Plagiostomum cilioejaculator, Brusa, Francisco, 2006

Brusa, Francisco, 2006, First record of Prolecithophora (Platyhelminthes) from Argentina: Plagiostomum cilioejaculator sp. n., Zootaxa 1223, pp. 47-53 : 49-50

Plagiostomum cilioejaculator sp. n.

Figures 1 , 2 .

Meterial

Holotype: one specimen, sectioned sagittally (MLP 5335). Collected from benthos at Punta Piedras (5/12/01; 5/3/03), where salinity varied between 1.5 and 5 ‰. Paratypes: three specimens, sectioned sagittally (MLP 5336, MLP 5337).

Type locality

Punta Piedras (35°21’23.1”S – 57°10’22.5”W), Buenos Aires province, Argentina.

Etymology

The species name refers to the presence of cilia in the ejaculatory duct.

Description

Anterior end of body rounded, posterior end tapering slightly. Live specimens are 2.4 mm long and fixed specimens are 0.92 mm long. Colour is opaque white; some live specimens with granules of black pigment forming anastomosing bands. Brain situated dorsal to the pharynx. Nerve cords run anteriorly from the brain. Numerous glands in the anterior body region. Eyes absent. Mouth anterior or antero­ventral. Pharynx occupying one third of the body length in juveniles and one­fourth in adults. Pharyngeal lumen lined by a very densely ciliated epithelium. Pharynx leading to short, very glandular oesophagus. Intestine with well­developed epithelium comprising high vacuolated cells without cilia. Intestine reaching the level of male copulatory organ.

Male reproductive system comprising a pair of dorsal testes, lateral to the intestine, caudal with respect to the ovaries. Spermatozoids spindle­shaped, 18–22 m long. Vesicula seminalis saculiform, with thick muscular walls and surrounded by many prostatic glands. This vesicle, which is full of prostatic secretions in adult organisms, narrows distally into a narrow duct that leads to the ejaculatory duct. Ejaculatory duct lined by a densely ciliated epithelium. Penis and surrounding sheath somewhat curved, with developed muscular walls, and approximately 260 m long. Penis protruding into a large genital atrium with high epithelium. Gonopore subterminal and ventral. Copulatory apparatus surrounded by numerous acidophilic glands, especially in the region of the genital atrium (atrial glands) and in the caudal end of body, near the gonopore.

Female reproductive system comprising extremely large paired ovaries, dorsal and lateral to the intestine. Vitelline glands surrounding the ovaries latero­dorsally. Vagina reaching the atrium dorsally.

Figures

FIGURE 1. Plagiostomum cilioejaculator sp. n. A, ventral view. B, sagital reconstruction. Scale A: 300 m. Scale B: 200 m. ag: atrial glands; b: brain; ed: ejaculatory duct; g: gonopore; ga: genital atrium; i: intestine; m: mouth; o: ovary; p: pharynx; pg: prostate glands; t: testis; v: vagina; vs: vesicula seminalis.

FIGURE 2. Sagittal sections of Plagiostomum cilioejaculator sp. n. A, general view. B, detail of the anterior region, pharynx and brain. C, detail of the brain. D, detail of the copulatory organ, atrium and atrial glands. E, detail of the ciliated pharyngeal epithelial cells. F, detail of the testis. G, detail of the posterior region of the body. H, detail of the ovary. Scale A: 100 m. Scale B – H: 50 m. ag: atrial glands; b: brain; ed: ejaculatory duct; g: gonopore; ga: genital atrium; i: intestine; o: ovary; p: pharynx; pl: pharingeal lumen; t: testis.