Editing Aspidogastrea (section)

==Morphology==

===Shared characteristics===
Shared characteristics of the group are a large [[ventral]] disc with a large number of small [[Pulmonary alveolus|alveoli]] ("suckerlets") or a row of suckers and a [[Tegument (Helminth)|tegument]] with short protrusions, so-called "microtubercles". Aspidogastreans are an understudied class of parasitic flatworms that possess unique anterior attachment structures and are found exclusively in freshwater and marine environments, infecting a variety of hosts including fish, amphibians, and reptiles.

===Larval physiology===
[[Larva]]e of some species have [[cilia]]ted patches. Those of ''Multicotyle purvisi'' have four patches on the [[anterior]] side of the [[Posterior (anatomy)|posterior]] sucker and six at the posterior side, those of ''Cotylogaster occidentalis'' have an anterior ring of eight and a posterior ring of six, while larvae of ''Aspidogaster conchicola'', ''Lobatostoma manteri'', ''Rugogaster hydrolagi'' lack cilia altogether. Larvae of some species hatch from eggs, others do not.

===Excretory system===
Like most [[platyhelminthes]], aspidogastreans use [[flame cell]]s as an [[excretion|excretory mechanism]]. The two excretory [[Gas bladder|bladder]]s are located [[Dorsum (biology)|dorsal]]ly, on the anterior side of the posterior sucker, connected to ducts, and three flame cell "bulbs" on each side of the body; the ducts contain [[cilia]] to aid the flow of excreta.

===Nervous system===
Aspidogastreans have a [[nervous system]] of extraordinary complexity, greater than that of related free-living forms, and a great number of [[sensory receptor]]s of many different types. The nervous system is of great complexity, consisting of a great number of longitudinal [[nerve]]s (connectives) connected by circular commissures. The [[brain]] (cerebral commissure) is located dorsally, in the anterior part of the body, the [[simple eye in invertebrates|eye]]s dorsally attached to it. A nerve from the main connective enters the pharynx and also supplies the intestine. Posteriorly, the main connective enters the sucker.

Sensory receptors are scattered over the ventral and dorsal surface, the largest numbers occurring on the ventral surface, at the anterior end and on the posterior sucker. [[Electron microscope|Electron-microscopic]] studies revealed 13 types of receptors.<ref name="RohdeWatson1990a">{{cite journal |last=Rohde |first=K. |author2=Watson, N. A. |year=1990 |title=Non-ciliate sensory receptors of larval ''Multicotyle purvisi'' (Trematoda, Aspidogastrea) |journal=Parasitology Research |volume=76 |issue= 7|pages=585–590 |doi=10.1007/BF00932567 |s2cid=52835654 }}</ref><ref name="RohdeWatson1990b">{{cite journal |last=Rohde |first=K. |author2=Watson, N. A. |year=1990 |title=Uniciliate sensory receptors of larval ''Multicotyle purvisi'' (Trematoda, Aspidogastrea) |journal=Parasitology Research |volume=76 |issue=7 |pages=591–596 |doi=10.1007/BF00932568 |s2cid=42418699 }}</ref><ref name="RohdeWatson1990c">{{cite journal |last=Rohde |first=K. |author2=Watson, N. A. |year=1990 |title=Paired multiciliate receptor complexes in larval ''Multicotyle purvisi'' (Trematoda, Aspidogastrea) |journal=Parasitology Research |volume=76 |issue=7 |pages=597–601 |doi=10.1007/BF00932569 |s2cid=11307808 }}</ref>