et al. (2019), showing a high richness of sessile fauna, including several NIS. Our study
took place for the duration of one year, from December 2017 to December 2018. We
deployed three artificial sponges fortnightly at 30 cm depth, in direct contact with the
quay, and collected them after two months, a time considered suitable for fouling
colonisation at these latitudes (Ros et al., 2020). During every sampling event, we used
a digital thermometer to measure water temperature. A total of 72 sponges were
collected and stored in plastic containers filled with 90% ethanol. The fouling
component was sorted under a stereomicroscope; all P. japonica individuals were
measured, and the total and mean abundance along with standard deviations (SD) were
determined for every sampling event. Mean length and SD were plotted, for the entire
population as well as separately for males, females, and juveniles alone.
Results
Over 1400 individuals of P. japonica in the Marina di Ragusa port were found across
the 12 months of study, sexed, and measured for total length; 63% were juveniles,
28.5% were females and 8.5% were males. The species presented a strong seasonal
pattern, surviving at very low densities during winter (minimum values observed in
February), while reaching its higher densities in summer (maximum values observed in
August). Size ranged between 1.172 mm and 11.884 mm. Both smaller and larger size
classes occurred through all the year, although with variable abundance.
Discussion and conclusions
The population of P. japonica in the Marina di Ragusa touristic harbour was well
established and persistent throughout the year. An interesting result of our study regards
the positive response of the population to increasing temperature: despite its native
origin in the cold Okhotsk Sea, (Richardson, 1909; Nunomura, 1975), it appears that P.
japonica has shown to have well adapted to the warm conditions of Mediterranean
summer. All artificial sponges were successfully colonised by mobile and sessile fauna,
and by P. japonica individuals, hence they can be considered a useful and reliable
substrate for quantitative mid/long-term studies on population dynamics of small marine
invertebrates.
Bibliography
NUNOMURA N. (1975) - Marine Isopoda from the rocky shore of Osaka Bay, Middle Japan
(1). OMNH Bull., 29: 15–35.
RICHARDSON H. (1909) - Isopods collected in the Northwest Pacific by the US Bureau of
Fisheriessteamer Albatross in 1906. Proc. U. S. Natl. Mus., 37: 75-129.
ROS M., NAVARRO-BARRANCO C., GONZÁLEZ-SÁNCHEZ M., OSTALÉVALRIBERAS E., CERVERA-CURRADO L., GUERRA-GARCÍA J. M. (2020) - Starting
the stowaway pathway: the role of dispersal behavior in the invasion success of low-mobile
marine species. Biol. Invasions, 22 (9): 2797-2812.
ULMAN A., FERRARIO, J., OCCHPINTI-AMBROGI, A., ARVANITIDIS, C., BANDI, A.,
BERTOLINO, M., BOGI C., CHATZIGEORGIOU G., ALI ÇIÇEK B., DEIDUN A.,
RAMOS-ESPLÀ A., KOÇAK C., LORENTI M., MARTINEZ-LAIZ G., MERGLO G.,
PRINCISGH E., SCRIBANO G., MARCHINI A. (2017) - A massive update of nonindigenous species records in Mediterranean marinas. PeerJ, 5: e3954.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
122
took place for the duration of one year, from December 2017 to December 2018. We
deployed three artificial sponges fortnightly at 30 cm depth, in direct contact with the
quay, and collected them after two months, a time considered suitable for fouling
colonisation at these latitudes (Ros et al., 2020). During every sampling event, we used
a digital thermometer to measure water temperature. A total of 72 sponges were
collected and stored in plastic containers filled with 90% ethanol. The fouling
component was sorted under a stereomicroscope; all P. japonica individuals were
measured, and the total and mean abundance along with standard deviations (SD) were
determined for every sampling event. Mean length and SD were plotted, for the entire
population as well as separately for males, females, and juveniles alone.
Results
Over 1400 individuals of P. japonica in the Marina di Ragusa port were found across
the 12 months of study, sexed, and measured for total length; 63% were juveniles,
28.5% were females and 8.5% were males. The species presented a strong seasonal
pattern, surviving at very low densities during winter (minimum values observed in
February), while reaching its higher densities in summer (maximum values observed in
August). Size ranged between 1.172 mm and 11.884 mm. Both smaller and larger size
classes occurred through all the year, although with variable abundance.
Discussion and conclusions
The population of P. japonica in the Marina di Ragusa touristic harbour was well
established and persistent throughout the year. An interesting result of our study regards
the positive response of the population to increasing temperature: despite its native
origin in the cold Okhotsk Sea, (Richardson, 1909; Nunomura, 1975), it appears that P.
japonica has shown to have well adapted to the warm conditions of Mediterranean
summer. All artificial sponges were successfully colonised by mobile and sessile fauna,
and by P. japonica individuals, hence they can be considered a useful and reliable
substrate for quantitative mid/long-term studies on population dynamics of small marine
invertebrates.
Bibliography
NUNOMURA N. (1975) - Marine Isopoda from the rocky shore of Osaka Bay, Middle Japan
(1). OMNH Bull., 29: 15–35.
RICHARDSON H. (1909) - Isopods collected in the Northwest Pacific by the US Bureau of
Fisheriessteamer Albatross in 1906. Proc. U. S. Natl. Mus., 37: 75-129.
ROS M., NAVARRO-BARRANCO C., GONZÁLEZ-SÁNCHEZ M., OSTALÉVALRIBERAS E., CERVERA-CURRADO L., GUERRA-GARCÍA J. M. (2020) - Starting
the stowaway pathway: the role of dispersal behavior in the invasion success of low-mobile
marine species. Biol. Invasions, 22 (9): 2797-2812.
ULMAN A., FERRARIO, J., OCCHPINTI-AMBROGI, A., ARVANITIDIS, C., BANDI, A.,
BERTOLINO, M., BOGI C., CHATZIGEORGIOU G., ALI ÇIÇEK B., DEIDUN A.,
RAMOS-ESPLÀ A., KOÇAK C., LORENTI M., MARTINEZ-LAIZ G., MERGLO G.,
PRINCISGH E., SCRIBANO G., MARCHINI A. (2017) - A massive update of nonindigenous species records in Mediterranean marinas. PeerJ, 5: e3954.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
122