AbstractsBiology & Animal Science

The effects of cryopreservation on the Pacific oyster Crassostrea gigas larval development

by Shalini Suneja

Institution: AUT University
Year: 0
Keywords: Crassostrea gigas; Crassostrea; Cryopreservation; Oyster; Larval development; Shell morphology
Record ID: 1311085
Full text PDF: http://hdl.handle.net/10292/7861


Aquaculture in New Zealand is an important growing export industry and around 66 % of its total production is exported, which is worth NZ $ 400 million every year. Based on the growth strategy of this industry, the aim is to achieve an annual production of U.S $ 1 billion by 2025. In New Zealand, the Pacific oyster Crassostrea gigas, is a leading cultivated species with significant exports, along with King salmon and the New Zealand GreenshellTM mussel. Pacific oysters are native to Japan, but now are well established in many parts of the world including New Zealand. Most of the culturing for Pacific oyster in New Zealand is conducted using wild seed, the majority of which are gathered in the Kaipara Harbour on the north-western coast of the North Island. However, this source is highly unreliable, for example recent outbreaks of Ostreid herpesvirus-1 (OsHV-1) led to mass mortality of Pacific oyster larvae in 2010 leaving huge losses within this industry. To overcome these natural disasters and seasonal constraints, use of cryopreserved larvae has been suggested by many scientists. With this method of storing, larvae can be thawed to meet hatchery demands at any time. However, the degree of success using cryopreservation technique is highly variable due to lack of optimum protocols which are highly species specific. Furthermore, little is known about the freezing and cooling effects on the viability of larvae and their subsequent development. Previous studies have been focused on high survival rates just after post-thawing but recently the need to study the effect of cryopreservation on the larval quality over a longer time frame has been recognized. Before cryopreservation techniques can be applied to oyster larvae, a good understanding of the basic larval development process is necessary under normal conditions. There is lack of literature available on the detailed larval development under normal hatchery conditions for Pacific oysters. Therefore, the present study is the first to comprehensively describe the various stages of development from D-stage through to settlement of Pacific oyster Crassostrea gigas larvae under hatchery practices. To supplement this project, details of the effect of 2 cryoprotectant solutions (CPA) on the larval development from D-stage through to settlement is provided. To achieve the above aims, we used a multi-technique approach involving light microscopy, scanning electron microscopy, immunochemistry and direct visual observations. The findings indicate that these complementary techniques provide the best approach to investigate the larval stages of Pacific oysters. Both cryopreserved and normal (controls) larvae were assessed for survivability, feeding consumption, shell length, shell morphology, organogenesis and neurogenesis at regular intervals. The methodology of this study included a larval rearing process conducted at Cawthron Aquaculture Park, Nelson. Larval samples were isolated and fixed every alternate day and later transported to Auckland University of Technology on…