Albinism and Polychromatism in Some Species of Woodlice from Mediterranean Regions (Isopoda, Oniscidea)

Various forms of albinism were studied in nine species of Oniscidea from fifteen populations, Agabiformius lentus; Armadillidium granulatum; Philoscia sp.; Porcellio sp., Porcellio dalensi, Porcellio laevis; Porcellionides pruinosus, Porcellionides sexfasciatus; and Soteriscus gaditanus, reared in the laboratory for more than three years. The populations studied originated from different geographical regions, i.e., Chefchaoun, Oued Laou, Rabat, and Targha (Morocco), Berkoukech, the Faculty of Sciences of Tunis, and Tabarka (Tunisia), Athens (Greece), and Saint-Martin-du-Fouilloux (France). The specimens collected were uniform grey or dark-brownish with black eyes, and these individuals were designated wild-type, from which the laboratory populations were bred. Subsequent generations were colour-polymorphic. Some differed from the wild-type in that the body was unpigmented, or white, or orange in colour, while others showed a variegated colour polymorphism, in which partial depigmentation, or albinism affected different parts of the pleon, pereion, cephalon, and antennae, or the whole of the body, irrespective of sex. Variation was also found in the eyes, where black, red, white, or depigmented-eyed individuals were observed. The populations studied exhibited significant inter- and intraspecific variation in the number of albinistic individuals. Except for Porcellio laevis, albinism was frequent and the number of albinistic specimens changed over the period of study. The incidence of albinism was greatest in populations of Porcellionides pruinosus and P. sexfasciatus from Morocco, reaching 43% in the latter. Nevertheless, no significant relationship was found between the sort of food and the number of albinistic individuals. Examination of new progeny of a population of P. sexfasciatus gathered from the wild, showed similar high frequencies of albinistic individuals.