The male repro- conuli; femae parts w th bursaand usLBlly a vagina. Members of the order Bursovaginoidea possess a vaginal orifice and a sperm-storage bursa, both as- The Gnathostomulid Body Plan sociated with the female gonopore, and a penis in the male system; members of the order Filosperrnoidea Body Wall, Support, and Locomotion lack these structures. Each outer epithelial cell bears a single cilium by which Mating has been only superficially studied in gna- the animal moves in a gliding motion. Movement is thostomulids Although the method of sperm transfer aided by body contortions produced by the contraction is not certain, suggestions include filiforrn sperm of fi- of thin strands of subepidermal cross striated muscle lospermoid gnathostomu lids boring through the body fibers- 1hese actions, plus reversible ciliary beating, wall. Among some bursovaginoid gnathostomulids, facilitate twisting, turning, and crawling among sand sperm is transferred directly to the mating partner's grains, and allow limited swimming in some species.
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The male repro- conuli; femae parts w th bursaand usLBlly a vagina. Members of the order Bursovaginoidea possess a vaginal orifice and a sperm-storage bursa, both as- The Gnathostomulid Body Plan sociated with the female gonopore, and a penis in the male system; members of the order Filosperrnoidea Body Wall, Support, and Locomotion lack these structures.
Each outer epithelial cell bears a single cilium by which Mating has been only superficially studied in gna- the animal moves in a gliding motion. Movement is thostomulids Although the method of sperm transfer aided by body contortions produced by the contraction is not certain, suggestions include filiforrn sperm of fi- of thin strands of subepidermal cross striated muscle lospermoid gnathostomu lids boring through the body fibers- 1hese actions, plus reversible ciliary beating, wall.
Among some bursovaginoid gnathostomulids, facilitate twisting, turning, and crawling among sand sperm is transferred directly to the mating partner's grains, and allow limited swimming in some species. In any case these animals appear to be gre some species The body is supported by its more or less garious, to rely on internal fertilization, and to deposit solid construction, with a loose mesenchyme filling the zygotes singly in their habitat.
Cleavage is reported as area between the internal organs. Nutrition, Circulation, Excretion, and Gas Exchange The mouth is located on the ventral surface at the "head-trunk" junction and leads mward to a complex Phylum Rotifera: muscular pharynx armed with pincerlike jaws and in The Free-Living Rotifers some species an unpaired anterior basal plate Figure The phylum Rotifera Latin rota, "wheel";fera, "to Curiously, the two known species of the genus bear" includes more than 2, described species of Agnaihiet!
Gnathostomulids in- microscopic about to urn long , generally gest bacteria and fungi by snapping actions made by free living animals. Furthermore, the parasitic, mac- the jaws or scraping with the basal plate. The pharynx roscopic acanthocephalan worms actually represent a connects with a simple, elongate, saclike gut. A per ma rotifer in group as well, but due to their considerable nent, functional anus is not present, but in a few gna- differences in biology and morphology, they will be thostomulids a tissue connection between the posterior discussed separately- Thus in this section the name Ro end of the gut and the overlying epidermis has been tifera refers to the microscopic, free-living rot.
The excretory system is com- pists, such as Antony van Leeuwenhoek in the late posed of serially arranged protonephridia that stretch seventeenth century; at that time they were lumped from the pharyngeal region to the terminal end of the with the protists as "animalcules" mainly because body.
Like the epithelial cells, the protonephridial ter of their small size. Besides the 2, or so known, minal cells are monociliated. For example, the species Brachionus The nervous system is intimately associated with the plicatilis has been subject to intensive studies, and at epidermis and as yet is incompletely described. Vari least 22 cryptic species have been identified within this ous sensory organs, such as sensory ciliary pits and species group.
Admeta, Embete Habrotro of this phylum are further characterized by being bias cha, Philod1na. They have a complete gut usually , proto- mar ne leptostrecan crustacean Nebalia; corona reduced nepluidia, show a tendency to eutely, and often have to bristtes: trophi fu crate piercng ; males fully developed syncytial tissues or organs Box The pharynx is and cons dered to have d plod chromosome numbers; modified as a mas tax comprising sets of internal jaws sexual fema es produce en y mictic ova.
The morphology of the trophi is of great Para seison and Se,sen systematic importance and often the main character to ident. Iy species and genera.
Asplanchna Brachionus 1 1. Lecsne, Notommata. Instead they have an inn acellular protein lamina located inside the BOX Characteristics of the epidermis, for protection and stabilization of the body. Phylum Rotifera This protein lamina may vary considerably in thickness 1.
Trip obtast c. Species blastocoe amates with a very thin protein lamina are called "illoricate ro- 2. Gut compete and reg anal y spec a zed tifers," and they often appear as very f. Phar vnx mod f'ed as a mastax, oonta ning jaw line animals that contract completely when disturbed. Anterior end bears variab e ciiated f elds as a much thicker and forms a body-armor, called a lorica, corona and these species are referred to as "loricate rotifers.
Poster or end often bears toes and adnes ve glands gards the absence of walls between the epidermal cells, 6 Ep dermis syncyt a, w th fixed number of nuc et: meaning that the epidermis is a syncyt.
Wrth protanephrda, but no spec a crcu atary or cies often bears spines, tubercles, or other sculpturing gas exchange structures Figure 16 3E. A foot is not present in all species, esis common but when present it is often elongate, with cuticular 10 With mod fed sp ral c eavage annuli that permit a telescoping action. The distal por- Bdelloids are prone to infection by an aggressive Aspianchua both are rotifers , are stimulated to devel- fungus, Rotiferophthora angustispora, that eats them op into larger bodied adults with an extra long anterior from the msideout.
Experiments have recently shown spine, thus rendering them more difficult to eat. Only a few studies have been conducted on the em- The Acanthocephalans bryogeny of rotifers see especially Pray 1, In spite As adults, the L or so described species of acan- of the paucity of data, and some conflicting interpreta- thocephalans are obligate intestinal parasites in ver- tions in the literature, it is generaHy thought that roti- tebrates, particularly in birds and freshwater fishes.
However, detailed l arvaJ development takes place in intermediate arthro- analyses of cell lineages are still needed to deiermine if pod hosts. The name AcanthocephaJa Greek ncanthios, the typical spiral pattern persists past the first couple of "prickly";cephalo, "head" derives from the presence of cell divisions in rotifers, especially with regard to the recurved hooks located man eversibJe proboscis at the origin of the mesoderm.
The isolecithal ova undergo anterior end. The rest of the body forms a cylindrical unequal ho1ob1astic early cleavage to produce a stereo- or flattened trunk, often bearing rings of sma11 spines. Gastrulation is by epiboly of the presumptive Most acanthocephalans are Jess than 20 cm long, al- ectoderm and involution of the endoderm and rneso- though a few species exceed 60 cm in length; females derm; the gastrula graduaHy hollows to produce the are genera11y larger than males.
The digestive tract has blastocoel, which persists as the adult body cavity. The been completely lost, and, except for the reproductive mouth forms in the area of the bJastopore. Definitive organs, there is significant structural and functional nuclear numbers are reached early in development for reduction of most other systems,a condition related to those organs and tissues displaying cutely.
The Errant rotifers undergo direct development. Sessile tia11y partitioned by mesentery-like ligaments. The "larva" eventually settles and attaches to cis hooks, the nature of the epidermal nuclei, spma- the substratum. In a11 cases, there is a total absence of tion patterns on the trunk, and nature of the reproduc- cell division during postembryonic life i. It is the expression Figure In all such animals studied Body Wall, Support, Attachment, and Nutrition to date, the alternative adult morphotypes appear to Adult acanthocephaJans attach to their host's intesti be products of flexible developmental pathways, trig- nal wa11 by their proboscis hooks, which are retractable gered by environmental cues and often mediated by into pockets, like the claws of a cat Figure The internal mechanisms such as hormonal activities.
In chemica] nature ofthe hooks is not yet known. In nearly one well studied genus of rotifers Asplanclma , the a11 species, the proboscis itself is retractable into a deep environmental stimulus regulating which of several proboscis receptacle, enabling the body to be pulled adult morphologies is produced is the presence of a dose to the host's intestinal mucosa. The Aspianchna obtains tocopheroJ from its diet of algae outer body wall is a multilayered, syncytial, living tegu or other plant material, or when it preys on other her- ment, which overlies sheets of circular and longitudinal bivores animals do not synthesize tocopheroJ.
The muscles. The tegument includes layers of dense fibers chemical acts directly on the rotifer's developing tis- as we11 as what appear to be sheets of plasma mem- sues, where it stimulates differential growth of the brane, and an intrace11u1arprotein lamina, such as the syncytial hypodermis after cell division has ceased. The tegument is per Predator-induced morphologies also occur among roti- forated by numerous canals that connect to a complex fers. This gonopore is often is not known.
These structures sup- within a ligament sac. Clumps of immature ova are port the reproductive organs and divide the body into released from this transient ovary and enter the body dorsal and ventral ligament sacs in the archiacantho- cavity, where they mature and are eventually fertil- cephalans and eoacanthocephalans. The female reproductive system comprises a g]e ligament sac down the center of the body cavity in gonopore, a vagina, and an elongate uterus that te r the palaeacanthocephalans Figure Within minates internally in a complex open funnel called the the walls of these sacs are strands of fibrous tissue uterine bell Figure The penis is inserted mto the vagina, a blastocoelom.
Sperm then travel up the female system, the hydrostatic qualities of the blastocoelom and Iacu- enter the body cavity through the uterine bell, and nar system. The muscles and ligament sacs add some fertilize the eggs. Cleavage is holoblastic. A stereoblastula is pro- Exchanges of nutrients, gases, and waste products duced, at which time the cell membranes break down occur by diffusion across the bodywa11 some Archia- to yield a syncytia] condition.
Eventually, a shelled canthocepha]a possess a pair of protonephridia and a acanthor Jarva is formed Figure The embryo small bladder. The lacunar fluid lar funnel; it accepts only the appropriate embryos into is moved about by action of the body wa11 muscles. Embryos in earlier stages are rejected and Ne1vous System pushed back mto the body cavity, where they continue development, The selected embryos pass through the As in many obligate endoparasites, the nervous system uterus and out the genital pore and are eventually re and the sense organs of acanthocephalans are greatly leased with the host's feces.
A cerebral ganglion lies within the proboscis Once outside the definitive host, the developing receptacle Figure Males possess a pair of genital ganglia. The cean to continue its life cycle. The acanthor larva proboscis bears several structures that are presumed penetrates the gut wall of the intermediate host and to be tactile receptors, and small sensory pores occur enters the body cavity, where it develops into an at the tip and base of the proboscis- Males have what acanthella and then into an encapsulated form ca11ed appear tobesense organs in the genital area, especially a cystacanth Figure Acanthocephalans are gonochoristic and females are generally somewhat Jarger than males- In both sexes, the reproductive systems are associated with the ligament sacs Figure In males, paired testes Phylum Micrognathozoa: usual1y arranged in tandem He within a ligament The Micrognathozoans sac and are drained by sperm ducts to a common A new microscopic animal, Limnognathia seminal vesicle.
Entering the seminal vesicle or the maerski. Due to the numerous lowing copulation. When nephridia are present, they unique features of this new microscopic animal, a also drain into this system.
The seminal vesicle leads new monotypic class, Micrognathozoa Greek, micro, to an eversible penis, which lies within a genital bursa "small," gnathos, "jaw": z,a, "animal" was erected.
Though L. Ventral jaw. Zur Morphologie und Systemati k der Sterrer, W. On the biology of Gnathostomulida. Syst, Evolutionsforsch. B: Herlyn, H. Systematics and evolution within the the pharynx of Cnathoetomu! Sterrer, W. Pp in S Parker ed Jenner, R. Platyhelminthes, Nermertea, and Cnathostomulida, with a Sterrer, W. Two species one new of Gnathostomulida critical reappraisal of cladistic characters Contrib.
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6. Filum Rotifera-Brusca et al., 2019.docx
The rotifers from Latin rota "wheel" and -fer "bearing" , commonly called wheel animals or wheel animalcules ,  make up a phylum Rotifera of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John Harris in , and other forms were described by Antonie van Leeuwenhoek in Some rotifers are free swimming and truly planktonic , others move by inchworming along a substrate, and some are sessile , living inside tubes or gelatinous holdfasts that are attached to a substrate. About 25 species are colonial e. Rotifers are an important part of the freshwater zooplankton , being a major foodsource and with many species also contributing to the decomposition of soil organic matter.
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