Population dynamics of the copepod invader Oithona davisae in the Black Sea

Abstract

During 2013-2016 in Sevastopol Bay, seasonal and interannual dynamics of the population density, age and sex composition, fecundity, and mortality of males and females of O. davisae were studied. A maximum population number (up to 554 ind × 10 3 m-3) was registered at the end of summer-end of autumn. In this period, the nauplii and early copepodite stages constituted up to 95% of the O. davisae population. During 1-2.5 cold winter-spring months, the population consisted only of females, who were not numerous. The phase of latent population development was recorded from April until July-August, with a high share of ovigerous females, maximum clutch size, and high egg production rate but low population density, which may be due to predator pressure from lobate ctenophores. The average share of adult males amounted to 32% at the end of spring and 27% at the beginning of winter, while the share of dead males reached maximum values (20.7%) during the winter degradation period for the population. On the basis of the studied successions of the population's developmental stages, from ovigerous females through nauplii and early copepodites to adults, the number of generations produced by O. davisae during the reproductive period (10-11) was determined.

The non-indigenous Oithona davisae in a Mediterranean transitional environment: coexistence patterns with competing species

“…Therefore, these survival strategies may explain how the species copes with these extreme conditions despite its thermophilic characteristics. However, as mentioned above, in the VL the maximum abundances of O. davisae are not comparable with those reached in the native areas 17 , or in the Black Sea 63 and in the Lakes of Faro and Ganzirri 18 . Another hypothesis regarding such relevant differences in abundance, could be related to the qualitative difference in food resources between VL and the aforementioned areas.…”

“…Another hypothesis regarding such relevant differences in abundance, could be related to the qualitative difference in food resources between VL and the aforementioned areas. The dominance of O. davisae , both in the Tokyo Bay and in Black Sea, was related to a shift from a diatom-based phytoplankton community towards one with prevalence of small flagellates 63 , 64 . Oithona davisae is, in fact, an ambush feeder that prefers motile preys like flagellates, ciliates and dinoflagellates 13 , 65 , 66 .…”

First distribution record of the invasive copepod Oithona davisae Ferrari and Orsi, 1984, in the coastal waters of the Aegean Sea

“…Their abundance increased only after this period peaking by mid‐June and decreased thereafter until late winter (Uye & Sano, ). Variations in the population density of O. davisae showed clear seasonal cycle in the Sevastopol Bay, where the total abundance of the species was proportionally low within the middle spring and late summer; it increased until late autumn and dramatically decreased until mid‐February to March after the previous period (Svetlichny, Hubareva, & Işinibilir, ). The highest abundance of O. davisae in many regions of the Black Sea was reported during summer until autumn (Altukhov et al, ; Gubanova & Altukhov, ; Mihneva & Stefanova, ; Üstün & Terbıyık Kurt, ; Yıldız et al, ).…”

Ecophysiological and behavioural responses to salinity and temperature stress in cyclopoid copepod Oithona davisae with comments on gender differences

“…According to , females kept at 8ºС during 2.5 months began to lay viable eggs over several days after their transfer to warm water. The lower critical temperature for laying eggs to the ovisac was determined to be 12ºС while the maximum egg production rate was registered at 20ºС, both in the field and under laboratory conditions (Svetlichny et al, 2018).…”

“…Only at temperatures higher than 12ºС are the males capable of swimming along the water column at a speed about 10-fold higher than that of the females. Based on these experimental pieces of evidence, the end of November/mid-December, when the temperature exceeds 10ºС-12ºС, turns out to be the most probable time of insemination of females before their wintering, followed by a massive death of the males (Svetlichny et al, 2018).…”