A comparative analysis of growth traits in Triploid and Diploid Genotypes of the South African abalone, Haliotis midae

[摘要] ENGLISH ABSTRACT: Abalone production is the largest financial contributor to aquaculture in South Africa andpractically all of the abalone produced is exported to Asia. This means that the productmust be globally competitive and many technologies have been applied to this cause.One that specifically shows great promise for bivalve mollusc production is triploidy; moreprecisely, sterility due to the induction of aneuploidy.Under normal maturation, energy is diverted from somatic growth through sexualmaturation, therefore inhibiting or retarding gametogenesis through a process such asaneuploidy is expected to increase growth and decrease the time to marketing.Two studies preceding this one investigated the induction of triploidy through hydrostaticshock (De Beer, 2004) and the comparative growth rate of triploid genotypes from 8 to 24months, prior to the onset of sexual maturation (Schoonbee, 2008). During thiscomparative growth stage, no convincing statistical evidence of faster growth or ofseasonal environmental effects could be obtained.It was recommended that growth between triploid and diploid variants be comparedduring the age period when sexual maturity becomes a factor to determine whethertriploidy in Haliotis midae is a useful biotechnological tool to improve biologicalproductivity and global competiveness of the abalone industry.The growth measured as shell length and wet weight in the period from 29 to 62 monthsshowed a statistically significant difference in mean weight and mean length with diploidsshowing a superior growth rate compared to their triploid siblings. This difference of 1.99mm and 5.13 g was however not perceived as being commercially significant.Important production parameters including canning yield percentage and gonadosomaticindex were also measured during this trial. For both these parameters, the triploidgenotype showed statistically and commercially significant improvement of 10.68%increased canning yield and 28.42% reduction in gonadosomatic index when comparedto their diploid counterparts.Triploid abalone was found to be not completely sterile; gametes and even maturegonads were observed in some instances. Even though complete sterility was notachieved there appeared to be a retarded gonadosomatic development in triploid variants. The delay in sexual maturation, together with the improvement in canning yield,may justify triploidy's commercial application, despite its reduced growth rate.

[发布机构] Stellenbosch University