Wu, Xugan (2013) Lipid nutrition of early life history of two commercially important tropical crustaceans, the blue swimmer crab (Portunus pelagicus) and the ornate rock lobster (Panulirus ornatus), with emphasis on highly unsaturated fatty acids. PhD thesis, James Cook University.

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Abstract

The blue swimming crab, Portunus pelagicus and ornate rock lobster, Panulirus ornatus are two commercially important crustacean species of high market value with wild populations distributed throughout the tropical and sub-tropical Indo-Pacific region. As the wild populations of P. pelagicus and P. ornatus have been over-exploited, there is an increasing interest in the development of their aquaculture to meet the rising market demand. However, one of the major challenges for closed-life cycle production of P. pelagicus and P. ornatus is the development of a commercially viable hatchery technology. Comprehensive and quantitative understanding of larval nutrition is very important for the development of a reliable hatchery technology of P. pelagicus and P. ornatus. However, basic knowledge of the nutritional requirements and physiology is very limited for the early life stage of both species.

It is well known that lipids play a crucial role on the survival, growth and development of crustacean larvae. To further knowledge in this area a series of experiments were initially conducted to understand the ontogenetic changes of key lipid composition, including lipid classes and fatty acids, during the embryonic and larval development. This was extended to measure changes of lipid composition during the starvation of newly hatched larvae of P. pelagicus and P. ornatus. From this foundation, four experiments were designed to assess dietary optimum 20:4n6 (ARA) levels and the 22:6n3/20:5n3 (DHA/EPA) ratios for P. pelagicus and P. ornatus larvae based on enriched Artemia, which is one of the commonly used hatchery feeds for marine crustacean larvae. Experiments included enriched Artemia containing different levels of dietary fatty acids which were fed to newly hatched larvae of P. pelagicus and P. ornatus. In these experiments the survival, development, growth and fatty acid composition of larvae were closely monitored to identify the dietary optimum HUFA composition.

Chapter 2 and 3 were conducted to investigate the changes of lipid class and fatty acid composition during the embryonic development of P. pelagicus and P. ornatus. For both species, there are significant increases of egg volume and moisture content while the total lipid content decreased dramatically. However, different trends were found between the lipid class profiles of P. pelagicus and P. ornatus, including the percentage of phospholipids (PL), free fatty acids (FFA) and cholesterol (CHO) (%total lipid). The principal fatty acids were 16:0, 16:1n7, 18:1n9, 18:1n7, 20:4n6 (ARA), 20:5n3 (EPA) and 22:6n3 (DHA) in the eggs of both species. Despite of embryonic stages, significantly higher DHA levels and DHA/EPA ratios were found in the eggs of P. ornatus compared to P. pelagicus. However the eggs of P. pelagicus contained higher ARA level than that of P. ornatus. During embryonic development, ARA, EPA and DHA were relatively conserved for P. pelagicus while 18:1n9, 18:2n6, ARA and EPA were relatively conserved for P. ornatus. These differences indicate that the two crustacean species have different lipid dynamics during their embryonic development.

Chapter 4 and 5 were designed to investigate the ontogenetic changes of growth and lipid composition during larval development of both species. Although individual biomass and body size increased significantly, the specific growth rate (SGR%/day) of body weight generally decreased significantly during the larval development of both species. The lipid class profile of early-mid Stages phyllosoma were dominated by PL (>85% total lipids) for P. ornatus while the significant lower PL levels were detected in the late stage P. pelagicus larvae compared the newly hatched P. pelagicus larvae and all early-mid Stages P. ornatus larvae. Generally, the fatty acid composition of larvae reflects that of their larvae diet. However, ARA and DHA were preferentially accumulated by later larval stage of P. pelagicus while early-mid Stage (II-V) phyllosoma preferentially sequestered and accumulated a higher proportion of ARA, EPA and DHA compared to the levels that present in their diet. These data indicate that larval P. pelagicus and P. ornatus have an ability to preferentially sequester, store or modify their dietary lipid composition to support normal growth and development.

Chapter 6 and 7 were designed to examine the effects of starvation on survival, biomass and lipid composition and to explain the preferential conservation of important fatty acids for newly hatched larvae of P. pelagicus and P. ornatus. The results showed that during starvation, significant decreasing trends were detected on individual body dry weight, total lipids (%dry weight) or per larva (μg/larva) for the newly hatched larvae of P. pelagicus and P. ornatus. During the starvation, more than 50% of PL was utilized for the larvae of both species, indicating the oxidation of membrane structural lipids. The higher reductions were found on EPA and DHA than other fatty acids during the starvation of P. pelagicus larvae while both DHA and ARA were highly conserved for newly hatched P. ornatus phyllosoma. These results suggested that the HUFA requirement of larval P. pelagicus is lower and different to early Stage P. ornatus phyllosoma.

Chapter 8 and 9 were designed to investigate the basis for the relative conservation of ARA during the starvation of newly hatched larvae of both species. Investigations included revealing the dietary optimum ARA contents for the survival, development and growth of P. pelagicus and P. ornatus larvae as supplied through the feeding enriched Artemia as larval food. For larval P. pelagicus, dietary ARA level significantly affected not only survival, development and vii growth of the larvae, but also the occurrence of moulting death syndrome (MDS) as well as the ratio of chela length/carapace length (CHL/CL) of zoea IV. For the early Stage P. ornatus larvae, dietary ARA levels did not significantly affect survival, but significant differences were detected on development time and growth among the different treatments. The results suggest that optimal ARA level is approximately 6.27 mg/g DW (2.97% of total fatty acids) in the enriched Artemia for P. pelagicus larvae, and around 3.69 mg/g DW (1.90% total fatty acids) for early Stage P. ornatus phyllosoma.

Although previous studies have shown dietary DHA/EPA ratios are very important for crustaceans, no available information could be found for its importance in the larvae of P. pelagicus and P. ornatus. Therefore, two experiments were conducted to investigate the dietary optimum DHA/EPA ratios for P. pelagicus and P. ornatus larvae. There were five treatments with newly hatched larvae fed enriched Artemia contained different DHA/EPA ratios. Although no significant difference was found on the survival of early stage larvae for both species, the highest survival was found on the treatment fed enriched Artemia contained medium DHA/EPA ratio until megalopal stage of P. pelagicus. The dietary DHA/EPA ratios also significantly affected the development time and growth for both species. The dietary optimum DHA/EPA ratios were estimated at ca. 0.53 and > 1.64 for P. pelagicus larvae and early Stage phyllosoma of P. ornatus, respectively, which clearly indicated the early Stage phyllosoma of the ornate rock lobster had higher DHA/EPA ratio requirement than P. pelagicus larvae. These findings indicated that the optimization of the fatty acid composition of hatchery food will be an effective means to improve seed quality and quantity for both species.

The current project utilized an integrated methodology approach to study fatty acid nutrition of P. pelagicus and P. ornatus larvae. The embryonic and larval development experiments related to ontogenetic changes of key lipid composition were targeted to obtain fundamental information, followed by growth trails to identify the specific fatty acids requirement or ratios. Fatty acid analysis was used to gain a deep understanding of underlying mechanisms. The findings have significantly enhanced our understanding of fatty acid nutrition for P. pelagicus and P. ornatus larvae, which will facilitate the further improvement of hatchery technology and formulated diets for the larval culture of both species.

Item ID:	41081
Item Type:	Thesis (PhD)
Keywords:	aquaculture; blue swimming crab; crustacean larvae; deposition; developmental pattern; fatty acids; growth; larval developmental pattern; lipid composition; lipid nutrition; mass mortality; moulting death syndrome; nutrition; ontogenetic change; ornate rock lobsters; Panulirus ornatus; Phyllosoma nutrition; Portunus pelagicus; rock lobsters; seedstock; spiny lobsters
Related URLs:	http://researchonline.jcu.edu.au/28568/ http://researchonline.jcu.edu.au/22660/
Copyright Information:	Copyright © 2013 Xugan Wu
Additional Information:	Publications arising from this thesis are available from the Related URLs field. The publications are: Chapter 4: Wu, X.G., Zeng, C.S., and Southgate, P.C. (2013) Ontogenetic patterns of growth and lipid composition changes of blue swimmer crab larvae: insights into larval biology and lipid nutrition. Marine and Freshwater Research, 65 (3). pp. 228-243. Chapter 5: Wu, Xugan, Smith, Greg, and Hall, Michael (2012) Patterns of larval growth, lipid composition and fatty acid deposition during early to mid stages of development in Panulirus ornatus phyllosoma. Aquaculture, 330-333. pp. 63-73.
Date Deposited:	29 Oct 2015 04:33
FoR Codes:	07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070401 Aquaculture @ 50% 07 AGRICULTURAL AND VETERINARY SCIENCES > 0702 Animal Production > 070204 Animal Nutrition @ 50%
SEO Codes:	83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830101 Aquaculture Crustaceans (excl. Rock Lobster and Prawns) @ 50% 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830106 Aquaculture Rock Lobster @ 50%
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