found by my family near Plymouth last August. They were picking up any litter they could find around the rockpools and at first sight thought the tiny( less than 2cm) blob of colour was another plastic fragment before quickly realising it was a sea slug. I was having a postsnorkel snooze on the beach at the time and my grandchildren apparently had to be persuaded to wake me up. I’ m very glad they did!
In terms of its appearance, the second and much larger species( up to 12cm) covered here is a relatively dour creature but, as with all sea slugs, there are colourful aspects to its life. It preys on sea anemones such as the beadlet and snakelocks, whose tentacles armed with batteries of stinging cells provide protection against most predators. These do not deter the grey sea slug, however, and are actually a crucial part of the‘ meal deal’. The slug ingests the anemones’ stinging cells without triggering them, passes them through its digestive system, and then transfers them into little pockets at the tips of the shaggy projections( called cerata) on its back. If another predator such as a fish attacks the sea slug and bites at the cerata, it gets stung by the second-hand sea anemone cells. That’ s what I call impressive recycling!
Without hard shells to hide in or the speed to escape, all sea slugs rely on some type of deterrent, whether it be stings or chemicals. The fact that these are typically reprocessed from their prey explains why they are so specific in their choice of food. The Rainbow Sea Slug,
In amongst its prey, a grey sea slug gets down to its meal of a large snakelocks anemone
for example, eats a particular species of hydroid( Candelabrum cocksii). Like sea anemones, hydroids have stinging cells and these are presumably recycled in a similar way.
Another common feature of these two species is their reproduction. All sea slugs are hermaphrodites with
Grey sea slug
every individual simultaneously male and female. When a pair mate, each slug both donates and receives sperm and each goes on to lay eggs; total equality! �
Paul’ s photos and video clips capturing UK marine life stories are on Instagram @ paulnaylormarinephoto
Grey sea slug with a crowd of painted gobies that often follow slower creatures to see what food they disturb
17