Pleurobranchaea maculata

Pleurobranchaea maculata, or the grey side-gilled slug, is a species of sea slug, specifically a side-gill slug or notaspidean. It is a marine gastropod mollusc in the family Pleurobranchaeidae.

Distribution
This species occurs around the North Island and South Island of New Zealand. In 2009 it was reported far outside its native range, on the coast of Argentina from where it spread rapidly, currently encompassing ca. 2,000 km along the southwestern Atlantic coast.

Habitat
This side-gill slug is found intertidally in harbours and to depths of up to 6 m or deeper off rocky coasts. It is often washed ashore during spring storms.

Description
This marine slug is 80 to 100 mm in length, with southern specimens somewhat larger. Its colour is a mottled pale grey, densely patterned with short, brown broken lines. The wedge-shaped head has two sensroy tentacles or rhinophores. The mantle is smooth in texture, but covered with folds and puckers, and the foot extends well beyond it. There is no remnant of a shell, and the feathery gill is tucked under the right side of the mantle.

Ecology
This slug eats mostly sea anemones but will take marine worms, mussels, dead or dying animals, and other Pleurobrachaea sea slugs. It lives for 2–3 years and dies after spawning in winter.

Toxicity
In 2009, a major scare in the Auckland Region of New Zealand was sparked after several dogs died of tetrodotoxin poisoning after eating Pleurobranchaea maculata on beaches. Children and pet owners were asked to avoid beaches, and recreational fishing was also interrupted for a time. After exhaustive analysis, it was found that the sea slugs must have ingested tetrodotoxin.