Abstract:
The New Zealand pea crab (Nepinnotheres novaezelandiae) is a parasite of green-lipped mussels (Perna canaliculus), which causes reduced size and growth rate in infected mussels. The Green-lipped mussel industry is worth NZ$260 million annually and the impact of this crab causes an estimated loss of US$2.16 million per year. More effective control of these pea crabs is therefore important because of their impact on aquaculture production as well as the risk of product rejection from foreign market biosecurity and negative consumer end rejection. Despite the economic importance of the New Zealand pea crab, little is known about their early life history or how to control their level of infection in mussel farms. Therefore, the development of N. novaezelandiae has been investigated from egg through to the first instar juvenile crab. The New Zealand pea crab demonstrated a prolific breeding ability; capable of storing enough sperm to lay at least three consecutive broods of eggs in the absence of male crabs. Temperate was shown to affect reproduction in this species, with cooler temperatures resulting in longer incubation times. The larval development of N. novaezelandiae has been described, consisting of three zoeal stages and one megalopa. The length of the pelagic larvae duration of this species indicated that the larval dispersal distance is over 20 km from the parental population. This represents a potentially significant impact on surrounding wild populations of green-lipped mussels. The megalopae post-larvae of this crab have not been observed to use acoustic cues during settlement. The specific nature of a green-lipped mussel habitat for the adults of this crab may mean a more specific cue is used in settlement which could result in a more successful method of population control. In conclusion, the results of this present study have improved our understanding of the early life history of the New Zealand pea crab which can be exploited for better control of this commercially important pest in New Zealand aquaculture.
