Pusillaplana rubella Sluys, 2025
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publication ID |
https://doi.org/10.11646/zootaxa.5686.4.2 |
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publication LSID |
lsid:zoobank.org:pub:D9093859-215B-41CC-8740-A3E55C624470 |
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persistent identifier |
https://treatment.plazi.org/id/03B7F005-FFBD-343A-FF14-14E0FE9BFDDD |
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treatment provided by |
Plazi |
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scientific name |
Pusillaplana rubella Sluys |
| status |
sp. nov. |
Pusillaplana rubella Sluys , sp. nov.
Material examined. Holotype: RMNH. VER.22265.1, east of Wild Cane Key , Bocas del Toro, Panama, 9.35169444° N, 82.16200000° W, 14–18 June 2010, in sediment, coll. Daniel Gouge, Ashleigh Smythe, Katrine Worsaae, sagittal sections on 1 slide. GoogleMaps
Paratypes: RMNH. VER.22265.2, ibid., sagittal sections on 1 slide ; RMNH. VER.22265.3, ibid., horizontal sections on 1 slide ; RMNH. VER.22265.4, ibid., whole mount on 1 slide ; RMNH. VER.22265.5, ibid., whole mount on 1 slide .
Other material: RMNH. VER.22266.1, sagittal sections on 1 slide.
Etymology. The specific epithet is derived from the Latin rubellus, red, and alludes to the red pigmentation of the animals.
Ecology and distribution. The animals were part of a highly diverse interstitial community collected from medium coarse sand on Wild Cane Reef in 1–1.5 m wide channels between coral heads at a depth of up to 6.4 m.
Diagnosis. As for the genus.
Description. In extended condition, living specimens up to 0.8 mm in length and 0.3 mm in width. The preserved holotype specimen was 0.62 mm long, as determined from histological sections. Head rounded and tail obtusely pointed. Dorsal surface provided with reddish pigment, which is arranged in two bands that run from the tail to shortly behind the eyes and converge to a single branch that extends between the eyes forwards to the frontal margin ( Fig. 5 View FIGURE 5 ). In living specimens, the pigment is more diffusely arranged in the middle part of the body, thus forming a broad pigmented area ( Fig. 5A View FIGURE 5 ), while in one of the paratype whole mounts (RMNH.VER.22265.5) the red pigment is here more distinctly arranged as two bands ( Fig. 5B View FIGURE 5 ). The ventral surface is pale and provided with a zone of adhesive papillae.
The eyes are positioned on top of the brain ( Fig. 6A View FIGURE 6 ) and consist of a pigment cup housing two retinal cells; an eye lens is absent.
The comparatively very short pharynx is fully situated in the anterior portion of the body and measures about 1/13 th of the body length in preserved specimens ( Figs 6A View FIGURE 6 ; 8 View FIGURE 8 ). The pharyngeal musculature is of the usual, planariid type. The mouth opening is situated at the posterior end of the pharyngeal pocket.
The testes are located in the middle of the body, i.e., the follicles cannot be considered to be situated closer to the ventral or to the dorsal body surface. The testis follicles extend posteriorly from about half-way between the brain and the root of the pharynx to a position between the penis papilla and the copulatory bursa; there may be no more than about 8 follicles on either side of the body.
Concerning the sperm ducts, we could only distinguish a single broad duct that penetrates the penis bulb and opens into an egg-shaped intrabulbar seminal vesicle ( Fig. 6B View FIGURE 6 ). Probably, this single duct represents a common vas deferens, resulting from the fusion of two sperm ducts outside of the male copulatory apparatus. However, separate sperm ducts or their point of fusion could not be traced in the histological sections.
The seminal vesicle communicates via a small opening with the proximal section of the penis that is traversed by many septa and thus forms a kind of mesh, which receives the abundant, erythrophilic secretion of penis glands ( Figs 6B View FIGURE 6 ; 9 View FIGURE 9 ). These septa converge towards the proximal end of the ejaculatory duct, which runs straight towards the blunt tip of the penis papilla; the duct is lined with a ciliated, probably infranucleated, epithelium. The penis papilla occupies almost the entire male atrium, which opens to the exterior via a separate gonopore ( Figs 6B View FIGURE 6 ; 7A View FIGURE 7 ; 8 View FIGURE 8 ).
The penis papilla is basically cone-shaped, with a blunt tip. The papilla is divided into a broad, conical basal section that is separated from a more narrow and tubular distal part by a slight constriction at about halfway the length of the penis papilla. The papilla is covered with a very thin epithelium, which is underlain by a well-developed layer of circular muscles, followed by a thin layer of longitudinal muscle fibres.
The tip of the penis papilla carries a ring of distinct, sclerotic spines. These spines are most clearly evident in slightly squeezed, live specimens, and thus, it was determined that there are about 20 spines encircling the tip of the penis ( Fig. 7B View FIGURE 7 ). Each spine measures about 7.4 μm in length.
The small ovaries are situated directly in front of the male atrium and the penis papilla, immediately dorsally to the ventral nerve cords ( Fig. 6A View FIGURE 6 ). Each ovary consists of one or two, big oocytes.
A conspicuous structure of the female copulatory apparatus is formed by a copulatory bursa that lies immediately behind the male atrium and opens ventrally to the exterior through its own, separate gonopore ( Figs 6A, B View FIGURE 6 ; 7A View FIGURE 7 ; 8 View FIGURE 8 ). The ball-shaped bursa is lined by a nucleated epithelium, while a large section of its lumen is filled with a coarsegrained, yellowish substance of unknown nature or origin. The bursa communicates via a very narrow opening with a well-developed gonoduct, leading to the gonopore. The histological sections suggest the presence of a connecting duct or bursal canal between the male atrium and the copulatory bursa or gonoduct. Unfortunately, only the section of this connecting duct opening into the male atrium is well-developed, whereas its connection with the female apparatus remains obscure.
The course of the oviducts and their communication with the female copulatory apparatus is complex. At the level of the gonoduct connecting the bursa with the secondary gonopore, each oviduct throws off a very short and narrow duct that quickly expands to form a balloon-shaped duct. The latter communicates with the copulatory bursa precisely at the point of the narrow connection between bursa and gonoduct ( Figs 6B View FIGURE 6 ; 10A View FIGURE10 ). The openings of these balloon-shaped sections of the oviduct into the bursa are symmetrical and situated close together, resulting in the fact that these sections actually also communicate with each other ( Fig. 10A, B View FIGURE10 ).
After having thrown off the small connecting ducts to the balloon-shaped sections, the oviducts continue their course backwards and join behind the gonoduct, thus forming a loop ( Fig. 10B View FIGURE10 ). The oviducts, including the balloon-shaped sections, are lined with a nucleated and ciliated epithelium.
From the oviducal loop arises a narrow duct, containing sperm, that runs dorsally and ends in close proximity of a gut branch.Although no open connection between duct and gut was observed, this is most likely a genito-intestinal duct ( Fig. 10A, B View FIGURE10 ).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.