Fussy Feeders: Phyllosoma Larvae of the Western Rocklobster (Panulirus cygnus) Demonstrate Prey Preference

Abstract

The Western Rocklobster (Panulirus cygnus) is the most valuable single species fishery in Australia and the largest single country spiny lobster fishery in the world. In recent years a well-known relationship between oceanographic conditions and lobster recruitment has become uncoupled, with significantly lower recruitment than expected, generating interest in the factors influencing survival and development of the planktonic larval stages. The nutritional requirements and wild prey of the planktotrophic larval stage (phyllosoma) of P. cygnus were previously unknown, hampering both management and aquaculture efforts for this species. Ship-board feeding trials of wild-caught mid-late stage P. cygnus phyllosoma in the eastern Indian Ocean, off the coast of Western Australia, were conducted in July 2010 and August-September 2011. In a series of experiments, phyllosoma were fed single and mixed species diets of relatively abundant potential prey items (chaetognaths, salps, and krill). Chaetognaths were consumed in 2–8 times higher numbers than the other prey, and the rate of consumption of chaetognaths increased with increasing concentration of prey. The highly variable lipid content of the phyllosoma, and the fatty acid profiles of the phyllosoma and chaetognaths, indicated they were from an oligotrophic oceanic food chain where food resources for macrozooplankton were likely to be constrained. Phyllosoma fed chaetognaths over 6 days showed significant changes in some fatty acids and tended to accumulate lipid, indicating an improvement in overall nutritional condition. The discovery of a preferred prey for P. cygnus will provide a basis for future oceanographic, management and aquaculture research for this economically and ecologically valuable species.

Condition of larvae of western rock lobster (Panulirus cygnus) in cyclonic and anticyclonic eddies of the Leeuwin Current off Western Australia

“…In addition, the higher lipid : protein ratio of phyllosomas in CEs than in AEs could suggest that there is better food availability for phyllosomas in CEs than in AEs, because lipid is known to be catabolised at a greater rate than protein and carbohydrate during food deprivation of phyllosoma (Ritar et al 2003). Furthermore, experimental feeding of P. cygnus phyllosomas of the same developmental stages as examined in this current study showed that lipid is rapidly accumulated when prey are readily available (Saunders et al 2012). To the contrary, previous research has shown that the CEs of the Leeuwin Current generally exhibit oligotrophic oceanic conditions by global standards, whereas AEs have been classed as mesotrophic in nature (Waite et al 2007a, Waite et al 2007b.…”

“…The results of the current study confirmed that there is pronounced lipid accumulation from Stage VI to VIII in phyllosomas of P. cygnus. This result suggests a possible change in diet in late-stage phyllosomas to prey with a high lipid yield, such as krill, as there is a narrow range of potential zooplankton prey in the wild with high lipid content (Saunders et al 2012;Wang et al 2013).…”

Fatty acid profiles of phyllosoma larvae of western rock lobster (Panulirus cygnus) in cyclonic and anticyclonic eddies of the Leeuwin Current off Western Australia

“…This has motivated further studies to examine other environmental factors that can influence the phyllosoma (Feng et al 2011). In particular, it has been suggested that the cause of the declining recruitment is changes in the feeding conditions for the oceanic larvae of P. cygnus, that are known as phyllosomas (Fitzgibbon et al 2013;Saunders et al 2012;Wilkin and Jeffs 2011). The phyllosoma phase lasts 9-11 months for P. cygnus accumulating significant lipid reserves that are then utilised by the lecithotrophic pueruli to actively swim onshore (Jeffs et al 2001b;Jeffs et al 1999;Phillips et al 2007;Takahashi et al 1994).…”

“…Recent experimental feeding trials with wildcaught P. cygnus phyllosomas showed they preferred to prey upon chaetognaths, although other prey, such as krill and salps were also taken, but in smaller numbers (Saunders et al 2012). However, DNA recovered from the gut of phyllosomas of this species captured in the same region was found to be composed mostly of transparent gelatinous zooplankton, including colonial radiolarians, tunicates, and scyphozoans, which may reflect differences in prey abundance or ease of catchability of prey in the pelagic environment (O' Rorke et al 2012).…”

An unusual fossil larva, the ontogeny of achelatan lobsters, and the evolution of metamorphosis

“…These biramous appendages appear long and fragile, are very thin and also translucent. The distal ends of the long pereiopods are specialized for grabbing small prey items; phyllosoma larvae are predators (Jeffs 2007, Saunders et al 2012. The "shrimp tail", i.e., the pleon of these larvae, is tiny and its appendages develop relatively late within the ontogenetic sequence.…”