Yolk-sac larval development of the substrate-brooding cichlid Archocentrus nigrofasciatus in relation to temperature.

In order to conserve and culture the cichlid fish Archocentrus nigrofasciatus, more information about its reproductive biology and its larval behavior and morphogenesis is necessary. Currently, temperatures ranging from 21 to 27 °C are used in ornamental aquaculture hatcheries. Lower temperatures are preferred to reduce the costs of water heating, and 23 °C is usually the selected temperature. However, there is limited information on culturing protocols for ornamental species and most of the information generated on this topic remains scarce. Thus, the present study examines the morphological development of Archocentrus nigrofasciatus during the yolk-sac period up to the age of 100 h post-hatching in relation to 2 temperature regimes used in ornamental aquaculture: a temperature of 27 °C (thermal optimum) and a decreased temperature of 23 °C (thermal tolerance). The results of this study suggest that the 27 °C temperature generates intense morphological changes in yolk-sac development in a shorter period. This has advantages as it reduces the time of yolk-sac larval development, and, thus, minimizes the transition phase to exogenous feeding and maximizes the efficiency at which yolk is converted into body tissues. The present paper provides necessary information to produce freshwater ornamental fish with better practices so as to increase larval survival and capitalize on time for growth.

Genetic differentiation among Greek lake populations of Carassius gibelio and Cyprinus carpio carpio.

The genetic structure of the Western Greece lake populations of Carassius gibelio and Cyprinus carpio carpio populations was characterized by using a PCR-based RFLP and sequencing analysis of mitochondrial rDNA genes and regions (16S rDNA, cytochrome b and D-loop). Our analysis was able to detect: (a) two haplotypes in C. c. carpio populations and two haplotypes in C. gibelio populations (b) a high nucleotide divergence between the two species and (c) two genetically distinct C. gibelio populations, one existing in the Amvrakia habitat (AMV1) with a second in Ozeros and Trichonida (OZE1 and TRI1) habitat. The present analysis indicates that genetic diversity observed was limited with a haplotype index between 0.0 and 55.6%, and a nucleotide diversity within and among populations between 0.0 and 1.27%. It also underlines a restricted mtDNA-based evaluation of the phylogenetic relationships among C. gibelio and C. c. carpio populations. In addition, the present study contributed knowledge on the genetic variation and structure of these populations which is absolutely necessary for any efficient fish management and/or conservation programme.