Conaperta cirrata, 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 : 44-48

publication ID	https://doi.org/ 10.5281/zenodo.176820
DOI	https://doi.org/10.5281/zenodo.5665130
persistent identifier	https://treatment.plazi.org/id/945B87AC-FFBA-FFE8-77BF-B0606FF1BD9E
treatment provided by	Plazi
scientific name	Conaperta cirrata
status	sp. nov.

Treatment

Conaperta cirrata sp. nov.

( Figs. 7–10 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10 )

Diagnosis. Conaperta with an unciliated vagina and paired prostatoid organs at about half of its length. Bursal nozzle is straight, ~70 µm long, and directed antero-ventrally. Penis sac is surrounded and filled with spongy gland cells. Penis is ~450 µm long, with outer longitudinal muscles and thick layer of inner circular muscles, its lumen is lined with the distal tips of gland cells. A single prostatoid organ lies ventral to the penis sac and protrudes into the atrium. Units: st 9, m 39, at 79.

Type Material. Holotype: USNM 1096739, one set of 1.5-µm-thick serial sagittal sections of epoxyembedded specimen stained with toluidine blue. Paratype: USNM 1096740, 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 and one whole mount for fluorescence microscopy.

Etymology. The species name relates to the Latin cirratus, meaning curly, and refers to the long, curled penis of the species.

Description. Mature specimens are ~ 2 mm long, ~800 µm wide, and lack enfolded sides ( Fig. 7 View FIGURE 7 A).

The epidermis is ciliated on the entire surface, with cilia ~6 µm long. On the dorsal side, numerous scattered clusters of refractive concrements are present ( Fig. 7 View FIGURE 7 D). Most nuclei of the epidermis are sunken beneath the body-wall musculature.

Bright zooxanthellae are scattered throughout the whole parenchyma, much denser dorsally than ventrally, and often they lie outside the body-wall musculature ( Figs. 7 View FIGURE 7 D, 8A, 9A). They are absent in the area of the bursal tissue and the male copulatory organ ( Fig. 7 View FIGURE 7 A).

The body color is predominately red due to the abundance of orange-red rhabdoid gland cells. Rhabdoid gland cells and mucous gland cells are scattered on the entire surface, most numerous dorsally ( Figs. 7 View FIGURE 7 A, D, 8A, 9A). Anterior to the mouth, the body is filled with frontal gland cells that protrude through a frontal pore ( Fig. 8 View FIGURE 8 A).

The statocyst is ~30 µm wide and lies ~100 µm behind the anterior tip.

Nervous tissue surrounds the statocyst. Paired ganglia lie dorso-lateral to the statocyst and give rise to a dorsal and central pair of nerve cords. Another pair runs along the lateral margins. On the ventral side, one pair of nerve cords runs along the thick lateral muscles, and another pair runs more centrally, terminating at the edge of the mouth.

The paired testes lie dorso-lateral to the paired ovaries. The germative zones of the testes extend behind the mouth. Sperm form paired false seminal vesicles in front the penis sac and enter it dorsally ( Fig. 7 View FIGURE 7 A).

The male and female copulatory organs open into an unciliated common genital atrium and share a common gonopore ( Figs. 8 View FIGURE 8 A, B, 9A).

The vagina is unciliated and lined with a thick layer of tissue ( Fig. 9 View FIGURE 9 A). At about half of its length, paired prostatoid organs protrude into it ( Figs. 8 View FIGURE 8 B, 10A). These organs are muscular, connected to each other with muscles ( Fig. 10 View FIGURE 10 A), and filled with the distal parts of gland cells containing small granules. The vagina opens to the caudal part of the seminal bursa. The bursal nozzle is straight, ~70 µm long, and directed antero-ventrally ( Figs. 8 View FIGURE 8 A, B).

The male copulatory organ consists of a glandular, muscular penis that is coiled twice and invaginated into a penis sac ( Figs. 7 View FIGURE 7 B, 8A, 9A, 10A, B). The penis sac is surrounded by gland cells, which protrude into it and form a spacious, spongy tissue, in which the penis is embedded ( Figs. 8 View FIGURE 8 A, 9A). The penis is ~450 µm long, with musculature consisting of outer longitudinal muscles and a thick layer of inner circular muscles ( Figs. 7 View FIGURE 7 B, 8A, 9A). The penis lumen is lined with the distal tips of gland cells that are densely packed with vesicles but often appear to be homogeneously stained ( Figs. 7 View FIGURE 7 C, 9A, B). At the proximal end of the penis these gland cells burst and release their vesicles into the penis lumen ( Fig. 9 View FIGURE 9 A). We could not determine if the nuclei of these cells lie beneath the penis musculature or outside the penis sac. A single prostatoid organ lies ventral to the penis sac and protrudes into the atrium ( Figs. 8 View FIGURE 8 A, B, 9A, 10A). The prostatoid organ consists of a cluster of bulbous gland cells. The gland cells contain fine granules, and taper toward their distal tips, which have sclerotized cell membranes.

Remarks. Historically, the genus Convoluta included species having separate male and female gonopores as well as species with a common gonopore until Antonius (1968) set aside those with a common gonopore into a newly erected genus Conaperta . Despite similar architecture of the male copulatory organ, however, both of these genera were shown to be polyphyletic by molecular and morphological analyses ( Hooge et al. 2002, Petrov et al. 2004), and in a major revision of the Convolutidae, Hooge and Tyler (2005) transferred a great number of species from the genera Conaperta and Convoluta to the family Isodiametridae . Most recently, two species of Conaperta were found to have separate male and female gonopores and were transferred to Convoluta (see Achatz & Hooge 2006). The genus Conaperta presently comprises C. flavibacillum ( Jensen, 1878) , C. lineata ( Peebles, 1915) , and the two species described here, C. antonii and C. cirrata . These species have in common a seminal bursa with a sclerotized bursal nozzle, a common gonopore, a common unciliated genital atrium, an opening to the male copulatory organ that is positioned posterior to the opening to the seminal bursa, and a tubular penis that is surrounded by a penis sac. The Conaperta species are individually distinct and easily distinguished from each other. Conaperta lineata is the only species lacking gland cells associated with the penis lumen, and it is without a frontal organ or symbiotic algae. Conaperta antonii has gland cells that fill the penis lumen entirely and paired prostatoid organs with large, sclerotized needles that open into the genital atrium. Conaperta flavibacillum is distinct in having sperm stored within the penis sac. Conaperta flavibacillum shares with C. cirrata the possession of a thick layer of circular penis musculature, gland cells lining the penis lumen, and prostatoid organs, which open into the vagina; however the two species can be distinguished by C. cirrata ’s large frontal organ, longer penis, absence of a sphincter on the vagina, and the presence of a prostatoid organ ventral to the penis sheath.

Interestingly, the posterior prostatoid organ of C. cirrata has a different structure than its anterior prostatoid organs, and is dissimilar to any found in the Convolutidae , but closely resembles the prostatoid organs occurring in species of the family Anaperidae , such as Achoerus pachycaudatus Dörjes, 1968 , Anaperus singularis Hooge & Smith, 2004, and Philachoerus johanni Dörjes, 1968 .