Proporus carolinensis Hooge and Smith, 2004

Hooge, Matthew D. & Tyler, Seth, 2007, Acoela (Acoelomorpha) from Belize, Zootaxa 1479 (1), pp. 21-33 : 29-31

Proporus carolinensis Hooge and Smith, 2004

( Figs. 7–8 )

Material. USNM 1096763, one set of 2-µm-thick serial sections of epoxy-embedded specimens stained with toluidine blue; living specimens in squeeze preparation.

Locality. Carrie Bow Cay (16°48’09” N, 88°04’55” W), from a patch of clean, medium-grained sand that abuts the southern edge of a Thalassia sp. bed, approximately 10 m from the northeast end of Carrie Bow Cay.

Description. Mature specimens 670 to 1000 µm long and ~ 200 µm wide ( Figs. 7A, B , 8A ). Body cylindrical. Anterior end rounded, posterior end blunt.

Mouth opening subterminal, ventral, anterior end of body. Mouth opens to ciliated pharynx ( Figs. 7C , 8A ).

Ovary unpaired, ventral. Testes paired, lateral; converge to central mass immediately anterior to seminal vesicle ( Figs. 8A, B ).

Female gonopore, vagina, and seminal bursa all absent. Male gonopore terminal at posterior end, opens to ciliated, tubular male antrum ( Figs. 7D , 8B ). Wall of antrum with circular and longitudinal muscles ( Fig. 8B ). Seminal vesicle at proximal end of male antrum; sperm in antrum aligned in parallel, longitudinally ( Figs. 7D , 8B ). Sperm of seminal vesicle surrounded by long, filamentous, metachromatic red strands ( Fig. 8B ), likely to be glandular secretions.

Remarks. Previously known only from its type locality at Oak Island, North Carolina ( Hooge & Smith 2004), P. carolinensis was uncommon in our samples and was found at only one collection site. The metachromatic red strands surrounding the sperm of the seminal vesicle in the newly collected specimens were not visible in the histological sections of the type material from North Carolina; however, we wonder if these strands contribute to the appearance in living specimens that the seminal vesicle contains sclerotized needles. It was previously thought that this appearance was caused solely by the sperm of the seminal vesicle being aligned in parallel ( Hooge & Smith 2004).

Figures

FIGURE 7. Proporus carolinensis; photomicrographs of living specimens. A. Dorsal view of unsqueezed specimen. B. Lateral view of squeezed specimen. C. Lateral view of anterior end, showing the pharynx. D. Lateral view of posterior end, showing male copulatory organ.

FIGURE 8. Proporus carolinensis; photomicrographs of sagittal histological sections. A. Whole specimen. B. Male copulatory organ. Arrowheads point to metachromatic red filamentous strands surrounding sperm of seminal vesicle.