Minutaplana dimaculosa Vila-Farré & Laumer, 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-FFB9-3434-FF14-1183FDDDF93C |
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treatment provided by |
Plazi |
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scientific name |
Minutaplana dimaculosa Vila-Farré & Laumer |
| status |
sp. nov. |
Minutaplana dimaculosa Vila-Farré & Laumer , sp. nov.
Material examined. Holotype: RMNH. VER.22264.1, Wild Cane Key / Reef at Bastimentos Island, Bocas del Toro Province, Panamá, 14–18 June 2010, coll. Christopher Laumer, Alejandro Martínez García, Barbara Eder, Sofia Pyataeva, sagittal sections on one slide.
Paratypes: RMNH. VER.22264.2, ibid., sagittal sections on 2 slides ; RMNH. VER.22264.3, ibid., sagittal sections on 2 slides ; RMNH. VER.22264.4, ibid., horizontal sections on one slide ; RMNH. VER.22264.5, ibid., horizontal sections on one slide .
Etymology. The specific epithet is derived from the Greek dis, twice, and the Latin adjective maculosus, spotted, and alludes to the two pigmented spots on the head of the animal.
Ecology and distribution. The species is known only from the type locality ( 9.350650° N, 82.172417° W) at the Wild Cane Key in the Caribbean Sea, in the interstitial sediments of a coarse sand area at a depth of 3 m.
Diagnosis. As for the genus.
Description. In elongated state, living sexually mature specimens up to 1.7 mm in length and 0.5 mm in width ( Fig. 1 View FIGURE 1 ). The preserved holotype specimen was 1.3 mm long, as determined from histological sections. Body broadly oval-shaped, with rounded hind end and with the greatest width of the body at about the posterior third of the animal. Anterior to the eyes the body shows a narrowing, after which the body margins slightly diverge to form a triangular-shaped front end with a small, rounded protuberance at its mid-point. The two eyes are far removed from the frontal margin and lie close together at a distance of 1/5-1/6 th of the width of the head. Dorsal and ventral body surfaces are hyaline, except for two brown spots at the level of the narrowing of the head. Histologically, the pigment granules of these spots resemble those of the eyecup, albeit being more irregular in shape.
The eyes (eyecup diameter 18–21 μm in histological sections) contain two retinal cells, and are placed dorsally, just below the body wall musculature and above the brain. The eye has an oval lens (10–14 μm diameter in sections) situated in the opening of the pigment cup ( Fig. 2A, B View FIGURE 2 ). The so-called “Substanzinseln” are present in the brain (cf. Sluys 1989).
In front of the brain of the holotype there is a cavity (maximum diameter 138 μm) lined with a brown structure that contains a brown glandular secretion, probably originating from the parenchyma dorsally to the cavity ( Fig. 2C View FIGURE 2 ). The same cavity is also present in other specimens, e.g. RMNH. VER.22264.4 and RMNH. VER.22264.3, either in front or behind the brain .
The anterior branch of the intestine extends anterior to the eyes and reaches almost the level of the pigment spots. The cylindrical pharynx lies approximately in the middle of the body and measures between 1/3 and 1/2 of the body length. The outer epithelium of the pharynx is ciliated, except at its proximal section (first third of the pharynx not ciliated in specimens RMNH.VER.22264.3 and RMNH.VER.22264.4), and is underlain by a layer of longitudinal muscles, followed by a layer of circular muscles. Very thick outer layer of circular muscles present underneath the inner pharynx epithelium, followed by an inner layer of longitudinal muscles fibres. The mouth lies at the posterior end of the pharyngeal pocket, close to the hind wall of the pharyngeal pouch. In specimen RMNH. VER.22264.2 the mouth is situated just behind the penis papilla and is connected to the pharyngeal pouch through an irregularly-shaped canal.
The ventral epidermis of the body is underlain by a layer of circular muscles, followed by a layer of longitudinal muscle. The longitudinal layer becomes very thick at the anterior end of the body (thickness of the layers at the anterior end: circular layer, 4 μm; longitudinal, 9 μm) ( Fig. 2B View FIGURE 2 ). A zone of ventral adhesive papilla is present.
The large and ventrally located testes extend posteriorly in two rows from a short distance behind the ovaries to the level of the copulatory apparatus; the follicles occupy about 3/5 th of the dorsoventral diameter, extending dorsally beyond the midline of the body.
At the posterior end of the pharyngeal pouch, the very narrow vasa deferentia widen to form very large, sac-shaped spermiducal vesicles that contain sperm. These spermiducal vesicles occupy approximately two-thirds of the dorsoventral diameter of the body. After penetrating the penis bulb, the vasa deferentia bend ventrally and open separately into the ejaculatory duct inside the penis papilla ( Figs 3 View FIGURE 3 ; 4 View FIGURE 4 ). The ejaculatory duct runs centrally through the penis papilla and widens just before the tip to form an intrapenial cavity. The ejaculatory duct is lined with a thin nucleated epithelium. Surrounding the ejaculatory duct and the walls of the penis papilla are numerous, densely redstaining nuclei, particularly near the tip of papilla, where they mix with the circular muscles underneath the lining epithelium ( Fig. 4A View FIGURE 4 ). The mesenchyme of the penis papilla receives an abundant cyanophilic secretion from the parenchyma around the atrium and houses septa that converge towards the dorsal wall of the intrapenial cavity ( Figs 3 View FIGURE 3 ; 4A View FIGURE 4 ). The rounded penis bulb is formed by longitudinal muscles intermingled with a few circular muscle fibres. The narrow male atrium is lined with a thin epithelium that is underlain by a layer of circular muscle fibres, followed by a layer of longitudinal fibres. The gonopore lies approximately under the tip of the penis papilla.
The ovaries occupy about 1/3 rd of the dorsoventral diameter of the body. They are located at the base of the posterior end of the brain, lying over the ventral nerve cords. There are no traces of oviducts in any of the specimens examined. Only the central section of the short and narrow bursal canal is visible and receives the openings of the shell glands all along it ( Fig. 3 View FIGURE 3 ).
The connection between the bursal canal and the atrium and between the bursal canal and the copulatory bursa is only faintly evident ( Figs 3 View FIGURE 3 ; 4A View FIGURE 4 ). The big and oval-shaped copulatory bursa is located just behind the atrium and is lined with a tall epithelium that is covered with a thin layer of muscle fibres. The bursa opens to the exterior through a canal, lined with a nucleated epithelium, that arises from its posterior wall and runs parallel to the ventral body surface before it bends dorsally to open through the dorsal epidermis near the end of the body, thus forming a secondary gonopore ( Figs 3 View FIGURE 3 ; 4B View FIGURE 4 ). This canal is surrounded by a thin muscle layer, while its diameter decreases progressively towards its distal end.
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.