Comparative tissue ascorbic acid studies in fishes

Comparative tissue ascorbic acid levels in four species of major carp viz., Labeo rohila, L. calbasu, Cirrhina tnrigala and Catla catla , were investigated. The ascorbic acid level was found to be the highest in the spleen in the four species studied (range 430–380 μg/g) followed by the anterior (adrenal) kidney, gonads, liver, renal kidney, brain and/or eye. Heart and blood had the lowest levels (range 26–18 μg/ml) amongst the tissues studied. Overall tissue ascorbic acid levels were the highest in L. rohita and the lowest in C. mrigala . Investigation on seasonal variations in blood and kidney ascorbic acid levels of Notopterus notopterus revealed peak levels in spring (February-April) and the lowest levels in the postspawning period (August-September).     

Replication banding studies in two cyprinid fishes

The use of the in vivo 5-bromodeoxyuridine (BrdU) incorporation technique made it possible to induce highly reproducible replication bands of the RBA type in two species of the order Cypriniformes (Teleostei), Rutilus rutilus and Scardinius erythrophthalmus. This allowed unequivocal identification of each individual chromosome by its banding pattern and the preparation of species specific karyotypes. Comparison of RBA-banded karyotypes of these two closely related fish species revealed that the majority of the chromosomes could be homoeologized either directly, or by assuming paracentric or pericentric inversions.by D. Schweizer     

Karyotype studies in thirteen species of fishes

The karyotypes of thirteen species of fishes belonging to nine families, studied in spermatogonial cells and in primary and secondary spermatocytes are reported. All these fishes were collected from the river Jumna near Delhi (India). The diploid number of chromosomes of these species ranges between 86 (Wallago attu) and 40 (Ompak bimaculatus). The karyotypes of seven species are characterized by exclusively possessing acrocentric chromosomes, while the remaining six species have varying numbers of metacentric chromosomes in addition to acrocentric chromosomes. Species belonging to the same family, and even the same genus, have been found to differ in chromosome number and morphology.On the basis of the data available, the author has endeavoured to discuss the relationship between cytologically known fish species and the various complications involved in their classification. The validity of the nombre fondamental hypothesis of Matthey in fish karyotypes has also been discussed.     

Cytogenetical studies in five Atlantic Anguilliformes fishes

The order Anguilliformes comprises 15 families, 141 genera and 791 fish species. Eight families had at least one karyotyped species, with a prevalence of 2n = 38 chromosomes and high fundamental numbers (FN). The only exception to this pattern is the family Muraenidae, in which the eight species analyzed presented 2n = 42 chromosomes. Despite of the large number of Anguilliformes species, karyotypic reports are available for only a few representatives. In the present work, a species of Ophichthidae, Myrichthys ocellatus (2n = 38; 8m+14sm+10st+6a; FN = 70) and four species of Muraenidae, Enchelycore nigricans (2n = 42; 6m+8sm+12st+16a; FN = 68), Gymnothorax miliaris (2n = 42; 14m+18sm+10st; FN = 84), G. vicinus (2n = 42; 8m+6sm+28a; FN = 56) and Muraena pavonina (2n = 42; 6m+4sm+32a; FN = 52), collected along the Northeastern coast of Brazil and around the St Peter and St Paul Archipelago were analyzed. Typical large metacentric chromosomes were observed in all species. Conspicuous polymorphic heterochromatic regions were observed at the centromeres of most chromosomes and at single ribosomal sites. The data obtained for Ophichthidae corroborate the hypothesis of a karyotypic diversification mainly due to pericentric inversions and Robertsonian rearrangements, while the identification of constant chromosome numbers in Muraenidae (2n = 42) suggests a karyotype diversification through pericentric inversions and heterochromatin processes.     

Cytological studies on six cyprinid fishes

The chromosome complements of six cyprinid fishes were studied, using the routine air-drying Giemsa staining technique. The diploid chromosome number recorded is 2n = 50 (8m+18sm+14st+10t) with NF = 90 in Aspidoparia morar, 2n = 50 (8m+12sm+12st+18t) with NF = 82 in Crossocheilus latius latius, 2n = 50 (6m+12sm–16st+16t) with NF = 90 in Labeo pangusia, 2n = 70 (16m+6sm+16st–32t) with NF = 108 in Perilampus atpar, 2n = 48 (4m+6st+38t) with NF = 58 in Puntius chrysopterus and 2n = 50 (2m+2sm+4st+42t) with NF = 58 in P. tetrarupagus. Sex chromosomes are not identifiable in any of these species. A pair of marker chromosomes has been observed in all species excepting A. morar.     

Nutritional programming in fishes: insights from mammalian studies

Reviews in Fish Biology and Fisheries - Epidemiological evidence and subsequent studies using mammalian models have established a strong correlation between suboptimal nutritional status during...     

Measurement of regurgitation in feeding studies of predatory fishes

Regurgitation of stomach contents in the predatory perch and pike captured in gill nets could be readily identified and occurrence measured. Stomachs following regurgitation, as opposed to true 'empty' stomachs, were large, distended, with a thin wall and little internal ridging. The mean percentage of genuinely empty stomachs over a 22-month period in perch was 20–21 % and in pike 7–10%. Regurgitation in perch was rare (<9% stomachs), normally only partial and restricted to water temperatures > 21°C: gill netting is therefore a legitimate means of sampling perch in food studies. In pike the sum of partial and complete regurgitation was important, with mean annual values in two lakes of 48 and 50%, and up to 84% in summer samples; it was related to water temperature ( x ) and described by the significant relationship y = 20.63+ x 2.84, but was unrelated to fish length and gill net mesh size. Food studies of predatory fishes using gill nets as a capture method should take account of regurgitation. Further information is required on the extent of regurgitation when other sampling methods are used.     

A new method for karyological studies in teleost fishes

A simple method employing CoCl₂, is described which has application in the rapid preparation of fish chromosomes for research and teaching. The benefits of this method include low initial skill level, relatively inexpensive equipment and supplies, and the production of a high number of metaphase spreads.     

Morphological studies of the spinal cord in tetraodontiformes fishes

The spinal cord of two tetraodontiform fishes, the Japanese file fish (Navodon modestus) and the panther puffer (Takifugu pardalis), are unusual among vertebrates in having a markedly abbreviated spinal cord with a long and flattened filum terminale. Only the rostral short part of the cord of both species is cylindrical; the greater part of the cord is markedly flat. The majority of the spinal nerve roots leave the short cylindrical part. The flattened part of the cord contains the central canal, myelinated nerve fibers, and a few motoneurons surrounding the cauda equina, and it is histologically similar to the filum terminale of amphibians and mammals. The spinal cords of other teleosts, the sun-fish and angler, also are abbreviated and possess a filum terminale and cauda equina. These orders possess an enormous head and short trunk. However, the correlation between this body form and an abbreviated cord is not causal, since the tetraodontiform species described here show ordinary body proportions. The spinal cord may be abbreviated in tetraodontiform fishes in general.     

Behavioural studies of freshwater fishes during a solar eclipse

Synopsis Effects of a total solar eclipse on fish have rarely been recorded. Three freshwater fish species — Amphipnous cuchia, Anabas testudineus and Colisa fasciata were studied during the past total solar eclipse on February 16, 1980. Behavioural studies pertaining chiefly to fish movement, fish breathing and colouration were made, and possible reasons for effects are discussed.     

The role of ecomorphological studies in the comparative biology of fishes

Synopsis The goal of an ecomorphological study is to understand the interactions between the morphology of organisms and their ecology. Both the morphology and the ecology presented by an organism are directly or indirectly under the influence of the environmental conditions that the organism experiences and its heritable composition. The development and interpretation of the central element of ecomorphological studies, the comparison between patterns of variation of morphological and ecological characters, depends heavily on the mechanistic framework provided by functional morphological and biomechanical studies. The cause-and-effect hypotheses derived from this comparison can be tested with performance trials. Ecomorphology forms an integral part of comparative biology, along with ecophysiology, behavioral ecology, and evolutionary ecology. Current issues in ecomorphological research that are addressed in this volume include application of a more functional approach to the choice of characters, integration of morphological, behavioral, and physiological information to address adaptation, and the expansion of spatial and temporal (ontogenetic and evolutionary) scales of ecomorphological questions. Future directions for Ecomorphology include broadening the knowledge base, further integration of information from other disciplines, examination of the role of environmental and genetic factors in producing and maintaining ecological and morphological diversity, and application of ecomorphological insights to questions of community structure.     

Cytogenetic studies in Brazilian marine Sciaenidae and Sparidae fishes (Perciformes)

Fishes from the families Sciaenidae and Sparidae, the former comprising coastal species associated with shallow waters on the continental shelf and the latter composed of typically marine species, are of significant economic value. Karyotypic data are available for about 20% of the total number of species in these groups. In the present study, cytogenetic analyses were carried out in three Sciaenidae species, Menticirrhus americanus, Ophioscion punctatissimus and Pareques acuminatus, as well as in the sparid fish, Archosargus probatocephalus, using conventional staining (Giemsa) and Ag-nucleolar organizer regions (NORs) and C-banding techniques. The diploid values (2n) and number of chromosome arms were equal to 48 in all species analyzed. NORs were located at pericentromeric positions, equivalent to large heterochromatic blocks, in M. americanus (1st pair), O. punctatissimus (10th pair), P. acuminatus (2nd pair), and A. probatocephalus (3rd pair). Heterochromatin was detected at the centromeric position in most chromosome pairs, being more conspicuous among Scianidae members. The remarkable karyotypic conservativeness detected in these species is similar to that observed in other perciform groups previously studied, regarding both the number of acrocentric chromosomes and NOR location. However, unusual events of heterochromatinization seem to have taken place along the karyotypic evolution of members of the family Sciaenidae. For the family Sparidae, distinct cytotypes between samples of Northeast Brazil and those previously analyzed on the southeastern coast were identified, suggesting that putative biogeographic barriers could be present throughout both regions on South Atlantic coast.     

New aspects of sex change among reef fishes: recent studies in Japan

New aspects of sex change in reef fishes are reviewed with special emphasis on recent studies in Japan. For protogyny, studies on both monandric and diandric species have been conducted, but the distinction of primary males from prematurational secondary males seems to need further examination. For protandry, detailed field studies on anemonefishes have revealed alternative life-history styles associated with movements between hosts before or after maturation. The most interesting new aspect has been the discovery of 2-way sex change within a species. Conditions for evolution of 2-way sex change are examined in relation to the size-advantage model and social control mechanisms. A fish may change sex when it becomes dominant in a mating group, but a dominant fish may also change sex in the reverse direction when its social status changes to subordinate through inter-group movement. Two-way sex change has hitherto been reported only from basically protogynous fishes (e.g., Gobiidae, Pomacanthidae, Cirrhitidae, Epinephelinae). Possibilities of the reverse sex change in the protandrous anemonefishes are discussed with data from some unpublished studies.     

Inadequacy of species-level designations for ecological studies of coastal migratory fishes

Synopsis The species is not always appropriate as a unit of measure when used in quantitative ecological studies. Analyses of fish trophic relationships in coastal areas indicate that, in many instances, more substantial ecological differences exist among life stages of a given species than among similar trophic units of different species. The use of a species in quantitative ecological studies can lead to problems of interpretation concerning the relationships of coastal fishes to complex habitats. Use of the species as a convenient unit of measure substitutes a basically taxonomic entity for more relevant life-history stages in ecological determinations. Niche breadth of a given species can be so extensive that quantitative determinations of significant ecological processes are difficult to make. Migratory coastal fishes undergo diverse ontogenetic trophic transformations. Without adequate recognition of the complex ecological stages that characterize such fishes, the oversimplification that characterizes many ecological studies in coastal areas will continue. This simplification, and the attendant overgeneralization that follows, tends to add to the continuing problem of unverified models and the inability to identify causal relationships in estuarine and coastal systems. Quantitative ecological studies would benefit from an approach that includes the use of identifiable, ontological trophic entities.