Crustacean Life Cycles

CRABS: The crab life cycle consists of a stage called a Zoea, which is usually planktonic. Zoea look nothing like adult crabs. They are transparent, have elongate, shrimp like abdomens, and have long spines protruding from their backs. Over time, they change into the Megalops, which has more of the adult crab features, including claws, though the abdomen still trails out behind them. As they mature, the abdomen retracts under the body, officially entering the juvenile stage. After that point, they mostly grow bigger, with minimal physical changes, until they reach reproductive maturity.

SHRIMP

The shrimp's life cycle undergoes many stages. It starts with a small, feathery, planktonic larva called a Nauplius. Over time, the Nauplius elongates, and turns into a Zoea, at which point its appendages begin to specialze, and mouth parts develop. It then undergoes a the Mysis stage, when the swimmerets and walking legs are distinguished fom each other. It then grows, through the juvenile stage, before finally becoming an adult.

LOBSTER:

The Lobster life cycle is much more linear, with a series of stages that progress over the course of several weeks. Then there are no physical changes for months, only size increase until reproductive maturity.

Speculative Evolution: Inventing a New Species of Cephalopod

My assignment was to invent a new species of cephalopod, incorporating characteristic features and adding a new adaptation.

Phylogeny:

Kingdom Animalia, Phylum Mollusca, Class Cephalopoda, Order Octopoda, Family Octopodidae, Genus Sauroctopus, Species autotomata. Its name means "Lizard Octopus that can sever a part of itself."

Description:

Characteristic Octopus Featrures:

Like all members of the octopoda, Sauroctopus autotomata has eight arms, which are covered with smooth suckers along the entire length of the arm. It has two vestigial peices of its former shell, called stylets. An octopus has one central brain, with the esophagus running through its center, and eight smaller brains that govern the arms. They are the only invertebrate group that uses tools, e.g coconuts for shelters. All octopuses are venomous.

New Adaptations:

S. autotomata was discovered off the eastern coast of Australia. It was named for its "scale like" chromatophores, and its capability of autotomy, which was discovered by researchers while trying to capture a specimen. When one of the researchers managed to corner it, it spontaneously amputated several of its own arms near the tips, and sprayed a cloud of ink to get away.

Later, a different individual was captured, and it also amputated one of its arms. The arm was observed to continue flailing and writhing for an hour after amputation.

It appears this trait evolved as a predator evasion tactic, but could be used as an offensive strategy as well.

S. autotomata also uses photophores in the arm tips, probably to lure the predator away from the rest of the animal. Laboratory specimens have been shown to use the glowing tips to lure prey as well. Another unique adaptation is that, instead of cutting off at the base, it can amputate at almost any point on the arm. It was capable of regrowing the arm, like other octopus species can. It appears that, upon amputation, a bundle of stem cells form at the site, and then develop into the cells needed to make an octopus arm. Studies are currently underway to see if a similar technique could be applied to human stem cell research.

Note: After I created the above concept, I discovered that Wunderpus photogenicus is capable of autotomy, however I modified the idea to include adaptations from Octopoteuthis deletron, a type of squid. I guess this shows how impressive the cephalopods are. Even the strangest ideas I could come up with have already evolved!

How Cephalopods Change Color

QUESTIONS:

1. Based on the data table (see below), what is the most common method used to change color?

Chromatophores.

2. What method is responsible for the metallic rings in the deadly blue ringed octopus?

Iridophores.

3. Write a summary of what you have learned by viewing these photographic images of cephalopods. Include the four waysin which cephalopods display color.

It appears to me that the most commonly used method is chromatophores. Chromatophores are small disks of color, which are expanded and contracted by muscles to create patterns. In many cases, they are connected directly to nerves, which trigger them, allowing the cephalopod to change color very rapidly.

Iridophores are the next most common. Iridophores are stacks of platelets that reflect light, and are often used to conceal organs, and to cover chromatophores to hide color. They emit irridescent greens, blues, and silvers.

Leucophores are not as common, based off of the data table. Leucophores reflect light, allowing an animal to conceal itself better. They are flat, branching cells. They typically reflect white or blue light.

The rarest by far are Photophores, which are bioluminescent cells, or small sacs with bioluminescent bacteria. Bioluminescence is a chemically created emission of light. Photophores are useful for concealment in deep ocean environments. Typically, in a deep ocean environment, they would produce a bluish color.

Cephalopods can use a combination of these methods, and can also change their texture.

DATA TABLE:

Cuttlefish: Kings of Camouflage Worksheet

My handwritng is bad, so i am going to type this up.

1. Cuttlefish are related to slugs, both of which are in the phylum Mollusca.
2. Cuttlefish are found off the coasts of Europe and Australia.
3. Cuttlefish can change their texture and color pattern.
4. The Broad Club Cuttlefish can either sneak up on its prey disguised as a coral, or it can use a dazzling pattern, which seems to stun their prey.
5. Yellow, Red, and Brown.
6. Blue, Green, Red, and Pink.
7. Muscles open the chromatophores, showing more color. When the muscles let go, the chromatophore shrinks and less color shows.
8. W-shaped.
9. Conditioning. At first, the cuttlefish ignored the toy. Once the toy was associated with food (by consistently providing food shortly after putting it in the tank), it became extremely important to the cuttlefish, even when they stopped giving the food along with it.
10. The males outnumber the females approximately 10 to 1, and the females are extremely selective.
11. A sneaker male cuttlefish is a smaller male, that acts like a female to sneak past the bigger, stronger male, so that they can mate with the females.
12. They join their 8 arms facing head to head, and the male reaches out with a specialized arm and gives the female a sperm packet, which she stores under her arms. She mates with several males, and then chooses which sperm package to use.
13. Sneakers, because they are showing intelligence. About 70% of matings are rejected, but only 30% of sneaker males are rejected.
14. Crevasses on the undersides of rocks.
15. Mating.
16. Because they have given up their body armor over the course of evolution, and therefore need to be intelligent to outwit predators and survive.
17.First, they have a vestigial cuttlebone, which means they walk on the seafloor most of the time, unlike other cuttlefish. Second, they are the only known poisonous species of cuttlefish.
18. As a warning to potential predators that it is highly poisonous.
19. They squirt acid from the tip of their tail to squirt acid through the eggshell.
20. The flesh and muscle.