The flatworms, flat worms, Platyhelminthes, or platyhelminths are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates, and have no specialised circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion and egestion ; as a result, the food cannot be processed continuously.
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson characterised parasites as "predators that eat prey in units of less than one". Parasites include single-celled protozoans such as the agents of malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms, lice, mosquitoes, and vampire bats; fungi such as honey fungus and the agents of ringworm; and plants such as mistletoe, dodder, and the broomrapes.
Mutualism describes the ecological interaction between two or more species where each species has a net benefit. Mutualism is a common type of ecological interaction, one that can come from a parasitic interaction. Prominent examples include most vascular plants engaged in mutualistic interactions with mycorrhizae, flowering plants being pollinated by animals, vascular plants being dispersed by animals, and corals with zooxanthellae, among many others. Mutualism can be contrasted with interspecific competition, in which each species experiences reduced fitness, and exploitation, or parasitism, in which one species benefits at the expense of the other.
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation and parasitoidism. It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as seed predators and destructive frugivores are predators.
Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their juvenile form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths as great as 9,000 meters (30,000 ft).
Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit from each other; amensalism, where one is harmed while the other is unaffected; and parasitism, where one is harmed and the other benefits.
In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis, biotic community, biological community, ecological community, or life assemblage. The term community has a variety of uses. In its simplest form it refers to groups of organisms in a specific place or time, for example, "the fish community of Lake Ontario before industrialization".
Aggressive mimicry is a form of mimicry in which predators, parasites, or parasitoids share similar signals, using a harmless model, allowing them to avoid being correctly identified by their prey or host. Zoologists have repeatedly compared this strategy to a wolf in sheep's clothing. In its broadest sense, aggressive mimicry could include various types of exploitation, as when an orchid exploits a male insect by mimicking a sexually receptive female, but will here be restricted to forms of exploitation involving feeding. For example, indigenous Australians who dress up as and imitate kangaroos when hunting would not be considered aggressive mimics, nor would a human angler, though they are undoubtedly practising self-decoration camouflage. Treated separately is molecular mimicry, which shares some similarity; for instance a virus may mimic the molecular properties of its host, allowing it access to its cells. An alternative term, Peckhamian mimicry, has been suggested, but it is seldom used.
The Mesozoic marine revolution (MMR) refers to the increase in shell-crushing (durophagous) and boring predation in benthic organisms throughout the Mesozoic era, along with bulldozing and sediment remodelling in marine habitats. The term was first coined by Geerat J. Vermeij, who based his work on that of Steven M. Stanley. While the MMR was initially restricted to the Cretaceous, more recent studies have suggested that the beginning of this ecological arms race extends as far back as the Triassic, with the MMR now being considered to have started in the Anisian or the Aalenian. It is an important transition between the Palaeozoic evolutionary fauna and the Modern evolutionary fauna that occurred throughout the Mesozoic.
Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word slug is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a small internal shell, particularly sea slugs and semi-slugs.
Platyceras is a genus of extinct Paleozoic sea snails, marine gastropod mollusks in the family Platyceratidae. This genus is known from the Silurian to the Middle Triassic periods and especially abundant in the Devonian and Carboniferous. It is the type genus of the family Platyceratidae.
Paleoparasitology is the study of parasites from the past, and their interactions with hosts and vectors; it is a subfield of paleontology, the study of living organisms from the past. Some authors define this term more narrowly, as "Paleoparasitology is the study of parasites in archaeological material." K.J. Reinhard suggests that the term "archaeoparasitology" be applied to "... all parasitological remains excavated from archaeological contexts ... derived from human activity" and that "the term 'paleoparasitology' be applied to studies of nonhuman, paleontological material." This article follows Reinhard's suggestion and discusses the protozoan and animal parasites of non-human animals and plants from the past, while those from humans and our hominid ancestors are covered in archaeoparasitology.
Littoraria irrorata, also known by the common name the marsh periwinkle, is a species of sea snail, a marine gastropod mollusk in the family Littorinidae. The specific epithet irrorata means 'moistened' or 'dewy.'
Enchophora sanguinea is a species of lantern bug, a type of hemipteran, found in Central and South America. It was first described by William Lucas Distant in 1887. They are 25 millimetres (1.0 in) long. Their colour varies, but is normally red to green; they have a scimitar-shaped process on their heads. They feed on the sap of trees, most commonly Simarouba amara, and they excrete honeydew out of their anuses.
Kelletia kelletii, common name Kellet's whelk, is a species of large sea snail, a whelk, a marine gastropod mollusc in the whelk family Austrosiphonidae.
Cenocrinus is a monotypic genus of stalked crinoids in the family Isselicrinidae. The great West Indian sea lily is the only species in the genus and is found in deep waters in the Caribbean Sea and Gulf of Mexico.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2018.
Endoxocrinus parrae is a species of stalked crinoids of the family Isselicrinidae. It is the most commonly found isocrinine species in west Atlantic Ocean.
Notocrinus virilis is a marine invertebrate, a species of crinoid or feather star in the family Notocrinidae. It is found in deep water in the Southern Ocean around the coasts of Antarctica and adjacent islands. A sea snail sometimes parasitizes it.
Cenometra bella is a species of crinoids belonging to the genus Cenometra. They can have up to 30 arms and can be of variable colours but are often characterised by a marked contrast between the extending free-arms and the feathery pinnules. This species clings to its support and moves around by its feet-like cirri.
