DIVE DRY WITH DR. BILL #461: PELT-O-DORIS
Strange title for a column, Dr. Bill. Just what does it mean? Are we talking about a mink pelt for a woman named Doris? Of course not. Even though I'm aghast at the tactics of groups like PETA, I am not one who advocates the wearing of animal skins... unless the entire critter has been properly used for food, tool making, greasing the wagon wheels, etc. You know, just how some of our "Native" American tribes used to show reverence for their kills by not wasting anything. No, Peltodoris has nothing to do with furry critters... only naked ones. And by naked, I'm only referring to the gills they use to breathe underwater. That's right, this is another hot story about nudibranchs... the shell-less snails with the naked gills!
During late summer and early fall, I made regular trips to the harbor end of the dive park where the wreck of the Suejac rests in about 60 to 90 feet. No, I'm not big on wrecks, just trying to avoid the sand and silt stirred up by open water SCUBA classes. I've had many sightings of "naked gills" of several species there. On one dive I was slowly working my way around the upper (stern) end of the ferrocement hull when my eagle eyes spotted a yellow and brown "slug" crawling on some seaweed. Holy mackerel, Batman... it was none other than Peltodoris mullineri... a nudie I've seen so seldom I can still count the times on my fingers. I've only filmed this nudibranch a few times, the first being back in 2003 right in the dive park. I saw it again there in 2007 and recorded it at Ship Rock in 2006 and Isthmus Reef in 2007.
This is a fairly rare nudibranch, and little appears to be known about it. Back in his 1980 field guide to the Pacific Coast nudibranchs, Dave Behrens simply listed it as an undescribed species in the genus Peltodoris. It wasn't until October of 2000 that Millen and Bertsch described it in an article in the scientific journal Veliger. They named it after David Mulliner who they refer to as "Sea Hunt before Lloyd Bridges." Mulliner has dived and studied marine life in the waters of San Diego and Baja California for many decades. The only common name for it I'm aware of is Mulliner's dorid.
One site referred to the maximum length for a "male/unsexed" individual being 7.0 cm or about 2 3/4 inches. The ones I've seen have been about that size. However, I don't understand the specimen referenced being "male/unsexed." Many species of nudibranchs are simultaneous hermaphrodites and contain both male and female organs. Of course they can't mate with themselves, so I hope this poor girl/boy finds a mate in the dive park or he could be as lonely as the "good" Dr. Bill (who'd like to be "bad" at least once in a while!). The same source says it is subtropical and lists the species' distribution as "the US and Columbia..." which seems to leave a lot of gaps in between based on my knowledge of geography. I found other sources that suggest it is known from the Pacific Northwest and the Sea of Cortez.
When diving deeper than about 100 feet in our waters, I see a related species, Peltodoris nobilis, which may be yellow to orange in color with small black spots on the dorsal (upper) surface. Peltodoris mullineri is yellowish-beige in color with large brown blotches on its back. From observation, I know that the first species feeds on sponges that are common at those depths. One source I looked at stated that most species in this genus do also, so I'm assuming Mulliner's dorid munches on them too. Don't worry, your kitchen sponge is probably made of cellulose... and they certainly won't come after that!
If you look at the accompanying pictures, you will see the nudibranch and its similarity to other gastropods or snails... well except for the shell, of course! They crawl on a well-developed muscular foot. Towards the forward (or anterior) end of the body, you can see two projecting structures known as rhinophores. They serve as sensory organs. The ones I've seen are all similar in color to the body, but friends of mine have seen black rhinophores on these nudibranchs out on our West End. At the rear (or posterior) end, you can see the cluster of gills, naked as a jaybird. Since these are critical structures for obtaining oxygen from the surrounding water, leaving them exposed seems very daring. However, different species of nudibranchs take time to train potential predators to avoid them. Some have a nasty taste causing a predator to spit them out, others incorporate stinging cells from their hydroid and anemone prey and use them to sting the predator. If a fish fails to learn this lesson, the nudibranch can retract its gills into its body.
I spent quite a bit of time filming this rare species before turning away to look for other subjects. Within fifteen feet I found one of the incredibly beautiful Hypselodoris californiensis nudibranchs on the hull of the Suejac. The California blue doris, its common name, has a beautiful deep cobalt blue body with light blue "racing stripes" on each side and bold spots of yellow on its dorsal surface. My still images and previous Dive Dry column on this rare species resulted in it being declared "Opisthobranch of the Week" by Slugsite earlier this year. They even featured some of my video footage, stating I was the only known person to have recorded the species on "film" (er, I mean using digital media).
It took no arm twisting to get me to dive again to relocate these nudies. All it took was a pair of dark sunglasses and a small tin cup to collect the $7 for an air fill from passing visitors. Within an hour I was in the water, and relocated the Peltodoris (but not the Hypselodoris). Quite an exciting day of diving! I didn't even mind the hours it took that night to edit all the raw video footage!
Image caption: Images of Mulliner's dorid in the Casino Point Dive Park.
Strange title for a column, Dr. Bill. Just what does it mean? Are we talking about a mink pelt for a woman named Doris? Of course not. Even though I'm aghast at the tactics of groups like PETA, I am not one who advocates the wearing of animal skins... unless the entire critter has been properly used for food, tool making, greasing the wagon wheels, etc. You know, just how some of our "Native" American tribes used to show reverence for their kills by not wasting anything. No, Peltodoris has nothing to do with furry critters... only naked ones. And by naked, I'm only referring to the gills they use to breathe underwater. That's right, this is another hot story about nudibranchs... the shell-less snails with the naked gills!
During late summer and early fall, I made regular trips to the harbor end of the dive park where the wreck of the Suejac rests in about 60 to 90 feet. No, I'm not big on wrecks, just trying to avoid the sand and silt stirred up by open water SCUBA classes. I've had many sightings of "naked gills" of several species there. On one dive I was slowly working my way around the upper (stern) end of the ferrocement hull when my eagle eyes spotted a yellow and brown "slug" crawling on some seaweed. Holy mackerel, Batman... it was none other than Peltodoris mullineri... a nudie I've seen so seldom I can still count the times on my fingers. I've only filmed this nudibranch a few times, the first being back in 2003 right in the dive park. I saw it again there in 2007 and recorded it at Ship Rock in 2006 and Isthmus Reef in 2007.
This is a fairly rare nudibranch, and little appears to be known about it. Back in his 1980 field guide to the Pacific Coast nudibranchs, Dave Behrens simply listed it as an undescribed species in the genus Peltodoris. It wasn't until October of 2000 that Millen and Bertsch described it in an article in the scientific journal Veliger. They named it after David Mulliner who they refer to as "Sea Hunt before Lloyd Bridges." Mulliner has dived and studied marine life in the waters of San Diego and Baja California for many decades. The only common name for it I'm aware of is Mulliner's dorid.
One site referred to the maximum length for a "male/unsexed" individual being 7.0 cm or about 2 3/4 inches. The ones I've seen have been about that size. However, I don't understand the specimen referenced being "male/unsexed." Many species of nudibranchs are simultaneous hermaphrodites and contain both male and female organs. Of course they can't mate with themselves, so I hope this poor girl/boy finds a mate in the dive park or he could be as lonely as the "good" Dr. Bill (who'd like to be "bad" at least once in a while!). The same source says it is subtropical and lists the species' distribution as "the US and Columbia..." which seems to leave a lot of gaps in between based on my knowledge of geography. I found other sources that suggest it is known from the Pacific Northwest and the Sea of Cortez.
When diving deeper than about 100 feet in our waters, I see a related species, Peltodoris nobilis, which may be yellow to orange in color with small black spots on the dorsal (upper) surface. Peltodoris mullineri is yellowish-beige in color with large brown blotches on its back. From observation, I know that the first species feeds on sponges that are common at those depths. One source I looked at stated that most species in this genus do also, so I'm assuming Mulliner's dorid munches on them too. Don't worry, your kitchen sponge is probably made of cellulose... and they certainly won't come after that!
If you look at the accompanying pictures, you will see the nudibranch and its similarity to other gastropods or snails... well except for the shell, of course! They crawl on a well-developed muscular foot. Towards the forward (or anterior) end of the body, you can see two projecting structures known as rhinophores. They serve as sensory organs. The ones I've seen are all similar in color to the body, but friends of mine have seen black rhinophores on these nudibranchs out on our West End. At the rear (or posterior) end, you can see the cluster of gills, naked as a jaybird. Since these are critical structures for obtaining oxygen from the surrounding water, leaving them exposed seems very daring. However, different species of nudibranchs take time to train potential predators to avoid them. Some have a nasty taste causing a predator to spit them out, others incorporate stinging cells from their hydroid and anemone prey and use them to sting the predator. If a fish fails to learn this lesson, the nudibranch can retract its gills into its body.
I spent quite a bit of time filming this rare species before turning away to look for other subjects. Within fifteen feet I found one of the incredibly beautiful Hypselodoris californiensis nudibranchs on the hull of the Suejac. The California blue doris, its common name, has a beautiful deep cobalt blue body with light blue "racing stripes" on each side and bold spots of yellow on its dorsal surface. My still images and previous Dive Dry column on this rare species resulted in it being declared "Opisthobranch of the Week" by Slugsite earlier this year. They even featured some of my video footage, stating I was the only known person to have recorded the species on "film" (er, I mean using digital media).
It took no arm twisting to get me to dive again to relocate these nudies. All it took was a pair of dark sunglasses and a small tin cup to collect the $7 for an air fill from passing visitors. Within an hour I was in the water, and relocated the Peltodoris (but not the Hypselodoris). Quite an exciting day of diving! I didn't even mind the hours it took that night to edit all the raw video footage!
Image caption: Images of Mulliner's dorid in the Casino Point Dive Park.
