Polychoerus ebenhochi Achatz, Hooge & Tyler, 2007, sp. nov.
Creators: name: Achatz, Johannes G.
name: Hooge, Matthew D.
name: Tyler, Seth
Publisher: name: Zenodo
Year: 2007
Subjects: Biodiversity
Taxonomy
Animalia
Xenacoelomorpha
Acoelomorpha
Acoela
Convolutidae
Polychoerus
Polychoerus ebenhochi

description: Polychoerus ebenhochi sp. nov.
(Figs. 18–20)
Diagnosis. Polychoerus with distinct dorsal concrement pattern, ciliated muscular vagina, and penis with ciliated and nucleated epithelium. Units: st 25, m 54, fgp 79, mgp 86.
Type material. Holotype: USNM 1096745, one set of 1.5-µm-thick serial sagittal sections of epoxyembedded specimen stained with toluidine blue. Paratype: USNM 1096746, one set of 1.5-µm-thick serial sagittal sections of epoxy-embedded specimen stained with toluidine blue.
Type locality. Submerged, fallen mangrove leaves and detritus underneath mangrove trees in Grouper Gardens at Twin Cays, Belize (16°49’46.3” N, 88°06’10.0” W).
Other material examined. Living specimens in squeeze preparations from Grouper Gardens and from a patch of sand at 2–3 m water depth on the east side of the barrier reef that lies on the east side of Carrie Bow Cay, Belize (16°48’9.4” N, 88°04’54.1” W), two complete sets of serial sections of epoxy-embedded specimens stained with toluidine blue, one whole-mount of an immature animal for fluorescence microscopy.
Etymology. The species is named in honor and memory of August Ebenhoch, Austria.
Description. Mature animals are 2–3 mm long and 0.5–1 mm wide. The anterior end is rounded, the lateral edges run parallel to each other except for an indentation in the mid-region of the body, and the posterior end bears two rounded lobes (Fig. 18 A). Adults commonly possess three caudal filaments, but some were observed with five or six. Juveniles possess one median caudal filament (Fig. 18 B). In reflected light, the animals generally appear milky-translucent with red rhabdoid gland cells, orange pigmentation of the digestive syncytium contents, and a bilateral pattern formed by concrements. These concrements, which appear white in reflected light and black in transmitted light, occur as dots within the dorsal epidermis, and cluster together to form larger spots and patterns: three spots at the anterior margin, a pair of spots ~ 1 mm behind the anterior tip, a transverse zigzag band behind the indentation of the lateral body margins, and a pair of spots at the posterior end of the body where the caudal filaments protrude (Fig. 18 A).
The epidermis is entirely ciliated; the cilia are ~7 µm long. Most nuclei of the epidermis are sunken beneath the body-wall musculature.
The body-wall musculature is thicker on the ventral side than on the dorsal side. On the ventral side it consists of outermost circular muscles followed by longitudinal muscles. The most lateral longitudinal muscles run along the lateral margins of the body, more centrally positioned are longitudinal muscles, which bend towards the body midline behind the mouth. Most centrally are longitudinal muscles, which bend towards the body midline and cross each other in front of the mouth. Radiating muscles run from the mouth to the body margin. They run straight from the anterior rim of the mouth to the anterior tip of the body. The further posterior the muscles originate, the more they spread away from the body midline, finally resulting in few Ushaped muscles, which bend around the posterior rim of the mouth at a low angle. Dorso-ventral muscles are numerous throughout the body.
Red rhabdoid gland cells dot the entire body wall, especially on the dorsal side. No mucous gland cells could be detected, and a frontal organ is absent.
The nervous system consists of two paired ganglia in front of, and lateral to, the statocyst. The statocyst lies ~ 500 µm behind the anterior tip. Juveniles have two brown eyespots lateral to the statocyst, but these are absent in adults (Fig.18 B).
The mouth lies slightly behind the middle of the body (Fig. 20 A). The digestive syncytium contains crustaceans in some specimens (Fig. 19).
The paired testes are positioned lateral and dorsal to the paired ovaries. Both, testes and ovaries originate behind the statocyst. The germative zones of the testes extend to the edge of the seminal bursa. Sperm migrate to the copulatory organ and accumulate on its lateral sides (Fig. 19). They enter the penis papilla through ventro-lateral openings and migrate to the proximal tip of the penis through ducts in glandular tissue that fills the space between penis and the wide meshed penis sac (Fig. 20 C).
Mature oocytes are highly lobulated and often surround other oocytes and parts of the seminal bursa and sometimes reach the dorsal peripheral parenchyma. Their cytoplasm contains numerous granules, which appear black in live observation under transmitted light (Fig. 19), and does not stain as darkly with toluidine blue as that of developing oocytes. At the plasma membrane, numerous necrotic nuclei of incorporated cells are present. After maturation the oocytes assume a spherical shape.
The female gonopore is transversely elliptical and lies ~500 µm behind the mouth and ~200 µm in front of the male gonopore (Fig. 20 A). The ciliated, muscular vagina is ~140 µm long, lined with a 20–30 µm thick epithelium and surrounded by vacuolated parenchymal cells, and it opens into the caudal part of the seminal bursa (Figs. 19, 20 B). Numerous parenchymal muscles attach it to the dorsal body wall. The seminal bursa is ~350 µm wide (Fig. 20 A) and bears 11–18 bursal nozzles in its ventral wall (Fig. 19). The cavity of the seminal bursa is filled with a finely granulated syncytial tissue. The bursal nozzles are ~24 µm long, directed ventrally, and often have a cluster of sperm at their proximal ends.
The male gonopore lies behind the female gonopore, ~400 µm in front of the posterior end. The penis lumen is lined with a nucleated, ciliated epithelium. Its musculature consists of numerous circular muscles and a few longitudinal muscles among them. It is surrounded by a wide meshed, weak penis sac, which measures ~170 µm in diameter. The space between the penis and the penis sac is filled with parenchymal glandular tissue through which two lateral ducts carry sperm to the proximal end of the penis (Fig. 20 C).
description: Published as part of Achatz, Johannes G., Hooge, Matthew D. & Tyler, Seth, 2007, Convolutidae (Acoela) from Belize, pp. 35-66 in Zootaxa 1479 on pages 57-60, DOI: 10.5281/zenodo.176820