A Molecular Cytogenetic Map of Scallop (Patinopecten yessoensis)

Establishment and Characterization of Bisexually Fertile Triploid Dwarf Surf Clam Mulinia lateralis

Triploids are widely used to rapidly achieve genetic improvements of organisms due to their fast growth and enhanced environmental adaptability. Artificially induced triploids are generally considered to be infertile owing to the obvious inhibition of gonadal development. Recently, some fertile individuals with reduced advantages have been found in triploid bivalves, which is a notable deviation from the original intention of artificially inducing triploids. This study utilized dwarf surf clams (Mulinia lateralis), a promising model organism of bivalves, to develop a model for exploring the potential mechanism of triploid reproduction. The results showed that the optimal induction condition for triploid M. lateralis, determined by orthogonal experiments, was 0.5 mg/L cytochalasin B (CB) to inhibit PB2 for 20 min, resulting in a triploidy rate of 95.57% and a hatching rate of 60.25%. By tracking the development of M. lateralis, we found that the induced triploids could develop normally to maturity and exhibited significant growth and survival advantages post-metamorphosis. Although the triploidy rate exhibited a slight decline overtime, it remained high, with a ratio of 90.63% at 120 dpf. Histological observation confirmed that the gonadal development pattern of triploid M. laterali was similar to that of diploids, but it also showed characteristics such as developmental retardation, few mature gametes, and gamete gigantism. The dynamic expression of genes related to gonadal development provided further molecular evidence for this phenomenon. Additionally, 82.6% of triploid M. laterali exhibited normal spawning behavior, produced fewer but larger viable gametes, and could generate offspring with full developmental potential. Flow cytometry analysis revealed that sperm of triploid M. laterali was aneuploid, with a DNA content of about 1.5 times that of diploid sperm, and the ploidy levels of mating offspring were 2N (DD, diploid female × diploid male), 2.5N (DT, diploid female × triploid male), 2.5N (TD, triploid female × diploid male), and 3N (TT, triploid female × triploid male), respectively. Overall, the artificially induced triploid M. laterali has been confirmed to be bisexually fertile, which will provide a unique model for exploring the underlying mechanisms of advantageous trait formation and fertility regulation in triploids, and offer a valuable platform for the study of ploidy control and polyploidization in bivalves. Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary. Yes, i have checked and it is OK.

A Comprehensive Integrated Genetic Map of the Complete Karyotype of Solea senegalensis (Kaup 1858)

Solea senegalensis aquaculture production has experienced a great increase in the last decade and, consequently, the genome knowledge of the species is gaining attention. In this sense, obtaining a high-density genome mapping of the species could offer clues to the aquaculture improvement in those aspects not resolved so far. In the present article, a review and new processed data have allowed to obtain a high-density BAC-based cytogenetic map of S. senegalensis beside the analysis of the sequences of such BAC clones to achieve integrative data. A total of 93 BAC clones were used to localize the chromosome complement of the species and 588 genes were annotated, thus almost reaching the 2.5% of the S. senegalensis genome sequences. As a result, important data about its genome organization and evolution were obtained, such as the lesser gene density of the large metacentric pair compared with the other metacentric chromosomes, which supports the theory of a sex proto-chromosome pair. In addition, chromosomes with a high number of linked genes that are conserved, even in distant species, were detected. This kind of result widens the knowledge of this species’ chromosome dynamics and evolution.