Cribellum

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Progradungula otwayensis (Gradungulidae) holding a snare made from silk spun from its cribellum Progradungula otwayensis immature male with catching ladder.jpg
Progradungula otwayensis (Gradungulidae) holding a snare made from silk spun from its cribellum

Cribellum literally means "little sieve", and in biology the term generally applies to anatomical structures in the form of tiny perforated plates.

Contents

In certain groups of diatoms it refers to microscopically punctured regions of the frustule, or outer layer.

In certain groups of spider species, so-called cribellate spiders, the cribellum is a silk spinning organ. Unlike the usual spinnerets of spiders, the cribellum consists of one or more plates covered in thousands of tiny spigots, tiny holes that hardly project from the surface, in contrast to the elongated spigots that project from spinnerets. [1] These minute spigots produce extremely fine fibers, merely tens of nanometres thick, which are combed out by the spider's calamistrum, producing silk with a woolly texture. The fibers are so small in diameter that they are strongly subject to Van der Waals forces. [2] In addition, the fibres have a surface that absorbs waxes from the epicuticle of insect prey on contact. This creates a powerful adhesion without any liquid glue that tends to dry out. [3]

The spider cribellum is a functional homolog of the anterior median spinnerets of Mesothelae and Mygalomorphae, which do not have a cribellum.

Ancestral trait

The presence or absence of a cribellum is used to classify araneomorph spiders into the cribellate and ecribellate (not cribellate) type. The distinction can be used to study evolutionary relationships. However, in 1967 it was discovered that there are many families with both cribellate and ecribellate members (Lehtinen, 1967). Some species, such as Amaurobius ferox , are also capable of switching between cribellate and ecribellate silk, primarily using cribellate silk for webs and ecribellate silk for trophic eggs.[ citation needed ] Today, it is believed that the precursor of all Araneomorphae was cribellate (symplesiomorphy), and that this function was lost in some araneomorph spiders secondarily (Coddington & Levy, 1991). Many of these still retain a colulus, which is thought to be a reduced cribellum, and is of unknown function. However, some "ecribellate" spiders seem to have evolved independently, without cribellate precursors (Foelix, 1979). In Austrochilidae, the cribellum is developed only in the second nymphal stage, so the ecribellate and cribellate conditions change during the spider ontogenesis. [4]

Prevalence

Only about 180 genera in 23 families (1991) still contain cribellate members, although the diverse Australian cribellate fauna is still mostly undescribed. However, that fauna may be an example of high diversity in Australian animals that are only relicts in other regions of the world, like the marsupials (Coddington & Levy, 1991).

Cribellate taxa are not very speciose, and for nearly all cribellate-ecribellate sister clades the cribellate lineage is less diverse (Coddington & Levy, 1991), for example:

Cribellate families

22 families of araneomorph spiders, namely Agelenidae, Amaurobiidae, Amphinectidae, Austrochilidae, Ctenidae, Deinopidae, Desidae, Dictynidae, Eresidae, Filistatidae, Gradungulidae, Hypochilidae, Miturgidae, Neolanidae, Nicodamidae, Oecobiidae, Psechridae, Stiphidiidae, Tengellidae, Titanoecidae, Uloboridae and Zoropsidae contain at least some cribellate spiders (Griswold et al. 1999). While some of these families are entirely cribellate, others contain both cribellate and ecribellate species.

Diatom cribellum

The perforated regions of the frustule, or outside layer of many forms of diatom also are called cribella. In such species of diatom the frustule consists of a thin siliceous plate with many small pores. [5]

Related Research Articles

<span class="mw-page-title-main">Uloboridae</span> Family of spiders

Uloboridae is a family of non-venomous spiders, known as cribellate orb weavers or hackled orb weavers. Their lack of venom glands is a secondarily evolved trait. Instead, they wrap their prey thoroughly in silk, cover it in regurgitated digestive enzymes, and then ingest the liquified body.

<span class="mw-page-title-main">Lampshade spider</span> Family of spiders

Lampshade spiders, family Hypochilidae, are among the most primitive of araneomorph spiders. There are two genera and twelve species currently recognized. Like mygalomorphs, most hypochilids have two pairs of book lungs, but like araneomorphs they have intersecting fangs, with the exception of some species which have chelicerae in an angle that is neither orthognathous or labidognathous. These long-legged spiders build typical "lampshade" style webs under overhangs and in caves. In the United States the fauna is primarily associated with the Appalachian, Rocky and California Mountains. Ten of the known species are found in these ranges, all in the genus Hypochilus. The genus Ectatosticta is found in China.

<span class="mw-page-title-main">Crevice weaver</span> Family of spiders

Crevice weaver spiders (Filistatidae) comprise cribellate spiders with features that have been regarded as "primitive" for araneomorph spiders. They are weavers of funnel or tube webs. The family contains 18 genera and more than 120 described species worldwide.

<span class="mw-page-title-main">Spider taxonomy</span> Science of naming, defining and classifying spiders

Spider taxonomy is that part of taxonomy that is concerned with the science of naming, defining and classifying all spiders, members of the Araneae order of the arthropod class Arachnida with more than 48,500 described species. However, there are likely many species that have escaped the human eye to this day, and many specimens stored in collections waiting to be described and classified. It is estimated that only one third to one half of the total number of existing species have been described.

<span class="mw-page-title-main">Phyxelididae</span> Family of spiders

Phyxelididae is a family of araneomorph spiders first described by Pekka T. Lehtinen in 1967 as a subfamily of Amaurobiidae, and later elevated to family status as a sister group of Titanoecidae.

<span class="mw-page-title-main">Stenochilidae</span> Family of spiders

Stenochilidae is a family of southeast Asian araneomorph spiders that produce ecribellate silk. First described by Tamerlan Thorell in 1873, it now contains twelve described species in two genera.

<span class="mw-page-title-main">Palpimanidae</span> Family of spiders

Palpimanidae, also known as palp-footed spiders, is a family of araneomorph spiders first described by Tamerlan Thorell in 1890. They are widely distributed throughout the tropical and subtropical regions of the world, the Mediterranean and one in Uzbekistan, but not Australia. They are not common and there is a high degree of endemism.

<span class="mw-page-title-main">Deinopoidea</span> Superfamily of spiders

The Deinopoidea or deinopoids are group of cribellate araneomorph spiders that may be treated as a superfamily. As usually circumscribed, the group contains two families: Deinopidae and Uloboridae.

<span class="mw-page-title-main">Agelenoidea</span>

The Agelenoidea or agelenoids are a superfamily or informal group of entelegyne araneomorph spiders. Phylogenetic studies since 2000 have not consistently recovered such a group, with more recent studies rejecting it.

The Dictynoidea or dictynoids are a group of araneomorph spiders that have been treated as a superfamily. The composition of the group has varied. Phylogenetic studies in the 21st century have failed to confirm the monophyly of the dictynoids as originally defined.

<span class="mw-page-title-main">Haplogynae</span> Infraorder of spiders

The Haplogynae or haplogynes are one of the two main groups into which araneomorph spiders have traditionally been divided, the other being the Entelegynae. Morphological phylogenetic studies suggested that the Haplogynae formed a clade; more recent molecular phylogenetic studies refute this, although many of the ecribellate haplogynes do appear to form a clade, Synspermiata.

<span class="mw-page-title-main">Entelegynae</span> Clade of spiders

The Entelegynae or entelegynes are a subgroup of araneomorph spiders, the largest of the two main groups into which the araneomorphs were traditionally divided. Females have a genital plate (epigynum) and a "flow through" fertilization system; males have complex palpal bulbs. Molecular phylogenetic studies have supported the monophyly of Entelegynae.

<span class="mw-page-title-main">Opisthothelae</span> Suborder of spiders

Opisthothelae is a suborder of spiders within the order Araneae, containing Mygalomorphae and Araneomorphae, but excluding Mesothelae. The Opisthothelae are sometimes presented as an unranked clade and sometimes as a suborder of Araneae. In the latter case, Mygalomorphae and Araneomorphae are treated as infraorders.

<span class="mw-page-title-main">Spider anatomy</span> Physiology of Spiders (order Araneae)

The anatomy of spiders includes many characteristics shared with other arachnids. These characteristics include bodies divided into two tagmata, eight jointed legs, no wings or antennae, the presence of chelicerae and pedipalps, simple eyes, and an exoskeleton, which is periodically shed.

Saltonia is a monotypic genus of North American cribellate araneomorph spiders in the family Dictynidae containing the single species, Saltonia incerta. It was first described by R. V. Chamberlin & Wilton Ivie in 1942, and has only been found in United States. Originally placed with the funnel weavers, it was moved to the Dictynidae in 1967.

This glossary describes the terms used in formal descriptions of spiders; where applicable these terms are used in describing other arachnids.

<span class="mw-page-title-main">Orbiculariae</span>

Orbiculariae is a potential clade of araneomorph spiders, uniting two groups that make orb webs. Phylogenetic analyses based on morphological characters have generally recovered this clade; analyses based on DNA have regularly concluded that the group is not monophyletic. The issue relates to the origin of orb webs: whether they evolved early in the evolutionary history of entelegyne spiders, with many groups subsequently losing the ability to make orb webs, or whether they evolved later, with fewer groups having lost this ability. As of September 2018, the weight of the evidence strongly favours the non-monophyly of "Orbiculariae" and hence the early evolution of orb webs, followed by multiple changes and losses.

<span class="mw-page-title-main">RTA clade</span> Clade of spiders

The RTA clade is a clade of araneomorph spiders, united by the possession of a retrolateral tibial apophysis – a backward-facing projection on the tibia of the male pedipalp. The clade contains over 21,000 species, almost half the current total of about 46,000 known species of spider. Most of the members of the clade are wanderers and do not build webs. Despite making up approximately half of all modern spider diversity, there are no unambiguous records of the group from the Mesozoic and molecular clock evidence suggests that the group began to diversify during the Late Cretaceous.

Zorodictyna is a genus of spiders in the family Udubidae native to Madagascar. It has been described as an intermediate genus between Zoropsidae and Dictynidae, though it is now placed in Udubidae. This genus was originally placed in the family Zoropsidae, but it has been reassigned several times since. In 1967, Lehtinen moved it to Miturgidae. In 1999, it was moved back to Zoropsidae, and in 2015, it was moved to Udubidae.

Paratheuma is a genus of cribellate araneomorph spiders in the family Dictynidae, and was first described by E. B. Bryant in 1940. Originally placed with the ground spiders, it was transferred to the intertidal spiders in 1975, and to the Dictynidae in 2016.

References

  1. Foelix, Rainer F. (1996). Biology of Spiders (2 ed.). Oxford University Press. pp.  118–122.
  2. Hawthorn, Anya C.; Opell, Brent D. (2002). "Evolution of adhesive mechanisms in cribellar spider prey capture thread: evidence for van der Waals and hygroscopic forces". Biological Journal of the Linnean Society. 77 (1): 1–8. doi: 10.1046/j.1095-8312.2002.00099.x .
  3. Bott, Raya A. Baumgartner, Werner Bräunig, Peter Menzel, Florian Joel, Anna-Christin. Adhesion enhancement of cribellate capture threads by epicuticular waxes of the insect prey sheds new light on spider web evolution. Proceedings of the Royal Society B. 31 May 2017. doi : 10.1098/rspb.2017.0363
  4. Hajer, J., Foberová, L. & Řeháková, D. (2017). Silk-producing organs of ecribellate and cribellate nymphal stages in Austrochilus sp. (Araneae: Austrochilidae): Notes on the transformation of the anterior median spinnerets into the cribellum. Israel Journal of Entomology 47: 21–33.
  5. Gordon, Richard; Dusan Losic; Mary Ann Tiffany; Stephen S. Nagy; Frithjof A.S. Sterrenburg (February 2009). "The Glass Menagerie: diatoms for novel applications in nanotechnology". Trends in Biotechnology. 27 (2): 116–127. doi:10.1016/j.tibtech.2008.11.003. PMID   19167770.