Nematomorpha are a phylum of parasitoid animals superficially similar to nematode worms in . “Biology of the phylum Nematomorpha”. Advances in. In this article we will discuss about Phylum Nematomorpha: 1. Characters of Phylum Nematomorpha 2. Taxonomic Retrospect of Phylum Nematomorpha 3. PHYLUM NEMATOMORPHA(nema, thread + morphe, form). Nematomorphs are a small group of about species. They are elongated worms. They are.
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The phylum Nematomorpha also known as horsehair worms is comprised of two orders: Nectonematoidea monogeneric Nectonemawith four known species pyylum Gordioideain which the remainder of the over described nematomorphan species are placed. There are 19 currently recognized genera within Nematomorphaand estimates of global species diversity for this phylum are as high as 2, While Nectonema species are marine, planktonic worms, gordioids are found in freshwater, most commonly along the banks of ponds and streams, and some are semi-aquatic and live in damp soil.
Nematomorphans are parasitic as larvae Nectonema species parasitize marine invertebrates, while gordioids utilize terrestrial arthropods and are free-living and aquatic as adults. Brusca and Brusca, ; Hanelt, et al. Nectonema species are found in coastal, marine, and pelagic environments as adults, and are found as parasites in decapod crustaceans as larvae.
Gordioids are found in freshwater streams and ponds ndmatomorpha adults a few are found in damp soil and most typically in terrestrial insects, as parasitic larvae.
They are known from every continent, with the exception of Antarctica. Brusca and Brusca, ; Shapiro, Generally speaking, nematomorphans are found in aquatic or occasionally terrestrial either as semi-aquatic individuals themselves or within terrestrial hosts environments throughout the world.
Adult Nectonema species are free-swimming and pelagic, and are sometimes found near the coast during high tides. They are most often collected as larvae from their decapod crustacean hosts. Gordioids may be found in nearly any freshwater environment, including not only rivers, lakes, and streams, but even puddles or grasses after a heavy rain. They are also found as parasitic larvae in their hosts, which are typically terrestrial arthropods and insects.
Nematomorphans can be up to 1 meter long 10 to 20 cm on average and 1 to 3 mm in diameter. They are typically tan to black in color. Adult nematomorphans are covered in a very thick cuticle that is secreted by the epidermis and is comprised of two layers.
The outer layer often bears areoles groups of bumps, warts or papillae.
Biology of the phylum nematomorpha.
Some areoles have an apical spine likely touch-sensitive or pore potentially lubricant producingand the spatial patterning of these areoles is often used as a diagnostic characteristic at the species level.
The epidermis is unciliated and very thin, covering a thin basal lamina and produced into either one dorsal or two dorsal and ventral cords containing nerve tracks.
Under these layers is a thick sheet of longitudinal muscles, which gives rise to the rete system hollow tubular extensions ; these muscles also play a large role in providing body support. Depending on the species, nematomorphans may have a spacious blastocoelom e. Although they are unciliated, nematomorphans possess natatory bristles that aid in swimming and floating. Some species have two or three caudal lobes at their posterior ends. Nematomorphans are somewhat sexually dimorphic, as a male’s cloaca may be swollen and serve as seminal vesicles.
Development of Nectonema species has not been studied in great detail, in contrast to that of gordioids. In these latter species, fertilized eggs are released by females and laid in gelatinous strings.
Cleavage is holoblastic, but not clearly spiral or radial, and leads to a coeloblastula stage. They have 2 to 3 rings of cuticular hooks and stylets, which they use to penetrate their hosts. Gordioid eggs develop into semi-sessile larvae over 7 to 14 days and can survive for up to two weeks before finding a host. They cannot swim and are found at the bottom of the water column. Larvae may be ingested directly by a host or, more often, they are ingested by paratenic hosts definitive hosts are not typically aquatic.
Once in a paratenic host, a larva will encyst, remaining there for up to a year. The encysted larvae are ingested by the definitive puylum when it feeds on the paratenic host. Larvae grow into juveniles within their hosts, which may take anywhere from 4 to 20 weeks.
They molt once before leaving their hosts, at which point they have usually reached their full adult sizes, often filling the entire buology cavities of their hosts.
Biology of the phylum nematomorpha.
Juveniles must be released into water and current research indicates that nematomorphans have the ability to influence their hosts’ behavior in order to insure this; infected cricket hosts such as Nemobius sylvestris are known to behave erratically, to the point of suicidally jumping into water when the juveniles are ready to be released.
Observations of mating indicate male nematomorphans become highly active during breeding in response to the presence of potential mates. Upon locating a receptive female, a male will wrap his body around her, dropping sperm near her cloacal pore. From there, it is assumed that sperm enter the cloaca, fertilizing eggs in the seminal receptacle.
Nematomorphans are sometimes found in large breeding knots. A female may lay millions of eggs during her lifetime. Nematomorphans are dioecious and reproduce sexually. Males have one or two testes, which open to a cloaca via a sperm duct.
The cloaca may become swollen, acting as a seminal vesicle. Females may have a pair of elongate ovaries, which open to the cloaca via a seminal receptacle, or no ovaries at all, with oocytes scattered throughout the body cavity.
A female may lay millions of eggs during a breeding season. Nematomorphans are known to breed during the late spring, summer, and early fall, and are capable of overwintering. A newly identified species of gordioidParagordius obamiis parthenogenetic, with no males; this is the only species of nematomorphan not known to reproduce sexually.
Phylum Nematomorpha – Oxford Scholarship
Integrated pest management around the home”, ; “Horsehair or Gordian Worm”, ; Brusca and Brusca, ; Hanelt, et al. Nematomorphans exhibit no parental investment beyond the production of gametes.
Nematomorppha and Brusca, Although a specific lifespan has not been reported for nematomorphan species, they are known to survive for multiple years. Integrated pest management around the home”, Although they are unciliated, nematomorphans possess natatory bristles which, when moved by the body wall muscles, aid in swimming and floating. They are solitary outside of breeding.
Nematomorphan larvae parasitize and can influence their hosts’ behaviors. Nematomorphans have a circumpharyngeal cerebral ganglion located in the region of the head known as the calotte, and single or paired nerve cords that run in the epidermal nerve tracks. Some species also have modified, pigmented cells located on their calottes, which may be photosensitive.
Nematomorphans are highly tactically sensitive; some of their cuticular areoles may be touch receptors. Areoles may also be chemosensitive. Brusca and Brusca, ; Schmidt-Rhaesa, Nematomorphan larvae are parasitic, eating and absorbing their hosts’ body tissues in early stages and feeding on nutrients from bodily fluids later. They do not feed as adults, but they may be able to absorb nutrients from the water through their body walls.
Known food sources hosts of gordioid species include crickets, beetles, grasshoppers, cockroaches and mantids. Known hosts of Nectonema species are most often decapod crustaceans, such as crabs and shrimps. Predators of nematomorphan larvae are those species that serve as paratenic and definitive hosts. Known predators of adult nematomorphans include fishes and frogs. Cochran, ; Cochran, et al. Nematomorphans are parasitic as larvae. They may infect paratenic hosts.
When in these intermediary hosts, the larvae encyst. Paratenic hosts often include trematode flatworms, insect larvae particularly flying insectssmall crustaceanssnailsand fishes.
Definitive hosts of gordioids are typically terrestrial insects and arthropodswhile definitive hosts of Nectonema species are marine decapod crustaceans. Baker, ; De Villalobos, et al.
Nematomorphan infestations have been used at times as a means of pest control, but it has not been widely successful. Additionally, their life cycle and, in particular, their parasitic behavior and control of their hosts has been a source of scientific research. Integrated pest management around the home”, ; Baker, ; Hanelt, et al. Nematomorphans do not parasitize humans, livestock, or other domestic animals. There are no known adverse effects of nematomorphans on humans.
Species in this phylum are not considered endangered or threatened in any way. It is the second largest ocean in the world after the Pacific Ocean. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico. In otherwords, Europe and Asia and northern Africa.
Referring to an animal that lives on or near the bottom of a body of water.
Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans below m are sometimes referred to as the abyssal zone. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.
Synapomorphy of the Bilateria. Bogs have a flora dominated by sedges, heaths, and sphagnum. Found on all continents except maybe Antarctica and in all biogeographic provinces; or in all the major oceans Nematomkrpha, Indian, and Pacific. Iteroparous animals must, by definition, survive over multiple seasons or periodic condition changes. A large change in the shape or structure of an animal that happens as the animal grows.
In insects, “incomplete metamorphosis” is when young animals are similar to adults and change gradually into the adult form, and “complete metamorphosis” is when there is a profound change between larval and adult forms.
Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis. An aquatic biome consisting of the open ocean, far from land, does not include sea bottom benthic zone. Referring to something living or located adjacent to a waterbody usually, but not always, a river phyluum stream.
Integrated pest management around the home.