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At least 19 recordsLinked to original sources
PubMed2002

A low genomic number of recessive lethals in natural populations of bluefin killifish and zebrafish.

Despite the importance of selection against deleterious mutations in natural populations, reliable estimates of the genomic numbers of mutant alleles in wild populations are scarce. We found that, in wild-caught bluefin killifish Lucania goodei (Fundulidae) and wild-caught zebrafish Danio rerio (Cyprinidae), the average numbers of recessive lethal alleles per individual are 1.9 (95% confidence limits 1.3 to 2.6) and 1.4 (95% confidence limits 1.0 to 2.0), respectively. These results, together with data on several Drosophila species and on Xenopus laevis, show that phylogenetically distant animals with different genome sizes and numbers of genes carry similar numbers of lethal mutations.

Alleles↗
PubMed2003

Phyllodistomum funduli n. sp. (Trematoda: Gorgoderidae) from Fundulus sciadicus Cope from Cedar Creek in western Nebraska.

Phyllodistomum funduli n. sp. is described from the urinary bladder and ureters of the plains topminnow, Fundulus sciadicus, from Cedar Creek in Keith County, Nebraska (41 degrees 11.18'N, 101 degrees 21.77'W). Phyllodistomum funduli differs from most other Phyllodistomum species reported in possessing an oral sucker that is larger than the acetabulum. Currently, 7 other species of Phyllodistomum have been reported to possess this trait. A comparison of P. funduli with these 7 other species indicates that P. funduli is a distinct species, lacking notches, posterior body folds, caudal projections, or cephalic glands found in some congeners. There is no published report on parasites other than monogeneans inhabiting the plains topminnow, and there is no other report of members from the Gorgoderidae inhabiting any members of the Fundulidae.

Animals↗
PubMed2005

Physiological basis for large differences in resistance to nitrite among freshwater and freshwater-acclimated euryhaline fishes.

Uptake of environmental NO2- by most freshwater fishes occurs at the gills where NO2- is actively transported into the blood by the Cl- uptake pathway. Some freshwater fishes do not concentrate NO2- in their plasma, regardless of environmental NO2- exposure and exhibit a high degree of resistance to NO2-. Recent studies indicate that freshwater-adapted killifish (Fundulidae: Fundulus heteroclitus) and European eel (Anguillidae: Anguilla anguilla) have no or minimal Cl- uptake activity at the gills relative to most freshwater fishes; rather, Cl- requirements are met in other ways (probably dietary). We hypothesized that different rates of Cl- uptake by the gill may explain the observed differences in NO2- uptake and consequent toxicity among freshwater fishes. Cl- influx rates of channel catfish (Ictaluridae: Ictalurus punctatus), a species that concentrates NO2- in the plasma and is sensitive to NO2-, and bluegill (Centrarchidae: Lepomis macrochirus), a species that does not concentrate NO2- in the plasma and is resistant to NO2-, were determined over a range of environmental Cl- concentrations. Channel catfish actively transported chloride into the plasma (Km = 155.6+/-101.2 micromol/L Cl-; Jmax = 414.9+/-51.4 nmol/g/h; +/-SEM). In contrast, bluegill exhibited no observable Cl- uptake. We placed our results and previously reported results in a phylogenetic context and concluded that differences in Cl- uptake mechanisms among groups of freshwater fishes may explain, in large part, the wide range of sensitivity to environmental NO2-. NO2- uptake determinations may also prove to be an easy screening method when studying the phylogenetic distribution and nature of Cl- uptake mechanisms in the gills of fishes.

Adaptation, Physiological↗
PubMed1993

The evolution of copulatory organs, internal fertilization, placentae and viviparity in killifishes (Cyprinodontiformes) inferred from a DNA phylogeny of the tyrosine kinase gene X-src.

Cyprinodontiforms are a diverse group of approximately 900 pantropical and temperate fishes, mostly found in freshwater. Whereas the vast majority of fishes lay eggs (i.e. are oviparous), this group is unusual in that four groups of cyprinodont fishes give birth to living young (i.e. are viviparous). A molecular phylogenetic hypothesis was based on partial DNA sequences of the tyrosine kinase gene X-src. The study included the major lineages of fishes of the suborder Cyprinodontoidei, order Cyprinodontiformes. Our phylogeny agrees with some but not all of the conclusions of a previous morphological cladistic analysis (Parenti (Bull. Am. Mus. nat. Hist. 168, 335 (1981)). The differences are: (i) the Profundulidae are the sister group to the Goodeidae, not the sister group to all other cyprinodontoids; (ii) Fundulidae are the sister group to the Profundulidae and Goodeidae; (iii) Cubanichthys and the Cyprinodontinae might not be sister taxa; (iv) Cubanichthys, and not the Profundulidae, might be the most basal member of the cyprinodontoids; and (v) the Anablepinae and Poeciliinae might be sister groups. The molecular phylogeny was used to reconstruct the evolution of major life-history traits such as internal fertilization, copulatory organs, livebearing and placentas. Internal fertilization, modifications of the male's anal fin to form a copulatory organ, and viviparity probably evolved independently three times in cyprinodontiform fishes: in the subfamilies Goodeinae, Anablepinae and Poeciliinae (sensu Parenti 1981). The evolution of bundled sperm, spermatozeugmata, is probably not a prerequisite for internal fertilization because at least one species with internal fertilization has free spermatozoa. Livebearing (viviparity), which takes the form of ovoviviparity (where embryos are nourished by their yolk sac only), evolved only in the subfamily Poeciliinae. Advanced forms of viviparity, in which the mother provides additional nourishment to the embryos through placenta-like structures, apparently evolved at least three times from egg-laying ancestors: in the subfamilies Goodeinae, Anablepinae, and more than once in the Poeciliinae.

Animals↗
PubMed2006

Chromaffin cells in the adrenal homolog of Aphanius fasciatus (teleost fish) express piecemeal degranulation in response to osmotic stress: a hint for a conservative evolutionary process.

The effect of severe osmotic stress on the ultrastructural morphology of chromaffin cells in the adrenal homolog of Aphanius fasciatus, a small eurhyaline teleost living in saltpans, was evaluated by electron microscopy quantitative analysis. Fishes were transferred from salt water, whose salinity was 3.7%, to dechlorinated tap water and chromaffin cells were studied at resting condition and after 2 and 48 hr from the beginning of the experiment. Ultrastructural examination revealed a series of granule and cytoplasmic changes highly specific for piecemeal degranulation (PMD), a secretory process based on vesicular transport of cargoes from within granules for extracellular release, which was previously described in chromaffin cells of the mouse, rat, and human adrenal medulla. There was indeed a significant trend toward loss of content material from chromaffin granules accompanied by enlargement of granule size. Remarkably, chromaffin granules maintained their individual close structure during the whole releasing process and eventually transformed into large empty containers. A dramatic increase in the density of small, membrane-bound, variably electron-dense vesicles free in the cytoplasm or attached to granules was recognized during the first 2 hr of stress response. These features fell to control levels after 48 hr. A similar time-course pattern was observed concerning the formation of budding projections from the surface of chromaffin granules. This study provides new insight into PMD physiology and suggests that PMD is part of an adaptive secretory response to severe osmotic stress in fishes. From an evolutionary point of view, this study lends support to the concept that PMD is a secretory mechanism highly conserved throughout vertebrate classes.

Adrenal Medulla↗
PubMed2002

Morphological studies on the mechanisms of pigmentary organelle transport in fish xanthophores and melanophores.

Pigmentary organelle translocations within fish chromatophores undergo physiological color changes when exposed to external signals. Chromatophores can be isolated in high yields, and their pigmentary organelles can be tracked readily by microscopy. The combined efforts of morphology and biomolecular chemistry have led to the identification of and determination of the interrelationships between cytoskeletal elements and accessory proteins, motor molecules, cytomatrix, and pigmentary organelles of various sizes. Fish chromatophores have been classified as fast, intermediate, and slow translocators, based on the relative numbers of microtubules. Studies on cultured goldfish (Carassius auratus L.) xanthophores for over 20 years have demonstrated that in this slow translocator, tubulovesicular structures of the smooth endoplasmic reticular (SER) cisternae are involved in the disperson and aggregation of associated carotenoid droplets (CD) with some involvement of cytoskeletal elements. Killifish (Fundulus heteroclitus L.) melanophore, a fast translocator, was also examined. Recent work demonstrates a bright fluorescent "starburst"-like spot that we call an actin filament-organizing center (AFOC) with radiating microfilaments, akin to the microtubule-organizing center (MTOC) with radiating microtubules. Melanosomes translocate single-file on microtubules and are not associated with SER cisternae. Slower CD dispersion or aggregation in goldfish xanthophores seems to be predominantly microfilament-based transport, or microfilament- and microtubule-based transport, respectively. Faster melanosome translocations in killifish melanophores are based on microtubules, with our evidence indicating microfilament involvement. Neural crest-derived chromatophores are models for vesicular transport in axons, and immunocytochemical and imaging technologies may help to elucidate the cellular transport mechanisms.

Animals↗
PubMed2002

Identification and functional characterization of hypoxia-inducible factor 2alpha from the estuarine teleost, Fundulus heteroclitus: interaction of HIF-2alpha with two ARNT2 splice variants.

The hypoxia-inducible factors (HIFs) are dimeric transcription factors that mediate changes in gene expression during adaptation of animals to oxygen stress. Both alpha (HIFalpha) and beta (ARNT) subunits are members of the basic helix-loop-helix/Per-ARNT-Sim family of proteins. Mammals have at least three different HIF-alpha subunits, paralogous proteins expressed in tissue-specific fashion (HIF-1alpha, HIF-2alpha, and HIF-3alpha). However, the diversity and functional properties of teleost HIFs are poorly understood. In efforts to characterize mechanisms of hypoxia adaptation in estuarine fish, we have isolated cDNAs encoding HIF subunits from Fundulus heteroclitus (Atlantic killifish or mummichog), including a HIF-2alpha homolog and ARNT2alt, a splice variant of ARNT2 that contains an additional exon encoding 16 amino acids near the amino terminus. HIF-2alpha protein synthesized in vitro binds cognate DNA elements in concert with either Fundulus ARNT2 splice variant or murine ARNT1. HIF-2alpha, ARNT2, and ARNT2alt mRNAs are expressed in all organs examined. The HIF-2alpha cDNA encodes a protein of 96.4 kDa, sharing 53-54% identity with mammalian and avian orthologs. The oxygen-dependent degradation domain, however, exhibits substantial divergence from well-conserved mammalian sequences, suggesting the possibility of important functional differences, perhaps in the sensitivity to induction of activity by hypoxia. Hypoxia-tolerant fishes such as F. heteroclitus represent a unique opportunity for the study of functional and evolutionary aspects of adaptation to hypoxia at the molecular, cellular, and organismal levels. This study extends the understanding of hypoxia signaling in fish, the evolution and diversity of HIF function, and the evolution of the PAS family of proteins.

Alternative Splicing↗
PubMed2002

Early estrogen exposure induces abnormal development of Fundulus heteroclitus.

Many chemicals released into the environment exhibit estrogenic activity, having the potential to disrupt development and the functioning of the endocrine system. In order to establish a model system to study the effects of such environmental chemicals on aquatic animals, we examined the effects of a natural estrogen, 17 beta-estradiol (E(2)), on early development of Fundulus heteroclitus. Embryos of F. heteroclitus were reared in seawater containing 10(-10), 10(-8), and 10(-6) M E(2) throughout the experiment. Hatching and survival rates decreased in a dose-dependent manner, and fry treated with 10(-6) M E(2) and 10(-8) M E(2) were dead by two weeks and 12 weeks after hatching, respectively. More than 85% of fry treated with 10(-8) M E(2) showed malformations: i.e., eye extrusion, crooked vertebral column, faded lateral-stripe pattern eight weeks after hatching. Body weight and head and body lengths were significantly reduced in E(2)-treated fry when compared to controls. Ossification was not completed in vertebrae, cranial bones, and other bones in fry treated with 10(-8) M E(2) even 12 weeks after hatching. Sex ratio of control fry was 57% male and 43% female, whereas fry treated with 10(-8) M E(2) were 100% female eight weeks after hatching. The present results demonstrate that exogenous estrogen induced death of embryos and fry, malformations, sex reversal, and incomplete ossification of vertebrae and cranial bones, which would result in shorter body and head lengths and in malformed vertebrae leading to a hunchback condition.

Animals↗
PubMed2003

Development of rhythmic melatonin secretion from the pineal gland of embryonic mummichog (Fundulus heteroclitus).

The pineal gland of vertebrates produces and secretes the hormone melatonin in response to changes in the light-dark cycle, with high production at night and low production during the day. Melatonin is thought to play an important role in synchronizing daily and/or seasonal physiological, behavioral, and developmental rhythms in vertebrates. In this study, the functional development of the pineal melatonin-generating system was examined in the mummichog, Fundulus heteroclitus, an euryhaline teleost. In this species, the pineal gland contains an endogenous oscillator, ultimately responsible for timing the melatonin rhythm. Oocytes from gravid females were collected and fertilized in vitro from sperm collected from mature males. Skull caps containing attached pineal glands were obtained from F. heteroclitus embryos at different embryonic stages and placed in static or perfusion culture under various photoperiodic regimes. Rhythmic melatonin secretion from pineal glands of embryonic F. heteroclitus embryos exposed to a 12L:12D cycle in static culture was observed at five days post-fertilization. The ontogeny of circadian-controlled melatonin production from F. heteroclitus pineal glands exposed to constant darkness for five days was also seen at day five post-fertilization. These data show that early development of the pineal melatonin-generating system in this teleost occurs prior to hatching. Pre-hatching development of the melatonin-generating system may confer some selective advantage in this species in its interactions with the environment.

Animals↗
PubMed2003

Teleost Fh14-3-3a protein protects Xenopus oocytes from hyperosmolality.

We have previously cloned and characterized a novel 14-3-3 gene from the euryhaline telost Fundulus heteroclitus, Fh14-3-3a (Kültz et al., 2001). The corresponding gene product is osmoregulated and most highly expressed in gill epithelium of this fish. In the present study we have expressed Fh14-3-3a cRNA in Xenopus laevis oocytes and investigated the survival and electrophysiological parameters of Xenopus oocytes in isosmotic and various hyperosmotic media. Xenopus oocytes expressing Fh14-3-3a show no mortality after a 16 hour exposure to hyperosmolality in the form of elevating medium K(+), Na(+), polyethylene glycol, or sorbitol concentrations up to 444 mosmol/kg. In contrast, 16 hours of the same hyperosmolality caused 100% mortality in control Xenopus oocytes injected with water. As a result of hyperosmolality the Xenopus oocyte membrane potential decreased between 10 and 70% in oocytes expressing Fh14-3-3a whereas it was completely abolished in control oocytes. We report that one potential cause for the osmoprotective effect of Fh14-3-3a on Xenopus oocytes could be its inhibition of an endogenous chloride current. Hyperosmotic urea was not as harmful to Xenopus oocytes as hypertonicity and maybe acting through a different mechanism. Coexpression of Fh14-3-3a with a human calcium channel in Xenopus oocytes did not affect the electrophysiological properties of this exogenous channel. Thus, the osmoprotective effect of Fh14-3-3a may prove a valuable tool for the characterization of exogenous ion channels in Xenopus oocytes exposed to hyperosmotic conditions.

14-3-3 Proteins↗
PubMed2005

Cortisol receptor blockade and seawater adaptation in the euryhaline teleost Fundulus heteroclitus.

To examine the role of cortisol in seawater osmoregulation in a euryhaline teleost, adult killifish were acclimated to brackish water (10 per thousand) and RU486 or vehicle was administered orally in peanut oil daily for five days at low (40 mg.kg(-1)) or high dose (200 mg.kg(-1)). Fish were transferred to 1.5 x seawater (45 per thousand) or to brackish water (control) and sampled at 24 h and 48 h after transfer, when Cl- secretion is upregulated. At 24 h, opercular membrane Cl- secretion rate, as Isc, was increased only in the high dose RU486 group. Stimulation of membranes by 3-isobutyl-1-methylxanthine and cAMP increased Isc in vehicle treated controls but those from RU486-treated animals were unchanged and membranes from brackish water animals showed a decrease in Isc. At 48 h, Isc increased and transepithelial resistance decreased in vehicle and RU486 groups, compared to brackish water controls. Plasma cortisol increased in all groups transferred to high salinity, compared to brackish water controls. RU486 treated animals had higher cortisol levels compared to vehicle controls. Vehicle treated controls had lower cortisol levels than untreated or RU486 treated animals, higher stimulation of Isc, and lower hematocrit at 24 h, beneficial effects attributed to increased caloric intake from the peanut oil vehicle. Chloride cell density was significantly increased in the high dose RU486 group at 48 hours, yet Isc was unchanged, suggesting a decrease in Cl- secretion per cell. Thus cortisol enhances NaCl secretion capacity in chloride cells, likely via glucocorticoid type receptors.

Adaptation, Physiological↗
PubMed2005

The effect of environmental hypercapnia and salinity on the expression of NHE-like isoforms in the gills of a euryhaline fish (Fundulus heteroclitus).

The current models for branchial acid excretion in fishes include Na(+)/H(+) exchange and the electrogenic excretion of H+ via H+-ATPase. The predominant route of acid excretion in some freshwater fishes is thought to be via the H+-ATPase/Na+ channel system. The euryhaline Fundulus heteroclitus may not fit this profile even when adapted to freshwater (FW). We hypothesize that the Na+/H+ exchanger (NHE) in this species may play a predominant role in acid-base regulation for both marine and FW adapted animals. Acidosis induced by ambient hypercapnia (1% CO2 in air), resulted in an increase in net H+ excretion to the water in F. heteroclitus pre-adapted to FW, brackish (isoosmotic; BW) and seawater (SW). Both FW and SW adapted mummichogs were tested for NHE protein expression using mammalian NHE antibodies, and we identified NHE-like immunoreactive proteins in gill membrane preparations from both groups. Hypercapnia induced a approximately three-fold elevation in gill NHE2-like protein in FW animals but SW adapted fish showed inconsistent NHE3-like protein expression. There was no change in NHE-1 levels in FW fish. In contrast, SW animals demonstrated a significant increase in both NHE1 and NHE3-like proteins following hypercapnia but limited expression of the NHE2 protein. We hypothesize that different isoforms of NHE may be preferentially expressed depending on the salinity to which the animals are adapted. Net H+ transfers during acidosis may be driven, at least in part by the action of these transporters.

Adaptation, Physiological↗