Larval Density Dynamics of Verruca spengleri (Crustacea, Cirripedia, Thoracica) in the Coastal Waters of Crimea.

Six species of barnacles belonging to three families have been recorded in the Black Sea. All of them have a pelagic stage of development in their life cycle. Verruca spengleri Darwin 1854, a representative of the family Verrucidae, is known to be a Mediterranean species that has invaded the Black Sea. The aim of this work was to study the dynamics of the population density of V. spengleri larvae in the coastal waters of Crimea. The studies were carried out in 2019–2021 along the coast of Sevastopol. Samples were taken monthly with a Juday plankton net (inlet diameter 36 cm, mill gas mesh 135 µm). The water layer of 10–0 m was investigated. Live samples were processed by total counting of the larvae in a Bogorov chamber, using MBS-9 and Mikmed-5 light microscopes. Larvae of V. spengleri were found in plankton only in the summer season. Single nauplii at the early stages of development were recorded in late May to early June when the water warmed up to 18–19°C. An increase in the density of verruca larvae was recorded in June–July at temperatures in the range of 20–25°C. In August, the number of larvae decreased approximately tenfold, while in September none were found. The data obtained indicate that the spawning period of V. spengleri off the Crimean coast lasts about three months. In recent years, near the coast of Sevastopol, the number of larvae of V. spengleri is noted to have increased significantly. Their density reached 1068–1556 ind./m3, while in the period 1994–2004 it did not exceed 153 ind./m3. The data obtained confirm that the barnacle V. spengleri has successfully naturalized and spread widely in the coastal waters of the northern part of the Black Sea. [ABSTRACT FROM AUTHOR]