Squid Virtual Dissection Lab

Loligo sp. By:Willaim Colton

Background Information

Loligo, like most squids, have 8 arms and 2 feeder tentacles and are predatory. Loligo also have a beak used to break up prey.These are common inshore squids from the Eastern Atlantic Ocean. They are fished and consumed by humans, therefore we do have an effect on them.

Reproductive System

Male loligo's reproductive system consists of the testis, penis, and the siphon which is used to release the sperm. The female loligo only have a single ovary with many clusters of eggs. During mating the males and females will mix and pair up. The males will then court the females by putting on a show using their color changing ability. Males also have a specially adapted arm used to transfer his sperm to the female. hence, fertilization occurs and mating is finished

Objective

Today we will be dissecting a Loligo sp. squid virtually. Begin by taking a close look at the squid in the video. You can clearly see its tentacles, arms, fins, eyes, and siphon. The head would be the ventral region and the other end with the fins is the dorsal region. The top of the squid without the siphon is the anterior and the side with the siphon is the posterior. Now make a crescent shaped incision just above the siphon on the posterior dorsal side. Then pin down the flaps of skin. You should be able to clearly see the squid's internal organs. The red clump you would see is the heart. The feathery organs attached to the pulled back flaps are the gills. The black organ you see below the heart is the ink sack used to produce ink that defends the squid from predators. Below the heart their is a "whitish finger like structure" that is the stomach. Then above the heart is the secum, the long white organ that produces digestive enzymes. Below these organs is the intestine which stretches the length of the body. This is a male squid, meaning it has male reproductive parts. The testis is located near the head and is a clear finger like structure in a pair with the vas deferens which the sperm passes through to get to the penis. In a female the ovaries would be the first thing you would see, because they would cover all the other organs usually visible with a male squid. The penis would be a whitish tube running the length of the squid behind the organs near the intestines. Next to the penis, finally, is the pen made of chitin used to support the squids body and protect its organs.
Squid Anatomy

Loligo Sp. Specifications

Taxanomy

Phylum- Mollusca

Class- Cephalopoda

Order- Teuthida

Family- Loliginidae

Genus- Loligo

Evolution

Squids are a cephalopod, meaning they are related to clams, conches, and octopi. The earliest know squid was around 60 million years ago. The physical variation of the squid body has not changed very much after all these years. This shows that they haven't had to change as much to survive. A feature in squids that might show they evolved from a type of shellfish is the internal gladius. This organ is only found in shellfish and the squid. The main problem is their are a lot of missing pieces to the squid's evolutionary puzzle and until we can find more we can only guess based on what is available.

Ecology

Squids can be characterized by their rapid growth, short life spans, early maturity and quick population turnovers. Squids play an important role as both a predator and a prey item in an ecosystem. Squid populations around the world are rising because of the removal of their natural predators by fisheries. The average squid life span is a year with tropical squids being closer to 200 days. With their fast reproduction rate and short life span the squid places a major role in ecosystems world wide.

Body Systems

Squids are bilateral in symmetry. They have a closed circulatory system with three hearts. Respiration is caused by the gills when oxygen and water are taken in through the mantel and carbon dioxide is released with feces through the siphon. The digestive system begins at the beak where it travels to the stomach in the mantel then back down through the intestines to the siphon. The squid feeds by catching prey in its tentacles, then bringing them it its beak.

Human Impact

Millions of tons of squids are harvested each year by the fishing industry, but the major problem that humans cause is water pollution. Squids reproduce at exponential rates allowing them to deal with predation, but when the water they need to live in is poisoned this can kill an entire population. Global warming also has an effect on the squid. The high the temperature the shorter the life span of the squid. The raised temperate also messes up their mating cycles and can cause a lack of reproduction. Currently their is not any major harm done to the squid population, and their is no recent risk of extinction, but we still need to keep a close eye on their environment and how we affect it.