barnacle
Euacasta sporillus
One pair of the wall plates in members of the genus Euacasta is extremely narrow giving them a squarish cross section. This particular species has long delicate spines that project into the host sponge tissues, presumably to help anchor them inside the sponge. The basal cup in this species can be extremely elongate. This elongation is a reaction to the growth of the sponge host whereby barnacles that have attached to an are of a sponge that is still actively growing need to keep pace by elongating the shell or risk being overgrown and smothered by the sponge.
Morphology
The egg-shaped shell is covered in fine spines that are easily broken when extracting specimens from their hosts. The spines appear to be hollow and then broken off near the base you see that the hole extends right through to the interior of the shell. Two pairs of plates form and operculum to block the entrance to the shell and helps protect the animal inside from predators and desiccation.
Evolution
The Acastinae appear in the fossil record during the mid to late Miocene 18–23 mya and have subsequently radiated into >80 species. While no fossil species has been definitively associated with a host, it is presumed that this radiation occurred as a direct result of being able to embed in the tissues sponge hosts. Current research being carried out by the WA Museum is investigating the evolution of this group and their relationship with their hosts.
Behaviour
Barnacles are sessile, being permanently attached to the substratum. Barnacles feed by filtering the water column for food using highly modified limbs, called cirri.
Method of reproduction
Hermaphroditic, internal fertilisation
Habitat
Marine
Embedded in sponges.
Distribution
Indo-West Pacific.
| Kingdom: | Animalia |
|---|---|
| Phylum: | Arthropoda |
| Subclass: | Thecostraca |
| Order: | Sessilia |
| Suborder: | Balanomorpha |
| Superfamily: | Balanoidea |
| Family: | Archaeobalanidae |
| Genus: | Euacasta |
| Species: | sporillus |
| Name Published Year: | 1854 |
|---|---|
| Rank: | species |
| Scientific Name Authorship: | Darwin |
| Commercial Impact: | None |
| Conservation Assessment: | Least Concern |
Cite this page
Western Australian Museum Collections https://museum.wa.gov.au/online-collections/names/euacasta-sporillus
Accessed 20 May 2024
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