Tuesday, August 31, 2010
This is Pteraster tesselatus, commonly known as a slime star. As its name implies, when disturbed this star can produce copious amounts of slime, which may protect it from predators . It eats sponges and the like and lives in the colder waters off the west coast of the US.
It also has an interesting feature common to many members of its family. It has a 'brood pouch'. The surface that you see is actually a soft covering which covers the true surface of the sea star. In other members of the family, females will release their eggs from their gonopores (like all other sea stars), but retain them under that covering until they develop into juvenile sea stars and crawl out. In this particular species, they do not brood their young, and instead send them shooting out of the osculum, an opening in the covering. The osculum is generally used for exchanging water from the water vascular system to the outside, and can be seen opening and closing even in individuals who are not spawning.
Thursday, May 28, 2009
She started laying eggs in the new enclosure, which I took as a sign of approval. However, I have suspected that the eggs that she has been laying may not be fertile, so we were really hoping to get a male for her. When Bug Fair rolled around we picked up 3 more beetles. We think we did get a male, as the smallest beetle likes to clamp on top of the identified females (ran up to stumpy first thing) and they always try run away.
One of the other beetles is most likely another female, as she exhibited egg-laying behaviour fairly soon after being placed in the tank. Hopefully, we'll have little ones in a few months, although I am worried about getting this larger tank up to the temperature that I suspect may be necessary for larval development (over 100 degrees F).
Thursday, February 12, 2009
This fish is the plainfin midshipman (Porichthys notatus). If you were looking at the top of the fish, you would see a plain grayish fish with a rather large mouth. One of the midshipman's interesting features actually lie underneath the fish. These interesting dots on the underside of the fish are photophores, which can produce a bright light pattern. Its still not clear what the light is for, but some speculate that the midshipman uses them to lure prey closer when hunting. The midshipman will hang in the water column and flash its light to attract prey items.
Interesting thing number 2 is how midshipman reproduce. Like most fish, males are responsible for maintaining the nest and attracting the females to lay their eggs. Male midshipman will hum for hours on end to attract females to their nest. The hum is produced by the fish vibrating their swim bladder, and can be so loud that people walking on a beach can hear it (and people living on boats often find it hard to sleep). Female midshipman who are producing eggs (more estrogen) are more sensitive to the humming noise and more likely to seek out its source .
Here's a nice news article on the midshipman's love life, with some sound bytes attached (for Quicktime viewers only).
Thursday, December 25, 2008
This was a bit of a tough choice for me, as I have an oddly large assortment of animal mating pictures (although I always kick myself for not having the camera on me the day I saw barnacles mating). I decided to go with this 'morning after' picture, as I find this type of procreation to be very bizarre.
These are Nereis sp. worms. They normally live on the benthos, but when these particular worms get ready to mate, their bodies undergo a startling transformation. Their internal organs degenerate, and their body cavity fills with gametes. They develop stronger podia (paddle-like feet) for swimming and better sensory organs. Then, when the moon is right, they swim up into the water column. Males will find a female and swim in circles around her... then they both explode.
So above you can see chunks of worm, white strands of sperm, and reddish-yellow eggs (both of which are released from the body cavity by the explosion).
Sunday, August 3, 2008
This is a picture of a cloud of sperm. You can see the green anemone which produced these clouds wedged in between the upper rocks. Anemones are broad-cast spawners, which means that they release their eggs and sperm in the water column and hope that they get fertilized. They do try to coordinate their spawning efforts by using external cues, such as temperature. When the water gets warm enough, they release their gametes (eggs or sperm). However, for those living in the shallow tidepools, this can get a little tricky, as the temperature of the tidepool's water is often warmer than the ocean water. So, during the reproductive season, you can sometimes find anemones that were fooled into releasing their gametes early.
Thursday, June 12, 2008
The above are sori, found on the underside of a 'true' fern frond. In each of the sori are spores which are haploid (have only half of the chromosomes as the adult stage). These spores are released into puddles of water, where they create a structure called a prothallus. This is a heart shaped structure, which is only a cell or two thick and fairly small. The prothallus produces either eggs, sperm, or sometimes both (depending on the species). The sperm have to swim to a different prothallus to fertilize an egg, as the eggs are retained there. The fertilized egg is what becomes the fern, and it grows out of the prothallus.
So the thin tissue that the small leaves are growing out of is the prothallus, and the leaves are the young fern. Later leaves will look more fern-like (shape depends on the species) and grow in the characteristic fiddle-head shape.
Wednesday, April 23, 2008
Wednesday, December 26, 2007
They found that there was no difference in egg size due to colony morphology or size, but smaller colonies were less likely to spawn a second or third time. They did find that chlorophyll concentration of the eggs increased with increasing size of the colony. This may have been due to the fact that larger colonies were deeper down, so packaged their eggs with more zooxanthellae than the smaller, shallow water colonies.
They also found that eggs sizes within the bundles varied, which interests me because I work on maternal provisioning in a colonial animal too. I find that larvae released by my bryozoans can have up to a 2-fold difference. I am most curious to know how much those eggs varied, since most researchers ignore within brood variability. They also found that the egg sizes varied among spawning events. Generally there was a decrease in the size of the eggs on subsequent spawning events, but a slight increase in the number.
This raises some interesting questions. It would be interesting to find out if the same amount of energy is expended for each of the broods (that is does the increase in number balance the fact that smaller eggs are made). Are these smaller eggs as fit as larger eggs? Are parent colonies more willing to take a chance by producing smaller eggs, since they are assured some reproductive success with the earlier large egg brood?
Finally, if would be fun to know if this down shift in egg size (energy into eggs) is accompanied by an up shift in sperm production. Since the eggs and sperm are packaged in the same bundle, it may be relatively interesting to quantify the egg/sperm ratio. It would also be interesting to see if that ratio is different among the different sizes of colonies. It's generally easier (energetically) to be a male, so would smaller colonies increase their reproductive success by packaging extra sperm?