According to the Columbia Electronic Encyclopedia (2009) horseshoe crabs are large primitive marine arthropods related to the spider. They are distinguished by a heavy dark brown exoskeleton or carapace, which is doomed and shaped like a horseshoe. Their body is divided into a broad flattened semicircular front part, the prosoma, a tapering middle part, the opisthoosma, and a pointed spiky tail like part, the telson. They have no jaws, and the mouth is flanked by a pair of pincer like chelicera that are used to crush worms and other invertebrates taken as food. Five pairs of walking legs attached to the prosoma enable the animals to swim awkwardly or burrow through the sand or mud. The respiratory organs are called book gills and are unique to horseshoe crabs. Each book gill is made of about 100 thin leaves, or plates; these are fitted like pages of a book onto one pair of flap like appendages on the opisthosoma. Rhythmic movement of the appendages circulates water over the gill surfaces and drives blood into and out of the gill leaves. They first appeared in the Upper Silurian period, and a number of fossil species have been described. Five species still survive; four of these are found along the Pacific coast of Asia. The American species, Limulus Polyphemus, is common along the Atlantic coast from Nova Scotia to Florida. They live in shallow water, preferring soft or sandy bottoms, and reach a maximum length of nearly 2 ft.
National Geographic (1999) reports horseshoe crabs resemble fossilized trilobites and eurypterids of the Paleozoic era. They have changed little since an ancestor was fossilized 150 million years ago. Spawning crabs swarm Delaware Bay beaches in spring, fueling an egg-eating frenzy of gulls and migratory birds. Fishermen kill crabs for bait. Studies suggest that populations are dropping, leading some states to restrict harvests. By decoding their visual system, researchers have learned much about human sight. Crabs are also bled to extract a reagent used to test drugs and medical devices for contamination.
Horseshoe crabs are members of the phylum Arthropoda, arthro meaning joint and poda meaning foot. This is the most numerous phyla of all living organisms in both number of species and number of individuals. Conservative estimates are that well over one million species of insects exist. As far as individuals are concerned there are more ants than anything else, and there are more kinds of beetles than any other species. Between 40 and 50% of all insect species are beetles. There are more insects than all other animals and plants combined (Carter, 1997).
Arthropods have segmented bodies covered by an exoskeleton made from chitin and other chemicals. The exoskeleton serves as protection and provides places for muscle attachment. Because their exoskeleton doesn’t grow with them Arthropods must molt. Their circulatory system is open and consists of a dorsal heart which collects blood from the body cavity and pumps it back into the body cavity again. In insects, the anterior portion of the heart, located in the abdomen, is extended into a tube, the aorta, which directs the blood forward as it goes out into the body cavity. Arthropods have a well-developed, mesodermal, ventral, solid nerve cord and well-developed sense organs. The body feature from which the phylum takes its name is the jointed appendages, which include antennae and mouthparts as well as walking legs.
Arthropods early ancestors had a number of body segments, each with a pair of jointed appendages and looked similar to a centipede. From there, some of these segments became fused to form a head and some of the appendages became modified to form mouthparts or antennae. Early on, there was an evolutionary split which led to the various modern subphyla and classes. Currently, three living subphyla are recognized, with trilobites representing an extinct fourth subphylum (Carter, 1997).
Horseshoe Crabs belong to the subphylum Chelicerata, and are in the class Xiphosura, xipho meaning sword and ura meaning tail. Also in subphylum Chelicerata is class Arachnida, arachni meaning spider. This class includes scorpions, mites, ticks, daddy-long-legs, and spiders.
Subphylum Crustacea, crusta meaning crust or rind, includes crayfish, lobsters, crabs, pillbugs. They have gills, thus terrestrial pillbugs need to maintain a 100% humidity environment around their gills to be able to “breathe.” Crustaceans have the head and thorax combined into one body region, the cephalothorax, as well as an abdomen. They have two pairs of antennae, mandible-type mouthparts (of different evolutionary origin than mandibles in insects), and other mouthparts which include two pairs of maxillae and three pairs of maxillipeds, all of which are formed from modified appendages.
Subphylum Atelocerata includes insects, centipedes and millipedes. Members of this subphylum have one pair of antennae, mandibles, and two other pairs of mouthparts, either two pairs of maxillae or one pair of maxillae plus a labium, which are modified appendages.
Members of the fourth subphylum, Trilobita, are now all extinct. Their bodies were divided into three sections, lobes, a head and a body region.
Carter, J.S. (1997). Phylum Arhropoda. UC Clermont College Biology Home Page. Retrieved September 14, 2010, from http://biology.clc.uc.edu/courses/bio106/arthrpod.htm
NAI. (1999, February). Horseshoe crabs. National geographic, Vol. 195, Issue 2. Retrieved September 14, 2010, from http://web.ebscohost.com/ehost/detail?vid=7&hid=7&sid=69110e3d-d254-4915-a7c7-bed5e36affaf%40sessionmgr12&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aph&AN=1440406
NAI. (2009, December 1). Horseshoe crab. Columbia electronic encyclopedia, 6th Edition . Retrieved September 14, 2010, from http://web.ebscohost.com/ehost/detail?vid=4&hid=7&sid=2bdf4e92-2120-48e7-9941-1005ce6b0446%40sessionmgr14&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aph&AN=39012259
Are you busy and do not have time to handle your assignment? Are you scared that your paper will not make the grade? Do you have responsibilities that may hinder you from turning in your assignment on time? Are you tired and can barely handle your assignment? Are your grades inconsistent?
Whichever your reason is, it is valid! You can get professional academic help from our service at affordable rates. We have a team of professional academic writers who can handle all your assignments.
Students barely have time to read. We got you! Have your literature essay or book review written without having the hassle of reading the book. You can get your literature paper custom-written for you by our literature specialists.
Do you struggle with finance? No need to torture yourself if finance is not your cup of tea. You can order your finance paper from our academic writing service and get 100% original work from competent finance experts.
While psychology may be an interesting subject, you may lack sufficient time to handle your assignments. Don’t despair; by using our academic writing service, you can be assured of perfect grades. Moreover, your grades will be consistent.
Engineering is quite a demanding subject. Students face a lot of pressure and barely have enough time to do what they love to do. Our academic writing service got you covered! Our engineering specialists follow the paper instructions and ensure timely delivery of the paper.
In the nursing course, you may have difficulties with literature reviews, annotated bibliographies, critical essays, and other assignments. Our nursing assignment writers will offer you professional nursing paper help at low prices.
Truth be told, sociology papers can be quite exhausting. Our academic writing service relieves you of fatigue, pressure, and stress. You can relax and have peace of mind as our academic writers handle your sociology assignment.
We take pride in having some of the best business writers in the industry. Our business writers have a lot of experience in the field. They are reliable, and you can be assured of a high-grade paper. They are able to handle business papers of any subject, length, deadline, and difficulty!
We boast of having some of the most experienced statistics experts in the industry. Our statistics experts have diverse skills, expertise, and knowledge to handle any kind of assignment. They have access to all kinds of software to get your assignment done.
Writing a law essay may prove to be an insurmountable obstacle, especially when you need to know the peculiarities of the legislative framework. Take advantage of our top-notch law specialists and get superb grades and 100% satisfaction.
We have highlighted some of the most popular subjects we handle above. Those are just a tip of the iceberg. We deal in all academic disciplines since our writers are as diverse. They have been drawn from across all disciplines, and orders are assigned to those writers believed to be the best in the field. In a nutshell, there is no task we cannot handle; all you need to do is place your order with us. As long as your instructions are clear, just trust we shall deliver irrespective of the discipline.
Our essay writers are graduates with bachelor's, masters, Ph.D., and doctorate degrees in various subjects. The minimum requirement to be an essay writer with our essay writing service is to have a college degree. All our academic writers have a minimum of two years of academic writing. We have a stringent recruitment process to ensure that we get only the most competent essay writers in the industry. We also ensure that the writers are handsomely compensated for their value. The majority of our writers are native English speakers. As such, the fluency of language and grammar is impeccable.
There is a very low likelihood that you won’t like the paper.
Not at all. All papers are written from scratch. There is no way your tutor or instructor will realize that you did not write the paper yourself. In fact, we recommend using our assignment help services for consistent results.
We check all papers for plagiarism before we submit them. We use powerful plagiarism checking software such as SafeAssign, LopesWrite, and Turnitin. We also upload the plagiarism report so that you can review it. We understand that plagiarism is academic suicide. We would not take the risk of submitting plagiarized work and jeopardize your academic journey. Furthermore, we do not sell or use prewritten papers, and each paper is written from scratch.
You determine when you get the paper by setting the deadline when placing the order. All papers are delivered within the deadline. We are well aware that we operate in a time-sensitive industry. As such, we have laid out strategies to ensure that the client receives the paper on time and they never miss the deadline. We understand that papers that are submitted late have some points deducted. We do not want you to miss any points due to late submission. We work on beating deadlines by huge margins in order to ensure that you have ample time to review the paper before you submit it.
We have a privacy and confidentiality policy that guides our work. We NEVER share any customer information with third parties. Noone will ever know that you used our assignment help services. It’s only between you and us. We are bound by our policies to protect the customer’s identity and information. All your information, such as your names, phone number, email, order information, and so on, are protected. We have robust security systems that ensure that your data is protected. Hacking our systems is close to impossible, and it has never happened.
You fill all the paper instructions in the order form. Make sure you include all the helpful materials so that our academic writers can deliver the perfect paper. It will also help to eliminate unnecessary revisions.
Proceed to pay for the paper so that it can be assigned to one of our expert academic writers. The paper subject is matched with the writer’s area of specialization.
You communicate with the writer and know about the progress of the paper. The client can ask the writer for drafts of the paper. The client can upload extra material and include additional instructions from the lecturer. Receive a paper.
The paper is sent to your email and uploaded to your personal account. You also get a plagiarism report attached to your paper.
PLACE THIS ORDER OR A SIMILAR ORDER WITH US TODAY AND GET A PERFECT SCORE!!!
We provide professional writing services to help you score straight A’s by submitting custom written assignments that mirror your guidelines.
Get result-oriented writing and never worry about grades anymore. We follow the highest quality standards to make sure that you get perfect assignments.
Our writers have experience in dealing with papers of every educational level. You can surely rely on the expertise of our qualified professionals.
Your deadline is our threshold for success and we take it very seriously. We make sure you receive your papers before your predefined time.
Someone from our customer support team is always here to respond to your questions. So, hit us up if you have got any ambiguity or concern.
Sit back and relax while we help you out with writing your papers. We have an ultimate policy for keeping your personal and order-related details a secret.
We assure you that your document will be thoroughly checked for plagiarism and grammatical errors as we use highly authentic and licit sources.
Still reluctant about placing an order? Our 100% Moneyback Guarantee backs you up on rare occasions where you aren’t satisfied with the writing.
You don’t have to wait for an update for hours; you can track the progress of your order any time you want. We share the status after each step.
Although you can leverage our expertise for any writing task, we have a knack for creating flawless papers for the following document types.
Although you can leverage our expertise for any writing task, we have a knack for creating flawless papers for the following document types.
From brainstorming your paper's outline to perfecting its grammar, we perform every step carefully to make your paper worthy of A grade.
Hire your preferred writer anytime. Simply specify if you want your preferred expert to write your paper and we’ll make that happen.
Get an elaborate and authentic grammar check report with your work to have the grammar goodness sealed in your document.
You can purchase this feature if you want our writers to sum up your paper in the form of a concise and well-articulated summary.
You don’t have to worry about plagiarism anymore. Get a plagiarism report to certify the uniqueness of your work.
Join us for the best experience while seeking writing assistance in your college life. A good grade is all you need to boost up your academic excellence and we are all about it.
We create perfect papers according to the guidelines.
We seamlessly edit out errors from your papers.
We thoroughly read your final draft to identify errors.
Work with ultimate peace of mind because we ensure that your academic work is our responsibility and your grades are a top concern for us!
Dedication. Quality. Commitment. Punctuality
Here is what we have achieved so far. These numbers are evidence that we go the extra mile to make your college journey successful.
We have the most intuitive and minimalistic process so that you can easily place an order. Just follow a few steps to unlock success.
We understand your guidelines first before delivering any writing service. You can discuss your writing needs and we will have them evaluated by our dedicated team.
We write your papers in a standardized way. We complete your work in such a way that it turns out to be a perfect description of your guidelines.
We promise you excellent grades and academic excellence that you always longed for. Our writers stay in touch with you via email.