DIVE DRY WITH DR. BILL #861: PHILIPPINE NUDIS
One positive thing this SARS-Cov-2 "stay at home" order has brought about is enough time to do some very important but long neglected tasks. I'm not talking about cleaning house... at this point that may require a specialist. No, it has given me enough time to finally edit the 25+ hours of video footage I shot in the Philippines back in 2013 into a three disc BluRay set.
I finished the vertebrate video a few weeks ago and am working feverishly (but without COVID-19) on the invertebrates. The past few days I've been focused on the beautiful nudis. No, I'm not referring to the lovely Filipinas... I took very little video of them even though many are amphibious. A nudi is a nudibranch, a snail without a shell. Often these are incredibly beautiful and great subjects to film. Even landlubbers appreciate their bright coloration.
My Bible for identifying the nudis is Gosliner, Valdés and Behrens Nudibranch & Sea Slug Identification: Indo Pacific. This incredible field guide has images for 2,100+ species in it. I've poured over every image twice already and still have not identified all the ones I filmed. I also search the Internet via Google for more images. My eyes usually demand I break from the computer frequently so they can rest.
One thing that makes this process difficult is that many species are simply not identified yet. Scientists have not had time to describe them and give them an appropriate scientific name. They generally can assign them to genus level, for example Gymnodoris #1-61! Relatively few even have a common name. To add to my confusion (as if it needed any help), a number of the species have variable coloration which makes it difficult to ID them from a single image. That is where Google searches really come in handy.
I find the latter issue quite interesting. Variation within members of the same species (intraspecific) is not unusual. Heck, look at our own Homo sapiens group. There is pretty wide diversity of skin color, hair color, eye color, body type, etc. Here in SoCal there doesn't seem to be much intraspecific variation in our nudis. They tend to be pretty uniform and therefore easier to ID.
As a curious marine biologist (some say too curious, but don't listen to them), I find the game of identifying marine critters to be far more interesting than playing card or board games all day in isolation. It is a real challenge, and I get great satisfaction from finally determining the identity of a new species. Yes, some of us get our kicks in strange ways!
Why so many different color patterns in nudibranchs you might ask. Even if you don't, I'm going to answer. Now I'm pretty sure nudis don't choose a potential mate based on appearance (as humans too often do). I doubt their vision is that great. I'm assuming it is through chemical means such as sex pheromones. I know gastropods (snails, etc.) can detect potential prey thru chemical signals so this makes sense.
The often vivid coloration and patterns of nudis must serve another purpose then. Marine biologists feel pretty certain it makes them hard to forget (like some of my old girl friends, sigh). A potential predator such as a fish may try to munch on one, and find it is either distasteful or in some cases has incorporated stinging nematocysts in its body from its own prey. It then remembers not to try that dish again. I did find several species that were white or nearly all white. Perhaps their predators think they've seen a ghost.
Fish that live in inshore, shallow, well-lit waters usually have good color vision. In fact some fish have more color sensors (cones) in their eyes than humans. We have red, blue and green cones in our eyes (although I'm partially red-green color blind). Some fish have ultraviolet sensing cones as well! Others can sense polarized light.
In closing I'll simply add a montage of nudis from the Philippines for your viewing pleasure. Just enjoy the beauty. I won't even give their scientific names here since it isn't necessary to enjoy them. However, as a scientists, I'll continue to search for names! It's my job.
© 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: A beautiful selection of nudis from the Philippines. Note the nearly all white one at the lower left.
One positive thing this SARS-Cov-2 "stay at home" order has brought about is enough time to do some very important but long neglected tasks. I'm not talking about cleaning house... at this point that may require a specialist. No, it has given me enough time to finally edit the 25+ hours of video footage I shot in the Philippines back in 2013 into a three disc BluRay set.
I finished the vertebrate video a few weeks ago and am working feverishly (but without COVID-19) on the invertebrates. The past few days I've been focused on the beautiful nudis. No, I'm not referring to the lovely Filipinas... I took very little video of them even though many are amphibious. A nudi is a nudibranch, a snail without a shell. Often these are incredibly beautiful and great subjects to film. Even landlubbers appreciate their bright coloration.
My Bible for identifying the nudis is Gosliner, Valdés and Behrens Nudibranch & Sea Slug Identification: Indo Pacific. This incredible field guide has images for 2,100+ species in it. I've poured over every image twice already and still have not identified all the ones I filmed. I also search the Internet via Google for more images. My eyes usually demand I break from the computer frequently so they can rest.
One thing that makes this process difficult is that many species are simply not identified yet. Scientists have not had time to describe them and give them an appropriate scientific name. They generally can assign them to genus level, for example Gymnodoris #1-61! Relatively few even have a common name. To add to my confusion (as if it needed any help), a number of the species have variable coloration which makes it difficult to ID them from a single image. That is where Google searches really come in handy.
I find the latter issue quite interesting. Variation within members of the same species (intraspecific) is not unusual. Heck, look at our own Homo sapiens group. There is pretty wide diversity of skin color, hair color, eye color, body type, etc. Here in SoCal there doesn't seem to be much intraspecific variation in our nudis. They tend to be pretty uniform and therefore easier to ID.
As a curious marine biologist (some say too curious, but don't listen to them), I find the game of identifying marine critters to be far more interesting than playing card or board games all day in isolation. It is a real challenge, and I get great satisfaction from finally determining the identity of a new species. Yes, some of us get our kicks in strange ways!
Why so many different color patterns in nudibranchs you might ask. Even if you don't, I'm going to answer. Now I'm pretty sure nudis don't choose a potential mate based on appearance (as humans too often do). I doubt their vision is that great. I'm assuming it is through chemical means such as sex pheromones. I know gastropods (snails, etc.) can detect potential prey thru chemical signals so this makes sense.
The often vivid coloration and patterns of nudis must serve another purpose then. Marine biologists feel pretty certain it makes them hard to forget (like some of my old girl friends, sigh). A potential predator such as a fish may try to munch on one, and find it is either distasteful or in some cases has incorporated stinging nematocysts in its body from its own prey. It then remembers not to try that dish again. I did find several species that were white or nearly all white. Perhaps their predators think they've seen a ghost.
Fish that live in inshore, shallow, well-lit waters usually have good color vision. In fact some fish have more color sensors (cones) in their eyes than humans. We have red, blue and green cones in our eyes (although I'm partially red-green color blind). Some fish have ultraviolet sensing cones as well! Others can sense polarized light.
In closing I'll simply add a montage of nudis from the Philippines for your viewing pleasure. Just enjoy the beauty. I won't even give their scientific names here since it isn't necessary to enjoy them. However, as a scientists, I'll continue to search for names! It's my job.
© 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: A beautiful selection of nudis from the Philippines. Note the nearly all white one at the lower left.
