Distribution, Abundance and Age Cohorts of Phorcus Turbinatus (Gastropoda) In Eastern Libya’s Mediterranean Sea (Published)
Distribution of Phorcus turbinatus along the littoral zones of Al-Haneah and Susah, eastern Libya’s Mediterranean Sea, at day, at low tide, was studied using belt transects with quadrates. P. turbinatus in both sites inhabited only the lower rocky littoral, many times in aggregates in tidal pools. P. turbinatus was absent in the mid and the upper rocky littoral, all the sandy shores, and the sublittoral. The abundance was maximum just above the shoreline (209 and 207 individuals/m2 in both sites), and decreased on moving up the littoral. Factors controlling the distribution were discussed. P. turbinatus showed no size gradient on moving upwards from the shoreline to the upper littoral. Frequency distribution of “height of shell from base to the apex” (HBA) indicated that P. turbinatus populations of both study sites exist in three age cohorts. Mean HBA of cohort 1 and 2 in Al-Haneah was 7 and 15mm, mean HBA of cohort 3 could not be determined; in Susah, HBA of cohorts 1 and 2 were 6 and 11.8mm.
Three hundred and five Phorcus turbinatus collected from the rocky littorals of Al-Haneah and Susah, eastern Libya’s Mediterranean Sea, were used to establish 15 measured shell-parameters and 18 calculated shell-shape indicators, which were then compared between sites, and related to shell height (HBA) and length of shell base (LB) by regression equations to find out how they vary as the animal grows. Al-Haneah P. turbinatus was larger than Susah’s (HBA = 13.729 and 12.818mm consecutively, corresponding to total weights (TW) of 3.766 and 3.179gm). As a result, the majority of Al-Haneah’s P. turbinatus measured parameters were of greater magnitude. The exponents “b” of the TW-HBA power regressions indicated negative allometric growth, while that of TW-LB indicated positive allometry. The values of the shell shape indicators of P. turbinatus in both sites were close, the shell apex was tilted to the front and to the left, the shell base was almost circular, the opening was slightly oval, and the operculum was circular. All the measured parameters, and most of the shell-shape indicators, increased with growth.
Citation: Adam Ali Faidallah, Ramadan A. S. Ali, Sayed Mohamed Ali, (2021) Morphology of Phorcus turbinatus (Gastropoda) in the Eastern Libyan Mediterranean Sea, International Research Journal of Natural Sciences, Vol.9, No.1, pp.12-18