Geoplana vaginuloides, (DARWIN, 1844)

Ana Laura Almeida, Fernando P. L. Marques & Fernando Carbayo, 2019, ‘ Endless forms most beautiful’: taxonomic revision of the planarian Geoplana vaginuloides (Darwin, 1844) and discovery of numerous congeners (Platyhelminthes: Tricladida), Zoological Journal of the Linnean Society 185, pp. 1-65 : 23-26

GEOPLANA VAGINULOIDES ( DARWIN, 1844)

Planaria vaginuloides Darwin, 1844 , p. 244.

Geoplana vaginuloides: Riester, 1938 , p. 72–75 [part]; Froehlich, 1956a, p. 314–315 [part]; Marcus, 1951, p. 54–56 (misidentification), 1952: p. 76–77 (misidentification).

Material examined

Neotype MZUSP PL 2074 (field number F6387): Parque Estadual da Pedra Branca , Rio de Janeiro / RJ, Brazil (22°56′13.5″S, 043°27′39.5″W). F. Carbayo et al., collected (coll.), 13 December 2014. Cephalic region: horizontal sections on two slides; ovarian region: horizontal sections on eight slides; piece behind ovarian region: horizontal sections on ten slides; prepharyngeal region: transverse sections on ten slides; pharynx: sagittal sections on five slides; copulatory apparatus: sagittal sections on ten slides.

SMF N574: Barreira, Teresópolis, Rio de Janeiro/ RJ, Brazil. E. Bresslau coll., 1914. Cephalic region preserved in balsam on one slide; pre-pharyngeal region: transverse sections on one slide; pharynx: sagittal sections on two slides; copulatory apparatus: sagittal sections on three slides; tail preserved in balsam on one slide.

SMF N628: Barreira, Teresópolis, Rio de Janeiro/RJ, Brazil. E. Bresslau, Coll. 1914. Cephalic region and tail preserved in balsam on one slide; pre-pharyngeal region: transverse sections on one slide; pharynx and copulatory apparatus: sagittal sections on three slides.

Note

We could not confirm conspecificity of some specimens studied by Riester (1938) and specimens examined by Froehlich (1955a, 1956a, 1958) (see Supporting Information, Table S1).

Distribution

Areas covered with Atlantic forest in the municipalities of Rio de Janeiro and Teresópolis, state of Rio de Janeiro.

Diagnosis

Dorsal colour pattern constituted by a median black band, bounded on either side by a fine white-yellow stripe, externally to which is a very thin black line, and this is externally bordered by a marginal reddish-iron band. Inner pharynx musculature with two layers. Anteroventral region of penis bulb more developed. Penis papilla with dorsal insertion strongly displaced anteriorly to level the ventral insertion.

Type locality

Rio de Janeiro, Brazil.

External aspect

Live animals ~70 mm long and 4 mm wide. Elongated body, with margins approximately parallel; anterior end rounded, posterior pointed. Dorsum convex, ventral side slightly convex. Dorsal colour constituted by a median black band (one-third of body width), bounded on either side by a fine white-yellow stripe (twoninths), externally to which is a very thin black line (one-ninth), and this is bordered externally by a marginal reddish-iron band (one-third) ( Fig. 4A ). Ventral body surface grey with dark margins at cephalic end, and saffron yellow on the remaining surface. After fixation, body colour faded slightly. Two types of eyes: (1) a conical type (zuckerhutförmig, sugarloaf shaped), 90 µm high and 40 µm in width; and (2) a cup-shaped type, 40 µm in diameter, with the former contouring the anterior end. Cup-shaped-type eyes spread as a band, one-third of body width on either side. In the posterior half of the body, the eyes even reach to the median black band. Sensory pits simple invaginations, 20 μm deep, located ventromarginally in a single row from the very anterior body tip up to at least the first one-quarter of body length. Relative position mouthto-body length, 48%. Relative position gonoporeto-body length, 61%.

Internal morphology

Creeping sole 97% of body width. Very abundant rhabditogen cells piercing dorsal and marginal epidermis. Glandular margin absent. The cutaneous musculature comprises three layers, namely a subepithelial circular layer, followed by a double diagonal layer with decussate fibres, and then a well-developed longitudinal layer. Muscle fibres of the longitudinal, innermost layer (30 µm thick) arranged into bundles with 15–35 fibres each. CMI, 8%. Three parenchymal muscle layers present, all weakly developed: dorsal layer of decussate diagonal fibres, supraintestinal layer of transverse and longitudinal fibres, and subintestinal layer with transverse and longitudinal fibres ( Fig. 4B ). Ventral nerve plate present.

Mouth situated at a distance from the root of the pharynx equivalent to 67% of pharyngeal pocket length. Pharynx cylindrical ( Fig. 4C ). Oesophagus-topharynx ratio, 12%. Outer pharyngeal musculature consisting of a subepithelial layer (6 µm) of longitudinal muscle, followed by a layer (30 µm) of circular fibres. Inner pharynx musculature consisting of a subepithelial layer of circular fibres (40 µm), followed by a layer of of longitudinal fibres (10 µm).

Testes dorsally located between supraintestinal parenchymal muscle layer and intestine; anteriormost testes at a distance equivalent to 17% of body length; posterior follicles near to the pharynx root. Penis bulb oval, relatively strongly developed, more developed ventro-anteriorly; it extends from 0.5 mm anterior to penis papilla to being level with the gonopore region (specimen MZUSP PL 2074). Penis bulb consists of tightly packed muscle fibres variously orientated anteriorly, and longitudinally and obliquely orientated posteriorly; in this posterior region, fibres on the right side run obliquely downwards to embrace the ventro-anterior portion of the female atrium and, subsequently, presumably anchor on ventral epidermis. Sperm ducts are dorso-internal to the ovovitelline ducts. Lateral to penis insertion, sperm ducts bend medially and then ventrolaterally to penetrate the bulb. The ducts subsequently run anteriad and join to continue posteriorly and sinuously as the ejaculatory duct ( Fig. 4D ). Ejaculatory duct traverses central region of penis papilla to open at its tip. Sperm ducts lined with a cuboidal, ciliated epithelium and surrounded by a 5-µm-thick layer of circular muscles. Wall of ejaculatory duct stained reddish, consisting of a cuboidal, ciliated epithelium, surrounded by circular muscles, which constitute a muscular cylinder with a diameter equivalent to three times the diameter of the duct ( Fig. 5A ).

Penis papilla very long, 5 mm, with dorsal and ventral insertions at the same horizontal plane ( Fig. 4D ). This papilla is cylindrical along most of its length; total length equal to 17 times its diameter, entirely occupying both male and female atria; dorsal insertion strongly displaced anteriorly and very ventrally, so that it projects from the anteroventral portion of the male atrium. Subepithelial musculature consisting of a dense, 42-µm-thick layer of circular muscle, tending to decussate distally, followed by a single layer of longitudinal muscle. Epithelium of papilla pierced by reddish secretions. Poor condition of sections does not display further histological details. Male atrium long and ample, not folded.

Ovaries oval shaped, 250 µm in maximal length, and situated at a distance from anterior end equivalent to one-fifth of body length. Ovovitelline ducts emerge from an unknown region of ovaries, lateral to female atrium. Then, they curve medially and join to form the common glandular ovovitelline duct, dorsally to the posterior third of this atrium ( Fig. 4D ). Common glandular ovovitelline duct as long as one-third of female atrium length and communicates with the female genital duct; this duct is a projection of the posterior region of the female atrium and is dorso-anteriorly orientated. The female genital duct is lined with an epithelium provided with intraepithelial gaps ( Fig. 5B ). Poor condition of sections does not display further histological details.

Female atrium without folds, two to three times as long as male atrium, lined with a tall epithelium, which posteriorly presents intraepithelial gaps. Atrial epithelium surrounded by a thin layer of longitudinal muscle fibres, followed by a layer of muscles with crisscross arrangement; thickness of both layers equal to 25 µm, distally doubling in thickness.

Remarks

The original description of the dorsal chromatic pattern of this species may be ambiguous (“Sides and foot coloured dirty ‘orpiment orange’; above with two stripes on each side of pale ‘primrose-yellow’, edged externally with black; on centre of the back a stripe of glossy black”; Darwin, 1844, p. 244). From Darwin’s description, Marcus deduced that ‘an additional black lateral stripe should exist on each side, albeit only the external stripe was mentioned’ ( Marcus, 1952 [original in Portuguese]). No specimen matching Marcus’ description was ever found, but this ambiguity is removed in Darwin’s field notes. In an entry on 17 June, 1832, he states: “Colours: back with glossy black stripe; on each side of this a primrose white one edged externally with black; these stripes reach to extremities, & become uniformly narrower. sides & foot dirty ‘orpiment orange’” (in Keynes, 2000, p. 47). We found this precise colour pattern displayed by the specimen MZUSP PL 2074 from the type locality. Hence, it is most probable that this specimen and that found by Darwin are conspecific. A conclusive comparison is not possible because there is no record of Darwin’s specimen in the Natural History Museum, London, where the material collected by Darwin is deposited (H. Jones, personal communication).

Neotype designation satisfies provisions of the ICZN code (Art. 75.3.1.–7.) as follows: (1) the neotype is designated with the express purpose of clarifying the taxonomic status or the type locality of the name Geoplana vaginuloides ; (2) the characters differentiating G. vaginuloides from any other taxa are stated in the diagnosis above; (3) these data and the description of the species are sufficient to ensure recognition of the specimen designated; (4) after Dr Hugh Jones [from Natural History Museum London (NHM)], the name-bearing type specimen is lost or even has never been deposited in the NHM; (5) the ‘Remarks’ section shows that neotype is consistent with the former name-bearing type from the original description and from Darwin’s field notes (in Keynes, 2000); (6) the neotype came from the original type locality; and (7) the neotype is the property of the Museu de Zoologia da Universidde de São Paulo (MZUSP), Brazil.

Figures

Figure 4. Geoplana vaginuloides (Darwin, 1844). Specimen MZUSP PL 2074. A, dorsal view of live specimen, ~60 mm in length. B, photomicrograph of longitudinal and transverse muscles of the subintestinal parenchymatic layer in a horizontal section. C, diagrammatic representation of the pharynx from sagittal sections. D, diagrammatic representation of the copulatory apparatus from sagittal sections.

Figure 5. Geoplana vaginuloides (Darwin, 1844). A, photomicrograph of part of the penis papilla of specimen N574 on a sagittal section, showing the ejaculatory duct and its surrounding muscle. B, photomicrograph of the female genital duct of specimen MZUSP PL 2074 on a sagittal section.