DIVE DRY WITH DR. BILL #853: GILLS ON THE SIDE
Just before my cancer was diagnosed, I had purchased a new buoyancy compensator (BCD) to try a "new" way of diving with lots of air. It was a sidemount rig, where the air tanks are attached on either side of the body. I could dive with enough air to rule Neptune's realm (as long as Aquaman didn't show up). I figured I was too old and frail to dive doubles... two tanks attached to the back of my BCD. Wouldn't be prudent.
Now there is a group of molluscs that some think are nudibranchs, but as an ex-spurt marine biologist, I'll inform you that they are not. However, they are related to the nudibranchs. I'm referring to the sidegills. As their common name suggests, they carry their gills on the right side instead of up on their back like the nudibranchs. Several of these species have a small remnant shell.
I first learned the sidegills as a unified group way back in my early days on Catalina. However, as my readers know, taxonomists are often revising evolutionary groupings based on molecular genetics. Of course any grouping, whether based on anatomy or genetics, is a human construct to make things "easier" for those of us to study the critters. In 2005 French biologists Bouchet & Rocroi determined that not all members of the group evolved from the same ancestral stock. I'll keep calling them all sidegills though. You can't always teach an old geezer a new trick.
I don't see sidegills very often in our waters, but there are a few. The most commonly seen one is Tylodina fungina. I love saying that scientific name for some strange reason. You may prefer one of its common names, perhaps the mushroom sidegill or the yellow snot snail. It has a bright yellow body due to its preferred prey, a yellow sponge. Its shell looks like a brown Chinese coolie hat.
One I've found particularly interesting is the California sidegill, Pleurobranchaea californica, in large part due to its unusual feeding structure which looks like a certain male organ and is used to chow down on small fish and various invertebrates including its own species. A voracious cannibal! The structure is usually covered by the large oral veil. It is light brown in color with a wide variety of small dark brown and white patches on the dorsal surface. There are also bumps or tubercles present. Although considered a deep water species, I have filmed it at recreational diving depths.
Berthella californica is another local species but has a wide geographic distribution from Alaska to Panama and the Galapagos. In most of their range they are white with opaque white spots. However, down here in SoCal they are a brownish color with the white spots... maybe due to something they eat? There is a distinct white line along the margin of the body. Previously they were known as Pleurobranchus californica and P. denticulatus.
Berthellina ilisima is normally found south of the border, down Mexico way (and all the way to the Galapagos). It is said to enter our waters during warm water events such as El Niños. I have filmed it right in our dive park, which is located in the region with the warmest waters in the Channel Islands. Its bright orange color is fairly distinctive. The Seri Indians in the Sea of Cortez called it xepenozaah ('sun in the sea'). Apparently the English common name is Engel's Gumdrop. Since I've frequently seen garibaldi try to eat them, including while I try to film them, I'm guessing those fish like orange gumdrops.
© 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: Sidegills Berthella californica and Berthellina ilisima; Tylodina fungina and Pleurobranchaea californica.
Just before my cancer was diagnosed, I had purchased a new buoyancy compensator (BCD) to try a "new" way of diving with lots of air. It was a sidemount rig, where the air tanks are attached on either side of the body. I could dive with enough air to rule Neptune's realm (as long as Aquaman didn't show up). I figured I was too old and frail to dive doubles... two tanks attached to the back of my BCD. Wouldn't be prudent.
Now there is a group of molluscs that some think are nudibranchs, but as an ex-spurt marine biologist, I'll inform you that they are not. However, they are related to the nudibranchs. I'm referring to the sidegills. As their common name suggests, they carry their gills on the right side instead of up on their back like the nudibranchs. Several of these species have a small remnant shell.
I first learned the sidegills as a unified group way back in my early days on Catalina. However, as my readers know, taxonomists are often revising evolutionary groupings based on molecular genetics. Of course any grouping, whether based on anatomy or genetics, is a human construct to make things "easier" for those of us to study the critters. In 2005 French biologists Bouchet & Rocroi determined that not all members of the group evolved from the same ancestral stock. I'll keep calling them all sidegills though. You can't always teach an old geezer a new trick.
I don't see sidegills very often in our waters, but there are a few. The most commonly seen one is Tylodina fungina. I love saying that scientific name for some strange reason. You may prefer one of its common names, perhaps the mushroom sidegill or the yellow snot snail. It has a bright yellow body due to its preferred prey, a yellow sponge. Its shell looks like a brown Chinese coolie hat.
One I've found particularly interesting is the California sidegill, Pleurobranchaea californica, in large part due to its unusual feeding structure which looks like a certain male organ and is used to chow down on small fish and various invertebrates including its own species. A voracious cannibal! The structure is usually covered by the large oral veil. It is light brown in color with a wide variety of small dark brown and white patches on the dorsal surface. There are also bumps or tubercles present. Although considered a deep water species, I have filmed it at recreational diving depths.
Berthella californica is another local species but has a wide geographic distribution from Alaska to Panama and the Galapagos. In most of their range they are white with opaque white spots. However, down here in SoCal they are a brownish color with the white spots... maybe due to something they eat? There is a distinct white line along the margin of the body. Previously they were known as Pleurobranchus californica and P. denticulatus.
Berthellina ilisima is normally found south of the border, down Mexico way (and all the way to the Galapagos). It is said to enter our waters during warm water events such as El Niños. I have filmed it right in our dive park, which is located in the region with the warmest waters in the Channel Islands. Its bright orange color is fairly distinctive. The Seri Indians in the Sea of Cortez called it xepenozaah ('sun in the sea'). Apparently the English common name is Engel's Gumdrop. Since I've frequently seen garibaldi try to eat them, including while I try to film them, I'm guessing those fish like orange gumdrops.
© 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: Sidegills Berthella californica and Berthellina ilisima; Tylodina fungina and Pleurobranchaea californica.
