Monday, 23 October 2017

Underwater Parents

 The photo shows the snail fusitriton cancellatus engaged in laying eggs - in its last 'cameo' appearance here this animal was practicing cannibalism so now we see that it does have parenting instincts. Larry took the photo here in Bahia Tom. We're safely weathering out the storm (blowing up to 60 knots - 70 mph) outside our anchorage. The anchor is laid out, and we're also tied to 4 trees with shorelines.

fusitriton cancellatus snail w eggs 
These safety lines have the added advantage of guiding us when we're scuba diving. We can use them to go straight over to the shore of our sheltered anchorage and straight back to the boat. The only disadvantage is that some of the dives are a bit pedestrian. You get both less security and more exciting creatures by diving out on open rocks.

dorid nudibranch eggs
The circular layout of eggs in the snail photo turns out to be a recurring theme for underwater egg-laying animals. Dorid nudibranchs favour a round-shaped spiral - normally coloured white - while the the Wellington nudibranch in New Zealand lays a bright orange eggmass. Other nudibranchs produce a white spring which you find hanging not far away on a kelp-leaf or on algae.

In North Pacific waters, it's quite shocking to see your first moon snail egg mass. It looks like a dun-coloured used tire cast off by some heedless boater. The colour is the result of eggs being inserted into a mass of sand which the snail has ingested and extruded into this amazing circular tire shape.
Wellington nudibranch egg mass
In all cases, very few of what must be hundreds or even thousands of eggs seem to make it to adulthood. Who eats them all, or how do they 'disappear'? In the case of moon snail eggs, it's hard to imagine another creature enjoying eating up all that sand along with the eggs!
A pair of Wellington nudibranchs mating

We humans find it difficult enough to bring up a couple of children - just think of the poor female octopus. After reaching maturity, she receives a sperm packet from a male, heads off over a period of time (up to a month), selects a suitable den, and - taking up to 42 days to accomplish the feat - lays up to 68,000 eggs. Then - in an act of complete martyrdom - she fans and tends her eggs for 9 months until they hatch. In all this time since her virginal act of accepting the eggs, she doesn't eat. Some time after they're hatched, she starves to death, having achieved maternity only once.

Moon snail
moon snail egg mass (in British Columbia)
Not all male sea creatures are uninvolved parents. In Vancouver, we got asked to dive with our Marine Identification teachers - Andy Lamb and Donna Gibbs - in a study sponsored by the Vancouver Aquarium. The Annual Lingcod Egg Mass Count was an attempt to monitor how all the fishes in the area were doing by using a Key species whose egg masses were (relatively) easy to use as a baseline. The aggressive, predatorial male lingcod waits outside his cave, leaning on his pectoral fins and looking 'muy guapo' as they say here. 'Hunky' would be the word for us Northerners. At any rate, he seeks to attract as many female passers-by as he can. They lay the eggs in his cave and he then fertilizes them and keeps away all predators as they hatch.

We often saw at least two egg masses (the varying colours of the eggs helped to distinguish how many there were). Each dive team left a distinctively coloured marble to alert other teams as to whether the particular cave had already been accounted for.

For the male lingcod, the female just takes off and leaves him to it.

For an even more engaged - and engaging - male, we female humans should point our prospective mates to seahorse males. They take in and incubate all the eggs in their own bodies until they're ready to hatch.

Seahorses are beautiful AND they make the most amazing fathers!

At 2017-10-22 13:58 (utc) our position was 50°11.64'S 074°49.39'W

1 comment:

  1. Ahoy Travesay 111. Looking for Katie and Maurice. I have lost contact ,