T
thomas712
Guest
Just thought I would do a little C&P and show you one of my favorite alien, spaceage battleship, looking nudibranches out there. Say hello to Glaucus atlanticus
T
thomas712
Guest
Glaucus atlanticus and its close relative, Glaucilla marginata, live in close association with what Sir Alistair Hardy described many years ago as "The Blue Fleet" - the siphonophores such as Physalia, Velella, Porpita and the other associated animals including the "Violet snails" of the genus Janthina. All these animals float on the surface of the ocean being carried by the currents and the winds. Most of us are only aware of their existence when days of onshore winds blow great fleets of them on to the beaches, causing pain and anguish for swimmers.
Both species spend their life floating upside down in the water, partially bouyed by a gas bubble in their stomachs.
The two nudibranchs feed almost exclusively on Physalia, (see below) and as Tom Thompson and Isobel Bennett reported some years ago, it appears that they are able to select the most venomous of Physalia's stinging nematocysts for their own use. Like most aeolids, they store the nematocysts in special sacs (cnidosacs) at the tip of their cerata .
There are a number of reports in Australia of kids engaged in "Bluebottle" fights - where they throw stranded Physalia at each other - being badly stung by inadvertently playing with Glaucus and Glaucilla, both of which, by concentrating the most venomous of Physalia's nematocysts, are much more deadly.
Another interesting feature of the two species is their colouration. They both exhibit a textbook example of colour countershading. Their foot and undersides of the cerata, (which because they float upside down is effectively their dorsal surface), is blue or blue and white which helps to camouflage them from predation (sea birds) from above. Their true dorsal surface, which faces down in the water, is silvery grey to effectively camouflage them from fish looking up from below.
THIS IS WHAT THEY EAT!
Physalia
'Portugese man-o-war' or 'Bluebottle'
Physalia is a siphonophore, a specialised group of cnidarians in which each 'animal' is really a colony of highly specialised individuals. In Physalia, one individual forms a gas-filled float and the other individuals are specialised for feeding and digestion, or for reproduction, or to form the extremely long tentacles which contain the nematocysts which sting and capture their prey
Both species spend their life floating upside down in the water, partially bouyed by a gas bubble in their stomachs.
The two nudibranchs feed almost exclusively on Physalia, (see below) and as Tom Thompson and Isobel Bennett reported some years ago, it appears that they are able to select the most venomous of Physalia's stinging nematocysts for their own use. Like most aeolids, they store the nematocysts in special sacs (cnidosacs) at the tip of their cerata .
There are a number of reports in Australia of kids engaged in "Bluebottle" fights - where they throw stranded Physalia at each other - being badly stung by inadvertently playing with Glaucus and Glaucilla, both of which, by concentrating the most venomous of Physalia's nematocysts, are much more deadly.
Another interesting feature of the two species is their colouration. They both exhibit a textbook example of colour countershading. Their foot and undersides of the cerata, (which because they float upside down is effectively their dorsal surface), is blue or blue and white which helps to camouflage them from predation (sea birds) from above. Their true dorsal surface, which faces down in the water, is silvery grey to effectively camouflage them from fish looking up from below.
THIS IS WHAT THEY EAT!
Physalia
'Portugese man-o-war' or 'Bluebottle'
Physalia is a siphonophore, a specialised group of cnidarians in which each 'animal' is really a colony of highly specialised individuals. In Physalia, one individual forms a gas-filled float and the other individuals are specialised for feeding and digestion, or for reproduction, or to form the extremely long tentacles which contain the nematocysts which sting and capture their prey
T
thomas712
Guest
See has he flys in his water space, man I wouldn't want to step on him with all those stinging cells.
T
thomas712
Guest
Last photo
