DIVE DRY WITH DR. BILL #865: THE BLACK SEA NETTLE
Some time ago I wrote a column about Chrysaora colorata, the purple-striped sea jelly (formerly known as Prince... er jellyfish). Today I thought I'd focus on one of its relatives... the black sea nettle (Chrysaora achlyos). It is also known as the black jellyfish or sarlacc jellyfish. This relationship has been confirmed by DNA studies although I didn't find it on Ancestry.com. I have only seen one individual in all my years of diving the Casino Point dive park, but have also seen them down in San Diego. Surprisingly it didn't receive its scientific name until 1997 although it was known for half a century by then.
The species is believed to range from about Monterey Bay to southern Baja California. However, they have occasionally been seen as far north as British Columbia.
This sea jelly is considered a giant among jellyfish. Its rounded bell may be three feet in diameter and the trailing oral arms may extend 20 feet with the tentacles around the margin of the bell reaching up to 25 feet. Ya just got to keep your distance from these stingers! The bell is described as dark purple to black, but my colorblind eyes see it as more reddish-brown. The Aquarium of the Pacific states that younger specimens may be reddish or maroon. Hanging below it is a structure known as the manubrium which houses the oral opening and four gonads. Around the bell's margin are eight sensory structures that can perceive light and gravity.
Like many sea jellies, the black sea nettle is a vicious and voracious carnivore... if you happen to be a zzoplankter or another sea jelly. Interestingly they do not eat their own or their close relative when kept in laboratories. Apparently they sense that genetically they are very similar. The tentacles capture food and transfer it through the oral opening on the underside of the bell into the gastrovascular cavity. Here it is digested and then excreted through the same opening.
Each tentacle is covered with thousands of tiny stinging cells containing nematocysts. They are triggered upon contact with prey, and then release toxins that will kill smaller prey or stun larger ones. In humans the sting is reported as mild to very painful. I guess that depends on how you rate the 1 to 10 pain scale.
If you are interested, Pitcairn Island has a 2011 $2 coin featuring this sea jelly and right now you can get it on E-bay for as little as $45 plus shipping. Head to Amazon and you can buy an iPhone or iPad case, lunch bag, shower curtain and bath mat, living room carpet or toilet bowl cover with images of this species. I'm still looking for prices for live individuals from the aquarium trade.
As my readers know, I mainly focus on two critical functions of any species... munching and mating. Munching is critical for the continuation of the individual... so they can eventually mate and ensure the survival of the species. One other important function is respiration, but of course that is generally a very boring (but very necessary) function. In sea jellies gasses are exchanged by diffusion between the ocean and the critter.
As for reproduction, the basics are like those described for its relative, the purple-striped sea jelly covered earlier. It is somewhat strange that the polyp stage has not been seen in the wild. Sorry to disappoint you readers by not revealing the gory details.
Scientists believe these large but somewhat fragile jellies may usually live in deeper water where there is less turbulence to tear them apart. However, on occasion they appear in large numbers along the coast, often associated with wind and currents. Blooms have been observed off San Diego in 1989 and then again ten years later. Other blooms occurred in 2010, 2012 and 2013. Another source mentioned earlier blooms in 1926 and 1965.
Marine biologists aren't certain why these blooms occurred. Some believe they were caused when nutrients from the land enriched the ocean and triggered more plankton growth, especially of the red tide organisms they feed on. Others think it may be related to the warm water El Niño events which have become more frequent.
© 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: The black sea nettle in Catalina's dive park and our garibaldi getting a spicy snack from it.
Some time ago I wrote a column about Chrysaora colorata, the purple-striped sea jelly (formerly known as Prince... er jellyfish). Today I thought I'd focus on one of its relatives... the black sea nettle (Chrysaora achlyos). It is also known as the black jellyfish or sarlacc jellyfish. This relationship has been confirmed by DNA studies although I didn't find it on Ancestry.com. I have only seen one individual in all my years of diving the Casino Point dive park, but have also seen them down in San Diego. Surprisingly it didn't receive its scientific name until 1997 although it was known for half a century by then.
The species is believed to range from about Monterey Bay to southern Baja California. However, they have occasionally been seen as far north as British Columbia.
This sea jelly is considered a giant among jellyfish. Its rounded bell may be three feet in diameter and the trailing oral arms may extend 20 feet with the tentacles around the margin of the bell reaching up to 25 feet. Ya just got to keep your distance from these stingers! The bell is described as dark purple to black, but my colorblind eyes see it as more reddish-brown. The Aquarium of the Pacific states that younger specimens may be reddish or maroon. Hanging below it is a structure known as the manubrium which houses the oral opening and four gonads. Around the bell's margin are eight sensory structures that can perceive light and gravity.
Like many sea jellies, the black sea nettle is a vicious and voracious carnivore... if you happen to be a zzoplankter or another sea jelly. Interestingly they do not eat their own or their close relative when kept in laboratories. Apparently they sense that genetically they are very similar. The tentacles capture food and transfer it through the oral opening on the underside of the bell into the gastrovascular cavity. Here it is digested and then excreted through the same opening.
Each tentacle is covered with thousands of tiny stinging cells containing nematocysts. They are triggered upon contact with prey, and then release toxins that will kill smaller prey or stun larger ones. In humans the sting is reported as mild to very painful. I guess that depends on how you rate the 1 to 10 pain scale.
If you are interested, Pitcairn Island has a 2011 $2 coin featuring this sea jelly and right now you can get it on E-bay for as little as $45 plus shipping. Head to Amazon and you can buy an iPhone or iPad case, lunch bag, shower curtain and bath mat, living room carpet or toilet bowl cover with images of this species. I'm still looking for prices for live individuals from the aquarium trade.
As my readers know, I mainly focus on two critical functions of any species... munching and mating. Munching is critical for the continuation of the individual... so they can eventually mate and ensure the survival of the species. One other important function is respiration, but of course that is generally a very boring (but very necessary) function. In sea jellies gasses are exchanged by diffusion between the ocean and the critter.
As for reproduction, the basics are like those described for its relative, the purple-striped sea jelly covered earlier. It is somewhat strange that the polyp stage has not been seen in the wild. Sorry to disappoint you readers by not revealing the gory details.
Scientists believe these large but somewhat fragile jellies may usually live in deeper water where there is less turbulence to tear them apart. However, on occasion they appear in large numbers along the coast, often associated with wind and currents. Blooms have been observed off San Diego in 1989 and then again ten years later. Other blooms occurred in 2010, 2012 and 2013. Another source mentioned earlier blooms in 1926 and 1965.
Marine biologists aren't certain why these blooms occurred. Some believe they were caused when nutrients from the land enriched the ocean and triggered more plankton growth, especially of the red tide organisms they feed on. Others think it may be related to the warm water El Niño events which have become more frequent.
© 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: The black sea nettle in Catalina's dive park and our garibaldi getting a spicy snack from it.
