DIVE DRY WITH DR. BILL #862: A PAPER THIN....
I've been diving Catalina for more than 50 years. People occasionally ask me if I don't get bored cruising through our kelp forests year after year. The answer I give is a forceful NO! Besides, at my age I can't remember where I left my glasses or why I entered a room... and you expect me to remember what I saw underwater a year ago? Actually, my mental acuity isn't that bad so yes I can. However, frequently enough I see a new species or a new behavior that adds an interesting new piece of information to my understanding of our underwater ecosystems.
For decades I've wondered about an infrequent sighting I've made in our waters. I'm referring to the calcite shells of the paper nautilus (Argonauta sp.). These species of pelagic (open water) octopuses are normally seen in warmer tropical and subtropical waters. Why was I seeing their "shells' here in our cooler temperate waters? This constituted one of the many "mysteries of the deep" I've pondered over during the past decades. Well, the answer came just recently.
Two divers have reported seeing live paper nautiluses right in Catalina waters. I have even seen footage of one swimming at night taken by a diver I know. I guess these individual critters are more tolerant of colder water than their warm water wussy relatives! So now I now that they do exist here and that explains the empty "shells" I've observed in the past. Now I'm hoping that in the time I have left to dive, I will see one myself. It gives me a good reason to continue flailing through our waters!
So why do these rather unusual octopuses construct this "shell." Most octopus species are benthic (bottom dwellers) that crawl along the rocky reefs and sandy bottoms (and even occasionally climb up the giant kelp!). The Argonauta are pelagic species that live in fairly shallow water. Actually only the female constructs a "shell." The reason is to provide buoyancy and a protective envelope for her eggs. Once the eggs hatch, the female often abandons the "shell."
These species are highly dimorphic sexually. That means that the female and male are quite different in size and appearance. Kind of like most males and females of our species. No one would confuse Arnold Schwarzeneggar and Scarlett Johansson. Female argonauts are about 600 times the size of their partners. In fact, early biologists thought the male of the species was some sort of parasitic worm that infected the female. This was due to their rather large (relatively speaking) body part known as the hectocotylus, which is a modified arm used to transfer sperm to his lady friend.
Some marine biologists and paleontologists believe the paper nautilus evolved from primitive cephalopods that existed in the early seas, and that they are evolutionarily older than.our more common benthic species. Our modern representatives are hardly the vicious predators that their ancestors were. Of course they are much too small to pose a threat to many species. Favorite prey items include small crustaceans, jellyfish and salps. In turn marine birds, tuna, billfish and turtles chow down on them.
Like other octopuses, the paper nautilus can eject a dark ink when they are threatened by a predator. They can also change color like other species. It is believed the white egg "shell" may be bright enough to frighten away some that try to attack them. They are surprisingly fast swimmers, using their siphons like a squid to quickly propel them from a hungry critter. I hope if I do encounter a living one in the time I have left, that it will pose for my camera!
© 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: Nautilus egg "shell" on the bottom and images of some I have collected; one in the hands of dive buddy Catherine Ngo and living specimens.
I've been diving Catalina for more than 50 years. People occasionally ask me if I don't get bored cruising through our kelp forests year after year. The answer I give is a forceful NO! Besides, at my age I can't remember where I left my glasses or why I entered a room... and you expect me to remember what I saw underwater a year ago? Actually, my mental acuity isn't that bad so yes I can. However, frequently enough I see a new species or a new behavior that adds an interesting new piece of information to my understanding of our underwater ecosystems.
For decades I've wondered about an infrequent sighting I've made in our waters. I'm referring to the calcite shells of the paper nautilus (Argonauta sp.). These species of pelagic (open water) octopuses are normally seen in warmer tropical and subtropical waters. Why was I seeing their "shells' here in our cooler temperate waters? This constituted one of the many "mysteries of the deep" I've pondered over during the past decades. Well, the answer came just recently.
Two divers have reported seeing live paper nautiluses right in Catalina waters. I have even seen footage of one swimming at night taken by a diver I know. I guess these individual critters are more tolerant of colder water than their warm water wussy relatives! So now I now that they do exist here and that explains the empty "shells" I've observed in the past. Now I'm hoping that in the time I have left to dive, I will see one myself. It gives me a good reason to continue flailing through our waters!
So why do these rather unusual octopuses construct this "shell." Most octopus species are benthic (bottom dwellers) that crawl along the rocky reefs and sandy bottoms (and even occasionally climb up the giant kelp!). The Argonauta are pelagic species that live in fairly shallow water. Actually only the female constructs a "shell." The reason is to provide buoyancy and a protective envelope for her eggs. Once the eggs hatch, the female often abandons the "shell."
These species are highly dimorphic sexually. That means that the female and male are quite different in size and appearance. Kind of like most males and females of our species. No one would confuse Arnold Schwarzeneggar and Scarlett Johansson. Female argonauts are about 600 times the size of their partners. In fact, early biologists thought the male of the species was some sort of parasitic worm that infected the female. This was due to their rather large (relatively speaking) body part known as the hectocotylus, which is a modified arm used to transfer sperm to his lady friend.
Some marine biologists and paleontologists believe the paper nautilus evolved from primitive cephalopods that existed in the early seas, and that they are evolutionarily older than.our more common benthic species. Our modern representatives are hardly the vicious predators that their ancestors were. Of course they are much too small to pose a threat to many species. Favorite prey items include small crustaceans, jellyfish and salps. In turn marine birds, tuna, billfish and turtles chow down on them.
Like other octopuses, the paper nautilus can eject a dark ink when they are threatened by a predator. They can also change color like other species. It is believed the white egg "shell" may be bright enough to frighten away some that try to attack them. They are surprisingly fast swimmers, using their siphons like a squid to quickly propel them from a hungry critter. I hope if I do encounter a living one in the time I have left, that it will pose for my camera!
© 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: Nautilus egg "shell" on the bottom and images of some I have collected; one in the hands of dive buddy Catherine Ngo and living specimens.
