Factors relevant to pre‐veliger nutrition ofTridacnidae giant clams

Abstract

Tridacnid giant clams are of commercial interest for their nutritional, economic, and ecological significance throughout the Indo‐Pacific and Oceania. A major impediment to culturing tridacnid giant clams is larval mortality, typically >96%. The effects of suspended and particulate nutrients on tridacnid veliger development have been examined, but factors relevant to the nutritional condition of oocytes and trochophore larvae are unknown. This is significant because the nutritional transition from trochophore to veliger coincides with rises in larval mortality. Our review examines culture techniques known to enhance gamete viability of several marine viable bivalves of commercial interest, and critically assesses whether such methods are applicable to tridacnids in culture conditions. Techniques for optimizing the nutritional requirements of pre‐veliger tridacnids such as broodstock conditioning by supplemental feeding, monitoring the condition of oocytes ready for release, water temperature, egg attributes such as size and biochemical composition, and nutrient loads in culture water chemistry are examined. We include suggestions for optimizing nutritional conditions from gametogenesis through embryonic development, and conclude with a primer of research opportunities based on gaps in our understanding of tridacnid pre‐veliger nutrition compared with other bivalves. A major conclusion is that culture protocols should include pre‐veliger nutritional fitness as a critical factor in enhancing larval survival, growth and development.

Microencapsulated algal feeds as a sustainable replacement diet for broodstock in commercial bivalve aquaculture

“…EPA is the primary energy source for gamete maturation, with higher levels directly increasing gamete quantity and development rate 32 . DHA is pivotal to the structure and function of gamete cell membranes, with higher levels increasing gamete quality and egg survival rates 31 – 35 . High levels of EPA and DHA in the Schizochytrium -based microcapsules are likely driving this increase 22 , 23 .…”

Microencapsulated diets to improve bivalve shellfish aquaculture for global food security

“…Other nutrients can be added to the microparticles to tailor diets to specific bivalve species, or specific geographies where key nutrients are lacking, and even the lipid encapsulant itself can be of high nutritional value (Knauer and Southgate, 1999). Such microencapsulated feeds could improve bivalve broodstock quality; broodstock quality is influenced heavily by dietary DHA intake, and DHA supplementation increases broodstock glycogen and lipid reserves, egg size, egg quantity, larval growth rate, and larval survivorship (Hendriks et al, 2003;Utting and Millican, 1998;Waters et al, 2016). Juvenile growth could be improved; juvenile bivalves will grow Fig.…”

Carry-Over Effects of Broodstock Conditioning on the Salinity Tolerance of Embryos of the New Zealand Geoduck (Panopea zelandica)

“…However, even when broodstock successfully spawn, the development of embryos and larvae might not be "optimal." Indeed, the energy required during early embryonic development is fully dependent on the resources provided for in the egg [11]. Also, the development of embryos into the first feeding larvae (i.e., D-veliger) is a process of intense cellular activity during which any impairment within a series of biochemical and physiological mechanisms can result in malformed larvae [12].…”

“…Also, the development of embryos into the first feeding larvae (i.e., D-veliger) is a process of intense cellular activity during which any impairment within a series of biochemical and physiological mechanisms can result in malformed larvae [12]. Thus, broodstock history tends to have a significant effect beyond gametogenesis and into embryonic development [11]. During development, embryos are more sensitive to environmental stressors compared to the juvenile and adult stages, especially with regard to salinity and temperature [13,14].…”