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https://teara.govt.nz/en/starfish-sea-urchins-and-other-echinoderms/page-2

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Kina - Starfish, sea urchins and other echinoderms - Te Ara Encyclopedia of New Zealand

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Young Ocean Explorers: Is this a sea hedgehog?

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Young Ocean Explorers: Is this a sea hedgehog?

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What's spiky and lives underwater? Meet our native New Zealand kina!

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Young Ocean Explorers has been on a mission since 2012 to inspire kids to love our ocean - through entertaining education. We want to capture children's imaginations through great storytelling, bringing the beauty, awe and fascination of the ocean and its inhabitants alive.

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Friends of Taputeranga Marine Reserve- kina page 

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Friends of Taputeranga Marine Reserve- kina page 

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Information about our most common, widespread NZ sea urchin

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Sea urchin - Kina Photo: M Francis

Kina are found all around the New Zealand coast in shallow water and down to 15 m. They are the most common of some 70 species of urchins in NZ waters. While kina can reach 15 cm diameter, about 10 cm would be more common for adult urchins. Small kina (1 - 2 cm) are found under rocks and overhangs and can be seen better at night. On the Wellington South Coast kina seem to prefer rocky reef habitats and moderate wave action, and adult urchins may be found attached to brown seaweeds even into the low intertidal zone. Individuals can live up to 20 years.

Kina, (Evechinus chloroticus), is mainly herbivorous, feeding on large brown algae, red algae and encrusting substrate. Looking a little like a hedgehog rolled up in a ball, the spines of kina seem to be impenetrable defences. They are, however, preyed upon by rock lobster, some sea stars and gastropods, and snapper. In the absence of these predators, often through over-fishing of the larger predators, kina can reach large numbers. If kina populations become out of control, kelp forest can be entirely eaten away, leaving bare rocks, also known as Kina Barrens. Thus these urchins can greatly alter or destroy sheltering kelp forests which provide some microhabitat for a large range of small animals, changing the marine environment on a significant scale. Research, especially at the Leigh marine reserve has demonstrated that, with a return of snapper and lobster, kelp forests can flourish again.

Kina barren, Northland Photo: Roger Grace

Kina have a nearly spherical test or shell which protects internal organs. The test carries long and short movable spines and tube feet. On the underside of kina there is a five-sided limy organ called Aristotle's lantern. This acts as a set of jaws and teeth, grinding up food. They spawn from November to March, and have a free-swimming larval stage that lasts for up to 3 months.

Wellington Harbour is the location for an interesting project that will show light on the role of kina in local sheltered environments. Steve Journee, of the Dive Guys, is project manager for a trial to restore inner harbour biodiversity. Around the Taranaki wharf there are masses of sea life but few algae. The project team found that kina rapidly devoured algae planted in the area, although there was clearly enough nutrients to support plant growth.

Kina existed in numbers but without any threats to the urchins, creating the same imbalance noted at Leigh through overfishing. As more plants were introduced into the area and became established Mr Journee devised an organic method of dealing with the burgeoning kina. The Dominion Post said:

They were moved to patches of Undaria, an invasive seaweed, at a rate of about 100 per dive. When that number had dropped to about 20 per dive, 11-armed star fish, a kina predator, were transported from rocks and piles under the wharf and placed around the weeds in a "defensive" formation to chase the kina away. Steve Journee reported:

"With less kina in the immediate area the weeds are doing well and other natural harbour weeds and algae are also coming back," he said. "Also the weeds are now being used by juvenile fish and pipefish as safe swimming zones, which is also bringing the short-tailed sting rays closer in to feed, thus creating a balance in the eco system which was the plan in the first place."

Sources: Te Ara, Wikipedia, and Dominion Post of 13 May 2013

Kina sculptures, Queen's Wharf, Wellington. Kina without their spines - as they are commonly seen cast up on NZ beaches. Ironically kina are celebrated here close to Steve's trial work to remove kina for better balance in the inner harbour marine environment. Photo: MH

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Wellington's very own Taputeranga Marine Reserve is a spectacular place to walk, kayak, snorkel, dive, surf, rockpool or simply watch. With support from the community it was created in August 2008. The reserve lies amongst three oceanic currents. These provide for a diverse range of plants and animals.

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http://www.marinelife.ac.nz/species/825

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Edit

Common habitat(s):

Rocky Reef Subtidal

Rocky Shore Intertidal

Other information:

Feeding:

Grazer Feeder

Distribution:

New Zealand

Edibility:

Edible

Size:

Shoulder width Sized

Identification:

Closely related to sea stars, the sea urchins are segmented into five sections. This species has short robust spines and slender purple tube feet interspersed between them, it resembles a rolled up hedgehog! It is the largest of our native urchins.

Habitat:

Found in the low intertidal in northern NZ. Common subtidally throughout NZ. Sea urchins can live in very dense aggregations, where these are found often the rocks are bare of algae and it is often wondered what they eat.

Diet:

As grazers, they feed mainly on kelp. They have an elaborate feeding structure, Aristotle's Lantern,and leave behind a star shaped hole in large kelp fronds.

Lifestyle:

It camouflages itself by holding bits of weed, shell and gravel on it's upper surface, a behaviour known as "hatting". A broadcast spawner. They were eaten by early maori and are considered a delicacy in many countries throughout the world. NZ has not managed to successfully break into this international market as the gonads (reproductive organs) often taste bitter and their colour ranges from bright orange, through yellow and brown. There has been a lot of research happening with sea urchins in NZ to try and improve these factors. There has been success in improving the bitter taste with artificial diets but the colour remains irregular. Approximately one in five have the lovely orange gonad that is sought after overseas.

References:

A Guide to the Plants and Animals of the New Zealand Marine Studies Centre: McKinnon

The Marine Life Database 2020

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Edit Common habitat(s): Rocky Reef Subtidal Rocky Shore Intertidal Other information: Feeding: Grazer Feeder Distribution: New Zealand Edibility: Edible Size: Shoulder width Sized Identification: Closely related to sea stars, the sea urchins are segmented into five sections. This species has short robust spines and slender purple tube feet interspersed between them, it resembles a rolled up hedgehog!

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Information and video about how kina make noise

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Kina are a particular species of sea urchin endemic to New Zealand. Most of us can identify a kina shell found on a beach as a mottled green globe (sometimes intact) with a hole in the base.

When alive, this green globe is covered with moveable spikes to protect the kina from predators. Kina like to live on shallow rocky reefs where they graze on seaweed and kelp. Kina are an important part of the reef ecosystem - and are very, very noisy.

How kina make sound

Kina eat seaweed through a hole in the base of their shell. Five small teeth extend out of the small gap in the shell and scrape and chew seaweed off the rocks. The mouth and teeth are often called 'Aristotle's lantern' because Aristotle first described this sea urchin structure in a book in approximately 380BC.

When the kina are scraping, chewing and processing the seaweed, the teeth move in and out of the body generating noise. This is a low-frequency crunching sound. You probably wouldn't expect to be able to hear a kina munching away on a piece of seaweed, especially under water, but researchers have recorded something that they think is kina feeding.

Recordings show an increase in noise levels of around 20dB when the kina start feeding around dusk - a phenomenon referred to as the 'evening chorus'. A 20dB increase would be perceived by a human ear as a four-fold increase in volume. That is a lot of noise from a very small kina, so how does a kina eating generate such a huge noise?

Kina and Helmholtz resonators

Dr Craig Radford at the Leigh Marine Laboratory has been able to prove that the shell of the kina acts as a sound amplifier. When the kina eats, the sound bounces around the inside of the shell, causing resonance

Anything that can vibrate has particular frequencies (called natural frequencies) at which it vibrates best. Resonance happens when the waves of sound from kina chewing match the natural frequencies for vibration within the kina. The sound vibration builds up, which amplifies the sound, making it louder.

The body and shell of a kina form a special type of structure known as a Helmholtz resonator - a structure with a small neck or opening that is filled with fluid or air.

Pressure fluctuations over the opening causes the fluid or air inside the structure to resonate, forming an audible sound.

A good example is blowing across the top of a bottle, which generates a sound of a certain frequency (pitch). Kina act in the same way. As the teeth move in the opening of the shell, they form a pressure fluctuation that resonates inside the fluid-filled shell.

Kina of different sizes have different resonant (natural) frequencies. The smaller the shell, the higher the resonant frequency, and the larger the shell, the lower the resonant frequency. This is the same as blowing across bottles of different sizes filled with air. The action of the teeth, the size of the shell and the resonant effect means that kina produce a range of noises that can be measured between 400-4,000Hz.

Testing the theory

Scientists have suspected for some time that the noise of the 'evening chorus' was due to the increased feeding activity of kina, and in 2008, Dr Radford was able to finally put this to the test.

He designed a laboratory experiment that would allow kina to feed in a tank, which meant he could record the sound they made over time. He proposed that, if kina were indeed working as a Helmholtz resonator, smaller kina would generate a higher frequency sound than larger kina.

When he compared the noise generated by kina of different sizes, he was able to conclusively show, for the first time, that kina do produce noise at the predicted frequency and at the predicted frequency related for their size. This directly correlated to the theoretical calculations based on a Helmholtz resonator. Also, Dr Radford proved that kina can generate enough noise to account for the evening chorus, at the frequencies and loudness detected in the ocean.

Kina are noisy, noisy critters.

Nature of science

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Kina are a particular species of sea urchin endemic to New Zealand. Most of us can identify a kina shell found on a beach as a mottled green globe (sometimes intact) with a hole in the base. When alive, this green globe is covered with moveable spikes to protect the kina from predators.

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More kina facts

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NIWA guide to NZ echinoderms (spiny skinned animals like sea urchins and sea stars) 

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NIWA guide to NZ echinoderms (spiny skinned animals like sea urchins and sea stars) 

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Extraordinary echinoderms is a NIWA guide to the fascinating world of echinoderms in New Zealand. The kina is a big feature- lots of sea urchin information and diagrams here!

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Young Ocean Explorers: what sea animals eat like a cow? 

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Young Ocean Explorers: what sea animals eat like a cow? 

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Learn how kina are similar to cows in how they feed!

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Young Ocean Explorers has been on a mission since 2012 to inspire kids to love our ocean - through entertaining education. We want to capture children's imaginations through great storytelling, bringing the beauty, awe and fascination of the ocean and its inhabitants alive.

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Includes information and a photo