The Phylum Loricifera

Etymology:- From the Latin Loricus for girdle or Lorica a corselet and Ferre to bear,
hence an animal with a girdle or corselet.

Characteristics of Loricifera:-
1)Bilaterally symmetrical.
2)Body has more than two cell layers and includes tissues and organs.
3)Has a body cavity, and a straight through gut.
4)Body has three distinct regions, a head a neck and a trunk.
5)Has one pair of gonads = gonochoristic.
6)Has a well developed nervous system with a brain and nerve ganglia.
7)Has a distinct larval stage.
8)Lives in marine environments.

First discovered in 1983, by Reinhardt Kristensen, these minute (less than 3mm long) animals are still relatively unknown.

They live in the interstitial marine shell-gravel at depths of between 15 and 480 metres. Though they are believed to be cosmopolitan aspect of the coastal marine fauna, little is yet known of their distribution genus Nanaloricus has been identified from the shores of France, USA (Carolina and Florida) and the Azores. The only other currently named genus is Pliciloricus.

 

Nothing is known about what they eat and not much about their life histories in general. The have a gut and that is similar in design (an example of convergent evolution) to that of the Tardigrades and this along with the stylets that surround their mouths suggests they feed by piercing plants or animals with these stylets and then sucking up body fluids. They may therefore be ectoparasites or predators. They are pseudocoelmates and they have no respiratory or circulatory organs, both these functions being performed by their body fluid.

What is known about them is that they have a body divided into 3 parts. The head which contains the mouth and the brain, a trunk region surrounded by six plates that make up the 'lorica' or corselet. In between these two is the neck region, in adults the head can be withdrawn into the neck and the the neck and head together can be withdrawn into the trunk where it is all protected within the lorica and by the scalids. The scalids are spines that occur on the head. There are nine rings or whorls of them and they stick out protectively when the head is extended but fold up to face outwards when the head is withdrawn.

Loriciferans come in two sexes, male and female, the two sexes are distinguished on the basis of differences in the anterior row of spines. The females seem to produce only one egg at a time and fertilisation is suspected to be internal. The larvae is similar to the adult except that it has a pair of caudal feet which can rotate in ball and socket joints allowing it to swim, a simpler small lorica and in the fact that while it can withdraw its head into its neck it can not withdraw the head and neck together into the lorica, or loricate trunk region.

Loriciferans have a well developed brain and each scalid is individually connected to the brain by nerves, there is also a ganglion in the trunk region connected to the stomach.

 




 

 

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