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Gasteracantha

Gasteracantha is a genus of orb-weaver spiders first named by Carl Jakob Sundevall in 1833. Species of the genus are known as spiny-backed orb-weavers, spiny orb-weavers, or spiny spiders. The females of most species are brightly colored with six prominent spines on their broad, hardened, shell-like abdomens.

Names

The genus name Gasteracantha derives from Ancient Greek (gastḗr), meaning "belly", and (ákantha), meaning "thorn".

Spiny-backed orb-weavers are sometimes colloquially called "crab spiders" because of their shape, but they are not closely related to the true crab spiders. Other colloquial names for certain species include thorn spider, star spider, kite spider, or jewel spider.

Other genera in the same family are also known as spiny orb-weavers.

Distribution

Gasteracantha species are distributed worldwide in tropical and subtropical climates. The genus is most diverse in tropical Asia, from India through Indonesia. One species, G. cancriformis, occurs in the Americas.

Sexual dimorphism

Members of the genus exhibit strong sexual dimorphism. Females are several times larger than males, which lack prominent spines or bright colors.

Predators and defense mechanisms

Some species of orb-weavers use stridulation. A 2020 study found that, while it resembled antipredator stridulation in other arthropods, there was no evidence that this was a defense mechanism. Orb-weavers' bites are generally harmless to humans.

Taxonomy and systematics

Gasteracantha has a complex taxonomic history, and many questions of species limits and distribution and generic interrelationships remain unanswered. Furthermore, challenges include the variability within individual Gasteracantha species (e.g., color polymorphism and variable length and shape of spines), a lack of male specimens and descriptions for many species, missing or damaged type specimens, and ambiguous initial descriptions in 18th- and 19th-century scientific literature. The around 70 species currently recognized by World Spider Catalog include dozens of synonyms and subspecies, many based on literature well over 100 years old.

A 2019 study examining three mitochondrial and two nuclear genes found that Gasteracantha is paraphyletic with respect to Macracantha, Actinacantha, and Thelacantha. M. arcuata is allied with G. hasselti and A. globulata, while T. brevispina is closer to G. kuhli and G. diardi. The authors, however, did not propose generic reassignments based on their findings.

Micrathena orb-weavers in North and South America also have hardened abdomens with variously shaped spines, but they are not closely related to Gasteracantha within the orb-weaver family.

Species

, this genus includes 67 species and eighteen subspecies:

References

External links