Pycnoclavella stanleyi

Pycnoclavella stanleyi
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Tunicata
Class:	Ascidiacea
Order:	Aplousobranchia
Family:	Clavelinidae
Genus:	Pycnoclavella
Species:	P. stanleyi
Binomial name
	Pycnoclavella stanleyi; Berrill & Abbott, 1949

Pycnoclavella stanleyi is a species of sea squirt that was initially described from specimens collected in the vicinity of Pacific Grove, California, including at Asilomar State Beach.

Description

Pycnoclavella stanleyi is a colonial ascidian with widely separated individuals sharing a base, a leathery tunic typically covered in sand grains. P. stanleyi can be recognized by its seven rows of gill slits and striking gold or yellow-orange pharynx coloration. This coloration overlaps with the introduced Botrylloides violaceus, but that species is chained without clear outer separation of individuals. Overall, this is a small species with individuals not exceeding 1 cm in height.

Reproduction

Like other ascidians, P. stanleyi can reproduce both sexually and asexually. Asexual reproduction takes place via budding. Sexual reproduction results in the formation of larvae, which resemble tadpoles, with an oval body with a long tail. Within the body, there is a dark spot, which is the ocellus, a type of simple eye. Unlike many other sea squirt larvae, they lack an otolith.

Range

Pycnoclavella stanleyi inhabits the Eastern Pacific shoreline, from British Columbia to Baja California.

Habitat

This tunicate prefers shallow water; it is found encrusting surf-pounded rocks near sandy bottoms from a depth of 0 to 10 m. It often occurs near seaweed holdfasts.

Ecology

Like other sea squirts, P. stanleyi is a sessile filter feeder; it pulls food particles from fast-moving water using its pharynx with gill slits. P. stanleyi is one of the vanadium-sequestering tunicate species, with circulating vanadocytes in the bloodstream.

Etymology

Pycnoclavella stanleyi is named after John Stanley, a colleague of N. J. Berrill, who initially described this species with D. P. Abbott.

References

↑ "Yellow Social Ascidian (Pycnoclavella stanleyi)". iNaturalist. Retrieved 30 January 2026.
1 2 3 4 5 6 7 Berrill, N. J.; Abbott, D.P. (1949). "The structure of the ascidian, Pycnoclavella stanleyi n. sp., and the nature of its tadpole larva". Canadian Journal of Research. 27 (2): 43–49.
↑ "Key to Class Ascidiacea (Tunicates, sea squirts)". Retrieved 30 January 2026.
1 2 "Pycnoclavella stanleyi Berrill & Abbott, 1949 Social tunicate". Seabase. Retrieved 30 January 2026.
1 2 "Subphylum Urochordata". Seabase. Retrieved 30 January 2026.
↑ Levine, Estees P. (1961). "Occurrence of Titanium, Vanadium, Chromium, and Sulfuric Acid in the Ascidian Eudistoma ritteri". Science. 133 (3461): 1352–1353. doi:10.1126/science.133.3461.1352.

[inaturalist-1] "Yellow Social Ascidian (Pycnoclavella stanleyi)". iNaturalist. Retrieved 30 January 2026.

[description-2] 1 2 3 4 5 6 7 Berrill, N. J.; Abbott, D.P. (1949). "The structure of the ascidian, Pycnoclavella stanleyi n. sp., and the nature of its tadpole larva". Canadian Journal of Research. 27 (2): 43–49.

[Salish_Key-3] "Key to Class Ascidiacea (Tunicates, sea squirts)". Retrieved 30 January 2026.

[seabase-4] 1 2 "Pycnoclavella stanleyi Berrill & Abbott, 1949 Social tunicate". Seabase. Retrieved 30 January 2026.

[Stanford-5] 1 2 "Subphylum Urochordata". Seabase. Retrieved 30 January 2026.

[vanadocytes-6] Levine, Estees P. (1961). "Occurrence of Titanium, Vanadium, Chromium, and Sulfuric Acid in the Ascidian Eudistoma ritteri". Science. 133 (3461): 1352–1353. doi:10.1126/science.133.3461.1352.