New locality records and morphological characterization of the invasive crab population Percnon gibbesi (Decapoda: Grapsoidea) in the extreme west of the gulf of Annaba (Algeria) (Article 11)

This study describes for the first time the presence of the subtropical crab Percnon gibbesi (H. Milne Edwards, 1853) on east Algerian coasts. The morphology was studied on 102 individuals sampled from Cap de Garde (West of the Gulf of Annaba). The crabs were sampled by free diving (< 2 m), between October 2015 and March 2016. The morphology was characterized using 16 metric descriptors and five meristic descriptors (number of spines on the anterior margin of the five pairs of pereiopods). The different parts of the body were expressed as a function of the length and width of the carapace. Measurements on the left and right chela were based on the length and width of the left and right chela. Possible variations of these dimensions were sought using linear regression with the method of the least rectangle (reduced major axis). The mean numbers, modes and extreme values of each meristic descriptor were calculated and the means were statistically compared between the two sides of the crabs.