DIVE DRY WITH DR. BILL #810: PARASITISM
Over the past few months, two dive friends of mine have published pictures of what they thought were California's beautiful golden gorgonian (Muricea californica). Twenty years ago, I might have thought they had correctly identified this species of soft coral, a relative of sea anemones and hydroids. However, about 2000, I started noticing a golden gorgonian on the wreck of the Suejac in Catalina's dive park. It was being taken over by another cnidarian with larger polyps of brighter yellow color.
Being the curious marine biologist that I am, I researched this and discovered the larger polyps belonged to a species of zoanthid known then as Parazoanthus lucificum. It is now named Savalia lucifica. according to Beneath Pacific Tides. Ah, so many name changes, so little time. I watched as the zoanthid slowly overgrew and killed the golden gorgonian. Yes, it was a parasite on the gorgonian!
Parasitism is common under the sea as well as topside. I don't want to imagine the endoparasites (internal) that have invaded the deepest recesses of my body! Ectoparasites (external) like ticks are bad enough! Loosely defined, a parasite is an organism that lives in or on another organism causing it harm. It may even kill the host, which seems a self-defeating strategy. Some parasites may only usurp food resources from the host while others actually castrate it. My Harvard mentor, Professor E. O. Wilson, calls them "predators that eat prey in units of less than one". Hmmm... I guess that could also be applied to me when I eat a steak or a fish filet.
Some parasites may rely on a specific host and are rather specialized. I long thought that the zoanthid only parasitized the golden gorgonian... until I saw it doing the same to a red gorgonian. This may involve a long period of co-evolution, or evolution in association with one another. Sometimes this history may deverlop into relationships between the parasite and host which are more benign. Other parasites are generalists and will be perfectly happy with several different potential hosts. Ticks and mosquitoes are good examples.
Divers are well aware of a parasite that affects our giant "sea bass" (which I prefer to call "fairly large polka-dotted wreckfish," which is really more what they are... but some names die slowly). These gentle giants are often covered in parasitic copepods believed to be Lepeophtheirus longipes. They don't seem to do much harm to their hosts. I find it interesting to watch them scurry about on the head of a GSB, especially when a kelp bass, sheephead, rock wrasse or other fish comes to clean them off.
Other fish in our waters carry parasitic copepods. If you look closely while underwater, you may see them on the bodies of kelp bass, sheephead, morays and other species. Many divers have observed the red rock shrimp (Lysmata californica) climbing on the head of a moray, or even into its mouth, to capture and crush the copepods for lunch. I've even seen these crustaceans pick parasites off blacksmith and garibaldi when they are sheltereing in the reef at night.
Those of us who venture to warmer water during the harsh California winter may encounter parasites of much larger size. Ones that I've filmed on occasion appear to be isopods of the family Cymothoidea. They can be observed attached near the gills of tropical species. One member, Cymothoa exigua, is called the tongue-eating louse. The female attaches to the host fish's tongue and bleeds it to the point that the tongue falls off. Hmmm, I wonder if they would do the same for a few Homo sapiens I know!
© 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: Parasitic zoanthid (yellow) parasiticizing a red gorgonian and copepods attached to the head of a giant sea bass; another parasitic copepod on the head of a kelp bass and a cymathoid isopod on a Creolefish.
Over the past few months, two dive friends of mine have published pictures of what they thought were California's beautiful golden gorgonian (Muricea californica). Twenty years ago, I might have thought they had correctly identified this species of soft coral, a relative of sea anemones and hydroids. However, about 2000, I started noticing a golden gorgonian on the wreck of the Suejac in Catalina's dive park. It was being taken over by another cnidarian with larger polyps of brighter yellow color.
Being the curious marine biologist that I am, I researched this and discovered the larger polyps belonged to a species of zoanthid known then as Parazoanthus lucificum. It is now named Savalia lucifica. according to Beneath Pacific Tides. Ah, so many name changes, so little time. I watched as the zoanthid slowly overgrew and killed the golden gorgonian. Yes, it was a parasite on the gorgonian!
Parasitism is common under the sea as well as topside. I don't want to imagine the endoparasites (internal) that have invaded the deepest recesses of my body! Ectoparasites (external) like ticks are bad enough! Loosely defined, a parasite is an organism that lives in or on another organism causing it harm. It may even kill the host, which seems a self-defeating strategy. Some parasites may only usurp food resources from the host while others actually castrate it. My Harvard mentor, Professor E. O. Wilson, calls them "predators that eat prey in units of less than one". Hmmm... I guess that could also be applied to me when I eat a steak or a fish filet.
Some parasites may rely on a specific host and are rather specialized. I long thought that the zoanthid only parasitized the golden gorgonian... until I saw it doing the same to a red gorgonian. This may involve a long period of co-evolution, or evolution in association with one another. Sometimes this history may deverlop into relationships between the parasite and host which are more benign. Other parasites are generalists and will be perfectly happy with several different potential hosts. Ticks and mosquitoes are good examples.
Divers are well aware of a parasite that affects our giant "sea bass" (which I prefer to call "fairly large polka-dotted wreckfish," which is really more what they are... but some names die slowly). These gentle giants are often covered in parasitic copepods believed to be Lepeophtheirus longipes. They don't seem to do much harm to their hosts. I find it interesting to watch them scurry about on the head of a GSB, especially when a kelp bass, sheephead, rock wrasse or other fish comes to clean them off.
Other fish in our waters carry parasitic copepods. If you look closely while underwater, you may see them on the bodies of kelp bass, sheephead, morays and other species. Many divers have observed the red rock shrimp (Lysmata californica) climbing on the head of a moray, or even into its mouth, to capture and crush the copepods for lunch. I've even seen these crustaceans pick parasites off blacksmith and garibaldi when they are sheltereing in the reef at night.
Those of us who venture to warmer water during the harsh California winter may encounter parasites of much larger size. Ones that I've filmed on occasion appear to be isopods of the family Cymothoidea. They can be observed attached near the gills of tropical species. One member, Cymothoa exigua, is called the tongue-eating louse. The female attaches to the host fish's tongue and bleeds it to the point that the tongue falls off. Hmmm, I wonder if they would do the same for a few Homo sapiens I know!
© 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: Parasitic zoanthid (yellow) parasiticizing a red gorgonian and copepods attached to the head of a giant sea bass; another parasitic copepod on the head of a kelp bass and a cymathoid isopod on a Creolefish.
