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Crustaceans

Maxillopods  

The Maxillopods are a class of the Crustaceans which includes Barnacles, Copepods, Tantulocarida, Branchiura (fish lice) and other animals. There are more than 1,200 species of barnacle, around 14,000 species of Copepods and about 30 species of Tantulocarida. They are generally small animals with short bodies, with the abdomen reduced in size, and usually without appendages. Barnacles can grow to around 7 cm in diameter and up to 2 cm high. whilst Copepods are usually less than 2 mm in length.

Apart from barnacles, which use their legs for filter feeding, most maxillopods feed with their maxillae (paired mouthparts located behind the mandibles usually used for swallowing). They body is made up of 5 head segments, 6 thoracic segments and 4 abdominal segments (which usually do not have appendages), followed by a telson (tail).

Tantulocarida are parasitic crustaceans that grow to less than 0.3 millimetres in length.

Branchiura (fish lice)

Almost all Branchiura are external parasites on fish, a few on amphibians. feeding on the mucus, tissues and blood of host marine fish. There are about 350 species of Branchiura.They have flat, oval bodies, almost completely covered by a wide carapace. They have large compound eyes, and the mouthparts and the first pair of antennae are modified to form a hooked, spiny feeding tube covered with suckers. They attach themselves behind the fish's gill cover (operculum).When they change hosts they swim using two pairs of thoracic appendages.


Barnacles


Copepod
Image © Adrian Ha Flickr

     

Fish louse (Argulus foliaceus)
Image © Jaap Cost Budde Flickr

They leave their hosts for up to three weeks in order to mate and lay eggs. In their free swimming (planktonic) stage they do not feed, living on stored food.

Sea lice cause damage to the fishes' tissues at their of attachment. This can decrease a fishes' immune responses and make them more likely to catch to other diseases and reduces their growth.


Pinkeye goby with fish louse
Image © Hung Chi-Feng Flickr
   

Sea lice on fish farms are affecting wild salmon populations on Canada's west coast.
Sea lice may be driving wild salmon to extinction.
Read more at www.newscientist.com/article/dn13046

References

http://en.wikipedia.org/wiki/Maxillopoda
http://www.eol.org/pages/1353
http://en.wikipedia.org/wiki/Sea_louse


A louse in the mouth of a fish
Image © Roxanne B Flickr

Next:  ... Barnacles  

 

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Maxillopods
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