Chromosomal and molecular characterization of 5S rRNA genes in the North American abalones Haliotis rufescens Swainson (red abalone) and H. fulgens Philippi (blue abalone).

Abalone is an extremely valuable food source derived from cultured and wild animals, the later from populations under intense fishing exploitation and of high conservation value. As part of a long-term study to characterize genes from abalone that can be used as markers for hybrids certification, we characterised 5S ribosomal DNA (5S rDNA) in red abalone (Haliotis rufescens) and blue abalone (H. fulgens). The 5S rDNA arrays occur to a single pair of metacentric chromosomes at interstitial positions in both species. Two types of 5S genes were found, named types I and II, each associated with different non-transcribed spacer (NTS) sequences. The structure of the 5S rRNA genes and the NTS indicate incomplete homogenisation of the 5S rDNA arrays. The divergence of the 5S genes between species provide polymorphisms which can be used to distinguish red from blue abalone in forensic analysis of commercial production.

Expression of the myostatin gene in the adductor muscle of the Pacific lion-paw scallop Nodipecten subnodosus in association with growth and environmental conditions.

The cDNA sequence of the myostatin gene in the Pacific lion-paw Nodipecten subnodosus (Ns-mstn) was characterized, and the temporal expression during grow-out was analyzed for the first time in a scallop. Ns-mstn encodes a 459-amino-acid protein in which two propeptide proteolytic sites were identified, the previously recognized (RSKR) and a second one at position 266-269 aa (RRKR). The alternative furin cleavage site could be related with post-translational processing, or it could be a tissue-specific mechanism for signaling activity. The Ns-mstn transcript was located by in situ hybridization in sarcomeres and around the nucleus of muscle fibers. The temporal expression analysis by qPCR in the adductor muscle showed that Ns-mstn expression was significantly different (P < 0.05) between months during the grow-out period, increasing largely during the summer months when both biomass and muscle weight did not increase or even decreased; muscle fiber size and number were found to decrease significantly. Exogenous and endogenous factors such as high temperature and low food availability, as well as gametogenesis and reproduction, can be associated with the growth pattern and Ns-mstn expression changes. Our results indicate that MSTN is involved in adductor muscle growth regulation in N. subnodosus as it occurs in vertebrate skeletal muscle although Ns-mstn expression in non-muscle organs/tissues suggests additional functions.

Allotriploid genotypic assignment in abalone larvae by detection of microsatellite-recombinant genotypes.

Abalone species are different from most mollusks utilized in aquaculture as they are known to hybridize in laboratory-induced matings. Allotriploidization of hybrid abalone has not yet been studied, and methodology useful in verifying the genotypic condition of such allotriploids do not exist. Genotypic verification of hybridization and allotriploidization in a cross of Haliotis fulgens and Haliotis rufescens was performed utilizing 6 crossamplifying microsatellite loci. Five H. rufescens spawns were used in this experiment, dividing each spawn into control and experimental hybrid groups and further into diploids and triploids. Two microsatellite loci developed for H. fulgens and H. rufescens allowed for the genotypic identification of hybrids within diploid and triploids. To further verify the percentage of allotriploids within the genotypic hybrids in the triploid hybrid groups, microsatellite loci originally developed in Haliotis corrugata and Haliotis kamtschatkana were tested for crossamplification in H. fulgens and H. rufescens. Of 21 loci, 4 were chosen for this study based on their crossamplification, heterozygosity in the females, and centromere recombination frequencies. Allotriploids in triploid-hybrid larvae were then detected by identifying larvae with recombinant genotypes at any of those loci. One family had low success verification associated with reduced recombination frequencies for all loci in that family. These results demonstrate that allotriploid verification at larval stages is feasible but depends on the number of loci available, their crossamplification in the species, and their recombination frequencies.