The organisms:
Aiptasia
True to their name, Aiptasia sp. anemones (which means ‘beautiful’) are elegant
creatures, but they are also invasive and aggressive competitors. Left unchecked,
they will often totally over-run an aquarium. I have watch a 5 mm diameter Aiptasia
overcome an upside down anemone 60X its size. They sport long tentacles armed
with particularly efficient nematocysts. Their nematocysts are capable of delivering a
potent sting that can cause tissue regression in sessile corals, immobilize prey, and
even kill unlucky neighboring corals and unsuspecting, crabs, snails or fish that
wander too close.
They reproduce both sexually and asexually, and are capable of regenerating and
entire creature from a single cell. In addition, Aiptasia swim by ciliary action in spirals
or by crawling on its side, progressing at about 4 cm per hour. To do this, the pedal
disc is pushed forward by contraction of circular muscles, the trunk shortened by
contraction of longitudinal muscles, and the oral disc pulled along after. Many times
Aiptasia will simply opt to disconnect and float around, or swim by moving in a spiral
motion, until they find a new attachment spot.
In the reef aquarium, Aiptasia will happily eat fish food and coral foods when the
opportunity presents itself. Many times Aiptasia can be found growing in an overflow
because it can easily take in fish food that has moved into the overflow with the
circulating tank water
Aiptasia contain zooxanthellae, or symbiotic dinoflagellate algae, which produce
oxygen and fix carbon by photosynthesis. Much of the carbon fixed is released to the
anemone, aiding in its energy needs while the Aiptasia, in turn, supplies the algae
with nitrogen and phosphates in the form of ammonia waste by-products. You will be
viewing these symbionts later in the course, but they are responsible for the brown
color if this anemone. Anemones that have lost their zooanthellae are white.
Endosymbionts from A. pallida
Sowbugs:
Phylum, Arthropoda
The immature isopod molts four or five times. They look like adults except for size,
proportion, color and sexual development. Eggs (up to 100) are held in broad pouch
on female. Juveniles look like adults and are soon liberated from pouch. Molting is in
two stages. First the back half molts, then two to three days later, the front half molts.
On the underside, females have leaf-like growths at base of some legs. These brood
pouches hold developing eggs and embryos. The first two appendages on the male
abdomen are modified as elongated copulatory organs.
Isopods are omnivores or scavengers feeding on dead or decaying plants or animals.
Some may eat live plants.
Isopods breathe with gills, so they are restricted to areas with high humidity, under
rocks or logs, in leaf litter or in crevices. Some species are nocturnal. Some species
roll up into a ball when disturbed.