Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 


Paddle Crabs; Cannibals Of The Seashore

No.2: Paddle Crabs Cannibals Of The Seashore

Ever had a crab nip your toe at the beach? The culprit is most likely the paddle crab.

This agile swimmer is found in the intertidal zone (between high and low tide marks) all around New Zealand and in southern Australia, down to depths of 100 metres. It’s one of nine species of swimming crabs in New Zealand.

“Paddle crabs prefer sandy bottoms, especially on sheltered surf beaches,” says Shane Ahyong, crab taxonomist at NIWA. They’re especially active at night and at high and low tides, although you’re most likely to see them at low tide. During the day, they spend most of their time buried in the seabed, with only their eyes and antennae protruding.

“If you’re not lucky enough to spot a live paddle crab, you’ll often see their discarded or dead shells washed up on the beach,” says Dr Ahyong.

“Paddle crabs can swim sideways very quickly using the paddles on their rear legs. They also use their paddles to dig themselves backwards into the sand, which they can do very quickly when threatened.”

Their main predators are stingrays, dogfish, snapper, and other predatory fish. Humans also fish them for meat and bait. As for their prey, paddle crabs will eat almost anything, and even cannibalise smaller paddle crabs, but their staples are shellfish and small fish.

“They are aggressive but would only attack a human in self-defence. If a paddle crab nips you, it’s probably because you stood on it,” says Dr Ahyong.

Like cicadas, paddle crabs ‘stridulate’ – producing sounds by rubbing parts of their body together. In the crab’s case, they rub one of their legs against a rasp on the underside of their claw to serenade prospective mates. Their deepwater cousins don’t have rasps, but instead have evolved iridescent patches on their bodies to signal other members of their species, says Dr Ahyong.

Species Fact File

*Common names: paddle crab, common swimming crab
* M?ori name: p?paka
*Scientific name: Ovalipes catharus
*Type: swimming crab
*Family: Portunidae
*Size: up to 15 cm across the shell
*Lifespan: 4 years
*Diet: Shellfish, small fish & crabs, whatever they can catch or scavenge
*Reproduction: Female lays fertilized eggs, from which larvae emerge. There are several larval stages.
*Things you need to know: They’re agile swimmers, can bury themselves quickly in the sand, and will only bite you in self-defence!
Something strange: When close to breeding, the male carries his mate underneath him until she moults, then mates with her.

ENDS

© Scoop Media

 
 
 
 
 
Business Headlines | Sci-Tech Headlines

 

Genetics: New Heat Tolerant Cow Developed

Hamilton, New Zealand-based Dairy Solutionz Ltd has led an expert genetics team to develop a new dairy cow breed conditioned to thrive in lower elevation tropical climates and achieve high milk production under heat stress. More>>

Fractals: Thousands More Business Cards Needed To Build Giant Sponge

New Zealand is taking part in a global event this weekend to build a Menger Sponge using 15 million business cards but local organisers say they are thousands of business cards short. More>>

Scoop Business: NZ Net Migration Rises To Annual Record In September

New Zealand’s annual net migration rose to a record in September, beating government forecasts, as the inflow was spurred by student arrivals from India and Kiwis returning home from Australia. More>>

ALSO:

Scoop Business: Fletcher To Close Its Christchurch Insulation Plant, Cut 29 Jobs

Fletcher Building, New Zealand’s largest listed company, will close its Christchurch insulation factory, as it consolidates its Tasman Insulations operations in a “highly competitive market”. More>>

ALSO:

Scoop Business: Novartis Adds Nine New Treatments Under Pharmac Deal

Novartis New Zealand, the local unit of the global pharmaceuticals firm, has added nine new treatments in a far-ranging agreement with government drug buying agency, Pharmac. More>>

ALSO:

Crown Accounts: English Wary On Tax Take, Could Threaten Surplus

Finance Minister Bill English is warning the tax take may come in below forecast in the current financial year, as figures released today confirm it was short by nearly $1 billion in the year to June 30 and English warned of the potential impact of slumping receipts from agricultural exports. More>>

ALSO:

Auckland Outage: Power Mostly Restored Overnight

Vector wishes to advise that all but 324 customers have been restored overnight. These customers are spread throughout the network in small pockets. The main St Johns feeder was restored around midnight allowing most of the customers in all affected areas to have power this morning. More>>

ALSO:

Get More From Scoop

 
 
Standards New Zealand

Standards New Zealand

Mosh Social Media
 
More RSS  RSS
 
 
 
 
 
 
 
Sci-Tech
Search Scoop  
 
 
Powered by Vodafone
NZ independent news