DIVE DRY WITH DR. BILL #827: YOU CAN TEACH AN OLD TRICK NEW DOGS!
If I thought I knew everything there is to know about marine life, even just here in Catalina waters, I probably would have quit diving and researching decades ago. Well, not really. One of the things that keeps me descending into the briny deep is that I often see new species or new behaviors that add to my knowledge about how our kelp forest ecosystems work.
When I was up at Howland's Landing to see Jean-Michel, Nan, Murph and Holly at Cousteau Family Camp recently, I was taught abit of information I either didn't know before... or my chemo brain had wiped the memory out of it from my RAM. Murph (otherwise known as Dr. Richard Murphy, former V.P. for Science and Education at The Cousteau Society) was "edumacating" attendees of the camp about our local critters.
Murph held up a snail in the murex family (Muricidae) and pointed to a "tooth-like" projection on the shell. He asked if anyone knew what it was for. I searched my memory banks and found them blank, so I made a guess. I thought it might increase stability of the snail in the face of waves and swell. WRONG answer. Murph then held out a barnacle and informed us the tooth was to puncture the valves of barnacles so they could chow down on them!
Members of this family are usually found in the tropics and subtropics and often have very ornate shells making them highly desirable for collectors. The ones in our waters are often pretty drab and unattractive, which is good because it mnakes them less desirable. Many snails in this family feed on barnacles, limepts and bivales such as mussels and oysters. Sometimes barnacles get their revenge by cementing their homes onto the shells of snails, including murexes. With the mussels and other bivalves, they drill a hole into the shell.
The leafy hornmouth snail (Ceratostoma foliatum) is a local species of murex that feeds on barnacles. In the lower left image you can see one with many tiny gray barnacles attached to its shell. I have often wondered why these murex shells are encrusted by various critters such as barnacles, bryozoa and tube worms. They also tend to be eroded while others are clean.
Thanks to the new field guide Beneath Pacific Tides I found the answer. Marine critters have a difficult time attaching to a substrate that is growing. The leafy hornmouth shell grows for the first four years of its life, but then stops for the next four (or so). Thus it provides a stable substrate for encrusters (just like the prop and hull of my old St. Pierre Michelin design dory did 45 years ago!
Our local murexes lay fairly distinctive eggs (if you look very closely), although they can be superficially similar to the eggs of some other local snail species. Once the larvae hatch out, they don't get a chance to join the plankton and see the world. Instead they simply crawl away to seek their fortune. I've done some crawling away in my "youth" too... usually around 2:00 am when the local bars closed.
© 2019 Dr. Bill Bushing. For the entire archived set of over 800 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Fancy pants tropical murex and less ostentatious local leafy hornmouth ; Murph "edumacating" and cluster of barnacles; barnacles getting revenge by attaching to leafy hornmouth and murex egg cluster.
If I thought I knew everything there is to know about marine life, even just here in Catalina waters, I probably would have quit diving and researching decades ago. Well, not really. One of the things that keeps me descending into the briny deep is that I often see new species or new behaviors that add to my knowledge about how our kelp forest ecosystems work.
When I was up at Howland's Landing to see Jean-Michel, Nan, Murph and Holly at Cousteau Family Camp recently, I was taught abit of information I either didn't know before... or my chemo brain had wiped the memory out of it from my RAM. Murph (otherwise known as Dr. Richard Murphy, former V.P. for Science and Education at The Cousteau Society) was "edumacating" attendees of the camp about our local critters.
Murph held up a snail in the murex family (Muricidae) and pointed to a "tooth-like" projection on the shell. He asked if anyone knew what it was for. I searched my memory banks and found them blank, so I made a guess. I thought it might increase stability of the snail in the face of waves and swell. WRONG answer. Murph then held out a barnacle and informed us the tooth was to puncture the valves of barnacles so they could chow down on them!
Members of this family are usually found in the tropics and subtropics and often have very ornate shells making them highly desirable for collectors. The ones in our waters are often pretty drab and unattractive, which is good because it mnakes them less desirable. Many snails in this family feed on barnacles, limepts and bivales such as mussels and oysters. Sometimes barnacles get their revenge by cementing their homes onto the shells of snails, including murexes. With the mussels and other bivalves, they drill a hole into the shell.
The leafy hornmouth snail (Ceratostoma foliatum) is a local species of murex that feeds on barnacles. In the lower left image you can see one with many tiny gray barnacles attached to its shell. I have often wondered why these murex shells are encrusted by various critters such as barnacles, bryozoa and tube worms. They also tend to be eroded while others are clean.
Thanks to the new field guide Beneath Pacific Tides I found the answer. Marine critters have a difficult time attaching to a substrate that is growing. The leafy hornmouth shell grows for the first four years of its life, but then stops for the next four (or so). Thus it provides a stable substrate for encrusters (just like the prop and hull of my old St. Pierre Michelin design dory did 45 years ago!
Our local murexes lay fairly distinctive eggs (if you look very closely), although they can be superficially similar to the eggs of some other local snail species. Once the larvae hatch out, they don't get a chance to join the plankton and see the world. Instead they simply crawl away to seek their fortune. I've done some crawling away in my "youth" too... usually around 2:00 am when the local bars closed.
© 2019 Dr. Bill Bushing. For the entire archived set of over 800 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Fancy pants tropical murex and less ostentatious local leafy hornmouth ; Murph "edumacating" and cluster of barnacles; barnacles getting revenge by attaching to leafy hornmouth and murex egg cluster.
