Mapuplana fjordica, Grau & Almeida & Sluys & Carbayo, 2022

Grau, José Horacio, Almeida, Ana Laura, Sluys, Ronald & Carbayo, Fernando, 2022, A new genus and two new species of land planarians (Platyhelminthes: Tricladida: Geoplanidae) from Southern Chile, Journal of Natural History 56 (13 - 16), pp. 947-967 : 958-963

Mapuplana fjordica sp. nov.

Material examined

Holotype ZMB 11512. Puerto Gaviota , Magdalena Island , Chonos Archipelago, Southern Chile (44°40′0″S, 73°8′0″W), coll. J.H. Grau, 27 January 2007. Transverse sections of the cephalic and ovarian region on 14 slides; horizontal sections of a portion behind the cephalic region on seven slides; transverse sections of the pre-pharyngeal region on four slides; sagittal sections of the pharynx and copulatory apparatus on 34 slides.

Type locality

Puerto Gaviota, Magdalena Island , Chonos Archipelago, Southern Chile . The worm was collected from beneath fallen wood near Puerto Gaviota in Magdalena Island, Southern Chile (44°40′0″S, 73°8′0″W) . This region is characterised by the Valdivian temperate rainforest and receives up to 4000 mm of rain per year.

Etymology

The specific epithet refers to the word fjord, alluding to the landscape of the Chonos Archipelago.

Diagnosis

Species of Mapuplana about 40 mm in length with yellowish dorsum with numerous short, longitudinal dark striae. Ventral cutaneous musculature thickest in the median region of the body. Male atrium 2.4 times longer than female atrium. Proximal portion of the female genital duct lacks openings of shell glands. Gonoduct obliquely oriented, with postero-dorsal inclination. Female atrium with irregular shape.

Description

External appearance. The live specimen measured about 40 mm in length and 3 mm in width; preserved it measured 25 × 6 mm, with a thickness of 1.4 mm. The body is lanceolate, dorsally convex and ventrally flat. The anterior tip is rounded and the posterior one obtusely pointed ( Figure 8 ). At rest, the dorsum is corrugated ( Figure 8 (a)). The ground colour of the dorsal body surface is yellow-orange (RAL 2000), while it is provided with a pair of thin, mid-dorsal, orange-brown (RAL 8023) longitudinal stripes. Furthermore, numerous short and anastomosing longitudinal stripes, with the same orange-brown colour, are spread all over the dorsum, except the paramedian region ( Figure 8 (a)). The ventral side of the preserved specimen exhibited the same pattern of pigmentation as the dorsum, albeit paler, while the anterior extremity was greyish ( Figure 8 (d)).

The eyes are monolobated, and measure approximately 40 µm in diameter. The eyecups contour the anterior tip of the body and extend in a single row along the entire lateral body margin. Sensory pits are absent. The creeping sole is about 80% of the body width ( Figure 9 (a)). The relative position of the mouth:body length is 77% in relation to the anterior tip of the body, while that of the gonopore:body length is 83%.

Epidermis and its secretions. The dorsal and ventral epithelia are about 27 µm in height and are pierced by the openings of gland cells, producing an erythrophil, granular secretion. Rhabditogen cells open onto the latero-dorsal surface, as well as the lateral body margins. A glandular margin is absent.

Cutaneous musculature. The cutaneous musculature consists of a subepidermal layer of circular muscle, followed by a double diagonal muscle layer and a layer of longitudinal fibres. The longitudinal muscle layer consists of large bundles and is about 85 µm thick dorsally, while it measures 240 µm ventrally ( Figures 9 and 10 (a,b)). A 30 µm thick portion of the ventral longitudinal muscle is subepidermal and consists of fibres that are gathered into bundles of 10–15 fibres, while a 210 µm thick portion of the ventral longitudinal muscle is composed of fibres joined into bundles of 8–25 fibres, and is sunken into the parenchyma. The cutaneous musculature thickness relative to the body height in the prepharyngeal region corresponds to 27%.

Parenchymal musculature. There are four parenchymal muscle layers, namely a dorsal layer of decussate fibres (28 µm thick, 2.0% of the body height), a supraintestinal transverse muscle layer (40 µm), a subintestinal transverse muscle layer (30 µm), and a layer of subneural muscle with diagonal decussate fibres (170 µm); the decussate fibres and those of the insunk ventral cutaneous muscle layer are intermingled ( Figures 9 (d) and 10(a,b)).

Musculature in cephalic region. Towards the anterior tip of the body the muscle layers gradually strengthen, so that the CMI here reaches a value of 28% ( Figure 10 (c,d)). Unfortunately, similar stain affinities of muscle fibres and gland cells hinder clear visualisation of the arrangement of the fibres.

Pharynx. The mouth is located at a distance from the anterior region of the pharyngeal pouch equivalent to 64% of its length ( Figure 11 (a)). The oesophagus is about 15% of the length of the pharynx, which is cylindrical and occupies most of the pharyngeal pouch. The epithelium of the pharyngeal pouch is underlain by a layer of circular muscle. The outer pharyngeal epithelium is underlain by a layer of subepidermal longitudinal muscle (6 µm thick), followed by a layer of circular muscle (12 µm thick). Immediately underneath this circular muscle layer is located a 100–110 µm thick layer of intermingled longitudinal and circular muscle fibres that projects from the pharynx anteriorly into the adjacent parenchyma. The inner pharyngeal epithelium is underlain by a layer of intermingled circular and longitudinal muscle fibres (130–145 µm thick) ( Figure 11 (a,b)). Radial muscle fibres are also present. Erythrophil and cyanophil granular secretions run through the parenchyma of the pharynx and are discharged at its tip.

Male reproductive apparatus. The testes are ovoid, measuring 150–170 µm in diameter; the follicles are located dorsally between the intestinal branches and the supra-intestinal transversal parenchymal muscle layer. They are arranged in multiple irregular rows on either side of the body. The testes are prepharyngeal, with the anterior-most ones being located at a distance of 2934 µm from the anterior tip of the body and the posterior-most follicles positioned just anterior to the root of the pharynx.

The sperm ducts run immediately above the sub-intestinal parenchymal muscle layer and slightly laterally to the oviducts. Behind the pharyngeal region, the sperm ducts gradually expand to form spermiducal vesicles, which are packed with spermatozoa. Shortly behind the pharynx these ducts curve dorsally and open separately into one of the tubules of the prostatic vesicle glands ( Figure 11 (c)). The latter communicate with the tubular prostatic vesicle by means of several connections, which are very difficult to discern and reconstruct. In point of fact, one of the sperm ducts communicates at a rather ventral position with a tubule of the prostatic vesicle gland and for this gland we were unable to find its connection with the prostatic vesicle. The latter consists of a winding, extra-bulbar duct with a diameter of about 25 µm, while it is considerably narrower at its anterior and posterior extremities. The prostatic vesicle penetrates the antero-ventral region of the penis bulb and, thereafter, ascends vertically in a coiled fashion to communicate with the ejaculatory duct ( Figure 11 (e)). This prostatic vesicle is lined with a cuboidal, nucleated and ciliated epithelium and is surrounded by a coat of circular muscle between 40 and 100 µm in diameter. This layer of circular muscle is followed by a muscle web that surrounds the entire prostatic vesicle and attaches to the penis bulb. In some histological sections, this muscle web seems to be a continuation of the common muscle coat.

There are two prostatic vesicle glands, one on either side of the body, consisting of highly branched tubules, lined with a cuboidal, nucleated and ciliated epithelium ( Figure 11 (c,e)). The numerous branching tubules, which are surrounded by a thin layer of circular muscle, collect the erythrophil, granular secretion produced by the surrounding gland cells.

The ejaculatory duct horizontally traverses the penis papilla to exit at its tip through a narrow opening ( Figure 11 (e)); the duct is lined with a ciliated, cuboidal epithelium and is surrounded by a 25 µm thick layer of circular musculature.

The small, conical penis papilla is horizontally oriented, projects from the antero-dorsal wall of the male atrium and measures about 10% of the length of the atrium. The musculature of the penis papilla consists of a subepithelial layer of circular muscle, followed by a layer of longitudinal fibres.

The male atrium is ample and provided with 2–3 large transverse folds, and is about 2.4 times as long as the female atrium. The epithelium of the male atrium is cuboidal and is pierced by openings of scarce glands, producing an amorphous, cyanophil secretion. This epithelium is underlain by a 20–30 µm thick layer of circular muscle, which is continuous with a net of abundant muscle fibres without any definite orientation.

Female reproductive system. A single pair of ovaries is located at the posterior end of the anterior third of the body, with the gonads being placed immediately above the ventral nerve plate and directly underneath the transversal sub-intestinal parenchymal muscle layer. The globular ovaries measure about 200 µm in diameter. The ovovitelline ducts arise from the dorsal surface of the ovaries and run posteriorly immediately above the ventral nerve plate. Posteriorly to the gonopore, the oviducts ascend to open into the female genital duct ( Figure 11 (e)). The latter receives the openings of shell glands along approximately 60% of its anterior length, while it curves antero-dorsad to open into the female atrium.

The gonoduct originates at the postero-ventral wall of the female atrium, the latter being rather small and having an irregular shape, while it is surrounded by a layer of circular muscle fibres. The female atrium is lined with columnar cells with basal nuclei in which an erythophil, granular secretion accumulates in the apical portions of the cells. A blind duct originates from the lateral wall of the female atrium on the left side of the animal, but quickly assumes a vertical orientation when it projects into the adjacent parenchyma, while being embedded in the musculature of the female atrium ( Figure 11 (e,f)). This duct measures about 200–300 µm in length and about 50–100 µm in diameter. Basically, the histology of this blind duct is the same as that of the female atrium, including the erythrophil secretion accumulating in the apical portions of the cells. However, in contrast to the female atrium, the epithelium of the blind duct is pierced by abundant openings of gland cells lying around the duct, producing an amorphous cyanophil secretion.

The common muscular coat surrounds the distal ascending portion of the prostatic vesicle, the male atrium, female atrium, and female genital duct and consists of longitudinal and obliquely running muscle fibres.

Figures

Figure 8. Mapuplana fjordica. External features. (a) Dorsal view of holotype during rest; (b) dorsal view of holotype while creeping; (c) dorsal view of preserved holotype; (d) ventral view of preserved holotype. Scale bars not available.

Figure 9. Mapuplana fjordica. (a) Diagrammatic reconstruction of a transverse section of the prepharyngeal region; (b) photomicrograph of a sagittal section of the body, showing cutaneous and parenchymal musculature; (c, d) photomicrographs of transverse sections of the pre-pharyngeal region.

Figure 10. Mapuplana fjordica. Photomicrographs. (a, b) Horizontal sections of a portion behind the cephalic region, showing (a) dorsal and (b) ventral regions; (c, d) transverse sections of the cephalic region, showing the musculature.

Figure 11. Mapuplana fjordica. Pharynx and copulatory apparatus. (a, b) Photomicrographs of sagittal section of (a) complete pharynx and (b) detail of pharyngeal musculature; (c) photomicrograph of sagittal section of tubules of prostatic vesicle glands; (d) photomicrograph of sagittal section of copulatory complex; (e) diagrammatic reconstruction of the copulatory apparatus; (f) photomicrograph of sagittal section of the blind duct.