Intraspecies and interspecies hybrids in Haliotis: natural and experimental evidence and its impact on abalone aquaculture

Abstract

Abalone is a highly valued seafood in many parts of the world. Depending on size and species, it can fetch between US$15 and US$30 per kg in some markets. Because of its high value, abalone is cultured in several countries, including China, Australia, Japan, Chile, South Africa, Canada, Mexico, the USA and many other Asian countries, such as Thailand, the Philippines and Korea. Hybridization is widely used to improve specific traits in animal and agricultural stocks by using a new genetic conformation in the offspring. In general, hybridization offers several benefits in aquaculture conditions, such as improvements in growth rate, survival, food conversion and stress resistance (to temperature and disease). Under commercial conditions, hybrids make it possible to diversify the industry and to offer new products and gain new markets. This review examines evidence of wild and experimental hybridization among abalone species from several biogeographical areas worldwide, and provides information on the phenotype characteristics of artificially produced hybrid abalone. Genetic and phenotypic approaches were analysed to determine whether there is a relationship between the genetic variability and positive heterosis in hybrid crosses. In this review, we also reported embryonic and larval development of hybrid and genetic studies derived from gene expression analysis of thermal tolerance. Furthermore, alloenzyme, cytogenetic and molecular DNA markers were reviewed to certify the hybrid status in Haliotis. This review will also discuss the impact of intra and interspecies hybrids on abalone aquaculture worldwide.

Transcriptome‐wide polymorphisms of red abalone (Haliotis rufescens) reveal patterns of gene flow and local adaptation

“…Abalone hybridization is presumed rare because of the species specific interaction of gamete recognition proteins (Swanson & Vacquier ; Clark et al . ), yet natural hybrids have been reported between Haliotis rufescens and all other North American species of abalone at an average rate of 0.2% (de la Cruz & Gallardo‐Escarate ). This rate was observed to be higher in areas of ecological disturbance or at the extreme range limits of one species.…”

Karyotype comparison betweenHaliotis rubra,H. laevigataand the interspecific hybrid

“…Karyological studies provide fundamental knowledge of chromosome complement including the number, size and morphology of chromosomes for genomic and phylogenetic studies. Chromosome number comparisons have been utilized effectively in plants (Li, Guo, Wang, Li, Chen, Wei, Wang, Wu & Long ) and some fish and shellfish species (Lafarga de la Cruz & Gallardo‐Escárate and references within) contributing to an increase in the understanding of hybrid stability and performance (Li et al . ).…”

“…Hybrids have been shown to be genetically superior to pure species due to heterosis (hybrid vigour), complementarity and exploitation of greater allelic diversity through recombination and selection, particularly first generation hybrids (Falconer & Mackay ; Potts & Dungey ). Interspecific hybrids improve phenotypic traits or improve fitness in relation to the parental species (Freeman ; Lafarga de la Cruz & Gallardo‐Escárate ).…”

Experimental hybridization and genetic identification of Pacific abalone Haliotis discus hannai and green abalone H. fulgens

“…Although the genetic basis of heterosis (the superiority of hybrids) remains enigmatic (Hochholdinger and Hoecker, 2007), crossbreeding has been widely used for genetic improvement in commercial shellfish species, such as oysters, scallops and abalones (Guo, 2009). Lafarga de la Cruz and Gallardo-Escárate (2011) reviewed the studies of intraspecies and interspecies hybrids in abalone from several biogeographical areas worldwide and the impact of these hybrids on aquaculture. Some interspecies abalone hybrids have been commercially used to improve growth rate, survival rate, food conversion and stress resistance.…”