Fundulus Majalis Research Articles

The influence of crowding upon the total number of vertebrae developing in Fundulus majalis (Walbaum)

The influence of crowding upon the total number of vertebrae developing in Fundulus majalis (Walbaum)

Effect of Thermal Shock on Predator Avoidance by Larvae of Two Fish Species

Larvae of two fish species, Menidia menidia and Paralichthys dentatus, were subjected to a 15-min thermal shock of 10 C above acchmation temperature, returned to acclimation temperature, and exposed to a predator, Fundulus majalis. Four- and six-week-old M. menidia were significantly more vulnerable to predation after being shocked than control larvae, but younger larvae were not. Shocked larvae of P. dentatus were less susceptible to predation than control larvae.

The morphological time of fixation of the total number of vertebrae in Fundulus majalis (Walbaum)

Three lots of embryos with epiboly about one-third complete were reared continuously in different fluctuating temperature regimes (16° – 20°, 22°–26° and 28°–32°C). At certain somite-number stages (3–6, 9–12, 15–23, 24–28 and 29–32) paired lots of embryos were transferred from the intermediate temperatures to the warmer and cooler regimes simultaneously. Mortalities were low (7.0%) to moderate (28.6%) in the 13 treatments. Embryos reared continuously in the three temperature regimes developed mean vertebral numbers showing a linear inverse relationship between temperature and mean vertebral count; on the average decreasing temperature induced an increased number of vertebrae. Among the transferred embryos only the 3–6 and 9–12 somite lots transferred to the cold regime responded to temperature changes. The response of presumptive vertebral tissue to cold temperature begins to decrease during the formation of the fifth and sixth somites and continues gradually until fixation occurs during formation of the tenth through twelfth somites. Cold temperatures influenced vertebral number more than warm and it is suggested that vertebral number in fishes spawning on rising water temperatures may be influenced more by cold water than by warm; conversely, fishes spawning on falling water temperatures may be influenced more by warmer than by colder water.

The Fishes of the Shore Zone of Rehoboth and Indian River Bays, Delaware

Twenty collections from 18 stations in Indian River and Rehoboth bays, June 1968 to April 1970, yielded 41,286 fishes representing 46 species. Five species, ecologically important as food for many local commercial species, comprised 89% of the total catch and were, in order of abundance: Fundulus majalis, Menidia menidia, Fundulus heteroclitus, Pseudopleuronectes americanus, and Anchoa mitchilli. Combined average biomass estimates for the five species were 55 kg/ha and 28 kg/ha for Rehoboth Bay in 1968 and 1969 respectively, and 76 kg/ha and 37 kg/ha for Indian River Bay in 1968 and 1969 respectively. Greatest species diversity and abundance occurred in summer, probably because this is when many of these species collected use these bays as nursery and feeding grounds. F. majalis, M. menidia, F. heteroclitus, P. americanus, Cyprinodon variegatus, and Syngnathus juscus apparently reside in these waters and spawn there during the spring and summer. Juveniles of many commercially important middle Atlantic species were also found in the bays during these seasons. P. americanus were the only fish available in any quantity to commercial and sport fisheries in the study areas. Other commercial fishes typical of the middle Atlantic region, such as Brevoortia tyrannus, Pomatomus saltatrix, and Paralichthys dentatus, were either scarce or occurred sporadically. Changes in species composition and numbers that have occurred in these bays during the past 12 years are probably the result of increased pollution and general environmental degradation.

Influence of Temperature Change on Number of Vertebrae and Caudal Fin Rays in Fundulus Majalis (Walbaum)

In two experiments embryos of this cyprinodontid fish were reared continuously in four fluctuating temperature regimes, 13–17°, 18–22°, 23–27° and 28–32°C to determine response of total vertebrae and total caudal fin rays to a diel-like temperature cycle. Fewer vertebrae and more caudal fin rays formed on the average in warmer temperature regimes. In one experiment transfers from cooler to a warmer regime at a three- to six-somite developmental stage produced vertebrae counts similar to those of embryos reared continuously in the warmer regime; transfers at a nine- to 12-somite stage produced vertebrae counts similar to those of embryos reared continuously in a cooler regime. In the same transfers the number of caudal fin rays formed was similar to those of embryos reared continuously at the warmer temperatures. Presumptive caudal fin ray tissue might still be influenced by temperature change at late prolarval or early postlarval stages. Two transfers from warmer to cooler temperatures at a 14- to 16-somite stage and at a 32- to 33-somite stage indicated no response by presumptive vertebrae tissue.

Cadmium Poisoning in Fundulus heteroclitus (Pisces: Cyprinodontidae) and other Marine Organisms

In acute toxicity bioassays with [Formula: see text] at 20 C and 20‰ salinity, the concentrations fatal to 50% of the organisms of various marine species in 96 hr ranged between 0.32 and 55.0 mg/liter Cd2+. The order of sensitivity was: sand shrimp, Crangon septemspinosa (0.32); hermit crab, Pagurus longicarpus (0.32); grass shrimp, Palaemonetes vulgaris (0.42); common starfish, Asterias forbesi (0.82); common soft-shell clam, Mya arenaria (2.2); green crab, Carcinus maenus (4.1); Atlantic oyster drill, Urosalpinx cinerea (6.6); eastern mud snail, Nassarius obsoletus (10.5); sandworm, Nereis virens (11.0); striped killifish, Fundulus majalis (21.0); blue mussel, Mytilus edulis (25.0); sheepshead minnow, Cyprinodon variegatus (50.0); and mummichog, Fundulus heteroclitus (55.0). Mummichogs were more susceptible to cadmium exposures at 20 C than at 5 C and at 5‰ salinity than at 15, 25, or 35‰. Additional studies with mummichogs clearly demonstrated that 96 hr was not sufficient to adequately evaluate cadmium toxicity to this species. Mummichog whole body cadmium residues determined by atomic absorption provided a useful index of cadmium body burden among fish surviving exposure. However, cadmium residue data from dead mummichogs were of limited worth owing to accumulation after death.

Studies on the Blood Morphology of Three Estuarine Cyprinodontiform Fishes

Specimens of Fundulus heteroditus, Fundulus majalis, and Cyprinodon variegatus were bled in the field at the site of capture. Blood was obtained during all seasons and in the laboratory at intervals over a 30-day period from specimens held in two types of holding aquaria. The circulating blood elements of these three estuarine species consist of erythrocytes, small and medium lymphocytes, eosinophils, and thrombocytes. The observations were made using both stained and fresh blood preparations.Variations occurred seasonally in the morphology of erythrocytes, eosinophils, and thrombocytes. Cytoplasmic inclusions were visible in erythrocytes prior to, and at the beginning of, the new breeding season. There were changes in the refringent properties of thrombocytic and eosinophilic granules, and cyclic variations in the number of eosinophilic granules. Seasonal variations occurred in the ratio of immature to mature thrombocytes, but there was little overall variation in the ratios of leucocytic cell types. The thrombocytes were characterized by thrombocytic granulation and nuclear indentations. Thrombocytes were capable of altering their form; mature cells formed thrombocytic networks.The concentration of eosinophils gradually increased to 18% above the usual level in Fundulus heteroditus held 30 days in 20-liter circular aquaria. The eosinophil level remained at the usual 2% in specimens held in 189-liter aquaria for the same time period. Values for specimens captured in a natural environment were also 2%. It is therefore plausible to relate the rise in eosinophils with an environmental stress associated with the circular holding containers.

Fine Structure of the Fibrillary Plate in the Central Head Scale of the Striped Killifish, Fundulus majalis

Fine Structure of the Fibrillary Plate in the Central Head Scale of the Striped Killifish, Fundulus majalis

Variations of the head scale pattern of the striped killifish,Fundulus majalis

Variations of the head scale pattern of the striped killifish,Fundulus majalis

A New Hemoflagellate (Genus Cryptobia) from Marine Fishes of Northern New England

A New Hemoflagellate (Genus Cryptobia) from Marine Fishes of Northern New England

Head Scale Pattern as a Characteristic for the Identification of Fundulus heteroclitus and Fundulus majalis

Head Scale Pattern as a Characteristic for the Identification of Fundulus heteroclitus and Fundulus majalis

Age, Growth, and Weight Relationships of the Striped Killifish, Fundulus majalis, near Solomons, Maryland

Age, Growth, and Weight Relationships of the Striped Killifish, Fundulus majalis, near Solomons, Maryland

The electrical response of the lateral line system of fish to tone and other stimuli.

1. The lateral line of Fundulus heteroclitus and Fundulus majalis is shown to react to tone at an intensity level of 20 dynes per sq. cm. at frequencies up to 200 or 300 cycles per second. 2. Evidence is given that the nerve can reproduce the stimulating tone frequency up to at least 180 cycles per second. 3. The response of the lateral line to the swimming movements of nearby fish is demonstrated. 4. Fundulus and several other species are shown to give strong spontaneous activity of the lateral line nerve.

SOME NEUROHUMORAL EVIDENCE FOR DOUBLE INNERVATION OF XANTHOPHORES IN KILLIFISH (FUNDULUS)

In a majority of over 50 Fundulus majalis tested, the part of a previously faded primary denervated caudal band flanked by two new secondary bands showed pigment dispersal in its xanthophores, as if affected by the stronger dispersal in those of the adjacent secondary bands. The effect appeared whether or not the radial blood vessels were cut by the incision that produced the primary band. Intact control bands, flanked identically, generally gave no sign of a like effect.A few experiments on F. heteroclitus revealed comparable responses by its xanthophores.These observations derived from the xanthophores were paralleled by some from the melanophores in F. majalis.Characteristically, slow changes in the xanthophores in response to bottom color proceeded axipetally in primary bands, and they took place in secondary bands by an analogous invasion from the edge adjoining an innervated sector rather than from the edge of the primary band.Quick pigment concentration apparently excited by handling, holding on th...

Color inheritance in Fundulus hybrids

In the hybrids of Fundulus heteroclitus and Fundulus majalis it was found that, in general, wherever the color characters were not concerned with the rate of development, the F. heteroclitus characters were dominant over those of F. majalis. These dominant characters were:1. Red yolk chromatophores large and abundant.2. Black yolk chromatophores large and usually polygonal in shape.3. An early first crop of head chromatophores is present, in addition to a later crop which is found in both pure species and both hybrids.4. There is a row of red chromatophores on the lateral line shortly before and immediately after hatching. As soon as the fish hatch the red chromatophores begin to fade, and within a few days disappear entirely.On the other hand, when the characters were concerned with the rate of development, the Mendelian dominance was partly or entirely obscured. These characters were:5. In F. heteroclitus there are no or very few black chromatophores on the lateral line at hatching; but they increase ra...