DIVE DRY WITH DR. BILL #749: CTENOPHORES
"Kookie, kookie... lend me your comb." Yep, I know the millenials and X-generation readers among you will probably not get that reference. It goes back to Ed "Kookie" Burns and the TV show "77 Sunset Strip" broadcast from 1958 to 1964. Yep, I know... I'm dating many of you. Well, I wish the ladies would agree to that!
What does Kookie's comb have to do with marine biology? Unless it was made out of turtle shell, probably nothing. But there is a whole phylum of "jellies" in the ocean known as comb jellies or ctenophores. It's been years since I've written about them, so the time has come to reintroduce my adoring public to these interesting critters.
Most of these marine invertebrates have eight distinctive rows of cilia (called ctenes or combs) that run along the side of the body. They have no fins or other mechanism for propulsion, so they beat these cilia to move themselves around in the water column. Movement is always accomplish with the anterior end leading the charge. They do not use reverse gear as often, saving it for escaping predators.
The rows of combs often exhibit what appears to be bioluminescence, displaying a rainbow of colors as they pulse along the body. However, the light seen is actually due to diffraction, or the scattering of light around the tiny cilia and is called iridescence. Many ctenophores do exhibit true bioluminescence, creating light through a biochemical reaction. However the colors produced are blues and greens and are too weak to see except at night.
Comb jellies do look similar to some jellyfish, but most have no sting for capturing prey or defense. There is an inner body wall and an outer one with a jelly-like mesoglea in between. Water flows into the "mouth" as the ctenophore moves along. There enzymes break up the organic matter which is then absorbed by nutritive cells and channeled to the "muscles" and other internal structures.
These are simple critters and lack a brain or central nervous system. Hmmm, reminds me of a few people I don't know. They do utilize a diffuse network of nerves to control the muscle-like cells that move the combs and the mouth. They do have sensory cells and also a structure known as a statocyst located near the rear. It contains a tiny piece of calcium carbonate (the statolith) balanced on four groups of cilia that maintains balance.
Some species have a pair of long, thin tentacles which are covered with structures known as colloblasts. They contain a glue-like substance that captures prey. I was surprised to learn that a few species of comb jellies feed on sea jellies (you, know... what used to be called jellyfish). They incorporate their prey's stinging cells (nematocysts) into their own body just like some nudibranchs do. Wow... I learn something new with almost ever column.
Other species of ctenophores have extended lobes or flaps that project to either side of the mouth. These act kind of like the cephalic (head) fins surrounding the mouths of manta rays in that they help funnel food into the mouth. Others like Beroe, which feed on their relatives, have big mouths with clusters of fused cilia. They can literally bite off pieces of prey without needing to fully ingest them whole. Gulp!
No "Dive Dry" column would be complete without a little... er, reproduction. Most comb jellies are simultaneous hermaphrodites, having male and female reproductive structures at the same time. In most species eggs and sperm are released into the water and fertilization is external. What fun is that? The eggs develop into tiny ctenophores (love the consonance) and do not result in a larval stage.
Wikipedia states that the mature specimens will continue producing eggs and sperm as long as they receive proper nourishment. If food is scarce and they experience malnutrition, they will stop production of gametes and focus on rebuilding strong bodies at least eight ways (without resorting to Wonder bread). This is consistent with the fact that individuals must maintain their health in order to reproduce and maintain the species. I'm pretty well nourished, but...
© 2017 Dr. Bill Bushing. For the entire archived set of over 700 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: The comb jelly Leucothera pulchra and enhanced version showing rows of combs; carnivorous Beroe forskalii with enhanced image by Kevin Lee showing some irridescence.
"Kookie, kookie... lend me your comb." Yep, I know the millenials and X-generation readers among you will probably not get that reference. It goes back to Ed "Kookie" Burns and the TV show "77 Sunset Strip" broadcast from 1958 to 1964. Yep, I know... I'm dating many of you. Well, I wish the ladies would agree to that!
What does Kookie's comb have to do with marine biology? Unless it was made out of turtle shell, probably nothing. But there is a whole phylum of "jellies" in the ocean known as comb jellies or ctenophores. It's been years since I've written about them, so the time has come to reintroduce my adoring public to these interesting critters.
Most of these marine invertebrates have eight distinctive rows of cilia (called ctenes or combs) that run along the side of the body. They have no fins or other mechanism for propulsion, so they beat these cilia to move themselves around in the water column. Movement is always accomplish with the anterior end leading the charge. They do not use reverse gear as often, saving it for escaping predators.
The rows of combs often exhibit what appears to be bioluminescence, displaying a rainbow of colors as they pulse along the body. However, the light seen is actually due to diffraction, or the scattering of light around the tiny cilia and is called iridescence. Many ctenophores do exhibit true bioluminescence, creating light through a biochemical reaction. However the colors produced are blues and greens and are too weak to see except at night.
Comb jellies do look similar to some jellyfish, but most have no sting for capturing prey or defense. There is an inner body wall and an outer one with a jelly-like mesoglea in between. Water flows into the "mouth" as the ctenophore moves along. There enzymes break up the organic matter which is then absorbed by nutritive cells and channeled to the "muscles" and other internal structures.
These are simple critters and lack a brain or central nervous system. Hmmm, reminds me of a few people I don't know. They do utilize a diffuse network of nerves to control the muscle-like cells that move the combs and the mouth. They do have sensory cells and also a structure known as a statocyst located near the rear. It contains a tiny piece of calcium carbonate (the statolith) balanced on four groups of cilia that maintains balance.
Some species have a pair of long, thin tentacles which are covered with structures known as colloblasts. They contain a glue-like substance that captures prey. I was surprised to learn that a few species of comb jellies feed on sea jellies (you, know... what used to be called jellyfish). They incorporate their prey's stinging cells (nematocysts) into their own body just like some nudibranchs do. Wow... I learn something new with almost ever column.
Other species of ctenophores have extended lobes or flaps that project to either side of the mouth. These act kind of like the cephalic (head) fins surrounding the mouths of manta rays in that they help funnel food into the mouth. Others like Beroe, which feed on their relatives, have big mouths with clusters of fused cilia. They can literally bite off pieces of prey without needing to fully ingest them whole. Gulp!
No "Dive Dry" column would be complete without a little... er, reproduction. Most comb jellies are simultaneous hermaphrodites, having male and female reproductive structures at the same time. In most species eggs and sperm are released into the water and fertilization is external. What fun is that? The eggs develop into tiny ctenophores (love the consonance) and do not result in a larval stage.
Wikipedia states that the mature specimens will continue producing eggs and sperm as long as they receive proper nourishment. If food is scarce and they experience malnutrition, they will stop production of gametes and focus on rebuilding strong bodies at least eight ways (without resorting to Wonder bread). This is consistent with the fact that individuals must maintain their health in order to reproduce and maintain the species. I'm pretty well nourished, but...
© 2017 Dr. Bill Bushing. For the entire archived set of over 700 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: The comb jelly Leucothera pulchra and enhanced version showing rows of combs; carnivorous Beroe forskalii with enhanced image by Kevin Lee showing some irridescence.
