Wednesday, November 27, 2013
Monday, November 25, 2013
Not a lot is known about shark reproduction because in many cases it has never been observed. Sharks have internal fertilization and the male shark has two claspers for sperm delivery. These can be seen on male sharks protruding from the pelvic fin.
Shark reproduction is violent with males biting the female. As a result female shark skin is much thicker than the males so that this practice does not ham or kill her. She fights a little to ensure that only strong males with good genes are able to fertilize her eggs.
Some sharks are oviparous and lay eggs (pictured). These egg cases are known as mermaid's purses. You can see the baby shark and its nutrient-rich yolk through the leathery egg case.
Some sharks are viviparous and have live birth a lot like mammals.
And some sharks are ovoviviparous and keep their eggs inside the uterus before releasing them... so its making eggs and then kind of having live birth.
Think you know it all? Try "Romancing the Shark," a quiz from Shark Week.
Follow this link for a cool interactive about how shark jaws stick out when they attack their prey! The interactive is down at the bottom.
If you are doing a final project on a shark... check out this new link! www.shark.ch
Wednesday, November 20, 2013
In the animal kingdom, males are typically brighter and more colorful. The males are trying to prove to the ladies that they have good genes, they are disease free, and they can escape predators.
Larger males can win contests against other males also proving their good genes. Though the males show off, it is the female's choice when she ultimately makes a decision. It is possible for a female to reject all males and choose none.
Differences in size and coloration indicate that there is female choice, the female will choose a male to fertilize her eggs and in most cases, his job is done, and she leaves to finish the baby-forming process. All she wanted was his genes.
When a large group of organisms all spawn at the same time, the organisms rely on luck and statistical chance for genetic variation. Males and females will look similar because there is no choice involved.
When males and females work together and take an equal role in raising young or protecting eggs, the males and females tend to look more similar. They look similar because of their equal roles and because the choice is longer-lasting. She is looking for more than just a pretty face (and pretty faces in the animal world do not indicate good egg care or being able to provide nesting materials, food, etc).
Differences in size between males and females varies widely. There is no set rule for who will be bigger, but there is usually a clear reason as to why one of them is bigger. Males can be bigger because they fight other males, because they have to guard eggs, or other reasons. Females can be bigger because they have to carry and nourish a fetus, carry and develop eggs, protect babies, or other reasons. To know why a male is bigger or a female is bigger the biology and reproductive strategies have to be understood.
Monday, November 18, 2013
1. Shrimp that are farmed in other countries are not as regulated as here in the states, so shrimp farm pollution is not as regulated and it damages coral reefs. Also many mangroves are cleared to build these farms.
2. US boats are required to have turtle excluder devices (TED) on trawl nets so that turtles do not get caught in shrimp nets and drown. Other countries do not regulate this and as a result catch and drown sea turtles.
To make a environmentally responsible seafood choices, choose shrimp that are farmed or caught in the US. For more sustainable seafood choices, check out Seafood Watch.
Friday, November 15, 2013
Netting is the most popular method of commercial fishing because a lot of fish can be caught in short amount of time without a lot of effort.
One the major problems with most commercial fisheries is the amount of bycatch. Bycatch is anything caught in the net that you do not want. This could include edible fish that your company is just not equipped to process.
Most organisms brought up in nets as bycatch do not survive because they are crushed or drowned. Sea turtles and dolphins sometimes get swept into nets and drown because they cannot make it to the surface to breathe.
Most scientists and fisherman agree that the oceans have been and are being overharvested. People may not like regulations, but without regulations, many fish species that we used to commonly consume would be extinct.
There are many ways to harvest fish. If you want more information, check out the links at Monterrey Bay Aquarium's Seafood Watch Organization.
Wednesday, November 13, 2013
Friday, November 8, 2013
Fish reproduce in a variety of ways. Most are broadcast spawners, meaning that when the time is right, the females release their eggs, the males release their sperm. The gamestes meet and mix producing fertilized eggs that develop into meroplankton fish fry and eventually into adult fish. These snapper are spawning and you can tell by the large cloud of gametes in the water.
By producing a lot of eggs, the snapper hope to overwhelm any predators trying to make a meal so that there is no way all the fry are eaten and some will have a chance of surviving.
Some fish do pair bond. In these instances one or both fish will guard the eggs until they hatch into baby mero-plankton, and then once again, the fish fry on their own. There are very very few fish that provide juvenile care.
In seahorses and their relatives, the female transfers the eggs to the male to care for until they hatch. He attaches them to his belly (or into his pouch) and once that set hatches, she gives him another to raise. This allows the seahorses and their relatives to constantly produce offspring. This photo is of a male leafy sea dragon carrying an egg mass (pink).
Wednesday, November 6, 2013
Many fishes are identified by looking at or into the mouth. The number of mouth-types exhibited by different species is nothing short of astonishing. Three lakes in Africa contained about 900 species of cichlids, nearly all differentiated mainly by the way their mouths are shaped. (This number is rapidly dwindling, by the way, as the cichlids in these lakes are driven to extinction). Cichlid mouths are variously adapted to eat other cichlids' eggs, scales pulled from fishes' living bodies, algae from rocks, tiny invertebrates, and many other forms of food. The arrowana of South America has a mouth adapted for spitting water with precision at insects perched on overhead branches. Parrotfish mouths have evolved to look and act like beaks, which they use to grind at coral, making the sand that surrounds coral reefs. Seahorses and pipefish have tubular mouths for sucking in small prey in narrow places like a vacuum cleaner. SOURCE
Fish with forward facing mouths eat what is in front of them - no surprise. Downward mouths eat algae, prey below them like crustaceans and molluscs, or they take in mouth fulls of gravel, eat the particles, and spit the gravel back out. Upward facing mouths indicate the fish eats prey above them - typical of benthic ambush predators. There are also bills and beaks. Bills are long and skinny used for poking in crevices and eating plankton one at a time. Beaks are used for chomping and can be seen on the parrotfish, a fish that chomps on the algae growing on the surface of dead coral. Fish can also have very large mouths common on filter feeders and fish that swallow large prey whole. Fish also have teeth - a surprise to many - and come in many shapes and size.
Body shape also tells you a bit about a fish. Com- pressed fish have flash and look skinny and can only be found in slow moving waters like coral reefs. Fusi-form fish are tapered like footballs and are very streamlined for constant fast swimming. Depressed fish are benthic and squashed looking. Eel shaped fish are poor swimmers and live on the benthos or in cracks and crevices.
Here is a website you can use to identify shapes - realize they are named a bit differently than how I do in class.
Fish tails (caudal fin) indicate how fast and how much a fish swims. For this class, we are focusing on the crescent (not pictured), forked (e), square (d), rounded (b), and funky (c, f, h). As you can see there are more fish tail shapes out there.
Crescent caudal fins indicate a very fast fish that is constantly swimming - not time for resting, it is time to go go go! Forked caudal fins are the second fastest, and very maneuverable. Square fins are for your every day swimming fish - they have ok acceleration ad maneuvering. Round fins and Funky fins are slooooooow swimmers that don't spend a lot of time swimming. They can be quick for very short bursts.
Monday, November 4, 2013
Pictured to the right, you can see five lamprey mouths and one lamprey head with blue eyes and seven gill holes.
Jawless fish include lampreys which are parasites and hagfish which are detritavores. Neither one will ever win a beauty contest.
Computer Lab Etiquette
You are in the computer lab to do work for this class. If you are not doing work, then we will have problems.
Do not pack up early. Work until the bell or until MsJ says.
SAVE OFTEN. And if you save to a key, also save it to your number. If you lose it, you will have to do it again.
If MsJ asks for your attention, stop what you are doing and listen to what she has to say.
You may watch videos about your organism through reliable websites.
You may listen to music through the computer if you have your own headphones. Rule1 MsJ cannot hear it. You get one warning. Rule2 Turn it on and listen – no million clicks and constant changing. Take both ear phones out when MsJ is talking.