Introduction:
On this laboratory each person will be assign a specific animal in which they will have to dissect and then present it to the classroom. The animal I was given was the Romalea guttata commonly known as the “Eastern lubber grasshopper”. The species name guttata is Latin for spotted. Common lubber name means a clumsy or lazy person referring to their slow movements. The Romalea guttata are well known for its size and its unique coloration. Males usually grow from 45 to 55 mm while females tend to reach at least 50 to 70 mm. They have a vivid yellow/red coloration and they are flightless. The eastern lubber grasshopper is limited to the southeastern and south central portion of the
The body of the Romalea guttata is surrounded by an exoskeleton. The benefits of an exoskeleton are: armor- like protection from physical and chemical damage, also is an excellent platform for attachment of muscles, and provides an effective barrier against disease. The only disadvantage is that growth is limited until the exoskeleton is shed or molted. Usually grasshoppers shed their exoskeleton around 5 to 6 times until they reach their full maturity. One of the major components of the arthropod exoskeleton is chitin. Chitin is a biological substance which may be compared to the polysaccharide cellulose. Insects use chitin to create a hard plastic-like substance around the entire body for protection.
The external anatomy of both male and female is divided in to three parts: head, thorax, and abdomen. The head is a functional unit that performs many various tasks: the major sensory area, the ingestion of food, and processes all body activities. The grasshoppers use the labrum, labium, and maxillae to hold the food between and against the mandibles which grinds the food. The palpi which are small muscles resembling antennas help manipulate the food and serve as taste detectors. In interesting fact is that grasshoppers have a hypopharynx that is a like a tongue that helps to digest food. The antennas are muscles that provide sensory structures for the sense of touch and smell. The most outstanding characteristic is their compound eyes. These eyes are made up of hundreds of separate lenses each with its on photoreceptor. All the lenses work together as one to form a unit called an ommatidium. Grasshoppers also have three simple eyes called ocelli, but they cannot form images. Their function is to sense changes in illumination. The thorax is the middle section of the grasshopper. It is divided into three smaller segments: the prothorax, mesothorax, and metathorax. Each of the segments has a pair of legs that has a coxa which joints the leg to the body, trochanter, femur, tibia and tarsus. We can also find a pair of wings in the thorax section. On the Romalea gutttata the wings never developed so they turn at small and useless for flight. The abdomen section is composed of eleven segments. The first eight segments have a pair of spiracles that is vital for respiratory system. The last three segments determine the animal’s sex and the last segment has the cerci which are sensory structures.
The respiratory system consists on a series of tubes or trachea that distributes gases throughout body tissues. The spiracles which are the openings were oxygen and carbon dioxide enters are located in the abdomen area. The air travels inside the tracheal tubes and is disperse throughout the body. The digestive system gives the energy the animal needs to survive. The hypopharynx or tongue manipulates the food for swallowing. Meanwhile the salivary glands are working together by providing saliva so that the food can be chewed with ease. The food then travels to the esophagus and then to the crop organ where the food is grinded into small particle for digestion. After that the food enters the stomach and digestive enzymes are released from the gastric ceca. The nutrients are later absorbed and the remains travel to the intestines where the water is being absorbed. This causes the waste material to dry up into a small pellet in the rectum where it will be release through the anus.
Grasshoppers have an open circulatory system, with most of the body fluid filling up body cavities and appendages. The heart is a dorsal vessel that extends from the head to the hind end. The hemolymph is the blood used by all arthropods it fills up all the interior of the body and surrounds all cells. The hemolymph travels through the body throughout a series of chambers inside the dorsal vessel called ostia. When it reaches the aorta located in the head segment the blood is dispersed around the front of the head. Then pumps carry blood around the entire body all the way back to the abdomen where it begins its cycle again. The hemolymph distributes nutrients all over the body. The excretory system is made of malpighian tubules located in the abdomen area. There function is to remove urea from the hemolymph. The hemolymph Is composed of water, inorganic salts, and organic compounds.
The nervous system is made of a series of ganglions that are masses of nerve cells that serve as processing centers. The brain has three ganglions called: optic ganglion, cerebral ganglion, subesophageal ganglion. Each of these has a specific function that it to help maintain vision, to process information and for digestion. Each segment in the body has its own ganglion and five are located in the rear end. All of ganglions are connected through the ventral nerve chord which is like a chain-like structure. Because of this you can remove the head of the insect and the animal will still be able to function properly.
The reproductive system consists on the male grasshopper introducing sperm into the ovipositor through its aedeagus. The aedeagus is a reproductive organ males have that secretes the sperm from the testes and then surrounds the sperm with a cover called spermatophores. Once inside the ovipositor the spermatophones travel to the ovaries where they join together with the eggs to from an embryo. Finally the female deposits the eggs on the soil through the ovipositor. The embryo has to be held at a constant temperature of 30 degrees Celsius. That is why most Romalea guttata are born during fall. They also appear to have a shutdown of growth hormones which makes their developed slow and have stages.
Purpose:
The purpose of this experiment is to identify and analyze the anatomy and physiology of the Romalea guttata. One of the purposes is to learn the external and internal anatomy of the organism we are assign. We must also learn the function that each organs has and how they work together to perform different tasks.
Procedure:
- Find a Romalea guttata for dissection.
- Have all the materials necessary for work. Including dissecting equipment, gloves, dissecting tray, apron, goggles, the specimen, and text book or any other reference.
- First you must identify all of your equipments with labels.
- You will commence the dissection by determining out the animal’s sex.
- Then you will cut off the Romalea six legs and wings.
- After that you will have to pin down the body to the dissecting tray with four pins.
- Once this is done you may commence cutting the grasshopper with the scalpel from the rear end to the thorax and then around returning to the starting point.
- Afterwards you can remove the exoskeleton and you will have all of the specimens organs exposed.
- Then you will need to identify all of the organs of the body.
- You will need to present it to the teacher with an oral presentation.
- Finally you can clean up all of the materials you used.
Scientific name: Romalea Guttata
Common name: Eastern Lubber Grasshopper
Type: Herbivorous insect
The three pairs of legs and the two pairs of wings were remove from specimen.
The exoskeleton was cut out so that the organs may be exposed.
All the major organs were identified.
- Brown - Crop
- Green - Gastric ceca
- Red - Stomach
- Orange - Oviduct
- Blue - Intestines
- Yellow- Rectum
- Violet - Malpighian tubules
Diagram that demonstrates the six stages of the grasshoppers development.
Diagram of a female grasshopper showing characteristic external features.
Grasshopper head, front, side, and top views.
Grasshopper pronotum, side and top views.
Grasshopper hindleg, views of outer and inner faces.
Bandwinged grasshopper with left wings spread, top view.
Grasshopper male abdomen, side view and enlarged side and dorsal views of end.
Discussion:
The experiment began by identifying the animal’s sex. After determining it was a female. I began cutting down the three pairs of legs and the two pairs of wings. Then I pin down the so that it will be facing up. I used the scalpel and the scissors to cut down the exoskeleton. The exoskeleton was completely removed leaving all the organs exposed while the right parts of the body staid intact. After removing the skin I went on to identifying all the major organs. The hardest problem was removing the exoskeleton without destroying the entire specimen. Since it is a small creature I had to very delicate and have patience. The organs were very easy to spot and identify.
Conclusion:
The experiment was a success and the purpose was accomplished. I was able to make a perfect dissection of the Romalea guttata and identified all of its major organs. I learn how they function together as a team so that the circulatory, reproductive, digestive, nervous, and excretory system can be performs. I had never done a dissection and I was a great experience to learn from. Cutting the Romalea was difficult because of its small size, but at then I was able to do it thanks to the help of my classmates. One of my classmates was kind enough to take pictures of my specimen so that I may put them on the blog later on. This dissection taught me the similarities us humans have with different animals. Some of the interior organs are the same that we have and their digestive system is a lot similar to ours. I would recommend that the next group be more prepare by gathering more background information on the specimen they choose.
Reflection:
I had a great time making this experiment. It was something new I have never done before. Last year we didn’t get to dissect any animals so it was a unique experience for me. The beginning was very difficult because I wasn’t sure on how I was going to open the body. After the help of a few fellow classmates I was able identify all the organs with ease. For our final test we will dissect a fetal pig I can’t wait for that experience. I manage to take a look inside the pig’s anatomy and it’s very much complicated than the grasshopper. It posses a challenge I want to face and learn from.
Reference:
- Grasshoppers: Their Biology, Identification and Management. Retrieved October 5, 2008, from ID Tools - Field Guide to Common Western Grasshoppers: External Anatomy Web site: http://www.sidney.ars.usda.gov/grasshopper/ID_Tools/F_Guide/extanat.htm#2
- Whitman D.(2006). Invertebrate Anatomy Online. Retrieved October 5, 2008; from http://webs.lander.edu/rsfox/invertebrates/romalea.html.
- Clay Scherer,
