Conaperta antonii, Achatz, Johannes G., Hooge, Matthew D. & Tyler, Seth, 2007

Achatz, Johannes G., Hooge, Matthew D. & Tyler, Seth, 2007, Convolutidae (Acoela) from Belize, Zootaxa 1479, pp. 35-66 : 41-43

publication ID	https://doi.org/ 10.5281/zenodo.176820
DOI	https://doi.org/10.5281/zenodo.5665128
persistent identifier	https://treatment.plazi.org/id/945B87AC-FFB5-FFED-77BF-B4CD6CF8BBD6
treatment provided by	Plazi
scientific name	Conaperta antonii
status	sp. nov.

Treatment

Conaperta antonii sp. nov.

( Figs. 4–6 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Diagnosis. Conaperta with 130 µm long, unciliated vagina, and a straight, 35 µm long, antero-ventrally directed bursal nozzle. Male copulatory organ consists of a penis sac, which is surrounded and filled by spongy tissue, and a penis, which is ~170 µm long, curled backwards and slightly broader at its proximal end. Its musculature consists of outer longitudinal muscles and inner circular muscles and the lumen of the penis is completely filled with the distal parts of cyanophilic gland cells. A pair of prostatoid organs with sclerotized needles lies ventral to the penis sac. Units: st 12, m 48, fgp 74, at 77.

Type Material. Holotype: USNM 1096737, one set of 1.5-µm-thick serial sagittal sections of epoxyembedded specimen stained with toluidine blue. Paratype: USNM 1096738, one set of 1.5-µm-thick serial sagittal sections of epoxy-embedded specimen stained with toluidine blue.

Type Locality. On algae in Grouper Gardens at Twin Cays, Belize (16°49’46.3” N, 88°06’10” W).

Other Material Examined. Living specimens in squeeze preparations, four complete sets of histological sections of epoxy-embedded specimens stained with toluidine blue, and one complete set of epoxy-embedded specimen stained with Heidenhain’s hematoxylin.

Etymology. The species is named in honor of Arnfried Antonius, for his work on the systematics of the Convolutidae .

Description. Mature animals are droplet-shaped, ~1100 µm long, ~600 µm wide, and lack enfolded sides ( Fig. 4 View FIGURE 4 A).

The epidermis is ciliated on the entire surface, with cilia ~7 µm long. The nuclei lie beneath the body-wall musculature, which is stronger on the ventral than on the dorsal side. Dorso-ventral muscles are distributed throughout the whole body, and are especially numerous at the body midline of the anterior third of the body where they insert on the ventral body-wall musculature ( Figs. 5 View FIGURE 5 A, 6A).

Body color is green due to the presence of zoochlorellae, which are scattered throughout the parenchyma ( Fig. 4 View FIGURE 4 A). Mucous gland cells and rhabdoid gland cells with translucent rhabdoids are numerous on the entire surface. Frontal gland cells fill the anterior third of the body and protrude through a frontal pore at the anterior tip ( Figs. 5 View FIGURE 5 A, 6A).

A statocyst, 25 µm in diameter, and surrounded by nervous tissue, lies ~80 µm behind the anterior tip.

The nervous system consists of paired ganglia lying dorsally, a plexus antero-ventral to the statocyst, and four pairs of longitudinal nerve cords: two dorsal, one lateral, and one ventral. Two rectangular ocelli composed of brown colored granules lie lateral to the statocyst ( Fig. 4 View FIGURE 4 A).

The mouth lies ~300 µm behind the anterior tip.

The paired testes lie dorsal and lateral to the paired ovaries. The germative zones of the testes extend from behind the statocyst to the edge of the bursal nozzle. Early spermatogonia have a big nucleus with a large nucleolus. Mature spermatogonia have a smaller nucleolus and their heterochromatin has more contact with the nuclear membrane. The highest number of mitotic figures observed in one follicle was sixteen. Sperm migrate to the male copulatory organ and consolidate in paired false seminal vesicles anterior to the dorsal lateral openings of the penis sac ( Fig. 4 View FIGURE 4 A).

The oogonia and their nucleoli are larger than the spermatogonia and their nucleoli. The euchromatin is stained more densely than the cytoplasm. The oogonia and oocytes incorporate symbiotic algae and abortive oocytes. Their cytoplasm contains necrotic nuclei of the abortive oocytes, most lying close to the plasma membrane.

The male and female organs open into an unciliated common genital atrium ( Figs. 5 View FIGURE 5 B, 6A, C).

The vagina is 130 µm long, unciliated, and opens into the seminal bursa caudally. The nozzle is straight, 35 µm long, and is directed antero-ventrally ( Figs. 5 View FIGURE 5 A, 6A).

The penis sac is surrounded by spongy, glandular tissue, and parenchymal muscles connect it to the body wall. Cyanophilic gland cells protrude into the penis sac and penis, most frequently from the ventral side. The lumen of the penis is completely filled with the distal parts of these cyanophilic gland cells ( Figs. 5 View FIGURE 5 B, 6C), which are also visible in live observation ( Fig. 4 View FIGURE 4 B). The penis is ~170 µm long, curled backwards and is slightly broader at its proximal end. Its musculature consists of outer longitudinal muscles and inner circular muscles ( Figs. 5 View FIGURE 5 B, 6C).

A pair of prostatoid organs is positioned ventral to the penis sac ( Fig. 6 View FIGURE 6 B). A prostatoid organ consists of a muscular bulb surrounding the distal parts of gland cells proximally and cells bearing sclerotized needles distally.