A massive, let’s say, affection apparatus.
Aplysia vaccaria, the largest species of sea slug on Earth. Image credit: HerbziKal
Aplysia vaccaria, commonly referred to as the black sea hare or California black sea hare, is a notably large species of sea slug found in the northeastern Pacific Ocean, specifically along the coasts of California, United States, and Baja California, Mexico, which includes the Gulf of California.
The black sea hare holds the title of being the largest species of sea slug worldwide. It can grow to remarkable sizes, with the biggest documented specimen stretching up to 99 cm (39 in) in length when fully extended and weighing nearly 14 kg (31 lb).
So, the one seen in the video below by YouTuber and TV host Coyote Peterson might actually be a smaller example, despite its appearance of being supersized (Peterson estimates it to weigh about ten pounds, or over four kilograms).
During Peterson’s exploration of tide pools, he was joined by a wildlife expert. However, even though these creatures’ gills are hidden, they still need water to breathe.
Therefore, it’s usually not recommended for the average individual to interact with sea slugs, including the tempting larger ones.
If you’re not a wildlife expert, it’s best to avoid handling sea hares. Photo credit: Alex Heyman.
Scientists have long suspected that sea hares produce toxins to defend themselves, as they lack natural predators. Unlike many of their relatives, A. vaccaria can’t produce ink for protection. Nevertheless, this species still faces minimal predation, indicating it secretes potent toxins that effectively deter predators.
Sea hares obtain their toxins from the compounds in their diet, with the specific toxins produced depending on the type of algae they consume. A. vaccaria primarily feeds on brown algae, which is the source of its unique toxins, unlike A. californica, which consumes red algae and produces different toxins. This also explains why A. vaccaria tends to appear dark brown or black, while A. californica has a red hue, as the coloration of sea hares is influenced by their food source.
Aplysia californica, a species closely related to the sea hare, is depicted here releasing a cloud of purple pigment, likely in response to disturbance. Image credit: Genny Anderson.
Similar to other sea slugs, sea hares are hermaphrodites, possessing fully functional male and female reproductive organs. Their penis is located on the right side of their head, while the vagina is positioned deep within the mantle cavity, beneath the shell. This physical arrangement prevents mating partners from simultaneously acting as both male and female.
But that’s not the end of the story. While sea hares can engage in paired mating, with one assuming the male role and the other the female, during mating seasons, they often gather in large numbers, forming daisy chains of three or more individuals mating together. In these chains, the first sea hare functions solely as a female, while the last acts solely as a male. Those in between serve as both males and females, enabling the sea hare receiving sperm to pass on its own sperm to a third sea hare.
So, while these sea slugs may not be considered aesthetically pleasing by human standards, they certainly have a fascinating sex life, which might pose some challenges for us to comprehend. Just like the creatures themselves, which are incredibly slimy. For both your sake and the sea hare’s, let’s allow them to remain in their natural habitat – the sea.
