Ovo-testis and disturbed reproductive cycle in the giant abalone, Haliotismadaka: possible linkage with organotin contamination in a site of population decline

Histological examination of gonads as well as chemical analysis of organoti n compounds in tissues of the giant abalone, Haliotis madaka, was conducted to evaluate possible endocrine disruption and to consider the causal facto rs for the decline of abalone stocks in Japan. Abalone specimens were colle cted from two different areas, Tsushima as a reference site and Jogashima a s a site representative of declining abalone populations, each month from S eptember 1995 to November 1996. Scores were given to the development stages of reproductive cells in the ovary and testis. The degree of sexual matura tion was evaluated by calculating the mean value of a histogram of these sc ores for the reproductive cells of each abalone. The temporal variations in degree of sexual maturation showed that female and male abalone from Tsush ima matured synchronously, while those from Jogashima did not. The observed maximum reproductive developmental score in abalone from Jogashima was muc h lower than that from Tsushima, because immature females were present at t he former site throughout the spawning season. Approximately 20% of the aba lone from Jogashima were masculinized females with an ovo-testis. The mascu linization of female abalone was similar to the imposer, typically induced in other gastropod molluscs by tributyltin (TBT) and triphenyltin (TPhT) fr om antifouling paints. Concentrations of TBT and TPhT in the muscles of aba lone from Jogashima (n=83) of 4.9+/-4.4ng/g wet wt and 6.3+/-6.6 ng/g wet w t, respectively, were significantly higher than those from Tsushima (n = 12 5) (P < 0.01) of 0.8+/-0.8 ng/g wet wt and 0.6+/-1.3 ng/g wet wt, respectiv ely. In situ exposure of abalone from Tsushima caged near a dockyard in Jog ashima for 7 months (from the immature to the mature stage) resulted in spe rmatogenesis in the ovary of approximately 90% of females. Endocrine disrup tion may be caused in the giant abalone by organotin compounds from antifou ling paints, which are possibly one of the causal factors for the decline o f Japanese abalone stocks. (C) 2000 Elsevier Science Ltd. All rights reserv ed.