Bony Fish Body Plans

Threre are three major body types in bony fish: Fusiform, Compressed, and Depressed.

I used Tinkercad software to build a digital 3D-model of each type.

A Fusiform body plan is streamlined, elongated laterally, with a long, muscular tail. This body type is helpful for predators to catch their prey, and for prey to try and escape. A good example of this would be a Sailfish (Istiophorus albicans).

A Depressed body plan is squahed vertically, like a pancake. This is advantageous to benthic dwellers, such as Hogchokers (Trinectes maculatus), who need to be able to grab food from the sea floor, and to hide from predators.

A Compressed body plan is flattened laterally, and is useful for maneuverability. and for hiding in tight spaces, like in a coral reef. One example is the Angelfish (Pterophyllum sp.)

Here are all 3 shapes together from several angles, for comparison.

Sharkwater

My assignment this week was to watch the filim "Sharkwater" and answer questions about it.

Shark Myths

1. Why are sharks so hard to photograph?

They often feel threatened by humans and avoid us.

2. What prey defenses have evolved in fish in response to predators like sharks?

Schooling, camouflage, speed, size, and communication

3. What strategies are given for repelling sharks in the black and white film?

Sounds, a stream of bubbles, shredding paper to confuse the shark.

4. According to the documentary, elephants kill more people than sharks. Why then, do people fear sharks so much more?

Psychological revulsion to a "cold monster of the deep".

5. What conditions around the Galapagos Islands of Darwin and Wolf make them so favorable for the hammerhead sharks?

Undersea currents bring plankton, which attracts creatures that eat the plankton, which attracts hammerheads.

6. What two additional senses do hammerhead sharks have that humans do not?

Lateral lines and electromagnetic detection.

7. How many humans have been killed by hammerhead sharks?

Zero

Long Line Fishing

8. List the fish found in the long line recovered by the film crew.

Sailfish, Dorado, Sharks, and Tuna

9. Explain why sharks are not equipped to tear flesh from animals larger than them. What causes moast human deaths from shark attack?

A shark's teeth are not designed for tearing flesh. Most shark related deaths are caused by blood loss.

10. As illustrated by the book Moby Dick, people used to be afraid of whales. How have public perceptions of whales changed since then.

People have come to see them in a new light as beautiful.

11. What does Captain Paul Watson and the Sea Shepherd Conservation Society do to protect whales and sharks from illegal fishing?

They intervene directly to provide enforcement of fishing and whaling regulationsm and treaties, sometimes at the request of governments, sometimes on their own. They sometimes ram whaling ships..

12. The Sea Shepherd caught the Varadero I, an illegal shark fishing boat. Why didn't the fishermen stop on orders from the ship? What are shark fins used for?

The fishermen would lose their ship, their fishing license, and their profits. Shark fins are used to make shark fin soup, which is seen as a status symbol in some Asian cultures.

13. What is the basis for the belief that shark fins have medicinal properties?

Sharks appear to be more resistant to disease, though there is no scientific basis for this. Some people think eating their fins will give them the shark's power to resist disease.

14. How did the Varadero I eventiually escape? Why was the crew of Sea Shepherd arrested?

Varadero agreed to follow Sea Shepherd to port, but they called the Guatemalan authorities and lied about what happened, saying the Sea Shepherd people tried to kill them. They paid off corrupt officials. Sea Shepherd was ordered to disengage, and the crew were charged with attempted murder.

15. Upon their return to the Galapagos Islands, the crew comes across fishermen hunting sea cucumbers. One of them was badly afflicted with the bends. What causes this sickness? Why weren't they returning to shore for treratment?

The bends are caused by rapid differential in pressure: diving too deep and surfacing too quickly. The fisherman did not want to return to shore because they would lose time and money.

16. Why did fishermen want long-line fishing legalized on the Galapagos Islands?

So that they could fish for sharks.

17. Overall shark population is estimated to have declined by ____.

90%

18. Explain how a decline in top predators like sharks can affect producers like plankton.

Plankton feeders are eaten by sharks When sharks decline, the plankton feeders increase their population and eat up more of the plankton, which provide most of our oxygen..

19. As Rob Stewart returns to Costa Rica, he was concerned about being arrested or caught by the mafia. What did he discover was happening there instead? What change was brought about in part because of public pressure?

Protests against finning and in favor of conservation were happening. Public pressure made long lining in the Galapagos illegal again.-More than 100 countries have banned shark finning.

For my assignment, I also had to look up the status of several shark species featured in the film:

A. Scalloped Hammerheads (Sphyrna lewini) often gather together in large groups, which makes them easy targets for fishermen. They have a long age of maturity, which means their population will not be sustainable, because they can not replace themselves as quickly as they are being killed. They are endangered.

B. Whale shark (Rhinchodon typus) fins are highly valuble, and juveniles are easy targets. It is estimated that there is a more than 50% decline in whale shark populations worldwide. They are also classified as endangered.

C. Carcharhinus longimanus, or the oceanic whitetip shark, is a common victim of by-catch. Although their population is declining, they have not reached endangered levels yet, and are classified as vulnerable.

Constructing an Elasmobranch Dichotomous Key

This is my attempt at a dichotomous key for sharks, rays and skates.

1. Is the body Fusiform or Depressed?

a. if depressed--------->2

b. if fusiform------------>5

2. Are the pectoral fins attached to the head?

a. yes ----------------->3

b. no-------------------> Order Squatiniformes (Angel Sharks)

3. More than one dorsal fin?

a. yes------------------>4

b. no------------------->Order Myliobatiformes (Manta and Sting Rays)

4. Produces electricity?

a. yes------------------>Order Torpediniformes (Electric Rays)

b. no------------------->Order Rajiformes (skates)

5. Number of gill slits

a. more than five------->Order Hexanchiformes (Frilled, Six Gill and Seven Gill Sharks)

b. five----------------->6

6. Eye position

a. in front of mouth---->7

b. behind the mouth----->Order Orectolobiformes (Carpet Sharks)

7. Anal fin?

a. no------------------->8

b. yes------------------->9

8. Does it have ventral gill slits and a dramatically elongated snout that resembles a saw blade?

a. yes------------------>Order Pristiformes (Sawfish)

b. no------------------->Order Squaliformes (Dogfish and Cookie Cutter Sharks)

9. Does it have different types of teeth in the front and back of its jaw?

a. yes------------------>Order Heterodontiformes (Horned Sharks)

b. no------------------->10

10. Do its eyes have nictitating membranes?

a. yes----------------->Order Charcariformes (Tiger, Bull, and Hammerhead Sharks)

b. no------------------>Order Lamniformes (Sand Tiger, Thresher, Megamouth, Basking, Mako, Goblin and Great White Sharks)

Prehistoric Sharks

Falcatus lived in the Carboniferous period, around 325 Million Years Ago ("MYA"). It was probably piscivorous (meaning it ate fish), and lived in deeper waters, which is why it has such large eyes. The most obvious feature of this shark was its long, forward pointed spine. However, specimens of Falcatus can be found without this spine, and it does not appear to have any specific purpose.

So what could it be? Well, since it is found on only some specimens, scientists have concluded that the spine was for mating purposes, most likely as a display. This is a great example of sexual dimorphism, common among many animals today.

Edestus lived in the late Carboniferous. It was related to Helicoprion, and had strange, outward curving tooth whorls that looked like a giant pair of scissors. It probably ate soft bodied animals, and attacked using a vertical thrashing strike.

Hybodus lived throughout the mesozoic era, approximately 260 to 66 MYA. Unlike some of the previous animals, these were generalists. They had two different types of teeth: sharp teeth for grasping prey, and rounded teeth, which could crush hard shells. They most likely ate whatever they could find, and that is probably why they lived for so long. Another adaptation that helped them to survive was long spines on their dorsal fins. These were probably used for defense.

Squalicorax lived during the late Cretaceous period (approximately 105 to 65 MYA). This shark looks a lot likee a modern shark. Its teeth were definately those of a predator, and we also find its teeth in fossils of other animals, includinng turtles, Mosasaurs, and even Hadrosaurs (duck billed dinosaurs)!

And now we get to Megalodon. Megalodon lived from the early Miocene to the late Pliocene (approximately 23 to 2.6 MYA), making it the most recent of these sharks to swim the seas. it was a massive predator, reaching about sixty feet in length. It would have eaten mainly small whales, which were common in the southern oceans at the time. Scientists believe that the whales began to adapt to northern climates and migrated, but megalodon could not adapt to follow their major food source, which likely explains its extinction.

Here is my attempt to estimate Megalodon's size:

And here is my measurement, which shows I was a bit off in my estimate:

I used a 120 inch, or ten foot, tape measure, and marked off each 10 foot distance with chalk.

This is a lifesize 3D model of a megalodon tooth. I created it with Tinkercad software.

It is 18 cm long (approximately 7 inches), which is about as big as they come.

And this is a fossil megalodon tooth that my mom gave me:

Chordate Evolution

My assignment was to "[c]reate a project that shows the evolutionary developments that helped to lead to true vertebrates in the following animals. Begin with the most primitive, and work your way up to the most advanced.

Amphioxus

Hagfish

Hemichordates

Lampreys

Tunicates"

Hemichordates came first, and they had two of the distinguishing features of chordates: gill slits and a dorsal nerve cord. (They also had a ventral nerve cord.)

Next came the Tunicates, or at least their larvae. They have the dorsal nerve cord and pharyngeal gill slits, like their predecessors, but they also have something new: the notochord. Thus, they have three of the four distinguishing chordate characteristics. However, most of these features are lost when they become adults, leaving only the gill slits behind.

Amphioxus was the first organism to have all four chordate features as an adult. The fourth chordate feature is a post-anal tail.

The hagfish was the first agnathan, and just barely scrapes across the boundary to vertebrates. Though more advanced than amphioxus, its spine (derived from the notochord) was a single cartilaginous rod, and it has no jaw.

The next step was the Lamprey. It had all the chordate features, plus fins, and individual vetebrae.( It still no jaw, though.)

Marine Invertebrate Safari

These photos are mostly from a recent family trip to the Georgia Aquarium. My mom took lots more photos of the whale sharks, skates and rays than of marine invertebrates, though, so a couple of pictures are from an earlier trip to the New York Aquarium.

My assignment was to do a photo safari of marine invertebrates, and identify their phylum and what features identify them as belonging to that phylum. I was supposed to identify them down to class or order if I could, and create a cladogram showing their evolutionary relationships.

In this first photo, we have two different creatures. First, there's a Sea Star, of the Phylum Echinodermata, Class Asteroidea. You can tell this by its pentaradial symmetry, its spiny skin, and by the thick attachments of its arms to the central disk. There is also an anemone in this photo, Phylum Cnidaria, Class Anthozoa. It has the radial symmetry and tentacles of a cnidarian, but it is sessile as an adult and has a polyp body form.

This second photo of anemones is of the bubbe tip anemone Entacmaea quadricolor of the phylum Cnidaria, Class Anthozoa.

This is some sort of clam, in the Phylum Mollusca, Class Bivalvia. It has two shells.

Here is a table coral. It is a Cnidarian (phylum), Anthozoan (Class), Sclereactinian (Order) coral. I know this since it is part of a larger reef structure, which are made by scleractinians.

This is a moon jelly, Aurelia aurita. Because it has radial symmetry, and tentacles with stinging cells, it must be a cnidarian. And due to its round bell with tentacles all along the rim, it has to be a member of class Scyphozoa, i.e., a true jellyfish.

Pictured here is a Japanese sea nettle, Chrysaora pacifica. It is also a Cnidarian, and a Scyphozoan, for the same reasons as above.

This is a Japanese Spider Crab, scientific name Macrocheira kaempferi, of the Phylum Arthropoda, Subphylum Crustacea, Class Malacostraca, and the Order Crustacea. I can tell that it is an arthropod based off its jointed legs, and that it is a decapod because it has ten legs.

This is a Nautiloid. It is from Phylum Mollusca, Class Cephalopoda. This is evident by its soft body with multiple tentacles, and its siphon for jet propulsion, as well as the fact that it has a shell.

This is a sea fan, a soft coral, from phylum Cnidaria, Class Anthozoa, Subclass Octocorallia.

It has a sessile polyp body form as an adult, lacks tentacles or an osculum, spongeocoel, or ostia, so it isn't an anemone or a poriferan, and must be a coral. It does not have a hard calcium carbonate skeleton, so it is a soft coral.

This is a sea urchin, of the Phylum Echinodermata and the Class Echinoidea. I can tell this because of the spiny skin, and the Aristotle's Lantern that is clearly visible.

This is a white striped cleaner shrimp, Lysmata ambonensis. Phylum Arthropoda, Subphylum Crustacea, Class Decapoda, which I know because of its ten, jointed limbs and hard carapace/exoskeleton.

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This is a sea snail, of Phylum Mollusca, Class Gastropoda. it has a radula, a soft foot, and a helical shell with one opening.

The second part of my assignment was to create a cladogram showing the evolutionary relationships between the animals I chose.

Sea Star Water Vascular System

The water vascular system starts with the Madreporite, where water enters the body. The water is then funneled into the starfish's core through the Stone canal, which then flows into the Ring canal. The ring canal distributes water around the center of the organism, where it then enters one of the radial canals. The radial canals take the water from the center of the creature all the way down the arms, into the ampulla, where it can then be used for locomotion, by hydraulically moving the tube feet, and assist in feeding (also with tube feet).