Response to salinity and temperature changes in the alien Asian copepod Pseudodiaptomus marinus introduced in the Black Sea

Abstract

The salinity tolerance and the effect of temperature were studied on the behavior and motor activity of the nonindigenous Indo‐Pacific calanoid copepod Pseudodiaptomus marinus, first found in Sevastopol Bay (Black Sea) in autumn 2016. According to the index of median lethal salinity (LS50), the salinity tolerance range of adult P. marinus collected at 18.0 psu in November 2016 and subsequently reared in the laboratory amounted to 5.0–44.0 psu, independently of the acclimation regime. Females of P. marinus collected in December 2016 at 12.0°C became torpid at 8.0°C, a value typical of winter–spring Black Sea coastal areas. An increase in temperature from 8.0°C to 27.0°C led to an increase in the beat frequency of mouth appendages, swimming speed, and time spent cruising. However, at the same high temperature, the mean cruising speed in the feeding‐current feeder P. marinus was 2‐fold lower than that of the native, similarly sized cruise feeder Pseudocalanus elongatus. On the contrary, mouthpart beat frequency while cruising was 2‐fold higher reaching 80 Hz, due to the creation of feeding currents in P. marinus. The results of our experiments confirm the euryhaline character of P. marinus, and point to an apparent ability to survive cold temperatures in a torpid state. This suggests the possibility of entering an overwintering stage to survive the adverse cold winter–spring environmental conditions of the Black Sea, similarly to the recent thermophilic Indo‐Pacific invader Oithona davisae which established a successful population in the same area.

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

“…The salinity tolerance range of this species in the case of the direct transfer to water of different salinity is similar to that scored under gradual changes, revealing that the salinity tolerance range is independent of the acclimation process. A similar salinity window has also been observed recently for Pseudodiaptomus marinus (Svetlichny et al, 2019), a calanoid species which, just like O. davisae, is renowned for its great ability to spread in environments covering a wide haline spectrum (Sabia et al, 2015;Uttieri et al, 2020). This shared trait suggests that haline flexibility and adaptability might represent a key to success in the introduction and establishment of non-indigenous species, allowing both species to adapt to environments characterised by different salinities.…”

WGEUROBUS – Working Group “Towards a EURopean OBservatory of the non-indigenous calanoid copepod Pseudodiaptomus marinUS”

“…1) adheres to these general characteristics. This species tolerates wide salinity (Islam et al 2006b;Sabia et al 2015;Suzuki et al 2013;Svetlichny et al 2019) and temperature (Liang and Uye 1997;Sabia et al 2015;Svetlichny et al 2019) ranges, alternating epibenthic and pelagic phases (Sabia et al 2014(Sabia et al , 2015 while exploiting both herbivory and detritivory feeding habits (Uye and Kasahara 1983).…”

“…The documented euryhalinity and eurythermicity of P. marinus (Sabia et al 2015;Suzuki et al 2013) can provide an additional advantage in the spreading into new environments. A recent investigation within WGEUROBUS framework (Svetlichny et al 2019) on a laboratory reared population showed that the salinity tolerance range of P. marinus adults is comprised between 3.0 and 45.0. Such a wide salinity window can represent a potentially advantageous trait, allowing this species to establish in extremely diverse environments.…”

“…Since 2007, its presence has additionally been documented in European waters (Mediterranean Sea, Black Sea, European Atlantic coasts, Southern North Sea), with a stably increasing number of records (as reviewed in Sabia et al 2015). Wide temperature and salinity tolerance (Sabia et al 2015;Suzuki et al 2013;Svetlichny et al 2019), behavioural plasticity (Sabia et al 2014), resistance to metallic stress (Tlili et al 2016) and possible presence of genetic divergence among populations (Sabia et al 2017) are some of the specific biological and ecological traits of P. marinus which may support its capacity to become established in new environments. Each of them, either alone or in combination, may provide an adaptive advantage by which adjusting to diversified environments and so facilitating the establishment in new areas.…”

Pseudodiaptomus marinus Sato, 1913 in the Black Sea: morphology, genetic analysis, and variability in seasonal and interannual abundance

“…This copepod thrives in habitats with temperatures ranging from 6.3 to 31.5 °C and 2.5 to 38.5 ppt salinity ( Sabia et al, 2015 ; Uttieri et al, 2020 ). According to an experimental study by Svetlichny et al (2019) , the adult P. marinus has a salinity tolerance ranging between 5.0 and 44.0 ppt, and a temperature tolerance ranging from 8.0 °C and 27.0 °C. P. marinus is epibenthic during the day, but swims up the water column at dusk and acts as a pelagic species during the night ( Uye & Kasahara, 1983 ; Sabia et al, 2015 ).…”