Geoplana apua, Ana Laura Almeida & Fernando P. L. Marques & Fernando Carbayo, 2019

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 : 26-29

GEOPLANA APUA ALMEIDA & CARBAYO SP. NOV.

Geoplana vaginuloides: Riester, 1938 , p. 72–75 [part]: Froehlich, 1956a, p. 314–315 [part].

Material examined

Holotype MZUSP PL 2072 (field number F5236): Nova Iguaçú/RJ , Brazil. Cristiano Sampaio et al., coll., 4–6 April 2012. Cephalic region: horizontal sections on eight slides; ovarian region: sagittal sections on five slides; pre-pharyngeal region: transverse sections on ten slides; pharynx: sagittal sections on six slides; copulatory apparatus: sagittal sections on 11 slides.

Paratype MZUSP PL 2090 (field number F7001): Teresópolis, Rio de Janeiro/RJ, Brazil. E. M. Froehlich coll., 20 July 1952. Copulatory apparatus: sagittal sections on 18 slides.

Paratype SMF N460: Barreira, Teresópolis, Rio de Janeiro/RJ, Brazil. Ernest Bresslau coll., 25 February 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 two slides.

Distribution

Areas covered with Atlantic forest in the municipalities of Nova Iguaçú and Teresópolis, State of Rio de Janeiro, Brazil.

Diagnosis

Dorsal colour pattern constituted by a median luminous orange band, bounded on either side by a black stripe, externally to which is a greenish-yellow stripe, and this again is bordered externally by a marginal black band. Inner pharynx musculature with two layers. Anterodorsal region of penis bulb more developed. Penis papilla with dorsal insertion strongly displaced anteriorly and very ventrally, as long as 18 times its diameter.

Etymology

The specific epithet is a Tupi (indigenous Brazilian tribe) word that means mound ( Tibiriçá, 1984), referring to the hilly terrain where the species was collected.

External aspect

Live animals 45 mm long when creeping. Body margins parallel; anterior end rounded, posterior end pointed. In preserved specimens, dorsum convex, ventral side slightly convex. Dorsal colour pattern of the preserved specimen F5236 constituted by a median luminous orange band (one-third of body width), bounded on either side by a black stripe (1/12th), externally to which is a greenish-yellow stripe (1/12th), and this again is bordered externally by a marginal black band (one-sixth) ( Fig. 6A ). Ventral body surface pale orange. In specimen F7001 (preserved for> 60 years), black became brownish, remaining colours became cream. Two types of eyes: a conical type, 80 µm high and 30 µm wide; and a cup-shaped type, 50 µm in diameter. The former type of eye contours the anterior portion of the body. Four millimetres behind anterior end, cup-shaped-type eyes spread dorsally onto the yellowish stripes until rear end of body, where the eyes are sparsely distributed. Sensory pits simple invaginations, 25 μm deep, located ventromarginally in a single row and extending from the very anterior end up to at least the first one-fifth of body length. Relative position mouth-to-body length, 55%. Relative position gonopore-to-body length, 67%.

Internal morphology

Creeping sole 77% of body width. Glandular margin absent. Cutaneous musculature same as in the type species of the genus in terms of organization. CMI, 7%. Muscle fibres of the longitudinal layer (15–20 µm thick) arranged into bundles with ten to 30 fibres each. Parenchymal musculature same as in the type species of the genus in terms of organization and relative development ( Fig. 6B ). Ventral nerve plate present.

Mouth situated at a distance from root of the pharynx equivalent to 54% of pharyngeal pocket length. Pharynx cylindrical ( Fig. 6E ). Oesophagus-to-pharynx ratio, 18%. Pharyngeal musculature ( Fig. 6D ) same as in the type species of the genus in terms of organization and development, with the exception of the inner longitudinal layer, which reaches 35 µm in thickness.

Testes dorsally located between supraintestinal parenchymal muscle layer and intestine; anteriormost testes at a distance from anterior end equivalent to 13% of body length; posteriormost near the pharynx root. Penis bulb oval shaped, relatively strongly developed, consisting of tightly packed muscle fibres variously orientated. The bulb is more developed dorso-anteriorly, and extends from 0.5 mm anterior to penis papilla up to the gonopore region (specimen MZUSP PL 2072). Diagonal fibres surrounding distal section of penis bulb run obliquely downwards on the right side of the body to embrace ventrally the anterior portion of the female atrium. Sperm ducts run laterally to the ovovitelline ducts. Laterally to ventral insertion of penis papilla, sperm ducts bend anteriorly and medially, then penetrate penis bulb ventrolaterally, and maintain this course until they join each other. From this point onwards, the ejaculatory duct runs posteriorly, centrally traversing the penis papilla to open at its tip. Sperm present in extrabulbar portion of sperm ducts; in one specimen, sperm was also present at the anterior section of the intrabulbar lumen.

Sperm ducts lined with a cuboidal, ciliated epithelium and surrounded by a 5- to 8-µm-thick layer of circular muscles. Proximal half of ejaculatory duct lined with cuboidal, ciliated epithelium and pierced by gland cells producing weakly erythrophil, fine granules; distal half lined with squamous, non-ciliated epithelium pierced by gland cells producing erythrophil, coarse granules. Anterior half of this duct surrounded by circular muscles, which constitutes a muscular cylinder in the distal portion with a diameter equivalent to five times the diameter of this duct.

Penis papilla thin, somewhat conical, because it narrows very gradually, and very long; total length equal to 18 times its diameter, occupying almost entirely both male and female atria; dorsal insertion strongly displaced anteriorly and very ventrally, so that it projects from anteroventral portion of male atrium. Squamous lining epithelium of the penis papilla pierced by numerous gland cells producing xanthophyl and erythrophil fine granules, and underlain by a dense 85-µm-thick layer of circular muscle, distally tending to decussate, followed by a single layer of longitudinal muscle ( Fig. 6F ).

Male atrium not folded ( Fig. 7A, B ), lined with a low, non-ciliated epithelium, and underlain by a 5-µm-thick layer of circular muscles, followed by an equally thin layer of longitudinal fibres. A set of muscle fibres is also present as longitudinal fibres extending around the gonopore canal laterally to the male atrium, and being intermingled with those of the penis bulb.

Ovaries oval shaped, 300 µm in maximal diameter, and situated at a distance from anterior end equivalent to 22.5% of body length. Ovovitelline ducts emerge from the dorsolateral aspect of ovaries. The oviducts run laterally to the female atrium, curve medially and then join to form the common glandular ovovitelline duct, dorsally to this atrium. Common glandular ovovitelline duct as long as 40% of female atrium length, communicating with female genital duct ( Fig. 7B ); this duct is a projection of the posterior region of the female atrium, bent dorsally and lined with a squamous, non-ciliated epithelium. A cyanophil fibrillar mass, 5–10 µm thick, is immediately present underneath this epithelium of the female atrium, with very thin circular filaments (<1 µm) resembling muscle fibres in stain affinity and orientation, followed by a layer of longitudinal muscle fibres.

Female atrium without folds, as long as three times that of male atrium, and lined with a cuboidal-tocolumnar epithelium, which is pierced by glands producing xanthophil granules and is underlain by a thin layer of muscle fibres in a criss-crossed arrangement, followed by a loose layer (25 µm) of longitudinal fibres.

Figures

Figure 6. Geoplana apua sp. nov. A, dorsal view of the MZUSP PL 2072 preserved specimen on millimetre graph paper after cutting off a piece of the body. B, photomicrograph of longitudinal and transverse muscles of the subintestinal parenchymatic layer in a horizontal section of specimen MZUSP PL 2072. C, diagramatic reconstruction of half of a transverse section of the pre-pharyngeal region of the holotype; dots represent longitudinal parenchymatic muscle fibres. D, photomicrograph of the two muscle layers of the internal musculature of the pharynx in sagittal section. E, photomicrograph of a sagittal section of the pharynx of specimen MZUSP PL 2072. F, photomicrograph of the ejaculatory duct and its surrounding muscle of specimen MZUSP PL 2072 in sagittal section.

Figure 7. Geoplana apua sp. nov. A, photomicrograph of a sagittal section of the copulatory apparatus of specimen MZUSP PL 2072. B, diagrammatic representation of the copulatory apparatus of specimen MZUSP PL 2072 from sagittal sections.