DIVE DRY WITH DR. BILL #869: THE ORANGE GUMDROP
Years ago I was carefully lifting up rocks in the dive park to see what was hiding beneath them. Of course there were the usual suspects: wriggling brittle stars, small crabs and the occasional flatworm. I was surprised to see a bright orange gumdrop under one. Using the few field guides I had at the time (Google was not around back then), I learned it was a species of sidegill snail known as Berthellina ilisima (formerly Berthellina engeli).
I did find several appropriate common names for it... the apricot slug, the orange blob and Engel's gumdrop. Back in the early 1970s, I spent some winters down at Bahia de Kino, Mexico, in the midriff islands region. The Seri indians there had a name for it, epenozaah which is translated as 'sun in the sea'.
Back then this species was considered occasional in our waters, and found mostly down south where the water is warmer. Even today the excellent field guide Beneath Pacific Tides states that it is only found up in SoCal during warm water events like El Niños. On a recent dive I found another one under a rock. A quick check of my dive computer proved that water temperature was not toasty. In fact, I've found this species in many years that were not blessed by warm temperatures.
The dive park, located at the SE end of Catalina Island, is considered one of the warmest regions in the offshore Channel Islands. We do get species considered more southern in origin in our waters with some frequency. Examples include the slate pencil sea urchin (Eucidaris thouarsii), the largemouth blenny (Labrisomus xanti), the whitetail damsel (Stegastes leucorus) and the Panamic fang blenny (Ophioblennius steindachneri). Heck, at my mature age I think I'm becoming a warm water species myself!
So what is a sidegill snail? As the common name suggests, they are snails that have their gills on the side. That makes sense. To the untrained eye, they look like their distant opisthobranch relatives, the dorid nudibranchs. However, the gills on that group are located in a cluster on the dorsal surface and are readily observed if they haven't been withdrawn. Also the rolled sensory rhinophores originate from beneath the oral hood above the head rather than from the dorsal surface. They also have a small shell located inside.
A related species, Berthellina citrina, has glands that produce sulphuric acid which is used as a defense mechanism. I'm not sure if Berthellina ilisima is capable of this. Based on the fish I've seen slurp them up, I wouldn't think so.Garibaldi often try to suck them up when exposed, as do sheephead. I often have to swat away these pesky predators when trying to film the sidegills.
Like many opisthobranch snails, the sidegills are mostly hermaphoroditic and contain both male and female organs. Like nudibranchs they line up on their right sides to "double their pleasure, double their fun" (and without any need for a stick of Wrigley's Doublemint gum). When it's time for munching rather than mating, they chow down on sponges. Even my cooking must taste better than that.
© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Images of Engel's gumdrop in the dive park and a garibaldi slurping up one before I could protect it.
Years ago I was carefully lifting up rocks in the dive park to see what was hiding beneath them. Of course there were the usual suspects: wriggling brittle stars, small crabs and the occasional flatworm. I was surprised to see a bright orange gumdrop under one. Using the few field guides I had at the time (Google was not around back then), I learned it was a species of sidegill snail known as Berthellina ilisima (formerly Berthellina engeli).
I did find several appropriate common names for it... the apricot slug, the orange blob and Engel's gumdrop. Back in the early 1970s, I spent some winters down at Bahia de Kino, Mexico, in the midriff islands region. The Seri indians there had a name for it, epenozaah which is translated as 'sun in the sea'.
Back then this species was considered occasional in our waters, and found mostly down south where the water is warmer. Even today the excellent field guide Beneath Pacific Tides states that it is only found up in SoCal during warm water events like El Niños. On a recent dive I found another one under a rock. A quick check of my dive computer proved that water temperature was not toasty. In fact, I've found this species in many years that were not blessed by warm temperatures.
The dive park, located at the SE end of Catalina Island, is considered one of the warmest regions in the offshore Channel Islands. We do get species considered more southern in origin in our waters with some frequency. Examples include the slate pencil sea urchin (Eucidaris thouarsii), the largemouth blenny (Labrisomus xanti), the whitetail damsel (Stegastes leucorus) and the Panamic fang blenny (Ophioblennius steindachneri). Heck, at my mature age I think I'm becoming a warm water species myself!
So what is a sidegill snail? As the common name suggests, they are snails that have their gills on the side. That makes sense. To the untrained eye, they look like their distant opisthobranch relatives, the dorid nudibranchs. However, the gills on that group are located in a cluster on the dorsal surface and are readily observed if they haven't been withdrawn. Also the rolled sensory rhinophores originate from beneath the oral hood above the head rather than from the dorsal surface. They also have a small shell located inside.
A related species, Berthellina citrina, has glands that produce sulphuric acid which is used as a defense mechanism. I'm not sure if Berthellina ilisima is capable of this. Based on the fish I've seen slurp them up, I wouldn't think so.Garibaldi often try to suck them up when exposed, as do sheephead. I often have to swat away these pesky predators when trying to film the sidegills.
Like many opisthobranch snails, the sidegills are mostly hermaphoroditic and contain both male and female organs. Like nudibranchs they line up on their right sides to "double their pleasure, double their fun" (and without any need for a stick of Wrigley's Doublemint gum). When it's time for munching rather than mating, they chow down on sponges. Even my cooking must taste better than that.
© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Images of Engel's gumdrop in the dive park and a garibaldi slurping up one before I could protect it.
