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Kato, 1937

Overview
Diagnosis: Micaplana misae Kato, 1937 can be recognized easily by the black band across the front end of the body and, with respect to its anatomy, by the presence of a large muscular process on the penis which is provided with characteristic glandular vesicles.
Habitus: Living animals, when fully extended, measure up to 5 mm in length and 1 mm in width. The body has an elongate lancet-shape, with the front and hind end pointed. A very small adhesive disk is present at the tip of the hind end.
The body is white, except for a black band across the anterior end and some black spots in front of the eyes. The eye cups are set very close together and are at a considerable distance from the lateral body margins.

Alimentary System
The pharynx lies in the middle of the body and measures about one-fourth of the body length. The mouth opening is at the hind end of the pharyngeal pocket.
The anterior ramus of the intestine does not extend anterior to the eyes but terminates at a short distance behind the brain. Behind the eyes the anterior gut trunk shows 7 pairs of lateral diverticula. The posterior rami unite in the hind end of the body. Each posterior ramus is provided with 15-17 lateral diverticula and behind the copulatory apparatus also with about 4 short median diverticula.

Male Reproductive System
Six testicular follicles occur between the ovaries and the root of the pharynx on either side of the anterior gut trunk. The follicles are situated between the bases of the intestinal diverticula and have a ventral position.
At the level of the mouth, the vasa deferentia turn dorso-medially and unite to a common vas deferens shortly before penetrating the penis bulb. Inside the bulb, the common vas deferens opens into a rounded, rather large, seminal vesicle which is lined with a folded epithelium. Two types of unicellular glands, which are situated in the penis bulb, discharge their secretion into the seminal vesicle. The openings of cyanophilous glands penetrate the entire surface of the vesicle, whereas a coarse, eosinophilous secretion is discharged into the distal portion of the vesicle and into the proximal section of the ejaculatory duct. The last-mentioned duct arises from the seminal vesicle and follows a winding course before it empties at the tip of the penis papilla. The ejaculatory duct is lined with tall, infranucleate cells and is surrounded by a thin layer of circular muscles.
The penis papilla is short and stubby. The penis bulb is rather large and rounded; it is covered with a dense network of muscle fibres.
A large structure is attached to the lateral surface of the penis and is also connected, in part, with the dorsal wall of the genital (common) atrium. This process may occur on either the left or the right side of the animal. The structure is more or less cilindrical and shows two lateral folds. It consists of parenchymatic tissue and is covered with a dense network of muscle fibres. Over the whole surface of this muscular process, but especially on the lateral folds, occur a large number of relatively large, glandular vesicles. These rounded or ovoid vesicles are surrounded by a relatively thick layer of muscle fibres. The vesicles discharge a cyanophilous, granular secretion into the atrium via a narrow and somewhat thickened pore. Long and narrow ducts connect the glandular vesicles with the actual gland cells, which lie scattered in the muscular process as well as in the dorsal body parenchyma.

Female Reproductive System
The ovaries are situated at a short distance behind the brain. The oviducts run laterally to the ventral nerve cords. The vitellaria are well developed and occur throughout the body length.
At a considerable distance behind the gonopore, the oviducts turn medially and unite to a short common oviduct which, subsequently, opens through the hind wall of the copulatory bursa. The bursa is an egg-shaped vesicle which is lined with cuboidal cells and which lacks any surrounding musculature. A broad bursal canal arises from the antero-ventral surface of the copulatory bursa and runs obliquely towards the postero-dorsal wall of the atrium and then empties into the latter. The proximal portion of the bursal canal is lined with cuboidal cells and is surrounded by muscles.
Well developed cement glands discharge a cyanophilous secretion into the gonopore.

Eyes
Unfortunately, no details on the histology of the eyes are mentioned in the original species description.

Ecology
Specimens have been dredged from a depth of 20 m (Kato 1937) and have been collected also from under stones in the intertidal zone (Kato 1955).

Distribution
Type locality: Susaki, Sizuoka Prefecture, Japan (33°22'N 133°16'E). The species has been reported from Susaki, the type locality, and from Seto, Wakayama Prefecture (35°14'N 137°06'E) (Kato 1955) in Japan.

Material Examined
The present account on the morphology of the species is based solely on the original description by Kato (1937).

Type material
No longer available.

Micaplana misae