Anaperus singularis Hooge, Smith & Iii, 2004, sp. nov.
Creators: name: Hooge, Matthew D.
name: Smith, Julian P. S.
name: Iii
Publisher: name: Zenodo
Year: 2004
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Dendrochirotida
Cucumariidae
Anaperus
Anaperus singularis

description: Anaperus singularis sp. nov. (Figs. 1–3)
Type Material. Syntypes. AMNH PLATY 1642 and AMNH PLATY 1643, two sets of 1.5­µm­thick serial sagittal sections of epoxy­embedded specimens stained with toluidine blue, collected October 2002. Paratype. AMNH PLATY 1644, epoxy­embedded whole mount.
Type Locality. Oak Island, NC, from shallow subtidal medium grained sand at the Lockwoods Folly Inlet (33° 55' 03"N, 78° 13' 58"W).
Other Material Examined. Living specimens in squeeze preparations; set of 1.5­ µm­thick serial sagittal sections of epoxy­embeded specimen; one whole mount for fluorescence imaging of musculature.
Etymology. Species name comes from the Latin singularis, alone, and refers to the single bursal nozzle in this species.
Synonyms. Anaperus sp.: Smith 1981, Smith & Tyler 1985.
Description. Mature specimens ~1100 µm long and ~200 µm wide (Figs. 1, 2 A). Body somewhat flattened. Anterior and posterior ends rounded.
Epidermis completely ciliated. By transmitted light epidermis reddish­brown in color due to pigment granules. Reddish­orange rod­shaped gland secretions present in long tracts underneath ventral epidermis (Fig. 2 C). Scattered mucoid glands present in epithelium (Fig. 2 B, 3A).
Body­wall musculature with circular muscles that encircle the body along entire length of animal; straight longitudinal muscles present between frontal organ and anterior edge of mouth; longitudinal muscles with a longitudinal orientation anteriorly that bend medially to cross diagonally over the body (longitudinal­cross­over fibers present in dorsal body wall; longitudinal muscles in the anterior half of body that wrap around the posterior rim of mouth (U­shaped muscles) present in ventral body wall (data not shown).
Frontal organ well developed; cell bodies of frontal glands positioned ~200 µm behind frontal pore in fixed specimens (Fig. 1 A–C).
Mouth opening on ventral surface, middle of body. Several examined specimens had conspicuous vacuole in immediate vicinity of mouth (Fig. 1 C).
Ovaries paired, ventral. Egg strands paired or unpaired; extend from position anterior of mouth posteriorly to bursal nozzle (Figs.1, 3 A).
Testes paired, lateral to eggs, follicular; separate from ovary. Testes extend from position near level of mouth posteriorly to level of bursal nozzle (Fig. 1).
Female gonopore absent. Unwalled seminal bursa leads to curved bursal nozzle ~40 µm long (Figs. 1, 2 D, 3A).
Male gonopore ventral at posterior end of body. Pore surrounded by mucoid glands that stain pink in toluidine blue. Male copulatory organ composed of a loose arrangement of muscles surrounding a small muscular penis. Copulatory organ surrounded by strands of darkly staining glandular secretions (Figs. 1 C, 2D, 3B). Several actin­rich stimulatory organs known as adenodactyls also present (Figs. 1, 2 D, 3B, C). Two adenodactyls present anterior to copulatory organ; extend through the ventral epidermis anterior to the male gonopore. Large adenodactyl positioned immediately behind copulatory organ; opens into male antrum (Figs. 1, 3 B, C). Additional adenodactyls, flanking lateral sides of male copulatory organ present in some specimens (data not shown).
Remarks. This species is placed in the family Anaperidae due to the presence of needle­like adenodactyls. The presence of a bursal nozzle along with an unwalled seminal bursa is characteristic of members of the genus Anaperus. Like other anaperids, the adenodactyls of Anaperus singularis are closely associated with gland cells, and our phalloidin stained specimen reveals that the adenodactyls in this species also contain a considerable amount of actin. Besides having a unique arrangement of adenodactyls, A. singularis is distinguished from all other known species in the genus Anaperus in having only a single bursal nozzle; other known species have two or more nozzles.
description: Published as part of Hooge, Matthew D., Smith, Julian P. S. & Iii, 2004, New acoels (Acoela, Acoelomorpha) from North Carolina, pp. 1-24 in Zootaxa 442 on pages 2-6, DOI: 10.5281/zenodo.157611