Kina
New Zealand Kina
Genus: Evechinus Species: chloroticus
Kina (also known as sea eggs) belong to a group marine invertebrates known in scientific terms as Echinoids, which in turn are part of a larger group of animals called Echinoderms (echino=spiny, derms = skins). The New Zealand Kina is endemic to New Zealand and its offshore islands and can grow to be as large as 190 mm diameter, making it arguably, the largest sea urchin species (Photograph 1). Sea urchins are an important traditional food of Maori, who prized their internal organs and gonads. Sea urchins are often represented in the diets of indigenous peoples from other parts of the world. More recently, a global sea urchin fishery and aquaculture has developed, mainly for the production of the valuable gonad.
Photograph 1: The New Zealand Kina, Evechinus chloroticus
Ecological importance
Sea urchins are a very important species ecologically. They are found from the intertidal to 60 to 80 m depth, and in most situations except estuaries and very wave exposed coasts. Sea urchins are mainly herbivorous, feeding on attached and drift algae, but will also graze on encrusting invertebrates such as sponges and ascidians. Their grazing activity often controls the distribution of kelps and other encrusting species. In the most extreme cases, sea urchin populations can, through over-grazing, turn productive kelp dominated marine communities in to low productivity sea urchin barrens (Photograph 2) devoid of kelp and associated species (including fish and paua).
Photograph 2: A sea urchin barren, with the effects of Kina grazing obvious
Age and longevity
Kina are probably long-lived. Modelling of their growth suggests that they reach a size of 40 to 50 mm diameter in 7 years, with larger individuals (>150 mm) probably 30 to 50 years of age and potentially older. Their growth rate will be affected by food levels and water temperatures, so there will be variation in growth rates and sizes at different sites along the New Zealand coast.
The life-cycle (see figure 1)
Kina has different sexes, and reach maturity at around 30 to 50 mm. They have an annual reproductive cycle, and spawn once a year, usually in the spring and summer months depending on location. Sea urchins can be very productive, with ripe females being 30% by weight gonad, and release over a million eggs in a single spawn. The eggs are small (around 1/10th of a millimetre) and are fertilized in the water column by sperm from an adjacent male. The eggs hatch in to free swimming larvae that will develop into a larval form called a pluteus. The plutei will spend about 4-6 weeks in the water column feeding on microscopic phytoplankton. At the completion of their planktonic larval development they will be about 1 to 1.5 mm in size, at which time they will settle to the sea floor and metamorphosis into a tiny sea urchin about half a millimetre in diameter. To avoid being eaten, they will quickly seek shelter under rocks, shells, or in crevices and will remain in this cryptic nature until they are about 20 to 30 mm in size.
Figure 1. Kina Lifecycle
Scientific publications
Barker MF (2001). The ecology of Evechinus chloroticus. pp245-260 In: The Biology and Ecology of Edible Sea urchins, Ed. J. M. Lawrence. Elsevier Science B.V. Amsterdam 432pp
Dix TG (1969) Larval life span of the echinoid Evechinus chloroticus (Val.). New Zealand Journal of Marine and Freshwater Research: 13-16
Dix TG (1970a) Biology of Evechinus chloroticus (Echinoidea: Echinometridae) from different localities. 1. General. New Zealand Journal of Marine and Freshwater Research 4: 91-116
Dix TG (1970b) Biology of Evechinus chloroticus (Echinoidea: Echinometridae) from different localities. 3. Reproduction. New Zealand Journal of Marine and Freshwater Research 4: 385-405
Lamare MD, Brewin PE, Barker MF, Wing SR (2002) Reproduction of the sea urchin Evechinus chloroticus (Echinodermata: Echinoidea) in a New Zealand fiord. New Zealand Journal of Marine and Freshwater Research 36(4): 719-732
Lamare MD, Mladenov PV (2000) Modelling somatic growth in the sea urchin Evechinus chloroticus (Echinoidea: Echinometridae). Journal of Experimental Marine Biology and Ecology 243 (1): 17-43
Lamare MD, Barker MF (2001) Settlement and recruitment of the New Zealand sea urchin Evechinus chloroticus. Marine Ecology Progress Series 218: 153-166
Lamare, MD (1999) Origin and transport of larvae of the sea urchin Evechinus chloroticus Valenciennes (Echinodermata: Echinoidea) in a New Zealand fiord. Marine Ecology Progress Series 174: 107-121
Lamare MD, Barker MF (1999) In situ estimates of larval development and mortality in the New Zealand sea urchin Evechinus chloroticus (Echinodermata: Echinoidea). Marine Ecology Progress Series 180: 197-211
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