Dugesia artesiana Sluys & Grant, 2007
- domain Eukaryota Whittaker & Margulis, 1978
- kingdom Animalia Linnaeus, 1758
- Bilateria Hatscheck, 1888
- Protostomia Grobben, 1908
- phylum Platyhelminthes Gegenbaur, 1859
- Rhabditophora Ehlers, 1985
- order Tricladida Lang, 1884
- suborder Continenticola Carranza et al., 1998
- superfamily Geoplanoidea Stimpson, 1857
- family Dugesiidae Ball, 1974
- genus Dugesia Girard, 1850
Original Published Description:
Dugesia artesiana Sluys & Grant, 2007 is a freshwater planarian found in Queensland, Australia. Just one more Dugesia species is known from Australia, Dugesia notogaea Sluys & Kawakatsu, 1998.
The specific epithet is derived from the English adjective “artesian” and alludes to the fact that the animals have been collected from the artesian system in the Great Artesian Basin.
Dugesia artesiana is characterized by a presumably central ejaculatory duct, asymmetrical openings of the oviducts into the bursal canal, infranucleated bursal canal, absence of ectal reinforcement, small diaphragm, and absence of a duct between intrabulbar seminal vesicle and diaphragm.
Preserved specimens up to 14 mm long and 2 mm wide. Dorsally a light yellow-brown base is consistent throughout all specimens, yet the density of the fine dark specks varies. Consequently, dorsal pigmentation ranges from dark brown to light yellow-brown. However, regardless of the level of pigmentation it always lightens considerably at the body margins and over the pharyngeal region. Likewise the ventral surface is always paler than dorsal, as pigment is less intense. Examination of the histological sections revealed that the dorsal surface of the holotype is densely pigmented, whereas pigment granules appeared to be absent or very sparse underneath the dorsal epidermis of the other specimen. In the preserved state the front end is rounded (Fig. 1), with no evidence of auricles, owing to preservation effects. A pair of small, pigmented eye cups sit at the point where head tapers in, and positioned closer to each other than to lateral margins. No other sensory structures are evident. The pharynx is positioned posteriorly, in most cases, occupying between one-fourth and one-fifth of the total body length. In the highly contracted holotype and in specimen V.Pl. 3054.1 the pharynx is located in the middle of the body and measures between 1/5-1/6th and 1/8-1/9th of the body length, respectively. The mouth opening is located at the posterior end of the pharyngeal pocket.
The small testes are situated dorsally and extend from the level of the ovaries, or slightly anterior to the female gonads, to well beyond the copulatory apparatus. The ovaries are located at about 1/3rd of the distance between the brain and the root of the pharynx. The oviducts arise from the dorsal surface of the ovarial wall, with these proximal ends of the ducts being much wider than the major part of the oviducts traversing the body; the oviducts do not branch, i.e. they do not extend backwards beyond the level of the copulatory apparatus.
The sperm ducts communicate separately with the very proximal, anterior section of an elongated, intra-bulbar seminal vesicle. The latter is lined with a relatively tall epithelium, receiving the secretion of erythrophilic penis glands. The distal, posterior end of the vesicle tapers to form a small diaphragm conus, which receives the abundant secretion of erythrophilic penis glands. The diaphragm conus projects into the funnel-shaped, proximal section of the ejaculatory duct, the latter receiving the secretion of the erythrophilic penis glands. It is difficult to ascertain whether the ejaculatory duct runs a central or an acentral, ventrally displaced course through the penis papilla. In the holotype the ejaculatory duct could be traced for only part of its length, while its opening at the tip of the penis papilla is not apparent (Fig. 2). In specimen V.Pl. 3054.1 the ejaculatory duct runs a central course through the penis, with a clear opening at the tip. However, in this animal the penis papilla is highly contracted, which may have resulted in an artefactual condition with regard to the course of the ejaculatory duct (Fig. 3). The penis papilla is covered with a nucleated epithelium.
The bursal canal arises from the lateral wall of the common atrium and runs anteriad latero-dorsally to the male atrium and the penis bulb. Immediately anterior to the bulb, the bursal canal communicates with the sac-shaped copulatory bursa. In the holotype the bursa contains remnants of a spermatophore. The bursal canal receives the asymmetrical openings of the infranucleated oviducts very close to the junction with the common atrium. One oviduct opens into the postero-ventral section of the bursal canal, or even into the atrium itself, whereas the other oviduct approaches the canal from a more ventro-lateral direction. Shell glands open into the ventral section of the bursal canal, i.e. in the region where the canal receives the openings of the oviducts. The bursal canal is lined with an infranucleated epithelium for most of its length; in specimen V.Pl. 3054.1 only a short section of the bursal canal immediately adjacent to the copulatory bursa is provided with nucleated cells. The most prominent muscle layer around the bursal canal is one consisting of circular muscle. However, in specimen V.Pl. 3054.1 a thin subepithelial layer of longitudinal muscle is also present; this layer of longitudinal muscle could not be traced in the holotype.
Ecology and Distribution
The species is known only from these two springs in the Great Artesian Basin at Edgbaston, which are separated by a distance of about 8 km.
Holotype: AM W.29441, Edgbaston Station, Blue eye spring (22°43’13’’S - 145°26’20’’E), Queensland, Australia.
Additional material: ZMA V.Pl. 3054.1, Edgbaston Station, spring 12, at spring head (22°45’20’’S - 145°25’31’’E), Queensland, Australia.
The holotype was collected from shallow water at the spring’s edge, and the other specimen was found in a flowing seepage at the head of another spring.