Christos Gkenas

The reproductive behavior of Economidichthys pygmaeus: secondary loss of sound production within the sand goby group?

In this study, the reproductive behavior of Economidichthys pygmaeus was investigated under laboratory conditions with simultaneous video and acoustic recordings. Males of the freshwater goby E. pygmaeus do not produce sounds either during the courtship/spawning phase or during aggressive interactions. A detailed analysis of the behavioral sequences revealed the absence of any digging and nest-building activities, whereas the other behavioral components of courtship and spawning are similar to those described for other goby species, showing also a similar function. Results were discussed in terms of secondary loss of sound production within the sand gobies, a group of highly soniferous fishes in the family Gobiidae.

Shrimps of an ancient Balkan lake: Bionomy and conservation

In order to have a comprehensive evaluation and classification of the natural biota of Lake Pamvotis, the present study aims at investigating shrimps’ bionomic traits. Information on shrimps’ habitat preferences, abundances, and syntopic species in relation to the physicochemical profile of the lake’s water are investigated for the first time. The study was carried out on a bi-monthly base, at six littoral sites of the lake. Samples’ study from different habitats and seasons revealed that the freshwater shrimp Atyaephyra thyamisensis was the most abundant species, accounting for 44.76% of the total taxa catch, while the grass shrimp Palaemonetes antennarius was less abundant (7.54%). Syntopic fish species in the littoral zone of Lake Pamvotis such as Economidichthys pygmaeus, Gambusia holbrooki, Knipowitschia caucasica and Rutillus panosi showed interannual differences with abundances of 24.12%, 19.13%, 4.26% and 0.20%, respectively. Correspondence analysis revealed clear patterns between species and stations. A. thyamisensis was predominant in shallow, well oxygenated water bodies rich with aquatic vegetation, but it was absent from deeper habitats. P. antennarius was found mainly in lentic water bodies, rocky substratum and deeper habitats. Taking into account the high ecological importance of the freshwater shrimps in ecosystems’ energy flow, ecological and biological data of lake’s shrimps are discussed and presented thoroughly. Threats and conservation measures for both shrimp species are debated also in detail.

Genetic structure of the South European toothcarp Aphanius fasciatus (Actinopterygii: Cyprinodontidae) populations in the Mediterranean basin with a focus on the Venice lagoon

ABSTRACT The genetic structure of Aphanius fasciatus populations has been analysed using two mitochondrial DNA (mtDNA) markers (16S rRNA and D-loop) obtained from specimens collected in nine sites from the Venice lagoon, Comacchio saltworks and Corsica. Available GenBank sequences were also included, in order to extend the results on a Mediterranean scale. Genetic polymorphism within the Venice lagoon was very low, with most of the specimens analysed (66% for 16S rRNA and 83% for D-loop) sharing the same haplotype for either of the two markers. The genetic homogeneity found within the Venice lagoon may be the consequence of the northward migration of southern Adriatic populations after the Last Glacial Maximum: mismatch analysis showed indeed clear signs of a rapid demographic and spatial expansion. To explain this genetic homogeneity other hypotheses were also suggested, such as adaptation to the high variability of brackish water habitats, and artificial introductions. On a Mediterranean scale, phylogenetic analyses showed the presence of five distinct geographical lineages: Aegean Sea, Greek coast of the Ionian Sea, Adriatic Sea, Tyrrhenian Sea and Southern Sicily. Analysis of molecular variance revealed a genetic partitioning mainly due to differences between groups presumably due to late Miocene geological events, while less polymorphism was present within groups and populations.