1 November 2004

Greetings from Kathy Conlan

For the last two days I have been sorting through buckets of mud that Andrew and I scooped up at the Jetty and picking out animals of interest. I am studying five species of crustaceans that are common there. Each of these brood their embryos in a pouch under their thorax. With steady hands and fine jewellerís forceps it is easy to tease out an embryo without harming the animal and determine what stage of development the embryo is at. I have been doing this since 1991 and I have found that each time I look, each species is carrying embryos at the same stage of development as it was the year before. So they never seem to deviate from year to year. Iíve also determined that it takes the embryos about 9 months to grow to a small hatchling. And Iíve also found that although each species is different in what they are carrying, some are timing the hatching of their eggs to Decemberís plankton bloom and others arenít. The ones that are, are the plankton eaters. So hatching their youngsters at the biggest feeding opportunity of the year makes sense. The ones that donít synchronize are predators. So presumably they can find food year round and synchronizing release of their youngsters to the bloom is not necessarily adaptive (maybe hatchlings all hatched at that time are vulnerable to being preyed on by the predators that come in with the plankton). So this is my little study, and one thing I have noticed is that it was a lot harder to find brooding females this year than previously. Are the populations down? Could this relate to our thick ice and minimal December blooms thanks to the big iceberg preventing ice breakup in McMurdo Sound? Once back home I will examine our annual samples at the Jetty to see if percentages of brooding females really are down. Populations cycle up and down for any species, so changes may not be related to that big iceberg jammed against Ross Island but itís an intriguing thought!

While sorting through the animal community that we had dug up I couldnít resist taking pictures and then thought you might be interested too. These are all the little animals that mostly burrow in the seabed so most people donít notice them. They are the ones that would be colonizing Stacyís spiked sediment dishes and that also we are using to monitor the effects of the sewage. They are good indicators because they donít move about much, so canít avoid the outfallís refuse, yet as larvae or hatchlings may be quick to invade new territory, like Stacyís dishes.

If you are interested in seeing more of the animals that we have been discovering on our dives, check out Peter Brueggemanís Field Guide at http://scilib.ucsd.edu/sio/nsf/fguide/index.html. Iíve taken the liberty of borrowing some of the neat facts that he cites.

Heterophoxus videns
This is one of the little crustaceans that I am studying. The male has the big eye and long antennae, the better to find females to mate with. The female has a load of unhatched pink oocytes in her ovary. When she molts, which is the only time that her cuticle will be soft enough for the oocytes to pass through, she will deposit her eggs into her brood pouch. The male must find her quickly to fertilize her oocytes (hence the big eyes and long sensory antennae). Then she will carry her eggs in her brood pouch for about 9 months while the embryos grow. In temperate regions the embryos would only take a few weeks to grow and hatch.

Nototanais dimorphus
Here is another of my crustys. It looks like a little lobster but it is actually only a few mm long. Like Heterophoxus, the male changes a lot when it is sexually mature. Its front pincers become huge and it loses its mouthparts and stops feeding. The big pincers are probably used for display to younger and smaller males that itís dominant and not to be tangled with.
Gnathia calva
Gnathia calva parasitizes fish when it is young, but when adult it leaves its host to take up residence in sponges. There it protects its harem of breeding females and uses its huge mandibles to fight other males, sometimes to death. The first picture is of the young parasite and the second, with the big mandibles, is of the adult. They hardly appear to be the same animals!

Onoba turqueti
This little snail glides over the seafloor, grazing on diatoms, microalgae, forams and detritus. When it has pulled in, you can see its eyes under its shell.
Spiophanes tcherniae
This little worm constructs it own tube and extends its palps to feed on particles around it on the sediment. Its palps have tiny hairs that beat in waves to draw the particles to its mouth. Spiophanes lives in dense mats of tubes and has been found in numbers as high as 3000 per square metre. Its tubes create hiding spaces for crustaceans, worms and snails, which are more abundant where Spiophanes occurs. It does not occur where pollution is high but is a quick colonizer of sediments denuded by ice scour.

Gromia oviformis
This is a large, single celled amoeba that extends its pseudopodia from its oral region. It eats diatoms and plant and animal debris.

Lets see the next day!