Monday, 19 October 2015

Siren

Image: Zruda
Sirens? Bah! Don't talk to me about Sirens. They sit on the rocks looking prettier than a dolphin. Sing better, too. And they're deadlier than... a dolphin. Essentially they're like sexy-but-evil dolphins. They sing to the sailors, and their song is death. It wreaks havoc on the tourism industry.

Err... not that kind of Siren.

Image: Ashley Tubbs
Lesser Siren (Siren intermedia)
Yup. We're not talking about those bird-brained (and oddly bird-bodied), sexy-but-evil sea nymphs of Greek mythology who used sweet song to lure sailors to their rocky doom. Not those arch-enemies of the lighthouse.

What do they have against lighthouses, anyway? I love a good lighthouse. They're so warm and romantic yet lonely and stoic. I particularly like the ones that rest on tiny islets completely surrounded by the raging sea.

Image: Todd Pierson
Lesser Siren
But we're not looking at lighthouses! Nor sirens that lure you to your doom or sirens on ambulances that try to save you from your own doom. We're looking at salamanders, and they have wisely kept out of the long-running dispute between sirens and lighthouses, even if the salamanders we're looking at happen to be known as Sirens.

Sirens belong to a strange family of salamanders known as Sirenidae. They're so strange you can actually divide all salamanders into two groups: Sirens, and the rest.

Image: USGS
Northern Dwarf Salamander (Pseudobranchus striatus)
You can also divide Sirenidae into two genera, the plain and simple Sirens (Siren) and the Dwarf Sirens (Pseudobranchus). And then you can divide both of those in two for a total of four species of Siren. They range in size from the Greater Siren (S. lacertina), who is more than 50 cm (20 in) long and can sometimes reach almost a metre (3 ft) in length, to the Northern, or Gulf Hammock, Dwarf Siren (P. striatus) which can reach a maximum of 25 cm (10 in) long.

In terms of distribution, Florida seems quite the hotspot for Siren kind. All four Sirens can be found there. The Eastern, or Everglades, Dwarf Siren (P. axanthus) lives nowhere else. Meanwhile, the Lesser Siren (S. intermedia) is the most widespread being found all around the eastern United States, across to Texas and northern Mexico and north to some of the states bordering Canada.


Video: brimi925
Greater Siren (Siren lacertina)

One thing they all have in common is that none of them is any help to the shoe-making industry. They just don't have much use for shoes. And it's not just because lack of shoes is a common trait among most wild animals. Sirens also have a lack of legs. They have no hind legs whatsoever! Their front legs meanwhile are remarkably tiny, and Dwarf Sirens have just three toes on each foot compared to the other Siren's more typical four.

With this dearth of legs and tootsies it's no surprise to learn that Siren s aren't one for climbing up trees, running across prairies or even strolling in the park. Sirens are very much aquatic. They like shallow ponds and swamps where a muddy bottom and a dense growth of weeds provide them with lots of places to hide.

Image: Todd Pierson
Southern Dwarf Siren (Pseudobranchus axanthus)
To help in their aquatic activities Sirens have bunches of gills on either side of their head for absorbing oxygen from the water. Even adults have them, which is unusual since most other salamanders only bear gills when they're larvae and lose them as they grow up. Siren's are neotonic, which means that like the Axolotl, they keep certain childish things long into adulthood. Things like their superhero collection and their ability to sit in the middle of a supermarket and wail with wild abandon because they didn't get enough chocolate bars.

Sirens don't eat chocolate, poor guys. They prefer all manner of meaty mouthfuls found in their aquatic home. Snails, worms, shrimp and, if the Siren's mouth is big enough, small fish. Also algae, because it doesn't hurt to vary your diet at least a little. Siren's are rather lacking in dentition and the whole front of their mouth is completely toothless, replaced with a kind of beak.


Video: PatrickS1968

All this feeding occurs at night, since Siren's are nocturnal. They spend the day nestled among the weeds or buried in the mud. They can also do something similar if the pond they're residing in magically disappears into thin air, or "dries up" as we call it. They can burrow underground, encase themselves in a cocoon of mucus and sleep through the driest months, much like the Lungfish... who is also known as the Salmanderfish. Kindred spirits! I think I'll doing something similar this winter, but using blankets rather than my own mucus. We're ALL kindred spirits! I'm not Salamander Man, though. That guy is just weird.

With all that day to day living sorted out, it's time for our Sirens to focus on more exciting things. Unfortunately, not much is known about their reproduction. It's thought that they probably use external fertilisation since their cloaca, the universal, all-in-one (or all-out-of-one) orifice that amphibians, birds and reptiles use for all their evacuatory needs, lacks the kind of glands and doodads other salamanders have.

Image: johnwilliams
Those other salamanders use internal fertilisation, where the male deposits a packet of sperm and the female comes along and picks it up to fertilise her eggs while they're still inside her. It seems that Sirens have to lay their eggs first, and only then can the male fertilise them.

Either way, the eggs hatch after a few weeks into lots of titchy, Siren tadpoles. They have a long dorsal fin to help with swimming, no legs at all and even their gills are small and don't work well at first since they can do all their breathing straight through their skin.

As the Siren grows, its tail will become longer, it'll lose a lot of its fin and gain a couple legs and bushier gills. So it will change, just not a lot!

3 comments:

Lear's Fool said...

OMG the little feets!

TexWisGirl said...

so cute!

Joseph Jameson-Gould said...

@Lear's Fool: Ridiculous, aren't they?

@TexWisGirl: Definitely!

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