Hermaphrodite:
A hermaphrodite is an organism having both male and female reproductive organs. In many species, hermaphroditism is a common part of the life-cycle, enabling a form of sexual reproduction in which the two sexes are not separated into distinct male and female types of individual. Hermaphroditism most commonly occurs in invertebrates, although it is also found in some fish, and to a lesser degree in other vertebrates.
Historically, the term hermaphrodite has also been used to describe ambiguous genitalia and gonadal mosaicism in individuals of gonochoristic species, especially human beings. The term comes from the name of the minor Greek god Hermaphroditus, son of Hermes and Aphrodite (see below).
Recently, intersex has been used and preferred by many such individuals, encouraging medical professionals to use the term.
Platyhelminthe:
The flatworms (Phylum Platyhelminthes from the Greek platy, meaning "flat" and helminth, meaning worm) are a phylum of relatively simple soft-bodied invertebrate animals. With about 25,000 known species they are the largest phylum of acoelomates. Flatworms are found in marine, freshwater, and even damp terrestrial environments. A troublesome terrestrial example is the New Zealand flatworm, Arthurdendyus triangulatus, which rapidly colonized large areas of Ireland and Scotland since its unintentional introduction in the 1960s and has since destroyed most of the indigenous earthworms. Most flatworms are free-living, but many are parasitic. There are four classes: Trematoda (flukes), Cestoda (tapeworms), Monogenea, and Turbellaria.
Turbellarian:
Turbellaria are a group of generally small (<1 - 60cm) and free-living members of the flatworm phylum Platyhelminthes. The latter is nowadays mostly considered obsolete (paraphyletic), so the Acoela and Nemertodermata are excluded from the class into a phylum of their own (Acoelomorpha).
Cestoda:
Cestoda is the class of parasitic flatworms, commonly called tapeworms, that live in the digestive tract of vertebrates as adults and often in the bodies of various animals as juveniles.
Trematoda:
The Trematoda is a class within the phylum Platyhelminthes that contains two groups of parasitic worms, commonly referred to as flukes.
Life Cycle:
A life cycle is a period involving 1 generation of an organism through means of reproduction, whether through asexual reproduction or sexual reproduction. In regard to its ploidy, there are 3 types of cycles:
a. Haplontic life cycle
b. Diplontic life cycle
c. Diplobiontic life cycle (also referred to as diplohaplontic, haplodiplontic, or dibiontic life cycle).
These three types of cycles feature alternating haploid and all germinates. To return to a haploid stage, meiosis must occur (see Cell division). The cycles differ in the product of meiosis, and whether mitosis (growth) occurs. Zygotic and gametic meioses have one mitotic stage and form: during the n phase in zygotic meiosis and during the 2n phase in gametic meiosis. Therefore, zygotic and gametic meiosis are collectively term haplobiontic (single mitosis per phase). Sporic meiosis, on the other hand, has two mitosis events (diplobiontic): one in each phase:
Ventral:
In fields of anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species. While these terms are standardized within specific fields of biology, they can differ dramatically from one discipline to another.
The problem in consistency of naming occurs when ambiguous terms like "top" are used, which would be considered the head of a human, whereas for a flounder, the "top" would be the left or right side. In human anatomy, all naming is based on positions relative to the body in a standing (standard anatomical) position with arms at the side and thumbs out. In veterinary anatomy, many terms are given relative to the parts of the body, often in relation to the spine, which allows for consistency in terminology between vertebrate species that naturally assume a variety of positions. While the ears would be superior to (above) the shoulders in a human, this terminology fails when describing the armadillo, where the shoulders are above the ears. In veterinary terminology, the ears would be cranial to (towards the head) the shoulders in the armadillo, the dog, the kangaroo, or any other vertebrate. Similarly, while the belly is considered anterior to (in front of) the back in humans, this terminology fails for the flounder, the armadillo and the dog (although it could work for the kangaroo). In veterinary terms, the belly would be ventral to (towards the abdomen) in all vertebrates. While the universal vertebrate terminology used in veterinary medicine would work in human medicine, the human positional terms are too well established to change.
In invertebrates, locational terminology becomes more complicated, as many species are not bilaterally symmetrical. In these species, terminology depends on the type of symmetry present (if any).
Flame cells:
A flame cell is a specialized excretory cell found in most "lower" freshwater invertebrates, including Nematode, Platyhelminthes (except the tubellarian order Acoela), flatworms, rotifers and nemerteans; these are the simplest animals to have a dedicated excretory system. Flame cells function like a kidney, removing waste materials. Bundles of flame cells are called protonephredia.
The flame cell has a nucleated cell body, with a "cup-shaped" projection, with cilia covering the inner surface of the cup. The beating of these cilia resemble a flame, giving the cell its name. The cup is attached to a tube cell. The inner surface of the tube cell is coated in flagella. The beating of the cilia and flagella help move liquid through the tube cell. The tube opens externally through a nephropore, or, in the trematoda, into an excretory bladder. The function of these cells is to regulate the osmotic pressure of the worm, and maintain its ionic balance. Microvilli in the tube cell may be used to reabsorb some ions.
Proglottid:
The body is composed of successive units posterior to the scolex, the proglottids. The sum of the proglottids is called a strobila, which is thin, resembling a strip of tape, and is the source of the common name tapeworm. Like some other flatworms, cestodes use flame cells (protonephridia) for excretion, which are located in the proglottids.
Mature or gravid proglottids are released from the mature tapeworm and leave the host in its feces.
Because each proglottid contains the male and female reproductive structures, they can reproduce independently. It has been suggested by some biologists that each should be considered a single organism, and that the tapeworm is actually a colony of proglottids.
Scolex:
The Scolex or "head" of the worm attaches to the intestine of the definitive host. In some groups, the scolex is dominated by bothria, which are sometimes called "sucking grooves", and function like suction cups. Other groups have hooks and suckers that aid in attachment. Cyclophyllid cestodes can be identified by the presence of four suckers on their scolex, though they may have other structures.
While the scolex is often the most distinctive part of an adult tapeworm, it is often unnoticed in a clinical setting as it is inside the patient. Thus, identifying eggs and proglottids in feces is important.
Parasite:
Parasitism is a type of symbiotic relationship between organisms of different species in which one, the parasite, benefits from a prolonged, close association with the other, the host, which is harmed. In general, parasites are much smaller than their hosts, show a high degree of specialization for their mode of life and reproduce more quickly and in greater numbers than their hosts. Classic examples of parasitism include the interactions between vertebrate hosts and such diverse animals as the tapeworms, flukes, Plasmodium species and fleas.
The harm and benefit in parasitic interactions concern the biological fitness of the organisms involved. Parasites reduce host fitness in many ways, ranging from general or specialized pathology (such as castration), impairment of secondary sex characteristics, to the modification of host behaviour. Parasites increase their fitness by exploiting hosts for food, habitat and dispersal.
Low Temperature Scanning Electron Microscope (LTSEM) image of the mite, Varroa destructor, on a honey bee hostAlthough the concept of parasitism applies unambiguously to many cases in nature, it is best considered part of a continuum of types of interactions between species, rather than an exclusive category. Particular interactions between species may satisfy some but not all parts of the definition. In many cases, it is difficult to demonstrate the host is harmed. In others, there may be no apparent specialization on the part of the parasite, or the interaction between the organisms may be short-lived. For example, because of the episodic nature of its feeding habits, the mosquito is not considered parasitic. In medicine, only eukaryotic organisms are considered parasites, to the exclusion of bacteria and viruses. Some branches of biology, however, do regard members of these groups to be parasitic
definitive host:
In parasitology, an intermediate host is an organism inside which a parasite does not sexually reproduce. It may grow or reproduce asexually, but there is no exchange of genetic material between individuals. The definitive host is the host in which the parasite reproduces sexually. For example, the broad fish tapeworm Diphyllobothrium latum develops in fish for part of its life cycle but only reproduces sexually when it is in a mammalian digestive tract, so its intermediate host is the fish and its definitive host is the mammal.
As the life cycles of many parasites are not well understood, so