Tetrablemmidae

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Tetrablemmidae
Tetrablemma ziyaoensis, female

Tetrablemma ziyaoensis , female

Systematics
Class : Arachnids (arachnida)
Order : Spiders (Araneae)
Subordination : Real spiders (Araneomorphae)
Partial order : Haplogynae
Superfamily : Tetrablemmoidea
Family : Tetrablemmidae
Scientific name of the  superfamily
Tetrablemmoidea
???
Scientific name of the  family
Tetrablemmidae
OP Cambridge , 1873

The Tetrablemmidae are the only family of the Tetrablemmoidea within the real spiders . They include 31 genera and 161 species .

Habitat and Distribution

They are distributed almost exclusively in the tropics of the southern hemisphere; only a few species reach temperate climates. Most genera appear in Southeast Asia ; only a few live in Africa , Central or South America . There the tiny (1 to 4 mm small) animals of bizarre beauty probably do not weave nets. They live in the litter and soil layer, but also in "hanging" soils of the epiphytes such as bromeliads or orchids of moist tropical forests; some live in caves. Some troglophilic and ground-dwelling species show typical adaptations such as the regression of eyes.

features

Tetrablemmids are also called "armored spiders" because they have a sclerotized abdomen . Here, Tergites and sternites stretched or compressed, so that more of them sclerotized plates are formed that cover the abdomen more or less. In some species, the abdomen is changed so much that the spinnerets point down.

The genus Tetrablemma has only four eyes - a trait it shares with the unrelated members of the Caponiidae family . Like the trembling spiders (Pholcidae) or the not distantly related, the real orb web spiders , the tetrablemmids lack the posterior respiratory organs ( beech lungs , fan trachea). However, a family relationship cannot be derived from this either. The tetrablemmids have one more thing in common with the dwarf six-eye spiders : on the tarsi of the front pair of legs, members of both families have another sense organ, the function of which has not yet been clarified and has only been found in these two families. In other spiders are slit sense organs and trichobothria the sound and - infrasound perception , and the perception of substrate vibrations.

Self-directed pollination of Indicoblemma lannaianum

An astonishing complexity of the female reproductive organs of Indicoblemma lannaianum allow the female of this species full control over which sperm they allow themselves to be fertilized . Sperm libraries arranged in pairs prevent the sperm from mixing between different males, so that sperm competition is ruled out. Sperm are temporarily stored in paired sperm libraries and encapsulated by secretions. These secretion balls, which are very numerous in the spermathec, are released into the uterus in a controlled manner by the female through a fertilization duct. The females seem to have preferences of the male sperm. Activated, fertile sperm can only be found in the female, which is a sign of internal self-fertilization.

The male testicles are connected to the ejaculation opening on the underside of the abdomen via an ejaculation duct. There the bulbi on the male's pedipalps are filled with semen. Very few sperm are present in the spherical deposited seminal fluid. They are encapsulated in a layer produced by the male's sex glands. The seminal fluid of the male is probably a nutrient solution for the sperm and possibly at least involved in the formation of balls in the spermatheque, but is also responsible for the activation of the sperm in the female.

As with other spiders, the bulbs are inserted with their appendages into the female genital opening on the female's belly in order to transfer the sperm.

Systematics

The World Spider Catalog currently lists 31 genera and 161 species for the Tetrablemmidae. (As of June 2016)

Web links

Commons : Tetrablemmidae  - Collection of images, videos, and audio files

Tetrablemmidae in the World Spider Catalog

Individual evidence

  1. ↑ a b c Natural History Museum of the Burgergemeinde Bern: World Spider Catalog Version 17.0 - Tetrablemmidae . Retrieved June 8, 2016.
  2. ↑ a b c d WA Shear (1978): Taxonomic notes on the armored spiders of the families Tetrablemmidae and Pacullidae. American Museum novitates, 2650 ( PDF - Abstract )
  3. ^ Foelix, Rainer F. (1979): Biology of the spiders. Georg Thieme Verlag Stuttgart. ISBN 3-13-575801-X
  4. ↑ a b M. Burger et al. (2005): Complex genital system of a haplogyne spider (Arachnida, Araneae, Tetrablemmidae) indicates internal fertilization and full female control over transferred sperm. Journal of Morphology 267 (2): 166-186. doi: 10.1002 / jmor.10394