Mugil Cephalus Linnaeus Research Articles

Ultrastructure of the scolex, rhyncheal system and bothridial pits of Otobothrium mugilis (Cestoda: Trypanorhyncha)

The ultrastructure of the scolex tegument, bothridial pits (=ciliated pits) and rhyncheal system of Otobothrium mugilis Hiscock, 1954 is described from plerocerci collected from the teleosts Arius graeffei Kner et Steindachner and Mugil cephalus Linnaeus. Scanning electron microscopy revealed that filamentous microtriches with shortened caps are abundant across the entire surface of the tegument. Palmate microtriches are dominant on the bothridia and their margins. The surfaces of bothridial pits were covered with large bifid microtriches. The bothridial pits are strongly muscularised invaginations of the tegument. Nervous tissues were not observed within the pits and it is probable that these structures function as accessory attachment structures. The wall of each tentacle sheath consists of one to three bands of fibrils, lined internally by a thin cytoplasmic layer. The tentacular walls are cellular, containing myofilaments. The fibrils of the tentacular walls are arranged into discrete blocks of parallel fibrils and appear to be intracellular. Tentacular walls are lined externally by a modified membrane with an external glycocalyx. Tentacular hooks are solid, bound externally by a membrane. The body of the hook contains numerous longitudinal canaliculi and an electron-opaque medulla lies at the centre of the hook.

Three new species of Polyclithrum Rogers, 1967 (Gyrodactylidae: Monogenea) from mugilid fishes from Australia and Brazil, with a redescription of P. mugilini Rogers, 1967.

Polyclithrum mugilini Rogers, 1967, a parasite of Mugil cephalus Linnaeus, is redescribed from type-material from Lake Seminole, Georgia, USA. Three new species of Polyclithrum Rogers, 1967 are also described: P. alberti n. sp. from M. cephalus from the Albert River, Queensland, Australia; P. boegeri n. sp. from M. platanus Günther from Rio da Guarda, State of Rio de Janeiro, Brazil; and P. corallense n. sp. from M. cephalus from Heron Island, Great Barrier Reef, Australia. The four species can be distinguished by the size and shape of haptoral sclerites, but in particular by accessory bar number 3, the dorsal bar, the marginal hooks and the hamulus point to shaft angle. The validity of Micropolyclithrum parvum Skinner, 1975, a parasite of M. cephalus in Biscayne Bay, Florida, is discussed, and a key to the species of Polyclithrum is presented.

Allozyme variation in global populations of striped mullet, Mugil cephalus (Pisces: Mugilidae)

The striped mullet, Mugil cephalus Linnaeus, 1758, is one of the few species of marine shore fish with a worldwide circumtropical distribution. Because of this distribution and the dependency of M. cephalus on coastal waters during various phases of its life cycle, as well as nearshore living habits, questions have been raised regarding levels of genetic divergence and gene flow among transoceanic populations. To cast more light on this, allozyme variation at 27 presumptive gene loci was investigated in ten globally diverse populations. The observed heterozygosity ranged from 0.018 (Hawaii) to 0.081 (Florida), averaging 0.050. The proportion of polymorphic loci showed a similar trend. Several populations were characterised by fixed allelic differences. Estimated gene diversities were very high, the allele frequency variation among populations was found to be 68%; genetic distances reached 0.242, with an average of 0.117. Estimated rates of gene flow were high among Mediterranean populations (Nm = 7.26), and between Mediterranean and East Atlantic populations (Nm= 2.86), but extremely low between non-contiguous populations within the Indian, Pacific and Atlantic Oceans, where Nm ranged from 0.03 to 0.05.

Genetic divergence and phylogenetic inferences in five species of Mugilidae (Pisces: Perciformes)

Allozyme electrophoresis was used to compare the genetic divergence of global populations of Mugil cephalus Linnaeus, 1758 and two congeneric [M.␣curema Cuvier & Valenciennes, 1836; M. gyrans (Jordan & Gilbert, 1885)] and two more distantly related [Liza ramada (Risso, 1826); Xenomugil thoburni (Jordan & Starks, 1896)] species on the basis of 18 enzyme loci. The amount of genetic divergence among the species examined is in agreement with their present systematic status, the differences being larger among non-congeneric species than among species of the same genus. Intraspecific genetic distances in M. cephalus (average Nei's D= 0.154), although higher than those reported for conspecific populations of fish, appear to be small when compared to the interspecific values among mugilid species (0.821 ≤ Nei's D ≤ 1.744). Phylogenetic trees obtained by genetic distance methods and discrete character parsimony analysis were of similar topology, except for the relationships within the genus Mugil and for the arrangement of M. cephalus populations.

Relationships between steric factors and bioconcentration of polychlorinated biphenyls (PCB's) by the sea mullet ( Mugil cephalus Linnaeus)

Isolation of the polychlorinated biphenyls (PCB's) from sea mullet ( Mugil cephalus) collected in the Brisbane River estuary indicated that these corresponded approximately to the Arochlor Grade 1260, although minor amounts of Grade 1254 were present. However the composition of the isolates similar to the 1260 Grade in all cases exhibited marked differences between the proportions of individual components present in the original mixture as compared to the mixture found in the fish. The number of chlorines in a PCB compound has an influence on bioconcentration, but with isomers it is suggested that variable uptake of the different PCB's occurs principally as a result of steric effects relating to the orientation of the two phenyl rings and the patterns of substitution of chlorine. A Steric Effect Coefficient has been empirically developed which correlates closely with relative uptake of PCB isomers.

Biochemical responses of the striped mullet Mugil cephalus to oil exposure I. Acute responses?Interrenal activations and secondary stress responses

Acute single exposures to the water-soluble fraction (WSF) of a No. 2 fuel oil influences several biochemical parameters in juveniles of Mugil cephalus Linnaeus. Plasma cortisol and glucose concentrations were measured at 1 and 3 h after exposure to 1, 5, 10 or 20% WSF. No elevation of plasma cortisol or glucose levels occurred in fish exposed to the lowest concentration of oil, whereas a dose-response relationship was observed at higher doses. The dynamics of plasma corticosteroid, glucose and cholesterol concentrations and osmolality as well as accumulation of naphthalenes in the fish tissues were monitored during exposure to 20% WSF. Circulating cortisol concentrations rose rapidly to 5 times normal values 1h after exposure to oil and subsequently declined to control levels 6 h after oil addition. A smaller secondary rise occurred at 12 h, but cortisol had returned to basal levels 12 h later. In contrast, plasma glucose, cholesterol and osmolality rose more slowly to reach maximum values between 3 and 4 h after oil addition. By 24 h plasma cholesterol and osmolality had returned to normal values whereas the hyperglycemia persisted. However, 72 h after the addition of WSF all biochemical parameters had returned to control levels. At this time considerable accumulation of total naphthalenes had occurred in several fish tissues, whilst the concentration of total naphthalenes in the exposure tanks had declined to background levels. When freshly prepared 20% WSF was added to the exposure tanks during this period, all biochemical parameters were again elevated. The results suggest that the volatile components of fuel oil in the water trigger the biochemical changes described in a dosedependent manner. The possible ecological significance of these changes and the potential use of these parameters as sublethal indicators of environmental contamination are discussed.

Experiments on induced breeding of the grey mullet in Taiwan from 1963 to 1973

The grey mullet ( Mugil cephalus Linnaeus) is widely distributed in the temperate and tropical zones of the world. It is fairly resistant to low temperature and is an omnivorous fish. In addition, it is euryhalic and can be stocked in both brackish and freshwater ponds. Therefore, the grey inullet is expected to play a very important role in future productivity as a result of efficient utilization of water area. The grey mullet is one of the commercially important fishes in Taiwan. Every year, 700 000 to 1 000 000 mullets are caught from the coastal waters of the central and south coast of western Taiwan in the season from December through February. Dried mullet roe is a gourmet food of very high price. Mullet fingerlings are collected from the estuarine waters along the west coast during the period from December through March, but there are unpredictable fluctuations in occurrence and abundance of the natural fingerlings. To ensure an adequate source of supply of fingerlings for culture operations, experiments on artificial propagation were gegun at Sanwei, Kaohsiung, in 1963, but were discontinued in the year 1967. From 1968 on, the experiments were carried out in the Tungkang Marine Laboratory. So far the experiments have been carried out for a total of 9 years. Experimental results, such as initial success of induced spawning in 1963, record of two fingerlings reared to stocking size in 1968, production of 21 688 fingerlings in 1973 when preliminary techniques of mass propagation were established, and unsolved problems, are summarized in this paper.

The culture of striped mullet ( Mugil cephalus Linnaeus) in ponds receiving heated effluent from a power plant

During 1972 and 1973, striped mullet ( Mugil cephalus Linnaeus) were stocked into six ponds (located on the upper end of the Galveston Bay system, Texas, U.S.A.) receiving heated effluent. Fish were fed commercially prepared feeds. In 1972, mean daily weight and standard length gains in two ponds were 0.71 and 0.66 g and 0.65 and 0.59 mm. In 1973, mean daily weight and standard length gains in four ponds were 0.64, 0.36, 0.67, and 0.59 g and 1.03, 0.81, 0.71, and 0.67 mm. During the two year study, survival rates ranged from 50 to 85%; production, from 293 to 804 kg/ha. Food conversion fluctuated from 2.24 to 3.31; commercial feed costs, from $0.61 to $0.87 per kg of fish.

Reproduction, growth and size allometry of Mugil cephalus Linnaeus (Pisces : Mugilidae) from north Queensland inshore waters

Aspects of growth and breeding biology of Mugil cephalus were studied in the tropical waters of North Queensland. A detailed study of size allometry was also included.

A kerosene-like taint in the sea mullet, Mugil cephalus (Linnaeus). I. Composition and environmental occurence of the tainting substance

A kerosene-like taint in sea mullet (Mugil cephalus) from south Queensland has been found to be due to a mixture of hydrocarbons closely resembling commercial kerosene in composition. Similar substances were isolated from sediments in certain areas of the Brisbane River and from effluents discharging into one of these areas. Hydrocarbon-containing sediments, consumed with food, were found in the gut of tainted sea mullet captured in the Brisbane River and are believed to cause kerosene-like tainting in the flesh. However, the presence of hydrocarbons in river water indicates the possibility of absorption through the gills. It is suggested that tainted fish from the Brisbane River join untainted fish from other rivers in the winter spawning run northwards. This may explain the capture of tainted fish, together with untainted fish, during the winter period when the commercial mullet fishery is at its maximum intensity.

Some Adult Digenetic Trematodes in Striped Mullet from the Northern Gulf of Mexico

Morphological information is given on the adults of 4 trematodes from Mugil cephalus from estuarine waters of the northern Gulf of Mexico with complementary information from specimens from Georgia. Lasiotocus glebulentus sp. n., from the Gulf, possesses a submedian genital pore and apparently differs from all known species by containing several large concretions in the excretory vesicle. Data are presented for Hymenocotta manteri Overstreet, 1969, Saccocoelioides beauforti (Hunter and Thomas, 1961) comb. n., and Dicrogaster fastigatus Thatcher and Sparks, 1958. These 3 species are now known from both the Gulf of Mexico and the western Atlantic coast. Carassotrema mugilicola Shireman, 1964, is transferred to the genus Chalcinotrema Freitas, 1947. The striped mullet, Mugil cephalus Linnaeus, is a cosmopolitan marine fish found in both fresh and salt waters of the tropical and warm temperate zones. It is a host for a large number of trematodes, many of which were cited by Doss and Farr (1969). In fact, mullet have been theorized by Manter (1957) and others as serving as an ecological bridge between trematodes of freshwater and marine fishes of coastal waters. Four adult species from the northern Gulf of Mexico are discussed below. Two others, Carassotrema mugilicola Shireman, 1964, not recovered by me, and a new species of Lecithaster Liihe, 1901, which will be described by me in a future paper, are also found in striped mullet from the Gulf region. The trematodes were examined alive, fixed in hot AFA solution under minimal coverslip pressure, and stained with Van Cleave's hematoxylin. Figures, except those designated otherwise, were drawn from mounted material with the aid of a camera lucida. All except the first are of material from the Gulf of Mexico region. Measurements are given in microns. Family Haplosplanchnidae Hymenocotta manteri Overstreet, 1969

Some Myxosporida from Marine Fishes in South Florida1

SYNOPSIS. Myxosoma cephalis n. sp. is described from the brain meninges, gills, jaw bone, crop tissue and buccal cavity of Mugil cephalus Linnaeus (striped mullet) of south Florida. The fresh spore is subspherical in front view, lenticular in side view and averages 14.1 × 11.0 × 9.0 μ (length, width, thickness). The sutural ridge is broad, the sutural line is faintly visible and the polar filaments are coiled 4–5 times. This parasite is apparently associated with an epizootic in mullet.Three species of beloniform fishes from south Florida waters were examined for myxosporidan parasites. New host records and extensions of ranges are provided for Myxidium sphaericum Thélohan in Strongylura timucu (Walbaum) (timucu), and Ceratomyxa aggregata Davis in Hyporhamphus unifasciatus (Ranzani) (halfbeak). A single spore of the genus Myxidium was found in the gall bladder of Hemiramphus brasiliensis Linnaeus (ballyhoo).

THE ECOLOGICAL SIGNIFICANCE OF FINE PARTICLE SELECTION BY THE STRIPED MULLET MUGIL CEPHALUS1

By tracer experiments using 32P and a comparison of sediment and stomach content particle sizes, Mugil cephalus Linnaeus is shown to prefer very fine particles wherever sediments are involved in feeding. It is suggested that these small inorganic and plant detrital sediment particles are much richer both in absorbed organic material and in adsorbed bacteria, Protozoa, and other microorganisms than the coarser material that the mullet rejects. This selectivity results in substantially higher organic values of the stomach contents than of the sediments.

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

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

A study of the structure and development of certain reproductive tissues of Mugil cephalus Linnaeus

A study of the structure and development of certain reproductive tissues of Mugil cephalus Linnaeus

Further Results of Tagging Sea Mullet, Mugil cephalus Linnaeus, on the Eastern Australia Coast

An account is given of tagging operations in eastern Australian waters on sea mullet. The operations involved fish of wide age and size ranges in a variety of habitats and localities, in all months of the year except July. The recoveries from these operations are analysed for information on movement, growth, and mortality. The results show the movement of the tagged fish to be predominantly northwards and require a postulate that southward movement takes place among the young fish (and possibly eggs). The movement of individual fish can be quite rapid and cover long distances, and each fish probably migrates a number of times during its lifetime. The proportion of the population involved in these movements probably exceeds 50 per cent. The results show that there is on the coast one continuous stock of this species, of which the populations occupying the numerous rivers and lakes constantly intermingle. Confirmation was obtained of the earlier workeon the technique of scale reading in this species, and of the general results on average growth rate. Growth occurs chiefly in summer, but possibly also in the latter part of spring and the early part of autumn. The physiology of scale growth and trhe formation of annual "breaks" are discussed. Proportional recoveries from each operation are reported but these cannot serve well a s an index of intensity of fishing. On the other hand, the longevity of the tags serves to indicate the probable life expectancy of these groups of fish; this is estimated as slightly more than 3 yr.