Fundulus Majalis Research Articles

Responses of juvenile Atlantic silverside, striped killifish, mummichog, and striped bass to acute hypoxia and acidification: Aquatic surface respiration and survival

Diel fluctuations in dissolved oxygen (DO) and pH create hypoxic conditions that alter the quality of shallow estuarine nursery habitats for juvenile fishes. Understanding how different species in these environments mitigate stress associated with intermittent hypoxia through compensatory behaviors, such as aquatic surface respiration (ASR), is important in determining the effect of these stressors on estuarine ecosystems. Behavioral responses of Atlantic silversides (Menidia menidia), striped killifish (Fundulus majalis), mummichog (Fundulus heteroclitus), and juvenile striped bass (Morone saxatilis) were independently observed during exposure to two levels of diel-cycling DO (3–9mgO2l−1 and 1–11mgO2l−1) each tested with both the corresponding pH cycle (7.2–7.8 and 6.8–8.1, respectively) and static pH (7.5) under controlled laboratory conditions. In treatments in which DO declined to ~3mgO2l−1, none of the species examined exhibited ASR behavior either with or without the associated pH decline. However, ASR was observed during both 4-hour and extended 16-hour exposure where DO declined to ~1.0–1.6mgO2l−1 in M. menidia and both Fundulus species. M. saxatilis did not exhibit ASR and no mortalities occurred during 4-hour low DO/pH treatments or during 16hour exposure to 1.5mgO2l−1. During extended 16-hour treatments, DO thresholds for ASR were not found to be different between F. majalis and F. heteroclitus, but both differed significantly from M. menidia. Across both 4-hour and 16-hour treatments, the onset of ASR was observed in M. menidia at or near lethal levels (1.31–1.62mgO2l−1). No evidence of a pH (pCO2) effect on ASR or survival was found in any species in response to naturally co-varying DO and pH swings, despite pH as low as 6.8 and high pCO2 levels of >~12,000μatm. These results suggest that utilization of ASR is a species-specific response influenced by the magnitude and duration of hypoxic exposure. ASR may serve as a last-ditch strategy by M. menidia to prolong survival for minutes to hours, but function as a means for F. heteroclitus to mitigate or reduce negative effects of hypoxia on a scale of days to weeks, with F. majalis exhibiting an intermediate response.

Nekton assemblages along riprap-altered shorelines in Delaware Bay, USA: comparisons with adjacent beach

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 548:209-218 (2016) - DOI: https://doi.org/10.3354/meps11685 Nekton assemblages along riprap-altered shorelines in Delaware Bay, USA: comparisons with adjacent beach Michael P. Torre1,2,*, Timothy E. Targett1 1University of Delaware, School of Marine Science and Policy, Lewes, Delaware 19958, USA 2Present address: University of Maine, School of Marine Sciences, Orono, Maine 04469, USA *Corresponding author: torrem27@gmail.com ABSTRACT: Riprap-reinforced shorelines are becoming more prevalent as a result of increasing coastal development and sea level rise. Altered morphology at the land-water interface, associated with riprap shorelines, has the potential to reduce shore-zone habitat quality for associated nekton species. The shore-zone nekton assemblage within a temperate, mid-Atlantic coast, USA, estuary was examined to identify differences in habitat use between sandy beach and riprap shorelines. We found that riprap can have a negative effect on a local scale. Overall nekton density, species richness, and density of dominant species were higher along beach shorelines relative to adjacent riprap, in most instances. Nekton association with shoreline habitat appears to be consistent over the diel cycle. Densities of Atlantic silverside Menidia menidia, striped killifish Fundulus majalis, spot Leiostomus xanthurus, and white perch Morone americana were generally reduced along riprap. In some cases, riprap shorelines also had altered species assemblages. Thus, our findings provide evidence of altered habitat quality for shore-zone nekton associated with shoreline hardening. These impacts were, however, variable spatially and temporally. Further research is needed to identify the biophysical mechanisms associated with riprap shorelines that are most responsible for altered habitat quality. KEY WORDS: Shoreline armoring · Riprap · Beach · Fish assemblage · Nekton density · Estuary · Delaware Bay Full text in pdf format PreviousNextCite this article as: Torre MP, Targett TE (2016) Nekton assemblages along riprap-altered shorelines in Delaware Bay, USA: comparisons with adjacent beach. Mar Ecol Prog Ser 548:209-218. https://doi.org/10.3354/meps11685 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 548. Online publication date: April 21, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

The effects of salinity on swimming performance of two estuarine fishes, Fundulus heteroclitus and Fundulus majalis.

Prolonged and high-speed swimming performance measurements were used to explore the swimming abilities of two species of estuarine fishes, the mummichog Fundulus heteroclitus and the striped killifish Fundulus majalis, under different salinities. Critical swimming performance was significantly higher for F. majalis in high salinity than in low salinity, but no difference was observed in brief constant acceleration swimming trials in this species; however, the swimming performance of F. heteroclitus was not significantly affected by salinity changes, indicating that this species is well adapted to regular estuarine salinity oscillations. Fundulus majalis displayed higher swimming speeds than F. heteroclitus in both high and low salinities, and while this cannot be explained by their respective salinity preferences, the specific habitat preferences of F. majalis for sandy subtidal habitats and F. heteroclitus for vegetated marshes could explain the better swimming performance of F. majalis.

Common functional targets of adaptive micro‐ and macro‐evolutionary divergence in killifish

Environmental salinity presents a key barrier to dispersal for most aquatic organisms, and adaptation to alternate osmotic environments likely enables species diversification. Little is known of the functional basis for derived tolerance to environmental salinity. We integrate comparative physiology and functional genomics to explore the mechanistic underpinnings of evolved variation in osmotic plasticity within and among two species of killifish; Fundulus majalis harbours the ancestral mainly salt-tolerant phenotype, whereas Fundulus heteroclitus harbours a derived physiology that retains extreme salt tolerance but with expanded osmotic plasticity towards the freshwater end of the osmotic continuum. Common-garden comparative hypo-osmotic challenge experiments show that F.heteroclitus is capable of remodelling gill epithelia more quickly and at more extreme osmotic challenge than F.majalis. We detect an unusual pattern of baseline transcriptome divergence, where neutral evolutionary processes appear to govern expression divergence within species, but patterns of divergence for these genes between species do not follow neutral expectations. During acclimation, genome expression profiling identifies mechanisms of acclimation-associated response that are conserved within the genus including regulation of paracellular permeability. In contrast, several responses vary among species including those putatively associated with cell volume regulation, and these same mechanisms are targets for adaptive physiological divergence along osmotic gradients within F.heteroclitus. As such, the genomic and physiological mechanisms that are associated with adaptive fine-tuning within species also contribute to macro-evolutionary divergence as species diversify across osmotic niches.

Variability in the density and sound-speed of coastal zooplankton and nekton

Abstract Forman, K. A., and Warren, J. D. 2010. Variability in the density and sound-speed of coastal zooplankton and nekton. – ICES Journal of Marine Science, 67: 10–18. Acoustic sampling techniques provide an advantage over traditional net-sampling by increasing scientist ability to survey a large area in a relatively short period, as well as providing higher-resolution data in the vertical and horizontal dimensions. To convert acoustic data into measures of biological organisms, physics-based scattering models are often used. Such models use several parameters to predict the amount of sound scattered by a fluid-like or weakly scattering animal. Two important input parameters are the density (g) and sound-speed (h) contrasts of the animal and the surrounding seawater. The density and sound-speed contrasts were measured for coastal zooplankton and nekton species including shrimps (Palaemonetes pugio and Crangon septemspinosa), fish (Fundulus majalis and Fundulus heteroclitus), and polychaetes (Nereis succinea and Glycera americana) along with multiple physiological and environmental variables. Factors such as animal size, feeding status, fecundity, gender, and maturity caused variations in g. The variations in g observed for these animals could lead to large differences (or uncertainties) in abundance estimates based on acoustic scattering models and field-collected backscatter data. It may be important to use a range of values for g and h in the acoustic scattering models used to convert acoustic data into estimates of the abundance of marine organisms.

Foraging by Two Estuarine Fishes, Fundulus heteroclitus and Fundulus majalis, on Juvenile Asian Shore Crabs (Hemigrapsus sanguineus) in Western Long Island Sound

The Asian shore crab, Hemigrapsus sanguineus, is a recent and particularly successful introduction to the east coast of the USA. Little research has been done on the utilization of Asian shore crabs for food by native species, a potential form of biocontrol. Over a 4-year period, we examined the gut contents of cogeners, Fundulus heteroclitus and Fundulus majalis, collected from two embayments in western Long Island Sound for the presence of juvenile H. sanguineus. Frequency (percent) of occurrence of food items in the guts of both species varied over year and study site. Asian shore crabs were consumed more often by F. heteroclitus than by F. majalis, but predation pressure by both species was low. Only 13% of F. heteroclitus and 7.7% of F. majalis found with food in their guts had ingested Asian shore crab remains. Of those, 1/3 had consumed whole crabs; the rest had only autotomized appendages in their guts. The mean carapace width of juvenile Asian shore crabs ingested by F. heteroclitus was 3.59 ± 2.22 mm (N = 33). Results of our study on killifish predation support the hypothesis that H. sanguienus abundance is partly explained by reduced impact of native predators (i.e., the “enemy release hypothesis”). Predation pressure of other potential enemies on both planktonic and benthic stages of the Asian shore crab must be investigated, however, to understand the full impact of predation on H. sanguineus population dynamics.

Characterization, dynamics, and ecological impacts of harmful Cochlodinium polykrikoides blooms on eastern Long Island, NY, USA

We report on the emergence of Cochlodinium polykrikoides blooms in the Peconic Estuary and Shinnecock Bay, NY, USA, during 2002–2006. Blooms occurred during late summer when temperatures and salinities ranged from 20 to 25 °C and 22 to 30 ppt, respectively. Bloom patches achieved cell densities exceeding 10 5 ml −1 and chlorophyll a levels exceeding 100 μg l −1, while background bloom densities were typically 10 3–10 4 cells ml −1. Light, scanning electron and ultrathin-section transmission electron microscopy suggested that cells isolated from blooms displayed characteristics of C. polykrikoides and provide the first clear documentation of the fine structure for this species. Sequencing of a hypervariable region of the large subunit rDNA confirmed this finding, displaying 100% similarity to other North American C. polykrikoides strains, but a lower similarity to strains from Southeast Asia (88–90%). Bioassay experiments demonstrated that 24 h exposure to bloom waters (>5 × 10 4 cells ml −1) killed 100% of multiple fish species (1-week-old Cyprinodon variegates, adult Fundulus majalis, adult Menidia menidia) and 80% of adult Fundulus heteroclitus. Microscopic evaluation of the gills of moribund fish revealed epithelial proliferation with focal areas of fusion of gill lamellae, suggesting impairment of gill function (e.g. respiration, nitrogen excretion, ion balance). Lower fish mortality was observed at intermediate C. polykrikoides densities (10 3–10 4 cells ml −1), while fish survived for 48 h at cell densities below 1 × 10 3 cells ml −1. The inability of frozen and thawed-, or filtered (0.2 μm)-bloom water to cause fish mortality suggested that the thick polysaccharide layer associated with cell membranes and/or a toxin principle within this layer may be responsible for fish mortality. Juvenile bay scallops ( Argopecten irradians) and American oysters ( Crassostrea virginica) experienced elevated mortality compared to control treatments during a 9-day exposure to bloom water (∼5 × 10 4 cells ml −1). Surviving scallops exposed to bloom water also experienced significantly reduced growth rates. Moribund shellfish displayed hyperplasia, hemorrhaging, squamation, and apoptosis in gill and digestive tissues with gill inflammation specifically associated with areas containing C. polykrikoides cells. In summary, our results indicate C. polykrikoides blooms have become annual events on eastern Long Island and that bloom waters are capable of causing rapid mortality in multiple species of finfish and shellfish.

Early stages of the Asian shore crab Hemigrapsus sanguineus as potential prey for the striped killifish Fundulus majalis

The Asian shore crab Hemigrapsus sanguineus is a recent invader of rocky intertidal shores along the U.S. Atlantic coast whose predators have not been well identified. One potential predator of settling larvae (megalopae) and small juvenile crabs is the striped killifish, Fundulus majalis, which forages on small benthic animals. Laboratory experiments were conducted with and without sediment, consisting of sand and rocks to mimic the rocky intertidal, in order to determine whether F. majalis can consume H. sanguineus and if habitat structure reduces predation success. F. majalis juveniles (< 60 mm total length and lacking signs of sexual differentiation) and male and female F. majalis 60–80 mm, 80–100 mm, and > 100 mm in total length were individually offered megalopae, 1st stage crabs, and crabs 3–5 mm and 5–7 mm in carapace width (CW). Megalopae and 1st stage crabs were consumed more readily than crabs ≥ 3 mm CW by all size classes and both sexes of F. majalis. Megalopae were eaten regardless of whether or not sediment was present, but predation of 1st stage crabs was less in the presence of sediment. Gut content analyses were performed on F. majalis collected from rocky intertidal shores to determine whether results from laboratory experiments were indicative of H. sanguineus consumption by F. majalis in the wild. No H. sanguineus or other crabs were found in the guts of 37 F. majalis analyzed. Common prey items included small blue mussels ( Mytilus edulis), hard-shelled clams ( Mercenaria mercenaria), and unidentified crustaceans. Although F. majalis readily preyed on Asian shore crab megalopae and newly-settled crabs in the laboratory, it might not utilize H. sanguineus as prey in nature.

Fish community structure and dynamics in a coastal hypersaline lagoon: Rio Lagartos, Yucatan, Mexico

Rio Lagartos, a tropical coastal lagoon in northern Yucatan Peninsula of Mexico, is characterized by high salinity during most of the year (55 psu annual average). Even though the area has been designated as a wetland of international importance because of its great biodiversity, fish species composition and distribution are unknown. To determine whether the salinity gradient was influencing fish assemblages or not, fish populations were sampled seasonally by seine and trawl from 1992 to 1993 and bimonthly during 1997. We identified 81 fish species, eight of which accounted for 53.1% considering the Importance Value Index ( Floridichthys polyommus, Sphoeroides testudineus, Eucinostomus argenteus, Eucinostomus gula, Fundulus majalis, Strongylura notata, Cyprinodon artifrons and Elops saurus). Species richness and density declined from the mouth to the inner zone where extreme salinity conditions are prominent (>80) and competitive interactions decreased. However, in Coloradas basin (53 average sanity) and in the inlet of the lagoon, the highest fish density and number of species were observed. Greater habitat heterogeneity and fish immigration were considered as the best explanation. Multivariate analysis found three zones distinguished by fish occurrence, abundance and distribution. Ichthyofaunal spatial differences were attributed to selective recruitment from the Gulf of Mexico due to salinity gradient and to changing climatic periods. Estuarine and euryhaline marine species are abundant, with estuarine dependent ones entering the system according to environmental preferences. This knowledge will contribute to the management of the Special Biosphere Reserve through baseline data to evaluate environmental and anthropogenic changes.

Larval Tapeworms (Cestoda: Dilepididae) from the Mummichog Fundulus heteroclitus (Linnaeus, 1766) and Striped Killifish Fundulus majalis (Walbaum, 1792) from South Carolina, U.S.A.

Larval stages (metacestodes) of 2 dilepidid tapeworms (Eucestoda: Cyclophyllidea) are reported from the mesenteries and liver of the mummichog Fundulus heteroclitus and striped killifish Fundulus majalis from South Carolina, U.S.A. Cyclustera ibisae (Schmidt and Bush, 1972) is reported for the first time from a fish intermediate host, whereas metacestodes of Glossocercus caribaensis (Rysavy and Macko, 1973) (syn. Parvitaenia heardi Schmidt and Courtney, 1973) have only recently been found in fish from southeastern Mexico (Yucatan).

Phylogenetic analysis of thermal acclimation of the glycolytic enzymes in the genus Fundulus.

Physiological acclimation that alters enzyme activity can compensate for the effect of temperature on function and may be achieved by altering enzyme concentration. This study uses phylogenetic analyses to investigate the evolutionary history of and to test several hypotheses about acclimation responses among all the glycolytic enzymes. These hypotheses are that (1) acclimation increases enzyme concentration at lower temperatures to compensate for reduced activity; (2) equilibrium enzymes tend to show acclimation responses; and (3) acclimation responses are more common in species whose populations experience either large temporal or geographical temperature variations. Using maximal activities as indices of enzyme concentration, the presence of acclimation responses in all the glycolytic enzymes in the heart ventricle was determined for five species in the teleost genus Fundulus. Three of these species are distributed along the steep thermal cline of the North American Atlantic coast, and thus these species experience both seasonal and geographical variation in temperature. The other two species are found in the Gulf of Mexico and experience seasonal variation similar to the Atlantic species but no geographical variation in temperature. Two Atlantic coast species, Fundulus heteroclitus and Fundulus majalis, have unique derived acclimation responses. No derived acclimation responses occur in the Gulf species. A conserved response in hexokinase was observed within one subgenus comprising both Atlantic and Gulf species. In F. heteroclitus, enolase responded to acclimation, and in F majalis, aldolase, triphosphate isomerase, and lactate dehydrogenase had acclimation responses. These enzymes are equilibrium enzymes, and the concentrations of all of them increase at lower temperatures, which would compensate for the effect of temperature on enzyme activity. The compensatory changes all occur in the Atlantic species and may be a mechanism for species to expand their ranges. These data suggest that physiological acclimation is evolutionarily labile.

Effect of Algal Cover on Size-Selective Predation of Gammarus mucronatus by the Striped Killifish, Fundulus majalis.

Predation on Lysianopsis was lowest (15.4%) in Cladophora (Fig. 1, bottom), which forms a thick intertwining mat. The amphipod’s strategy for avoiding predation was to burrow deep into the algae, putting itself out of the reach of the predator. In the field, however, such behavior might be hindered by the anoxic conditions often found in the mat. The experimental methodology of this study allowed for a fairly complete exchange of the interstitial mat water, which resulted in aerobic conditions throughout the mat. Predation was high (73.8%) in the eelgrass, probably because crawling and burrowing amphipods cannot take advantage of the vertical structure of the plant. Predation was highest (93.3%) in the ‘no vegetation’ treatment because there was no substrate available to provide protection. Predation rate was analyzed in a one-factor ANOVA (P = 0.05). Differences among treatment means were evaluated using Fisher’s PLSD (P = 0.05). There were strong differences in predation rates between prey in different vegetation types (F = 227.6 15). All predation rates were different from each other except in the ‘no vegetation’ treatment. Many invertebrate species are highly dependent upon macrophyte structure and color for protection against predation (2). Alteration of the primary producer community due to eutrophication may change the structure of the habitat and may potentially have second-order effects on the invertebrate community. This study was supported by the Boston University Marine Program and the Cox Foundation.

Analysis of a hybrid zone in Fundulus majalis in a northeastern Florida ecotone

Fundulus majalis and F. similis are small fish that inhabit the coastal waters of eastern North America. Fundulus majalis occurs from New Hampshire to northeastern Florida where it is replaced by F. similis. Past morphological studies of these species have suggested the existence of a hybrid zone in the Flagler County area of northeast Florida; this location also corresponds to an ecological transition from northern Juncus–Spartina marsh to southern mangrove marsh. We used protein electrophoresis to test the hypothesis that there is a significant barrier to gene flow between the two species in the area of Flagler County, FL. Twenty populations were surveyed electrophoretically for 26 protein producing loci. Significant allozyme variation was observed for five loci: adenosine deaminase, an esterase, isocitrate dehydrogenase, malate dehydrogenase and phosphoglucomutase. Allele frequencies at these loci vary clinally from a ‘majalis’-like distribution in more northern localities to a ‘similis’-like distribution in southern localities. The steepest portion of the cline occurs over a 30 km portion of intracoastal salt marsh bordered by the northern and southern boundaries of Flagler County, FL, which led us to examine eight populations from within this area. We speculate that the nominal F. majalis and F. similis were allopatric and in the process of speciation when they recontacted one another, and the process of differentiation broke down and secondary intergradation occurred. The width of the genotypic clines (only sMdh-A is fixed at both ends), Nm estimates, and the absence of significant linkage disequilibria support the hypothesis that the rapid shift in genotypes and morphology in Flagler County is a dispersal-independent cline maintained by selection across the rapid ecological transition of an ecotone.

Interactions among Some Dominant Estuarine Nekton Species

Interactions between pairs of numerically dominant species collected at inlet and creek shorezone and channel habitats within a high salinity estuary in northeastern South Carolina were examined using two-way contingency tables and binomial tests. Of the significant species interactions, over 71% were positive and these primarily occurred within shorezone habitats. The strongest positive interactions were between young-of-the-year spot (Leiostomus xanthurus) and blue crab (Callinectes sapidus) juveniles in both shorezone habitats, and between striped killifish (Fundulus majalis), white mullet (Mugil curema), and striped anchovies (Anchoa hepsetus) in the inlet shorezone habitat. One of the most positive species associations in channel habitats was between the bay anchovy (Anchoa mitchilli) and the Atlantic brief squid (Lolliguncula brevis). These positive relationships between species may be explained by one species enhancing the habitat for another, both species responding to similar environmental conditions, cooperative social interactions such as mixed schooling, or the attraction of predators to prey. Negative interactions were found between schools of Atlantic silversides (Menidia menidia) and striped killifish in the inlet shorezone and between schools of Atlantic silversides and bay anchovies in the creek shorezone. Schools of Atlantic silversides may either displace or compete with other common shorezone species. Positive and negative interactions suggest that relationships between some species pairs did not occur randomly within certain habitats and may have contributed to the organization of the estuarine nekton community. Differences in the strengths and direction of interactions of certain species pairs among habitats and seasons were probably related to the differences in the physical characteristics of those habitats and/or changes in the relative abundance of dominant species and life stages over time.

Coarse woody debris as a refuge from predation in aquatic communities : An experimental test.

This study demonstrates experimentally that coarse woody debris (CWD) can provide refuge from predation in aquatic habitats. In the Rhode River subestuary of Chesapeake Bay, Maryland, (USA), we (1) measured the abundance of CWD, (2) examined the utilization of CWD by mobile epibenthic fish and crustaceans, and (3) tested experimentally the value of CWD as a refuge from predation. CWD was the dominant above-bottom physical structure in shallow water, ranging in size from small branches (<2 cm diameter) to fallen trees (>50 cm diameter). In response to experimental additions of CWD, densities of common epibenthic cpecies (Callinectes sapidus, Fundulus heteroclitus, Fundulus majalis, Gobiosoma bosc, Gobiesox strumosus, Palaemonetes pugio, and Rithropanopeus harrisii) increased significantly compared to control sites without CWD. In laboratory experiments, grass shrimp (P. pugio) responded to predatory fish (F. heteroclitus and Micropogonias undulatus) by utilizing shelter at CWD more frequently than in absence of fish. Access to CWD increased survivorship of grass shrimp in laboratory and field experiments. These experimental results (1) support the hypothesis, commonly proposed but untested for freshwater habitats, that CWD can provide a refuge from predation for epibenthic fish and invertebrates and (2) extend the recognized functional importance of CWD in freshwater to estuarine and marine communities. We hypothesize that CWD is an especially important refuge habitat in the many estuarine and freshwater systems for which alternative physical structure (e.g., vegetation or oyster reefs) are absent or in low abundance.

Interannual Variation in Diet and Condition in Juvenile Bluefish during Estuarine Residency

We examined the diets and weight–length relationships of juvenile bluefish Pomatomus saltatrix from Sandy Hook Bay, New Jersey, during 1981, 1983, and 1984. Diets consisted of a variety of polychaete, crustacean, and fish prey. Opossum shrimp Neomysis americana, sand shrimp Crangon septemspinosa, grass shrimp Palaemonetes vulgaris, bay anchovy Anchoa mitchilli, striped killifish Fundulus majalis, and Atlantic silverside Menidia menidia dominated the diet in terms of biomass and frequency of occurrence. Consumption of invertebrate and fish prey varied between years. Bluefish condition factor was highest in 1981, when fish were the predominant prey, and lower in 1983 and 1984, when the diets consisted mostly of invertebrate prey. The diets of juvenile bluefish in Sandy Hook Bay contained more invertebrate prey than has been described previously.

Copper uptake by two sympatric species of Killifish Fundulus heteroclitus (L.) and F. majalis (Walbaum)

Differential copper uptake within brain, visceral, gill, somatic and residual tissue was examined in the two sympatric species of killifishes Fundulus heteroclitus and F. majalis. Various salinities and copper concentrations were tested on both juvenile and adult stages to examine their effects on copper uptake. Salinity played a significant role in copper uptake in both species of killifishes. However, the effect of salinity was specific for each species and life history stage. Copper content of various tissues was directly related to the uptake pattern exhibited by whole adult fishes. Fundulus majalis brain tissue and F. heteroclitus muscle tissue were exceptions. Severe body lesions and subcutaneous haemorrhaging were observed after 2–3 day exposure to both 2 and 8 ppm copper.

The influence of temperature change on number of pectoral fin rays developing in Fundulus majalis (Walbaum)

The influence of temperature change on number of pectoral fin rays developing in Fundulus majalis (Walbaum)

The influence of temperature change on number of dorsal fin rays developing in Fundulus majalis (Walbaum)

The influence of temperature change on number of dorsal fin rays developing in Fundulus majalis (Walbaum)

The influence of temperature change on number of anal fin rays developing in Fundulus majalis (Walbaum)

In each of two experiments embryos of this cyprinodont fish were reared continuously in four fluctuating temperature regimes, 13°–17°, 18°–22°, 23°–27°, and 28°–32°C to determine response of presumptive anal fin-ray tissue to temperature change. Because of excessive mortality among embryos in the 13°–17°C temperature regime, only one transfer lot from this regime could be used. In both experiments a positive linear relationship was indicated between mean anal fin-ray count and temperature, more anal rays developed on the average with increasing temperatures. In one experiment the transfer of embryos from one of the cooler regimes to the warmest at a three-to-six-somite stage of development produced a mean anal fin-ray count similar to that of embryos reared continuously in the warmest regime, but significantly different from the mean of those reared continuously in the original cool regime. The transfer of embryos from one of the cooler regimes to the warmest at a nine-to-twelve-somite stage produced a mean anal fin-ray count similar to that of embryos reared continuously in the cooler regime, but significantly different from the mean of those reared continuously in the warmest regime. In regard to morphological time of fixation of anal fin-ray tissue in this species temperature can influence the number of anal fin rays at the three-to-six-somite stage of development; although the nine-to-twelve-somite stage showed no response to temperature influence, later stages may be sensitive.