B chromosomes in {Palinurus gilchristi} (Crustacea, Decapoda) Coluccia E, Cannas R, Salvadori S, Cau A, Deiana AM Dipartimento di Biologia Animale ed Ecologia, Università di Cagliari, Italy We analyzed mitotic and meiotic chromosomes of {Palinurus gilchristi} Stebbing, 1900, a South African spiny lobster exploited by intensive fishery activity. So far the chromosome complement of this species is unknown. Mitotic and meiotic chromosomes from testis tissue were studied. Metaphase plates, obtained by air-drying techniques were Wright’s stained and C-banded. Late prophases/metaphases I bivalents showed cross, ring and dumb-bell figures; some unpaired chromosomes, completely C-positive, were present. To study the chromosome number, mitotic and metaphase II chromosomes and metaphase I bivalents were counted. Numerical variability was observed (2n=120 ÷132, n=60 ÷ 72), that could be due to the presence of heterochromatic, asynaptic B chromosomes. Two types of Bs have been identified depending on their size: small and micro Bs; their total number varied from 3 to 7. It is noteworthy that in the two other congeneric species, {P. elephas} and {P. mauritanicus} we studied, B chromosomes with similar morphology have been Among Decapoda, B chromosomes have been found in two Nephropidae species, {Nephrops norvegicus} and {Homarus americanus}.