engleski

Population of the snail Cerithium lividulum Risso 1826 in Mrtvo more, Lokrum Island

Marine snail Cerithium lividulum Risso 1826 (Gastropoda: Caenogastropoda) is one of the most abundant benthic species in marine lake Mrtvo more on Lokrum island, inhabiting rocky substrates covered in algae, in the intertidal zone. There is an extreme inter- and intraspecies morphological shell variability for the smaller species of genus Cerithium, which is making it difficult to define morphological characteristics of an individual species. There is a significant lack of data in the available literature on morphometric characteristics of snail Ceritihium lividulum, and individuals from Mrtvo more were identified according to the shape of protoconch (Garilli and Galleti, 2006 ; Evangelisti et al, 2016). The aim of this research was to contribute to the knowledge of morphometric shell characteristics - height (h) and width (w) and their relations. Measurements were carried out from September 2018 to May 2018 with caliper precision 0.05 mm, five times in total, in situ. There were at least 100 individuals in each sample. Recorded data were put into tables (Microsoft Excel) and analysed with statistical package Minitab. Population (n=519) mean shell height values ranged from 11.07 ± 0.51 mm to 16.09 ± 0.12 mm, while shell width ranged from 4.57 ± 0.16 mm to 6.06 ± 0.06 mm. Maximum and minimum values of shell height and width were recorded during sampling in September 2017 (hmax= 20.00 mm, hmin= 3.00 mm, wmax=7.00 mm, wmin=1.10 mm). Average shell height in population measures 15.52 mm, while average shell width measures 5.57 mm. The largest recorded individual measured 20.00 mm shell height, which is, according to the literature, the maximum size this species can reach. Most population (n=519) had shell height between 14.50 and 17.50 mm (64.1%), and width in a narrow range between 5.50 and 6.50 mm (54.1%). Only two individuals measured shell height more than 19.00 mm, and the same two individuals had shell width larger than 7.50 mm. There is a statistically significant difference between height and width (T-test ; p<0.05, t-value = 55.94). The mean height value of an overall sample population is significantly larger than the mean width value (hsv = 15.52 ± 0.15, wsv = 5.57 ± 0.05). The Pearson's correlation coefficient (r=0, 869, p=0, 000) determined there is a strong positive correlation between height and width which means there is a compatible growth of both values. Regression analysis confirmed a positive allometric growth ; for every 1.00 mm increase in width, there is a 2.80 increase in height. This relation between height and width is also recorded in juvenile individuals. The highest abundance of juveniles was noted in September 2017, which was confirmed by the smallest mean value of height and width during that sampling (h=11.07, w=4.57).

benthic fauna ; Gastropoda ; marine lake ; morphometric characteristics ; protected area

nije evidentirano