Toward Understanding Mechanistic Regulation of Body Size and Growth Control in Bivalve Mollusks

Bivalves possess a pair of valves connected to a stretchable ligament that facilitates the opening and closing of the shell. The growth bioprocess commences when the supplemental materials secreted from the edge are added to the early-constructed shell. Here, we endeavor to provide a glimpse into physiological responses, mechanistic control, and omics applications toward understanding this complex trait. In the first section, we review studies that have been performed to investigate the effects of food availability, temperature, salinity, contaminants, and climate change in natural ecosystems and under experimental conditions. These conditions affect some internal promotors and alter the concentration of particular neuropeptides and neurotransmitters that induce neuroendocrinal signals crucial for regulating this peculiar process. Besides, we provide a predicted concept for organs' size control and maintaining body size homeostasis via intertwining networks, including the Hippo pathway. On the other hand, we discuss the findings of studies employing genomics, transcriptomics, proteomics, and metabolomics approaches to uncover the mechanistic modulation of growth-related traits in different bivalve species. We recommend further research to decipher organ size control and its intricate relationship with the entire body homeostasis. Future genetic dissection studies are also recommended to identify new key genes with a major effect that profoundly influences this trait, facilitating their potential editing to develop new strains with enhanced growth rates.