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

 

Interest Rates: Wheeler Hikes OCR To 3% On Inflationary Pressures, Eyes Kiwi

Reserve Bank governor Graeme Wheeler lifted the official cash rate for the second time in as many months, saying non-tradable inflationary pressures were "becoming apparent" in an economy that’s picking up pace and he's watching the impact of a strong kiwi dollar on import prices. More>>

ALSO:

Scoop Business: Equity Crowd Funding Carries Risks, High Failure Rate

Equity crowd funding, which became legal in New Zealand this month, comes with a high risk of failure based on figures showing existing forays into social capital have a success rate of less than 50 percent, one new entrant says. More>>

ALSO:

Scoop Business: NZ Migration Rises To 11-Year High In March

The country gained a seasonally adjusted 3,800 net new migrants in March, the most since February 2003, said Statistics New Zealand. A net 400 people left for Australia in March, down from 600 in February, according to seasonally adjusted figures. More>>

ALSO:

Hugh Pavletich: New Zealand’s Bubble Economy Is Vulnerable

The recent Forbes e-edition article by Jesse Colombo assesses the New Zealand economy “ 12 Reasons Why New Zealand's Economic Bubble Will End In Disaster ”, seems to have created quite a stir, creating extensive media coverage in New Zealand. More>>

ALSO:

Thursday Market Close: Genesis Debut Sparks Energy Rally

New Zealand stock rose after shares in the partially privatised Genesis Energy soared as much as 18 percent in its debut listing on the NZX, buoying other listed energy companies in the process. Meridian Energy, MightyRiverPower, Contact Energy and TrustPower paced gains. More>>

ALSO:

Power Outages, Roads Close: Easter Storm Moving Down Country

The NZ Transport Agency says storm conditions at the start of the Easter break are making driving hazardous in Auckland and Northland and it advises people extreme care is needed on the regions’ state highways and roads... More>>

ALSO:

Get More From Scoop

 
 
Computer Power Plus
 
 
 
 
 
 
 
 
Sci-Tech
Search Scoop  
 
 
Powered by Vodafone
NZ independent news