Sea swallow

G L A U C U S     A T L A N T I C U S 

also known as 

t h e   s e a s l u g,  t h e  s e a  s w a l l o w,   b l u e   d r a g o n,  b l u e   s e a  s l u g

or the

b l u e  g l a u c u s,  b l u e  o c e a n  s l u g,  b l u e  s w a l l o w  s l u g

Phylum: Mollusca

Class: Gastropoda

Body Structure: Sea Swallows grow up to 3-5 cm. They have flattened bodies and six appendages which branch out into attachable cerata which help in respiration. Most have exactly 84 cerata. They have radula with barbed teeth. Their heads contain oral tentacles and rhinophores used to smell/taste food. They have eyes but they can only detect light or dark, they are severely limited compared to our eyes. Most interestingly, they have an anus on the side of their bodies. They have stomachs to puff in air which I will mention more later. Structurally and colour-wise, they are closely related to Glaucilla marginata.  

Ventral Side Anatomy

Feeding: G atlanticus are carnivores. They will eat venemous Portugese Man O Wars and steal their cnidocysts and use it for themselves on their cerata; toxic blue snails, by-the-wind jellyfish, blue buttons and other sea swallows. They seem to only eat blue things as their main source of prey. Everywhere the Portugese Man O War can be found, the Sea Swallow more or less follows. Due to this, they can be found in tropical and temperate waters. 

Counter-clockwise from top left: By the Wind Jellyfish (prey), Portugese Man O War (prey) and the Blue Button (prey)

Digestion/Excretion: The mouth has a sharp radicle which thrusts into the prey. Food goes through a simple gut and through the anus which ultimately removes waste. On most nudibranchs, the anus is on the "forehead." There are digestive glands in the gut that break down the food into enzymes. The mouth has a sharp radicle which thrusts into the prey. Protective hard-barrier discs lining their guts can handle the poisons from the Portugese Man O Wars and such. Somehow, these species have a gas-filled stomach, but nudibranchs are supposed to not have stomachs, so I suspect that these are not "true stomachs." In fact, its stomach is only for swallowing air bubbles so it can float upside down. More on that later. 

Dorsal Side

Circulatory System: Nudibranchs, like abalones, have a two chambered heart and an open circulatory. The blood flows through gaps in the tissue. The blood will pass through a kidney and then the heart again to complete the cycle. 

Respiration: Gas exchange takes place in the cerata mostly but also everywhere on the body. Fun fact: Nudibranchs fart too. 

Anatomy of the average nudibranch. 

Movement: The Sea Swallow has an air sac on what seems to be the dorsal side.  It spends its life after the larval stage floating upside down. So while it can wriggle sometimes for movement, it mostly lets itself get carried by the sea currents. It is like a balloon. As such, these sea swallows can get beached very easily, as Florida and Miami and Hawaii may attest. 

The "Beads"
in sexual reproduction

Defence Mechanisms: The Sea Swallow has cerata which it can detach, spewing a milky substance and wriggling around in hopes to distract a predator. By re-using the defense organisms that it eats, the sea swallow carries all the stingers it steals from its food. After eating jellyfish and other cnidarians, the sea swallow will digest their stinging cells and accumulate them in their cerata and "arms." In this sense, they are very resourceful. They can hurt humans and especially children with their borrowed nematocysts and cnidocysts. 

Reproduction: The Sea Swallow is hermaphroditic. It has a hole on its right side which contains both the male and female reproductive organs. Apparently, the Sea Swallow has a penis that's usually longer its entire body. The female organs produce strings of 10 to 12 eggs. Sometimes, in the thrill of sex, Sea Swallows will try to eat each other's penises. 

Most important thing to keep in mind, sea swallows are a species of------

N U D I B R A N C H S

-bilaterally symmetrical-

(internally and externally)

and

contain three germ layers!

(epi-, meso-, endo-)

AND

they are protosomes!

(spiral cleavage, ventral nerve cord)

They are carnivores that eat, grazing on algae, sponges, anemones, corals, barnacles, and even other nudibranchs. Nudibranchs get their coloring from the food they eat, which helps in camouflage, and some even retain the foul-tasting poisons of their prey and secrete them as a defense against predators.

Nudibranchs are simultaneous hermaphrodites, and can mate with any other mature member of their species. Their lifespan varies widely, with some living less than a month, and others living up to one year.

Anyways, 

G. atlanticus are very important species because they eat other dangerous cnidarians like bluebottles. Turtles, fish and sea stars all eat this specific type of sea slug in turn. At the same time, for nudibranchs in general, they may eat unwanted algae that damage coral.  The more these soft-bodied mollusks appear in the environment, the healthier the ecosystem. They are also brightly coloured and beautiful. They look like candy, which is why I like them because I like candy. Without the sea swallow, the ocean would be less strange and beautiful. If it went extinct, I think everybody would think that's a shame. Why are nudibranchs so brightly coloured? This is because they will appear toxic to their predators--and sometimes, they are. 

I like this species because they are so colourful and epic and regal while being only a few centimeters long. Although they seem so perfect, they are very strange, spending their lives floating upside down and eating each other's penises. 

In conclusion, respect the sea swallow. 

Australia, East of Grafton in the North

These were found in Florida. This one is albino. 

Locality: Byron bay, washed onshore, N.S.W, 2 feb 2010, beach. 

Length: 17 mm. Photographer: steff.

SOURCES

http://www.seaslugforum.net/find/22413

http://animalfacts.tumblr.com/post/8646741171/glaucus-atlanticus-is-a-specialist-predator-of

http://www.thecephalopodpage.org/marineinvertebratezoology/glaucusatlanticus.html

http://www.zimbio.com/Fish/articles/2O5IRsBbAKS/Glaucus+atlanticus

http://animals.nationalgeographic.com/animals/invertebrates/nudibranch/

SquidZhong

On Thursday, we dissected squids (phylum Mollusca, class Cephalopoda), creatures stranger than fiction and oddly endearing with their squiggling tentacles and wide eyes. The purpose of the lab was to identify in person the different adaptations and unique body parts of the squid and to observe how a simple funnel, crown of tentacles and fins can operate a weirdly shaped organism which such a big head. Cephalopods are excellent examples of biodiversity, unique organisms that heighten our appreciation when we compare how different they are from humans. We examined the external  and internal parts of the squid carefully because there's a difference between tentacles and arms on the squid and although the innards of the squid may seem just like a mass of goop, there is a  little ink sac like a silvery fish and gills and even a pen, something of an internal shell, similar in touch to plastic--not as simple as a mass of goop. The funnel and the ink sac are very funny but vital parts for escape and movement. When you compare a squid with snails and other slow mollusks, squid seem even more unique. Their 'feet' have evolved into tentacles, of all things--and even two very flexible tentacles, or arms, for additional survivability skills. Squids have some of the largest eyes in the animal kingdom, in fact, the colossal squid is the largest invertebrate alive. In conclusion, squid, like all cephalopods, are very unique from all other animals--certain squid can even fly short distances, their pen is like a glass/plastic pen for their ink, certain squid also have penises 60 cm in length and their feeding system of using jet propulsion, snaring tentacles and a snapping beak is very interesting too, reminiscent of a jungle of living vines and bird all rolled into one organism.
When we dissected the squid, it was very surprising how easy it was to cut through it. There was some confusion between me and my partner about differentiating between the funnel and the ink sac or the pancreas and the digestive glands, or what was the caecum. However, we got our footing eventually. Jaimie correctly identified the squid beak to be constructed of chitin. Throughout the dissection, I thought it was interesting how squid could be "as small as a  thumbnail or as large as a house." Maybe this is because their adaptations are so successful they can survive in any number of sizes. It was a shame throwing the squid into the garbage can; they looked very chewy, destined to be pan-fried.

Here is a picture of a squid,
similar to one we dissected in colour and size. 

Here is a picture of what could've been. 

                                                              EXTERNAL ANATOMY

1.
Our squid, not mutilated even at the tips,
has eight arms and two tentacles,
depending on how you classify
arms and tentacles. The arms are small.
The tentacles are longer and snaring.

2.
Squid have long tentacles with suckers at the tips.
However, arms have suckers that run down the
length of the arms. In this way, tentacles can
grab at prey far away and arms make sure
that the prey stays clung to the squid.
I believe octopi have
8 tentacles,
no arms.

3. The squid will move opposite
to the direction that the jet is propelled
from. The funnel draws water
into the mantle cavity by expanding
its muscles.

4.
a. Tentacles/arms are essential to the squid
as they shoot out to catch prey
and then draw them in and keep a snake-
like grip on them, strangling
before eating.
b. The beak is the kind of like
the second half of the
squid's feeding plan. The beak
allows the squid to eat many large
organisms as it is responsible for chopping
apart the organism
into many digestible pieces.

5.
Mollusks have feet and visceral mass.
The visceral mass in this squid
is contained as shown. While
cephalopods do not have the usual
mollusk feet, they have
tentacles and arms that evolved
from feet.

INTERNAL ANATOMY

1. The squid has two pairs of gills,
one on each side.

2. I think the ink sac empties into the water, surprising
and blinding any predators trying to eat
the squid. I like to think that the squid
does it just to piss off other fish, sometimes.

3. The pen is all that remains of the squid's cell
from its ancestral past. It is located by the mantle,
made up of chitin. Without it, muscles
would not be attached to the squid. 

4. I think the waste exits the
squid through the anus. I remember
that the radula is connected to the
mantle cavity. Maybe the mantle
cavity is connected to the digestive
tract and from the digestive tube,
the waste leaves through the anus. 

Annelid Dissection!

On Friday, in conjunction with our lessons on the anatomy of annelids, the entire class was was involved in a worm dissection lab. This was all done for the sake of observation, to understand the works of digestion, and more interestingly, sexual reproduction. Differentiating between the dorsal side of a worm and the ventral side are important when we consider worms, as is the relationship between the external and internal parts of the worm. While the worm may appear primitive, it's very surprising to see how many functions it contained! It was very exciting to handle the organism like a surgeon, trying to be as neat and quick as possible--even incisions are an art, I suppose. The setae we studied in the textbook appeared even smaller and sparser under the microscope, little silver hairs on a mound of pink flesh. The food digesting inside the dead worms appeared as watery dirt. Even the Clitellum was much more subtle as a real specimen than in a diagram. Compared to scientific diagrams, our worms were raw but red in flesh, but I was very proud of the work I did-- the pinning which was enjoyable as well, like I was creating an undead diorama. However, beyond my interest, I learned that annelids had very definite organs and many adaptions: how externally, sperm grooves and setae, like grips on the rungs of ladders, will help with transferring sperm and also traction for movement, but also how internally, a cut on the dorsal blood vessel would be so fatal to the worm because it is so important and one large part of the circulatory system. Worms also have a digestive system kind of similar to our's, where food goes through an esophagus and intestine, though we lack gizzards.
Unfortunately, my partner and I could not upload the phone photos onto the computer, however I made due with Nathan's, thank you Nathan. Earthworms are oligochaetes and this makes me curious about what it might be like to dissect a polychaete. This lab was  very hands-on and there is nothing I'd rather do for a period than look at things under a microscope or taking photos, so I was lucky to do both. I would recommend all courageous Biology classes to step up to the B.C. standards and do this lab. Here's an idea of what it looks like: http://www.youtube.com/watch?v=u9HHS1uPFSo

1. What is the name of the pumping organs of an earthworm?
They are called the aortic arches, which are hearts, although
they do not contain valves and chambers.

2. Trace the parts of the digestive tract?
The food passes through the pharynx and
passes through the esophagus, then the crop
and the gizzard and finally through the
intestines.

3. Which parts of the earthworm serve as its brain
The brain is above the pharynx and connected
to the ventral nerves; it is firmly attached 

4. Which parts of the worm/excretory system?
The excretory system goes hand in hand with the
digestive system above. However, a pair of nephridia
in literally each body segment helps remove waste

5. How can you find out whether an earthworm eats soil?
Put it in soil and examine its excrement in a glass jar. Try
adding different things in soil (rotting vegetables, dead
animal corpses, fertilizer). Since earthworms live in the
earth, its also logical to assume that everything
they eat exists in the soil. 

6. What are Setae? Well, they aren't as grey and silver
as I thought. They are like little black stubbles.
Setae are the small bristles that are good
for brushing against the soil, basically, providing
traction in the soil.

7. Highlighted in green are the special organs that
help take in small amounts of soil from large amounts of
food. The gizzard mashes the food while
the churned-up products are moved to the intestines,
so it's a continuous process. Also, their mouths
don't shove in a continuous amount of dirt, I assume
they can close.

8. Why didn't we go past segment 32? As you can see
fromt he worm already, tons of digesting food and faeces
in the making are visible. The lower we go, the more
dirty gooky stuff we'd see, perhaps dangerous things
that could be breathed in by our noses.

9. These worms are having the time of their lives. I'm
not sure if I was supposed to keep the paper or just post
all my findings on a paragraph online, but I'll do both, in
the honour of vertebrates everywhere.
It's important to remember that worms are hermaphrodites
so they have both MALE GENITAL PORES and
FEMALE GENITAL PORES. Sperm is produced from these pores
and it transfers to the female pores., which also produce pheromones.
Both these pores are located within one segment of each other.
According to cronodom.com, the sperm are transferred
along SPERM GROOVES through the muscle spasms during
worm sex. After going inside the female genital pore of another worm, the
sperm goes the OVARIES, where the eggs are stored. Again, the
ovaries are only within one segment away from the female
genital pore. In conclusion, the multiple sperm pores
on a worm compared to the single female genital pore makes it
easier for one worm to transfer genetics, taking three times
shorter, I suppose. Due to the close proximity of these pores
and grooves, this sexual reproduction can also be
done more conveniently.