Hooded spiders
| Hooded spiders | ||||||||||||
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Cryptocellus goodnighti |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Ricinule | ||||||||||||
| Thorell , 1876 |
The hooded spiders (Ricinulei) are an order of the arachnids (Arachnida) within the jaw-claw carriers (Chelicerata). About 40 species are known worldwide that live in tropical forests in Africa and South America .
features
The known types of hooded spiders all look very similar. Characteristic is a strong chitin armor as well as a movable appendix of the fore body back, which is placed at rest over the mouthparts. The spiders got their German name from this Cucullus. The very short rear body ( opisthosoma ) consists of only a reduced number of segments (only four are visible), the front segments are transformed into a narrow hinge between the front body ( prosoma ) and the abdomen, the rearmost segments are drawn into the abdomen like a telescope .
The hooded spiders use the second pair of legs as a button, for this reason it is longer than the rest of the legs. As pairs of walking legs, they only use the first and the last two pairs of legs, on which they move very slowly. The jaw claws ( chelicerae ) are two-part and form a pair of scissors. The pedipalp also forms scissors. Eyes are not visible in the hooded spiders, but they react to light with a deadlock reflex .
Way of life
Hooded spiders, like almost all arachnids, are hunters and eat various small arthropods , especially springtails . These are felt with the extended second pair of legs and caught by being pinched between the limbs of the feet and the lower legs. The prey is then shredded by the scissor-reinforced pedipalps and chelicerae.
Reproduction and development
The males of the hooded spiders have specially trained copulation organs on the foot members of the third pair of legs, which consist of a sperm store and a transmission device. They remove the sperm as sperm balls ( spermatophore ) from their own sexual opening and transfer it to that of the female they have previously climbed.
The eggs, which are quite large, are laid one by one, the eggs are then also individually held by the mother under the hood with the pedipals and carried into a hiding place. The embryonic development of the animals is unknown, from the egg hatches a larva which, like the mites, has only three pairs of legs and develops into an adult hooded spider after three moults.
Systematics
The exact position of the hooded spiders in the phylogenetic system has not yet been clarified, but they are usually classified as a sister group of the mites . The larva with only three pairs of legs and the three larval stages are good arguments for this position. The reason given for an alternative position as a sister group of the harvestmen is the extended second pair of legs, which, however, does not exist in the original harvestmen and is therefore invalidated as an argument.
The order includes only one living ( recent ) family with the following three genera.
- Family Ricinoididae
Ewing , 1929
- Cryptocellus Westwood , 1874
- Pseudocellus Platnick , 1980
- Ricinoides Ewing , 1929
literature
- Peter Weygoldt: Ricinulei, hooded spiders. In Westheide, Rieger (Hrsg.): Special zoology part 1: single-cell and invertebrate animals. Gustav Fischer Verlag, Stuttgart, Jena 1997; Pages 488-489.
