Marcus, 1954
Overview
Diagnosis: Miava evelinae Marcus, 1954 can be distinguished easily from other Bdellourids by the presence of three eye lenses in each pigment cup, by the extremely short connecting duct between oviducts and lateral bursae, and by the fact that the oviducts arise from the ventro-lateral wall of the ovaries.
Habitus: Preserved specimens 3.2-4.0 mm long and at the level of the copulatory apparatus reaching a width of 1.7-1.3 mm. The body is pear-shaped, with a rounded front end and a broadly rounded, almost hemispherical, hind end. Auricles are absent.
The greater part of the dorsal body surface is black, changing to orange-red towards the body margins; the head region is rusty red. The black marking of the dorsal surface is interrupted by two orange-red patches, viz. one at the mid-dorsal surface and another one above the male copulatory apparatus. The body margins and the ventral surface are pale yellowish. The eyes are set in pigment-free areas.
Alimentary System
The pharynx lies at about the middle of the body and measures about one-sixth of the body length. The inner circular muscle layer of the pharynx is considerably thicker than the outer layer of circular muscles. The mouth opening is at the hind end of the pharyngeal pocket.
The anterior ramus of the intestine gives rise to an unbranched precerebral coecum. Behind the eyes the anterior intestinal ramus gives off about 5 pairs of lateral diverticula. Each of the caudally running gut trunks gives off about 6 lateral diverticula; the posterior rami do not meet in the hind end of the body.
Male Reproductive System
About 15 testicular follicles are present on either side of the body, extending from directly behind the ovaries up to the level of the male atrium. The rather large follicles are situated ventrally, but their dorsal portion extends beyond the mid-line of the body.
The vasa deferentia expand to form false seminal vesicles which do not decrease in size where they penetrate the penis bulb. The vasa deferentia enter the penis bulb separately, albeit closely together. Within the penis papilla both ducts run side by side and, subsequently, unite in the intrapenial papilla to form a common vas deferens.
The intrapenial papilla constitutes the central column of a number of radiating septa which project into the proximal part of the ejaculatory duct. The septa and the ejaculatory duct are pierced by numerous openings of penis glands, which produce an abundant, granular secretion; the glands lie outside the penis bulb.
The penis is oriented parallel to the body surface and consists of a shallow, but well-muscularized bulb, and an elongated, conical papilla. The latter is lined with an extremely flat, nucleate epithelium. The penis papilla is provided with a thick layer of circular muscles, entally being bounded by a very thin layer of longitudinal muscles. The male atrium is lined with nucleate cells and is surrounded by a subepithelial layer of circular muscles and a layer of longitudinal muscles.
Female Reproductive System
The ovaries lie at a short distance behind the brain, dorsally to the ventral nerve cords. The vitellaria extend from just anterior to the ovaries into the hind end of the body, occupying the entire space between dorsal and ventral body surface. The oviducts arise from the ventro-lateral wall of the ovaries and run laterally to the ventral nerve cords.
Each oviduct communicates with a lateral bursa that lies on either side of the gonopore. The oviducts run so close to the medial wall of the lateral bursae that there hardly is any question of a connecting duct between bursa and oviduct. Nevertheless, this extremely short connection is surrounded by well developed circular muscles. The lateral bursae are large, sac-shaped vesicles, reaching from dorsal to ventral body surface; the bursae are lined with tall, vacuolated and nucleate cells. The lateral bursae open ventrally to the exterior, their openings being situated at the level of the gonopore and laterally to the ventral nerve cords.
After having communicated with the lateral bursae the oviducts curve medially and unite to form a common oviduct that opens into the bursal canal via the ventral wall of the latter. The bursal canal, which is lined with cuboidal, nucleate cells with well-developed cilia, connects the copulatory bursa with the poorly defined female atrium. At its distal section, i.e. near the opening into the atrium, the bursal canal receives the openings of extensive shell glands.
The copulatory bursa is a moderately sized, sac-shaped vesicle that is lined with nucleate cells of which the vacuoles contain sperm.
Eyes
Each pigment cup contains three retinal cells and three eye lenses.
Ecology
The specimens from the type series were collected in the tidal zone; in one case specimens were collected from green algae (Marcus 1954a).
Distribution
Type locality: North coast of Isla de Chiloé, Chile (42°30'S 73°55'W). M. evelinae has been reported from three localities on the north coast of the island Chiloé, viz. Punta el Morro (41°52'42"S 73°50'46"W), between Punta San Antonio and Punta Colorada (41°51'30"S 73°49'40"W), Punta Corona (41°47'S 73°53'07"W), and from two localities in the Canal Moraleda (Cayo Blanco at 44°48'20"S 73°35'W and Penon Blanco at 44°24'S 73°34'W).
Material Examined and Type Material
S.M.N.H.: Syntypes: Canal Moraleda (44°30'S 73°30'W), Cayo Blanco, Chile, Lund University Chile Expedition, Station M71, 21.02.1949, one set of sagittal sections on 2 slides; ibid., one set of sagittal sections of immature specimen on 1 slide.
Present location of possible remaining material examined by Marcus (1954a) is unknown.