I’m not quite sure how it happened – in fact, I at one point tried to actively avoid it – but it is now impossible to deny. I am a gastropod enthusiast. I love snails and slugs and have from a young age. I have distinct memories of walking ahead of my parents and scanning the walkway from the car to the door of the house to make sure they wouldn’t inadvertently squash any snails. As a graduate student I had planned to avoid studying snails. Instead, I find myself studying marine snails and squealing for excitement when I see an unfamiliar species or a cool color morph or interesting behavior. As it turns out, Lough Hyne has no shortage of gastropods.
Without even having to get wet, you can find at least half a dozen different species of marine snails in the intertidal zone: up to 4 types of winkles (the edible, rough, flat, and smooth winkles), 3 types of topshells (the grey, flat, and toothed topshells), a dogwelk, and 2 limpets. If you go underwater, into the subtidal zone, the number of potential species you might encounter skyrockets. There are cowries, blue-rayed limpets, snails reaching maximum sizes of only a few millimeters (such as Rissoa parva), miniature sea slugs like Doto coronate (almost too small to see with the naked eye), blue and bubbly sea slugs (Janolus cristatus), and ‘sea lemons’ (the sea slug Doris pseudoargus). And these are just the common snails and slugs. Every once in a while another critter shows up. And when it does, it doesn’t disappoint.
Without even having to get wet, you can find at least half a dozen different species of marine snails in the intertidal zone: up to 4 types of winkles (the edible, rough, flat, and smooth winkles), 3 types of topshells (the grey, flat, and toothed topshells), a dogwelk, and 2 limpets. If you go underwater, into the subtidal zone, the number of potential species you might encounter skyrockets. There are cowries, blue-rayed limpets, snails reaching maximum sizes of only a few millimeters (such as Rissoa parva), miniature sea slugs like Doto coronate (almost too small to see with the naked eye), blue and bubbly sea slugs (Janolus cristatus), and ‘sea lemons’ (the sea slug Doris pseudoargus). And these are just the common snails and slugs. Every once in a while another critter shows up. And when it does, it doesn’t disappoint.
This year an aggregation of an unexpected slug, of the Order Cephalaspidea, was found within the lough. Animals within this group are morphologically halfway between a snail and slug (at least as we commonly think of them); snails have a shell which they grow, carry, and live within; slugs lack the shell to protect their soft bodies. Cephalaspideans retain their shell, but in a reduced form, generally as a flattened oval piece at the posterior end of the animal. One species within this order has been commonly observed for many years: Philine aperta. These white, semi-translucent animals can be found burrowing into sandy or muddy sediments in search of worms or small bivalves to consume.
Less commonly observed—one not seen in large numbers for nearly a decade—is Akera bullata. Like their relative Philine, these organisms are also found on soft sediments, but the list of similarities between these two organisms is short. These animals are herbivorous and have the ability to swim. Picture a ray or skate flapping its “wings” to smoothly glide through the water. In similar fashion, Akera swims using enlarged fleshy lobes. According to researchers Dr. Colin Little and Penny Stirling, these incredible animals were once observed swimming in a swarm in the lough.
Less commonly observed—one not seen in large numbers for nearly a decade—is Akera bullata. Like their relative Philine, these organisms are also found on soft sediments, but the list of similarities between these two organisms is short. These animals are herbivorous and have the ability to swim. Picture a ray or skate flapping its “wings” to smoothly glide through the water. In similar fashion, Akera swims using enlarged fleshy lobes. According to researchers Dr. Colin Little and Penny Stirling, these incredible animals were once observed swimming in a swarm in the lough.
While I didn’t observe any swimming, I did see an equally fascinating aggregation. I first noticed a bubble on the bottom of the seafloor. Then I saw a dark purple sausage shape, Akera. As I looked around I started seeing more and more of these bubbles and purple slugs, hundreds in fact. After several minutes of dumbfounded staring, I realized I was observing a mating aggregation. In some cases I could find an individual and follow its mucus trail in the mud to another individual that was creating these mucus bubbles. All cephalaspideans create characteristic mucus bags attached to the sea floor, resembling little balloons, in which they lay their eggs. These hermaphroditic (each individual has both male and female reproductive organs) animals will form mating groups in which they exchange sperm to fertilize their eggs. I can’t say how many individuals you might theoretically observe, but I saw groups of up to four individuals mating simultaneously!
The mating aggregation was brief. A week later egg masses could still be found, but the adult Akera had dispersed back to their feeding grounds. It just goes to show that there is always something new and exciting to discover at Lough Hyne.
By: Sara Edquist
By: Sara Edquist