Geoplana multicolor sensu Graff, 1899

Rossi, Ilana, Boll, Piter Kehoma & Leal-Zanchet, Ana Maria, 2024, Multispecies multicolor: resolving the century-old taxonomic trouble of Geoplana multicolor (Platyhelminthes: Geoplanidae), Zoologia (e 23093) 41, pp. 1-10 : 3-7

Redescription of Geoplana multicolor sensu Graff, 1899

Length* 45

Material examined: Holotype: ZMH V2657: J. Metz coll. 1894. São Paulo, state of São Paulo, Brazil: anterior tip: transverse sections on 17 slides; anterior region: horizontal sections on 37 slides; pre-pharyngeal region in two fragments: transverse sections on 11 slides and horizontal sections on 39 slides; pharyngeal region: sagittal sections on 41 slides; copulatory apparatus in two fragments: sagittal sections on 45 slides and 19 slides, respectively.

Width* 4.5

DM* 23 (51)

DG* 29 (64)

DMG* 6

DPVP –

Ovaries –

Anteriormost testes –

Posteriormost testes –

Prostatic vesicle** –

External features: Preserved, specimen approximately 40 mm in length and with a maximum width of 4 mm; body with parallel margins, dorsal surface strongly convex and ventral side flat; anterior tip rounded ( Fig. 2A ). Mouth and gonopore at the third quarter of the body from the anterior end ( Table 1).

Penis papilla** –

Male atrium** –

Female atrium** 1.8

Common glandular ovovitelline duct** 0.06

Conical eyes (sugarloaf shaped), 110 µm in length and 25 µm in width, surround the anterior tip ( Figs 2B , 3A–B). After the second millimeter of the body (approximately 4% of body length), the eyes become monolobate and dorsal, with pigment cups about 25–35 µm in diameter.

Internal morphology:Sensory pits (Fig. 3A, B), as simple invaginations (20–40 µm), contour the anterior tip and occur ventromarginally in an irregular, single row in the first 14 mm of the body (approximately 30% of body length). The creeping sole occupies 78% of the body width in the pre-pharyngeal region (Fig.3C, Table 2). Two types of gland discharge through the epidermis of the pre-pharyngeal region: rhabditogen glands with xanthophil secretion and cyanophil glands with finely granular secretion.Cyanophil glands with fine granules are more abundant in the ventral epidermis, while rhabdito - gen glands are more abundant in the dorsal epidermis (Fig. 3C, D). Glandular margin absent (Fig. 3E).

Cutaneous musculature with the usual three layers as in Geoplaninae (circular, oblique, and longitudinal), with longitudinal muscle fibers organized in thick discrete bundles (Fig. 3C–E). Thickness of cutaneous musculature becoming progressively lower towards the body margins. Ventral musculature thicker than the dorsal musculature at the sagittal plane in the pre-pharyngeal region, 1.5 times thicker than the epidermis ( Table 2). Mc:h 6%; however, the measurement of the body height is not fully accurate due to artifacts in the histological preparation.

Mesenchymal musculature (Fig. 3A, C, D, F) consisting of three layers: dorsal subcutaneous, located close to the cutaneous longitudinal muscle bundles, with oblique decussate fibers; supra-intestinal transverse; and sub-intestinal transverse. In addition, there are longitudinal fibers around the intestine, forming a poorly developed muscular tube (Fig. 3F), as well as dorsoventral fibers.

The pharynx is not visible in any of the analyzed body fragments.

Testes arranged in one irregular row on either side of the body, located between the dorsal transverse mesenchymal muscles and the intestinal branches. Vitellaria (Fig. 3E, F) scattered between intestinal branches, poorly developed. In the region of the copulatory apparatus, the only visible structures are the gonopore, the female atrium, and the female canal (Fig. 4A, B). Female atrium lined by pseudostratified epithelium (about 50 µm high), laterally filled by epithelium of stratified appearance (100–225 µm high) with large lacunae (Fig. 4C, D), receiving the openings of abundant erythrophil and cyanophil glands, both with finely granular secretion, and scarcer amorphous xanthophil secretion. Erythrophil

A

C

B

D

E F Figure 3. Geoplana multicolor , holotype (V2657), in transverse (A–E) and horizontal sections (F; anterior tip to the left): (A) anterior region of the body; (B) detail of the anterior region of the body; (C) detail of the ventral surface of the pre-pharyngeal region; (D) detail of the dorsal surface of the pre-pharyngeal region; (E) detail of body margin of the pre-pharyngeal region; (F) detail of the longitudinal mesenchymal musculature around the intestine, in the anterior region of the body. (ce) Conical eyes, (cg) cyanophil glands, (cs) creeping sole, (de) dorsal epidermis, (dm) dorsal cutaneous musculature, (dsm) dorsal subcutaneous mesenchymatic musculature, (eg) erythrophil glands, (i) intestine, (lm) longitudinal mesenchymatic musculature, (n) nerve cord, (rg) rhabditogen glands, (sbm) sub-intestinal transverse mesenchymatic musculature, (sp) sensory pit, (spm) supra-intestinal transverse mesenchymatic musculature, (v) vitelline follicles, (vm) ventral cutaneous musculature. Scale bars: A = 0.5 mm, B–F = 0.2 mm.

A

B

C D Figure 4. Geoplana multicolor , holotype (V2657), photomicrographs of the copulatory apparatus in sagittal sections: (A) gonopore and female atrium; (B) detail of female canal; (C–D) details of the female atrium. Anterior tip to the left. The arrow indicates the lacunae. (cg) Cyanophil glands, (cov) common glandular ovovitelline duct, (eg) erythrophil glands, (fa) female atrium, (go) gonopore. Scale bars: A = 0.5 mm, B–D = 0.2 mm.

and cyanophil secretions occur in the lumen of the female atrium. Muscularis of the female atrium (about 30–55 µm thick) composed of a thin subepithelial longitudinal layer, followed by a thicker circular layer, besides scarce external longitudinal fibers (Fig. 4C). Gonoduct vertical at the sagittal plane, lined with ciliated, columnar epithelium, receiving the openings of abundant xanthophil amorphous secretion and cyanophil glands producing a finely granular secretion, besides scarcer erythrophil glands with finely granular secretion. Muscularis of gonoduct consisting of a subepithelial layer of circular fibers, followed by a longitudinal layer.

It is important to emphasize that the centenary specimen, borrowed from Zoologisches Museum Hamburg, was preserved in alcohol, presenting signals of previous damage at about the middle of the body as a possible result of accidental crushing. This is likely why we were unable to see the pharynx and most of the copulatory apparatus.

Figures

Figure 2. Geoplana multicolor, holotype (V2657): (A) anterior tip of the fixed specimen in dorsal view; (B) anterior tip of the specimen in clove oil. Anterior tip to the left. (ce) Conical eyes. Scale bars: A = 0.2 mm, B = 0.5 mm.