphanius and three only by Gambusia. A comparison of these localities indicated that Gambusia is better adapted to high salinity and polluted water whereas Aphanius tolerates stronger currents. Possible negative effects of Gambusia on the indigenous aquatic fauna of Syria are briefly discussed.

The predators of insects

Abstract. 1. Insect–insectivore trophic relations were reviewed using presence–absence data from sixty‐one invertebrate‐dominated food webs and fifteen food webs from Briand's (1983) original forty web collection. From counts of prey links in higher taxa (orders, classes, phyla), six phyla and thirteen classes of non‐insect insectivores and fourteen orders of insect predators and prey were found.2. Detritus‐based habitats (phytotelmata, felled logs, carcasses, dungpads) harboured fewer orders of insects, that interact with other insects, than webs from grazer‐based (host plants, some galls) and mixed‐based systems (aquatic webs). Consumer–resource networks of higher insect taxa in these webs shared several features found in some species‐level biological networks: the trend was towards few pairs of strong asymmetrical links, several weak links and many null interactions.3. From counts of insect predator–insect prey links, hymenopterans as terrestrial predators and parasitoids interacted with the most number of higher insect taxa. Hymenopterans were also linked as prey more often than other terrestrial insects. In freshwater habitats, plecopterans were linked as predators more often than other aquatic taxa, whereas dipterans were listed as prey more often than other insects.4. Dipterans were linked in the diets of non‐insect insectivores from seven of eight common taxonomic classes. Arachnids were identified as insect predators by food web researchers in the largest number of webs, followed by passerine birds and cyprinodont fishes. From analysis of prey links at the ordinal level, predaceous insects were less polyphagous than other predators (other ectotherms and endotherms).5. Analysis of chain lengths, as expected, showed that insect prey occupied mostly lowermost trophic levels, non‐insect insectivores were found mostly at uppermost trophic levels, and predaceous insects were found mostly at intermediate trophic levels across most habitats.6. This analysis offers evidence that insects are not just occupying intermediate trophic levels in some communities. Indeed, some taxa feed at the upper ends of long food chains, for example eupelmids in galls, staphylinids in carcasses, and perlid plecopterans in streams.

Cytogenet Genome Res of bisexual/unisexual species of <i>Poecilia</i>

Three populations of the North American cyprinodont fish Poecilia latipinna, considered to be one of the progenitor species of the gynogenetic unisexual P. formosa, were analyzed by C-banding and Ag-staining. C-bands were found to be polymorphic, and Ag-staining showed a high degree of variability in both the number and location of nucleolus organizer regions. The C-banding and Ag-staining patterns allow, to a certain extent, to distinguish individual specimens from each of these populations. Females of the three populations were found to have a heteromorphic chromosome pair, which was frequently identifiable with Giemsa staining and always after C-banding. This pair could be interpreted as sex chromosomes of the ZW/ZZ type.

The ultrastructure of prolactin cells in the annual cyprinodont Cynolebias whitei during its life cycle. A morphometric study in freshwater- and saltwater-reared fish.

Prolactin (PRL) cells were studied electron-microscopically and morphometrically in the annual cyprinodont fish, Cynolebias whitei during its life cycle. In prehatching larvae, PRL cells possessed small secretory granules, giant mitochondria and a well-developed Golgi apparatus. During hatching, no changes were observed in the volume density of the secretory granules, indicating that no increased release of PRL occurs at hatching. A significant change in the composition of PRL cells, i.e., the volume densities per cytoplasm volume of the different organelles, occurred between one day and one week of age. Thereafter, only minor differences were observed between age groups, indicating that no major changes occur in PRL cell activity during the lifespan of C. whitei. However, the volume density per cell volume of the nucleus decreased steadily with age during the lifespan. A comparison of the PRL cells in young and adult fish reared in fresh water (FW) with siblings reared from hatching in diluted sea water (1/3 SW) did not reveal any differences with respect to the volume densities of the organelles, including the secretory granules. However, significant differences were observed with respect to the diameter, electron-dense content and affinity to anti-PRL serum of the secretory granules. These differences indicate that, despite the similar volumetric composition of the PRL cells, their secretory granules contain a substantially higher concentration of PRL in FW-reared fish than in 1/3 SW-reared fish.

Allometric relations of total volumes of prolactin cells and corticotropic cells to body length in the annual cyprinodont Cynolebias whitei: effects of environmental salinity, stress and ageing

An analysis of the allometric relations of the total volumes occupied by prolactin (PRL) and corticotropic (ACTH) cells (PRL volume and ACTH volume, respectively) to body length and a study of the immunocytochemical staining intensity of PRL and ACTH cells were used to determine the differences in activity of PRL and ACTH cells in freshwater-reared and in saltwater-reared Cynolebias whitei during the entire lifespan of this annual cyprinodont fish. An inflection in the allometric relation of PRL volume to body length was observed in fish of one-week old. The relatively large PRL volume in younger fish may be related to PRL cell activity before hatching. No inflections were observed in the allometric relations of PRL volume and ACTH volume to body length at the onset of maturation and the onset of ageing, indicating that the increased pituitary growth in maturing and ageing C. whitei is not the result of changes in PRL or ACTH cells. The slope of the allometric relation of PRL volume to body length in freshwater-reared fish was significantly steeper than the slope in saltwater-reared fish. The PRL volume in adult freshwater-reared fish was eight times larger than that in saltwater-reared fish of the same length. The intensity of immunocytochemical staining of saltwater PRL cells was significantly reduced. These volumetric and staining differences correspond to the low functional demand put upon PRL cells in saltwater-adapted fish. In contrast, the slope of the allometric relation of ACTH volume to body length and the intensity of immunocytochemical staining of ACTH cells were similar in freshwater-reared and in saltwater-reared fish.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the light-dark cycle and scheduled feeding on behavioral and reproductive rhythms of the cyprinodont fish, Medaka, Oryzias latipes.

Medaka were maintained on a 16:8 light-dark cycle and fed once daily on one of 5 different feeding schedules. The daily rhythm of agonistic behavior rapidly entrained to the scheduled feeding time and maintained this entrainment during a 3-day starvation period. In contrast the daily rhythms of egg laying and courtship stayed entrained to the L:D cycle regardless of the feeding schedule. Thus, temporal integration of this fish with its daily environment can involve multistimuli which concurrently and differentially entrain externally expressed circadian systems.

Meristic variation in a clone of the cyprinodont fish Rivulus marmoratus related to temperature history of the parents and of the embryos

Parents from one clone of the self-fertilizing cyprinodont fish Rivulus marmoratus were held at 25 or 30 °C, and their offspring were subjected to either a sustained temperature of 25 or 30 °C or to a temperature break (abrupt transfer in either direction between 25 and 30 °C) at various developmental stages. Effects of parental temperature before fertilization on meristic counts of offspring were determined both by comparing offspring produced either soon or long after parents had been transferred to a new temperature, and also by examining meristic responses of developing embryos to temperature breaks. Both line of evidence indicate that a parental temperature of 30 °C produces fewer vertebrae (0.31), pectoral rays (0.54), and caudal rays (1.11) than does one of 25 °C, in offspring reared under comparable temperature regimes. Neither line provides clear evidence of an effect of parental temperature on number of anal or dorsal rays in offspring. Responses of all five meristic series to temperature breaks in either direction were extralimitary (beyond the counts produced by sustained incubation at either temperature) and were satisfactorily fitted by an "atroposic" model described previously. Embryos transferred to fresh water during development tended to have higher meristic counts than those with sustained rearing in brackish water, but counts among embryos transferred to fresh water at different developmental stages differed significantly only for caudal rays. Only dorsal ray numbers differed significantly among embryos retained within parents for different times after fertilization. Previous studies claiming uniquely high thermolability of vertebral number in R. marmoratus are re-evaluated; thermolability of vertebral number in R. marmoratus is concluded to be within the range reported for other species.

Influence of reproductive history of parents on meristic variation in offspring in the cyprinodont fish Rivulus marmoratus

Parent fish from one clone of the self-fertilizing cyprinodont fish Rivulus marmoratus were held under constant conditions, and their offspring were examined for meristic variation associated with their position in the oviposition sequence of parents. In all meristic series counted (vertebrae, and anal, dorsal, pectoral, and caudal fin rays) those offspring produced soon after their parents had begun to lay eggs tended to have fewer parts than did those produced longer after the onset of oviposition. Most meristic differences were due to the low counts produced in embryos laid within 8 days of first oviposition; counts differed little among embryos laid at averages of 22, 86, and 158 days after first oviposition. Differences were most significant for dorsal and anal rays and not significant for caudal rays.

Fish‐flamingo‐plankton interactions in the Peruvian Andes1

The zooplankton and flamingo populations of 20 high elevation (3,700–4,700 m) lakes in the Andes of southern Peru were assessed on one to three occasions each. Some of these lakes have cyprinodont fish (Orestias spp.), others do not. Lakes with fish usually have a sparse zooplankton dominated by cyclopoid copepods and chydorid cladocerans; the others tend to have an abundant zooplankton dominated by calanoid copepods and daphnids or by Artemia. Chilean flamingos (Phoenicopterus chilensis) are usually absent or scarce on lakes with fish and present in large numbers where fish are absent. We suggest that the distribution of this flamingo in the Central Andes, and in South America generally, is determined primarily by the distribution of fish, with which it competes for invertebrate prey. The patterns above are complicated by the impact on Orestias populations of man, of fish‐eating birds, and of introduced, non‐native fish (Salmo gairdneri, Basilichthys bonariensis).

Genetic divergence in wild populations of Medaka, Oryzias latipes (Pisces: Oryziatidae) from Japan and China

Allozyme studies of the cyprinodont fish Oryzias latipes have revealed that the wild populations of this species have differentiated regionally, and that Japanese wild populations are composed of two distinct groups, the Northern Population and the Southern Population. In order to elucidate the genetic relationship and the origin of the two major populations, allozymic characters of the specimens from 21 localities in Japan and China were compared. Although Chinese populations could be distinguished from Japanese ones, they were more closely related to the Southern Population, and showed few allozymic traits of the Northern Population. It is likely that the latter is a relic population which has survived the glacial period along the western coast of north-eastern Japan.

Premiére decouverte d'<i>Aphanius crassicaudus</i> (Agassiz) (Poisson teleosteen . Cyprinodontidae) dans le Messinien post-evaporitique d'Andalousie

The ocurrence of Aphanius crassicaudus (AGASSIZ), a Cyprinodont fish, already known in the Messinian of Italy and Crete, is, for the first time, mentioned in Andalusia, in the post-evaporitic Messini an sediments, near Sorbas (Province of Almeria). The palaoecological significance of these Fishes is examined.

Species-specific expression of parvalbumins in the genus Oryzias and its related species

1. 1. Several species-specific proteins were identified by polyacrylamide gel electrophoresis of skeletal muscle extracts from five species of Oryzias. 2. 2. The diffuse appearance, rapid anodal mobility, and low mol. wt suggested that these proteins belong to calcium-binding protein or parvalbumin class. 3. 3. Immunochemical studies indicated that five components in three distinct zones had common antigenic property in part and could be divided into two types. 4. 4. The application of parvalbumins to systematic studies and the evolution of this class of proteins of cyprinodont fishes were discussed.

Environmental influences on prolactin cell development in the cyprinodont fish, Cynolebias whitei.

A combined immunocytochemical and morphometric study on the development of the prolactin (PRL) cells of the annual cyprinodont Cynolebias whitei, transferred as newly hatched larvae to water with different salinities and/or Ca2+-concentrations, was carried out. The percentage of the pituitary volume occupied by PRL cells and the affinity of PRL cells for immunocytochemical staining were used as criteria for their activity. Exposure of the larvae for one day to salt water (260 mOsm/kg) led to a significant reduction in the pituitary volume occupied by PRL cells, indicating an osmoregulatory function of PRL shortly after hatching. In fish reared in diluted artificial seawater (70 and 260 mOsm/kg) or Na+-enriched fresh water the development of PRL cells was significantly retarded, but such an effect was not observed in fish placed in Ca2+-enriched fresh water. These experiments show that in C. whitei the development and activity of PRL cells are influenced by changes in environmental osmolarity and not by changes in ambient Ca2+-concentration.

An early stage of ZW/ZZ sex chromosome differentiation in Poecilia sphenops var. melanistica (Poeciliidae, Cyprinodontiformes)

The mitotic and meiotic chromosomes of the American cyprinodont fish Poecilia sphenops var. melanistica were analysed. All 46 chromosomes are telocentric. By specific staining of the constitutive heterochromatin with C-banding and various AT-specific fluorochromes, the homomorphic chromosome pair 1 could be identified as sex chromosomes of the ZW/ZZ type. All female animals exhibit a W chromosome with a large region of telomeric heterochromatin that is not present in the Z chromosome. These sex chromosomes cannot be distinguished by conventional staining; they represent the first demonstration of sex chromosomes in fishes in an early stage of morphological differentiation. The W heterochromatin and the telomeric heterochromatin in the two autosomes 18 show a very bright fluorescence when stained with AT-specific fluorochromes. This allows the direct identification of the chromosomal sex by examining the interphase nuclei: females exhibit three, males only two brightly fluorescent heterochromatic chromocenters in their nuclei. The significance of these ZW/ ZZ sex chromosomes and their specific DNA sequences, the dose compensation of the Z-linked genes, and the experimental possibilities using sex-reversed “ZW males” are discussed.

Immunoreactive prolactin in the pituitary gland of cyprinodont fish at the time of hatching.

In the developing pituitary gland of embryos of the annual fish Cynolebias whitei and the medaka, Oryzias latipes, prolactin cells have been identified before hatching by means of a light-microscopic immunocytochemical method with antiserum against ovine prolactin. At the time of hatching, changes in the intensity of the immunoperoxidase staining occur. Histological staining by Cleveland and Wolfe's trichrome shows differentiation of cell types in the adenohypophysis only later in ontogeny. Our results indicate that, in teleosts, differentiated prolactin cells are present before hatching and that prolactin may be involved in the endocrine control of the hatching process.

Aging changes in lymphopoietic and myelopoietic organs of the annual cyprinodont fish, Nothobranchius guentheri

The thymus of aging annual, cyprinodont fish, Nothobranchius guentheri and Cynolebias adloffi begins to undergo senescent changes at approximately four months. At this time, the histopathology reveals increased amounts of connective tissue, epithelial cysts and myoid cells, but decreased numbers of thymocytes. At 12 months, of the 50 fish observed at 10 stages from day 15 and 1, 2, 4, 6, 8, 9, 10, 11, 12 months the maximum time of senescence, there was an increased incidence of tumors in the oral cavity, connective tissue, kidney and liver in all 5 fish. At least in the kidney, the malignant transformation was classified as nodular-type histiocytic lymphoma. It is of interest that development of these tumors occurs during peak senescent changes in the thymus, supporting the view that as fish age, accompanied by atrophy of the thymus, the immune system is less vigorous and there is an increase in the incidence of cancer.

Le peuplement de Cyprinodontes du bassin de l'Ivindo, Gabon

Le peuplement de Cyprinodontes du bassin de l'Ivindo, Gabon

Analysis of the variability in cleavage times and demonstration of a mitotic gradient during the cleavage stages of Nothobranchius guentheri.

Living embryos of the annual cyprinodont fish Nothobranchius guentheri were observed under the microscope. Detailed records were made of the time of cell division, disappearance of the nucleus and of the position of each cell within the blastoderm up to and includig the sixth cleavage. Combination of these data revealed the presence of a mitotic gradient, a cell division gradient and a gradient of cell cycle duration in the 8-cell, 16-cell and 32-cell stage. Comparison of the variabilities in the duration of the interphase and mitosis reveals that differences between sister cell intercleavage times in the 8-, 16- and 32-cell stage are, for the most part, due to the variability in the duration of the mitotic process. It is concluded that the DNA-division cycle is composed of at least two parallel series of events. We found the random transition model of cell cycle control, originally based on the analysis of intermitotic times of mammalian cells in tissue culture, helpful also in analysing intercleavage time variability in embryonic cells.

The evolution of the premaxillary protrusion system in some teleostean fish groups

Changes in the acanthopteran (acanthopterygian) system of premaxillary protrusion are traced from its incipient representation in the iniomous (myctophiform) genus Aulopus to its fully evolved form in the percoids. Two complementary components of the system are differentiated. One is the protrusion of the premaxillary, brought about primarily by the anteroventral movement of a ligament attached to the rostral cartilage. The second, which distinguishes the acanthopteran system from other types of jaw protrusion, is the emplacement of a bony maxillary wedge between the skull and the protruded premaxillary.The acanthopteran type of protrusion appears to have evolved in large‐mouthed fishes, with the lateral expansion of the gape that occurs in such forms a fundamental element of this system's mechanics. The modifications that occur in small‐mouthed fishes with little or no lateral expansion of the gape are discussed.Premaxillary protrusion was investigated in available fish groups sometimes placed between the iniomous fishes and the percoids in classifications. Of these groups, the beloniform and cyprinodont fishes have developed protrusion systems of non‐acanthopteran types.