Abstract
The food habits of the warty crab, Eriphia verrucosa and the marbled rocky crab Pachygrapsus marmoratus are examined during this study using the frequency occurrence (% F) and point assessment (% P) methods. The overall annual stomach contents exhibited that E. verrucosa tends to be carnivore; whereas P. marmoratus is herbivorous. The two species consume a wide variety of benthic organisms comprised benthic animals as well as macro and micro algae. The stomach contents of E. verrucosa contained 57.40 % of animal origins, 23.26 % from algae and 19.34% of bottom sediments. In P. marmoratus, the stomach contents comprised 53.85 %, 27.30 % and 18.85 % of the benthic animals, benthic algae and bottom sediments, respectively. The benthic animals in the stomachs of the two species belong to different phyla, dominated by Mollusca representing 24.95 % in E. verrucosa and 21.68 % in P. marmoratus, followed by Crustacea, which have 14.04 % and 11.68 % in the two species, respectively. Results have also shown remarkable seasonal fluctuations in the diet composition and stomach fullness (feeding intensity) of the two species. The highest ratios of algae was 32.58 % and 27.32 % recorded during winter in P. marmoratus and E. verrucosa, respectively, declined sharply to the minimum values (21.49% and 19.12 %) during autumn, associated with the lowest values of sediments during winter. Animal ratios reached the maximum (60.11 % and 63.42%) in autumn and winter, but declined to the minimum (46.36% and 53.26 %) during summer in P. marmoratus and E. verrucosa, respectively. These results indicated that, both of E. verrucosa and P. marmoratus had succeeded in sharing their food resources and escape or decrease competition between them by changing types of food items either temporally or spatially according available foods.
Highlights
The brachyuran crabs, Eriphia verrucosa (Foråskal, 1775), Family Eriphiidae and Pachygrapsus marmoratus (Fabricious, 1787), Family Grapsidae, are Mediterranean species, commonly occurring at the intertidal and shallow subtidal rocky zones (Campbell, 1982; Holthuis, 1987; European Virtual Aquarium, 2009)
A- Diet composition and food items: Results of stomach contents for E. verrucosa and P. marmoratus species are given in Tables (1&2) and presented in Figure (2)
The present results showed that P. marmoratus tends to be omnivorous, with food items composed of 53.2 % animal origins, 27.5% algal fragments and 19.3 % of bottom sediments associated with bottom flora of blue green algae
Summary
The brachyuran crabs, Eriphia verrucosa (Foråskal, 1775), Family Eriphiidae and Pachygrapsus marmoratus (Fabricious, 1787), Family Grapsidae, are Mediterranean species, commonly occurring at the intertidal and shallow subtidal rocky zones (Campbell, 1982; Holthuis, 1987; European Virtual Aquarium, 2009). E. verrucosa, sometimes is called the warty crab or yellow crab (Campbell, 1982)and is the only species of Family Eriphiidae has wide distribution in the eastern and western Mediterranean, in addition to the Adriatic and Black Seas, as well as eastern coasts of Atlantic Ocean from south Brittany (France) to Morocco and Mauritania and Azores (Campbell, 1982; Holthuis, 1956, 1987; European Virtual Aquarium, 2009) Individuals of this species have been caught as far north as Cornwall and were frequent in the Black Sea, but decreased in numbers since the 1980s and became listed in the Ukrainian Red Data Book of endangered species (Dumitrache, 2009; Dan, 2013). It is semi-terrestrial crab (Cannicci et al, 1999, 2002, 2007; Warburg, et al, 2007, 2008) and lives in the shallow water habitats along the intertidal and shallow subtidal rocky shores of the Mediterranean Sea
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