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At least 397 records · Page 22Linked to original sources

Gene action in fish of tetraploid origin. II. Cellular and biochemical parameters in clupeoid and salmonoid fish.

By use of cell size, protein and hemoglobin content, and enzyme activities as markers, it becomes apparent that in the course of evolution the gene expression of anciently tetraploid fish of the order Ostariophysi was diploidized, but no such regulatory mechanism has evolved in the phylogenetically tetraploid species of the order Isospondyli. This finding is discussed in terms of possible selective neutrality of tetraploid expression and the phylogenetic age of Isospondyli.

Animals↗

[The development of the nervous system: from fly to fish, from fish to man....].

The nervous system of vertebrates is more complex and less tractable than that of current model organisms such as the fly and the nematode. Here we present a vertebrate sensory system which is structurally simple, experimentally accessible and genetically suitable: the lateral line of the zebra-fish. We review our recent work on the development of this system, with a particular emphasis on the migration events that shape the pattern of sense organs. Some of the factors involved in these migration events turn out to be similar to the factors that direct the formation of metastases in specific types of human cancers, illustrating once again the remarkable conservation of developmental mechanisms and genes throughout the animal kingdom.

Animal Structures↗

Biting cleaner fish use altruism to deceive image-scoring client reef fish.

Humans are more likely to help those who they have observed helping others previously. Individuals may thus benefit from being altruistic without direct reciprocity of recipients but due to gains in 'image' and associated indirect reciprocity. I suggest, however, that image-scoring individuals may be exploitable by cheaters if pay-offs vary between interactions. I illustrate this point with data on cleaner-client reef fish interactions. I show the following: (i) there is strong variation between cleaners with respect to cheating of clients (i.e. feeding on client tissue instead of parasites); (ii) clients approach cleaners, that they observe cooperating with their current client and avoid cleaners that they observe cheating; (iii) cleaners that cheat frequently are avoided more frequently than more cooperative cleaners (iv) cleaners that cheat frequently behave altruistically towards their smallest client species; (v) altruistic acts are followed by exploitative interactions. Thus, it appears that cleaners indeed have an image score, which selects for cooperative cleaners. However, cheating cleaners use altruism in potentially low-pay-off interactions to deceive and attract image-scoring clients that will be exploited.

Adaptation, Physiological↗

An aromatic-dependent mutant of the fish pathogen Aeromonas salmonicida is attenuated in fish and is effective as a live vaccine against the salmonid disease furunculosis.

Aeromonas salmonicida is the etiological agent of furunculosis in salmonid fish. The disease is responsible for severe economic losses in intensively cultured salmon and trout. Bacterin vaccines provide inadequate protection against infection. We have constructed an aromatic-dependent mutant of A. salmonicida in order to investigate the possibility of an effective live-attenuated vaccine. The aroA gene of A. salmonicida was cloned in Escherichia coli, and the nucleotide sequence was determined. The codon usage pattern of aroA was found to be quite distinct from that of the vapA gene coding for the surface array protein layer (A layer). The aroA gene was inactivated by inserting a fragment expressing kanamycin resistance within the coding sequence. The aroA::Kar mutation was introduced into the chromosome of virulent A. salmonicida 644Rb and 640V2 by allele replacement by using a suicide plasmid delivery system. The aroA mutation did not revert at a detectable frequency (< 10(-11). The mutation resulted in attenuation when bacteria were injected intramuscularly into Atlantic salmon (Salmo salar L.). Introduction of the wild-type aroA gene into the A. salmonicida mutants on a broad-host-range plasmid restored virulence. A. salmonicida mutant 644Rb aroA::Kar persisted in the kidney of brown trout (Salmo trutta L.) for 12 days at 10 degrees C. Vaccination of brown trout with 10(7) CFU of A. salmonicida 644Rb aroA by intraperitoneal injection resulted in a 253-fold increase in the 50% lethal dose (LD50) compared with unvaccinated controls challenged with a virulent clinical isolate 9 weeks later. A second vaccination after 6 weeks increased the LD50 by a further 16-fold.

4-Aminobenzoic Acid↗

Ontogeny of feeding morphology and kinematics in juvenile fishes: a case study of the cottid fish Clinocottus analis

The development of feeding morphology, kinematics and behavior was examined in the juveniles of the cottid fish Clinocottus analis. The attacks of 18 juvenile C. analis, between 17.59 mm and 42.15 mm in standard length (SL), feeding on brown worms were filmed using high-speed video. Feeding mode, ram- or suction-dominated, kinematic variables and morphology were quantified and compared over the juvenile period. The analysis of these three factors was based on the following questions: (1) do they change over ontogeny; (2) how do their values compare with those of larvae, juveniles and adults of other species; and (3) what is the level of stereotypy, as measured by the variance in these factors, at this stage in ontogeny and does it change? Small C. analis juveniles have the small gape and large buccal cavity of a suction feeder, and this morphology becomes more pronounced as they become larger. The kinematic variables of C. analis juveniles are similar to those of adult suction-feeding cottids and least-squares regression analysis showed significant changes in only two variables (time to prey capture and absolute attack predator&shy;prey distance) over the juvenile period. Feeding mode, as measured by the ram-suction index, shows an increase in the suction component of the strike with increasing size. This study demonstrates that, in C. analis, suction feeding behavior develops during the juvenile period. Within the juvenile stage, morphology, prey-capture kinematics and feeding mode are not tightly linked ontogenetically such that suction-feeder kinematics (short predator&shy;prey distance and low attack velocity) and basic morphology (small gape, large buccal volume) develop much earlier than the employment of a large suction component during the strike.

Journal Article↗

Fish gonadotropin-releasing hormone gene and molecular approaches for control of sexual maturation: development of a transgenic fish model.

The prepro-GnRH gene and mRNA primary structure were fully established from Atlantic salmon (Salmo salar) and partially from rainbow trout (Oncorhynchus mykiss). Results show that the GnRH coding region of 30 base pairs is well conserved during evolution. In contrast, the GnRH-associated peptide (GAP) sequence shows very limited homology when the GnRH genes from mammalian and teleost species are compared. A simple method for selecting transgenic fish after transfer of the firefly luciferase gene was developed. The method involves bioluminescent measurement of live animals in a scintillation counter.

Amino Acid Sequence↗

Split centromeric alpha-satellite FISH signals in a whole arm translocation 5p;10p: consequences and implications for interphase FISH studies.

This is a case report of an apparently balanced whole arm translocation between the short arms of chromosomes 5 and 10 in which the centromeric alpha-satellite DNA is split between both derivative chromosomes for both probes, leading to abnormal signal patterns. The patient requested preimplantation genetic testing for the unbalanced products of the translocation. However, using centromeric alpha-satellite DNA probes as controls for the subtelomeric-specific probes in interphase was not informative because of the split signals. The ramifications of such variation in the alpha-satellite regions of chromosomes for other interphase FISH tests are discussed.

Journal Article↗

Reverse genetics on fish rhabdoviruses: tools to study the pathogenesis of fish rhabdoviruses.

Rhabdoviruses, mainly in rainbow trout, are among the most devastating viruses for worldwide aquaculture. To date no effective treatments to fight against these viruses are available. During the past years, several approaches to develop efficient vaccines have been undertaken such as the use of immunogenic recombinant viral proteins, naked DNA or inactivated viruses. However, although these vaccines have been proven to be very effective on a small scale, they have never been used in the field because the vaccines would have to be injected into thousands of yearling trouts. The only alternative to injection consists of the development of attenuated live vaccines that can be administrated to trouts by bath immersion. Reverse genetics on trout rhabdoviruses offer the possibility of recovering a series of live recombinant viruses in which the viral genome has been irreversibly modified to generate cost-effective live, safe vaccines.

Animals↗