Genotype frequencies in the Calafuria population of Balanophyllia europaea at the analyzed loci

1. Genetic evidence of an unusual breeding system in the Mediterranean solitary coral Balanophyllia europaea Mezzomonaco L., Goffredo S., Zaccanti F.  Department of Evolutionary and Experimental Biology, University of Bologna, via F. Selmi 3, I-40126 Bologna, Italy An adult specimen of Balanophyllia europaea photographed at 6 m depth in at Calafuria (Leghorn, NW Mediterranean) during a night dive . Bar, 5 mm. Histological studies performed on samples of Balanophyllia europaea have shown that it is a simultaneous hermaphrodite with no physical separation between male and female gametogenesis and a brooder species. We also observed that when the gonads reach full maturity encounters may occur between gametes of the opposite sex produced by the same individual, an indication of possible self-fertilization. A gene-enzyme systems analysis has been undertaken on polyps collected at Calafuria (Leghorn, eastern Ligurian sea) through cellulose acetate electrophoresis. We assayed eighteen enzymes using three buffer systems, but resolution was good for only ten of them ( PGI, PGM, PGD, HK, ME, MPI I, MPI ll, AK, SOD, LDH ). Population genotypic frequencies for the ten loci scored differed significantly from Hardy-Weinberg’s equilibrium, showing a marked deficiency of heterozygotes. Preliminary studies on the existing genetic relationship between adult polyps and brooded offspring were performed on 6 homozygous adults with 2-15 young per adult. The offspring were identical to their parents. We have not up to now examined offspring of heterozygous adults. On the whole, we have identified an unusual breeding system in B. Europaea in which cross-fertilization is rare; the data thus fare collected does not, however, let us to determine which among the different reproductive modes, i.e., self-fertilization, parthenogenesis, and asexual reproduction, is the prevailing breeding system in this species. Studies in progress will contribute to the understanding of the selected reproductive strategy in B. europaea. Hermaphroditism in Balanophyllia europaea. In this histological section a vitellogenic oocyte (o) and three clusters of mature spermatozoa (szoi) are visible in the same mesenterial septum (ms). cc, coelenteric cavity; ss, skeletal septum. Bar, 50 mm. Brooding in Balanophyllia europaea. Embryos (e) at the gastrula stage of development are visible in this cross-section of the basal region of an adult specimen. o, vitellogenic oocytes; s,speramatocysts. Bar, 400 mm. Genotype frequencies in the Calafuria population of Balanophyllia europaea at the analyzed loci (n = number of individuals) 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 P1 o1 P2 o2a o2b o2c o2d Balanophyllia europaea. Parental individuals (P1, P2) and offspring (o1, o2a-d ) phenotypes at the Pgi locus. Balanophyllia europaea. One heterozygous (lane 3) and seven homozygous adult individuals are shown for the Pgm locus Balanophyllia europaea. Eight homozygous adult individuals are shown for the Pgi locus Acknowledgements : This work are supported by grants from Scuba Schools International Italia, Mobby’s, the Italian Ministry for University and Scientific and Technological Research, and sponsored by the Underwater Life Project. We wish to thank Prof. B. Mantovani, Dr R. Falconi, Dr M. Cesari, Dr A. Luchetti, Mr M. Manca, Bologna Scuba Team, Marine Science Group