Monday, August 31, 2009

Marine Biology Boat Trip - Port Phillip Bay, Vic.

The Port Phillip Bay on Victoria's south coast is a pleasant place to spend a few hours looking at some of the interesting marine life we have here. Any day on a boat ride you might see seals, dolphins, a number of different water birds and if you were really lucky maybe even a whale. I had the opportunity to go out on one of these trips last week and take photos of some of the things that are common - and some things that are not so common.

These two photos are of pied cormorants taken near a spot known as the Chinamans Cap which is a place where bachelor Australian Fur-seals hang out (shown in the following pics).

The next three photos are of the seals. They are interesting to watch and there are more seals than there is room on this platform so there is a continual jostle for the best spots to sun yourself.

Aside from birds and mammals there are representatives from a number of different phylums (animal groups) in the bay. To see what some of them are we collected a few buckets of seaweed from about 12m of water and looked through it closely. It takes a few moments but you start to see all sorts of things moving in amongst the weed. The weed is put in trays with water so that creatures can be put back in the water after we inspect what is living there.
So what did we find?
All the animals with back bones are chordates and this includes all the birds, marine mammals, fish and the most simple of all the chordates - the sea-squirts (ascidians). Sea-squirts can be hard to see as an animal - especially one that is a chordate. Something similar to this is what all back boned creatures evolved from. The sea squirt only has a notochord(primitive backbone) when it is in larval form. The photo below is an ascidian called a Sea Tulip-it is shown about actual size but this is a juvenile. They have a fairly simple body plan - one opening that is an inlet for water and and outlet to squirt water out after it filters food from it. They live attached to seaweeds or rock.

Short -snout seahorse. Seahorses are fishes that belong to a family called Syngnathidae.

Another marine phylum known as the Echinoderms (meaning spiny skin) is represented by a few different types of related animals. Sea-stars, sea-urchins, sea-cucumbers, are all in the group. This one in the pic below is an Eleven-armed sea-star (juvenile). Echinoderms are the only other group apart from vertebrates that have an internal calcareous skeleton. They have a water vascular system and many can regrow a lost arm ( even the arm that is removed will grow into a new individual as well if it isn't too damaged). This one is growing new arms - eventually they will all be even in size. The spines on sea stars are often not sharp at all but like like little projections all over the body.
Sea-urchins are ball shaped creatures that are mainly hollow inside unless they are in reproductive mode and then they are filled with eggs or sperm. They have spines to protect themselves.

Molluscs form another phylum. (molluscs include octopus, squid, cuttlefish, seaslugs, bivalves and gastropods) These bivalves above live attached to seaweeds and they are in the same family as Pearl Oysters. The thing I find interesting about this photo is that these shells are a micro-habitat. There are quite a few different species in this picture: 5 different types of algae, a sea-anemone, a gastropod (seasnail), bivalves and the little white spots which look like the start of sponge colony (phylum - Porifera). Many of the creatures that live in the bay have cryptic lifestyles and are hard to spot.

Gastropods (sea-snails)

2. Gastropod - Pheasant Snail.

3. Sea Hare-Aplysia parvula. These creatures feed on seaweed. This species takes on the colour of the seaweed that it feeds on. It appears to have been feeding on red seaweed. All the members of this family are capable of releasing purple ink if they feel threatened. The dark colouration is a feature of this species that makes it easy to identify.
4. Gastropod- The thing I like about this photo is they way you can see not only its tiny eye but also tentacles from all around its body.

5. Gastropod - This is an Anemone Cone. These are some of the more evolved gastropods. They are carnivores and from the proboscis (snout) protruding from the front of they creature they are able to shoot a poisonous harpoon which paralyses their prey. This species feeds on bristle worms. Some species of this family are extremely dangerous and have been known to kill people. This southern variety is not considered to be extremely dangerous but handling them is probably not a good idea. An attack by one of these may not be life threatening but it apparently feels a bit like a bee sting.

6. Gastropod

Many molluscs lay their eggs on the weed. These ones may be from a Sea-hare.

  Phylum - Echinoderms.
1. This creature is a sea cucumber. The picture is a little larger than actual size. They are related to sea-stars and urchins. They have a mouth one end and an anus at the other. Many of them take in large quantities of sand and eat the algae off it so that their waste looks like something out of a toothpaste tube except that it is sand paste.

This is a sea-star - part of a group called Feather-stars. They attach themselves to weed or rock with the smaller leg like tentacles while the feathery arms sit in the current catching tiny food particles. The next few photos are also of feather stars.

The next two photos are bristle stars. They are the greyhounds of the seastar world in that they can actually move quite quickly.

Phylum - Crustaceans
The next few photos of crustaceans. Crabs Crayfish and Prawns are the well known members of this group but there are many other lesser known creatures like amphipods and isopods.

These two photos are two different species of hermit crabs. Both are in shells about 10mm in size.

These next three photos are of the same species but all with slightly different colouration. They are tiny flat shelled crabs with ornamentation on their back that looks like encrusting growth - It is the near symmetry that gives it away to our eye but in amongst the weed or debris this crab would be hard to spot. Crabs are able to regrow lost legs but only when they moult and get their new shell. Sometimes they don't form completely or are a different colour. If you look closely at the next three pics you can see some have lost legs and some have legs that have grown back.

This is a type of marine slater, an isopod. They have a body that is flattened and they are much more wide than thick. Others in this family are not so colourful.

This is also an isopod sometimes called a sea centipede.

This photo is of an amphipod - similar to an isopod except that their body is compressed sideways.

This pic is also of an amphipod sometimes called a skeleton shrimp. This was taken on a previous trip on the bay but I added it here as I think it is rather bizzare and interesting. These are usually on weed and have evolved to suit where they live.

Phylum - Cnidarians - Sea anemones
Sea-anemones, corals and sea-jellies are in this group. We found a 3 different anemones amongst the weed.
This photo and the two below shows somthing I find really amazing. Some anemones reproduce sexually by releasing eggs and sperm into the water and are fertilised externally. Some form little minature clones of themselves on the surface of their body and some are able to split into two. This is none of those. It is one of a few anemones that give birth to live young. If you look at the mouth you can see the little round individuals waiting to be ejected. As this was moved many little creatures filled the water around the parent. In the last photo if you look carefully you can see some of the little baby ones about 20 minutes after they were "born". If your wondering how this can be its like this: early in the reproductive season the parent forms eggs (it is a functioning female) once the eggs are formed it then does a sex change and makes sperm which fertilise the eggs which then develop inside the parent anemone. When they are sufficiently developed they are expelled and then find their own place to settle and grow. The common Waratah anemone, found on rocky shores also reproduces like this. I havnt been able to work out exactly what type of anemone this is yet.

This next anemone is called a walking anemone as it doesnt stay attached to the substrate like many other anemones. All anemones have stinging cells (nematocysts) in their tentacles that they use for catching food. These anemones will eat fish larger than themselves, catching them with their tentacles after the stinging cells have paralised it, taking many hours to eat the whole thing. The other anemone we saw is the Orange and White anemone which is on the bivlaves in the beginning of the post.

Ascidians (sea-squirts)
The creatures in the next two photos are related to the Sea tulip at the begining of this post except that these ones are colonial. Eack creature is still a simple animal with an inlet and outlet valve but they are joined together with none living as individuals. Each individual has its own inlet but they share a common waste outlet with those nearby. They are soft jelly like masses and I find these creatures really beautiful. Remember these are very similar to the ancestors of all backboned creatures!