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Kawakatsu and Mitchell, 1984

Overview
Diagnosis: Oahuhawaiiana kazukolinda Kawakatsu and Mitchell, 1984 can be distinguished from other free-living bdellourids by the following features: oviducts which open separately into the bursal canal, well developed copulatory bursa, genito-intestinal duct, lateral bursae which receive the posterior branches of the oviducts, absence of an intrapenial papilla.
Habitus: Live, mature animals 6-8 mm long and 0.5-0.8 mm wide. The front end is bluntly pointed, showing a pair of indistinct auricles; the body margins run more or less parallel; the hind end is broadly rounded (Kawakatsu and Mitchell 1984).
The dorsal surface is yellowish-brown and has a paler, yellow, mid-dorsal band. The eyes are set in pigment-free patches. A non-pigmented auricular sense organ is situated on either side of the head, somewhat posteriorly to the auricles (Kawakatsu and Mitchell 1984).

Alimentary System
The pharynx measures about one-fifth of the body length (Kawakatsu and Mitchell 1984) and is situated in the middle of the body. The inner circular muscle layer of the pharynx is much thicker than the outer one. The mouth opening is at the hind end of the pharyngeal pocket.
The anterior intestinal trunk gives rise to 8-10 pairs of lateral diverticula (Kawakatsu and Mitchell 1984) and extends anterior to the brain. Each posterior trunk bears 10-12 short lateral branches, whereas there are three or four commissures behind the copulatory apparatus (Kawakatsu and Mitchell 1984).

Male Reproductive System
The relatively small testes are situated dorsally, extending from the level of the ovaries to behind the copulatory apparatus. There are 25-30 follicles in total. The testicular follicles are arranged in a double row on either side of the body in front of the pharynx, and in single rows alongside and posterior to the pharynx (Kawakatsu and Mitchell 1984).
At about the hind end of the pharyngeal cavity the vasa deferentia expand to form well developed false seminal vesicles. The latter narrow while curving mediad, and unite at the ventral base of the penis bulb, thus forming an intrabulbar common vas deferens. The distal section of the last-mentioned duct expands to form a seminal vesicle, which opens into the ejaculatory duct. Common vas deferens, intrabulbar seminal vesicle, and the proximal section of the ejaculatory duct are lined with nucleate cells. The distal portion of the ejaculatory duct, however, has an infranucleate lining, which is penetrated by the openings of penis glands, the latter being situated outside the penis bulb.
The penis consists of a large, moderately muscularized, bulb and a broad cone-shaped papilla, the latter having an oblique orientation. The papilla is lined with relatively tall epithelial cells which, however, become flat at the tip. Underneath this lining occurs a thick basement membrane which resumes its thin appearance again on the tip of the penis papilla and underneath the lining epithelium of the atrium.

Female Reproductive System
The small, rounded, ovaries are situated at a short distance (about 0.25 mm) behind the brain, lying dorsally to the ventral nerve cords. The oviducts arise from the ventro-lateral surface of the ovaries, immediately after which they bifurcate to a posteriorly running section and a short (about 100 µm) anteriorly directed branch. The posteriorly directed branches of the oviducts run laterally to the ventral nerve cords and bifurcate at the level of the female copulatory apparatus. Thus, the oviducts give rise to medially directed branches which open separately into the bursal canal, and to posteriorly running sections that communicate with the lateral bursae.
The vitellaria are only moderately developed. They occupy the entire space between dorsal and ventral body surface and range from the level of the ovaries into the hind end of the body, the major portion of the vitellaria being situated laterally to the testes (Kawakatsu and Mitchell 1984).
The bursal canal runs from the hind wall of the atrium, parallel to the body surface, towards the copulatory bursa with which the duct communicates through a short, dorsally directed section. The bursal canal is lined with cuboidal, nucleate cells which bear well-developed cilia. The canal is surrounded by a thin layer of circular muscles and it receives the secretion of shell glands anteriorly (ectally) to the openings of the oviducts.
The copulatory bursa is lined with tall, nucleate cells but its tissue is only weakly differentiated from the surrounding parenchyma. The bursa communicates with the intestine through a short and poorly differentiated genito-intestinal duct, which is lined with nucleate cells. This genito-intestinal duct appears to have no fixed position, i.e. it may open in either the posterior or the anterior section of the copulatory bursa.
The paired lateral bursae are more or less sac-shaped structures which are lined with tall, nucleate and vacuolated cells. The bursae are weakly muscularized. Their anteriormost portion consists of a short, thick-walled, duct-like section that meets the posterior branch of the oviducts. This duct-like section has a rather narrow lumen and is surrounded by a layer of muscles which is slightly stronger than on the rest of the lateral bursae. The bursae may contain sperm; their openings to the exterior occur laterally to the ventral nerve cords.

Eyes
Each pigment cup contains three retinal cells, while an eye lens is absent.

Reproduction
Life Cycle: The spherical cocoons measure 0.3-0.4 mm in diameter and do not possess a pedicel; cocoons have been collected in the field on June 18th (Kawakatsu and Mitchell 1984).

Ecology
Oahuhawaiiana kazukolinda is known only from its type locality, which is a small (1.5 m wide, 10 cm deep) freshwater stream at about 3.5 km from Waikiki beach and at an altitude of about 300 m; at the time of collecting water temperature was 22-25 degrees C and pH was 6.2-6.4 (Kawakatsu, Mitchell, Hirao and Tanaka 1984).

Distribution
Type locality: Manoa Stream, St. Louis Heights, Honolulu, Oahu Island, Hawai. The species is known only from the type locality.

Material Examined
N.S.M.T.: NSMT-Pl.2969 Holotype (h-1), June 1966, sagittal sections on 1 slide; NSMT-Pl.2969 Paratype (p-1), June 1966, sagittal sections on 1 slide.

Type Material
N.S.M.T.: NSMT-Pl.2969 Holotype (h-1), June 1966, sagittal sections on 1 slide; NSMT-Pl.2969 Paratype (p-1), June 1966, sagittal sections on 1 slide.
N.S.M.T.: Paratypes: NSMT-Paratype (w), whole mount; NSMT-Pl.2969 Paratype (p-1), see above.
Several paratypes are retained in Kawakatsu's private collection under the catalogue numbers 596a, 596 i-m, 596-o, 596 q-s, 596-u.

Oahuhawaiiana kazukolinda