The reproductive cycle of a local population the aspidochirote Holothuria tubulosa in Kaštela Bay (Adriatic Sea) was analysed from July 1994 to August 1995 by histological examination and observations of macroscopic features of the gonads. Five gonadal stages were described: recovery stage, growing stage, mature stage, spawning stage, and post-spawning stage. The distinguishing features used to describe gonad stages in both sexes included the main features of reproductive cells and gonad wall. The reproductive cycle showed a clear annual pattern and was synchronous in both sexes. Spawning occurred during the warm season, from July to September, when the surface water temperature ranged from about 22°C to 26°C. From October to January individuals were in resting phase and had no gonads. In both sexes, variations in maturity indices were related to the seasonal changes in temperature.

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Three colonies of warm-water coral Astroides calycularis were found at the eastern part of the middle Adriatic Sea during the 1990^2001 period. For each specimen, depth distribution and habitat were recorded. Previous and recent knowledge of this species in the Adriatic Sea and in the Mediterranean Sea was discussed in relation to climatic changes. Occurrence of A. calycularis in the Adriatic Sea was related to the increased temperatures of the surface marine layer. Variable temperature conditions were connected to the climatic changes on the hemispheric scale through the North Atlantic Oscillation index. The prevailing sea current system together with the coastal con¢guration and bottom type favours the presence of the studied warm-water coral on the eastern Adriatic coast.

Formation of biofouling communities on the surfaces of steel panels coated with two different TBT-free copper-based and one TBT-based antifouling paint was examined following submersion for periods of 3, 6, 9 and 12 months in Kastela Bay, Croatia. Test panels coated with Shopprimer and anticorrosive paint were used as control panels. Thirty five taxa of benthic algae and 32 taxa of benthic animals were found. Diatomeae dominated by frequency and abundance on test panels coated with antifouling paints, while the animal species Serpula vermicularis, Mytilus galloprovincialis and Balanus amphitrite amphitrite dominated the fouling communities on control panels. On panels protected by antifouling paints, low values of biomass were found compared to the very high values associated with control panels.

Coralline red algae are significant components of sea bottom and up to now considered as exclusively marine species. Here we present the first coralline alga from a freshwater environment, found in the Cetina River (Adriatic Sea watershed). The alga is fully adapted to freshwater, as attested by reproductive structures, sporelings, and an inability to survive brackish conditions. Morphological and molecular phylogenetic analyses reveal the species belongs to Pneophyllum and is described as P. cetinaensis sp. nov. The marine-freshwater transition most probably occurred during the last glaciation. The brackish-water ancestor was preadapted to osmotic stress and rapid changes in water salinity and temperature. The particular characteristics of the karst Cetina River, such as hard water enriched with dissolved calcium carbonate and a pH similar to the marine environment, favoured colonization of the river by a marine species. The upstream advance and dispersal is facilitated by exceptionally pronounced zoochory by freshwater gastropods. Pneophyllum cetinaensis defies the paradigm of Corallinales as an exclusively marine group.