Geoplana ibiuna, 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 : 41-43

GEOPLANA IBIUNA ALMEIDA & CARBAYO SP. NOV.

FIG. 16

Material examined

Holotype MZUSP PL 2066 (field number F3562): Parque Estadual do Jurupará, Ibiúna / SP, Brazil. F. Carbayo, coll., February 2009. Cephalic region: horizontal sections on 14 slides; ovarian region: horizontal sections on 12 slides; pre-pharyngeal region: transverse sections on ten slides; pharynx and copulatory apparatus: sagittal sections on 33 slides.

Paratype MZUSP PL 2081 (field number F6907): Santana de Parnaíba/SP, Brazil (23°26′57.2″S, 047°00′43.8″W). F. Carbayo coll., 15 December 2015. Cephalic region: horizontal sections on 12 slides; ovarian region: horizontal sections on six slides; region behind ovaries: horizontal sections on six slides; prepharyngeal region: transverse sections on 19 slides; pharynx and copulatory apparatus: sagittal sections on 21 slides.

Paratype MZUSP PL 2082 (field number F6908): Santana de Parnaíba/SP, Brazil (23°26′57.2″S, 047°00′43.8″W). F. Carbayo coll., 12 December 2015. Pharynx and copulatory apparatus: sagittal sections on 11 slides.

Paratype MZUSP PL 2083 (field number F6909): Santana de Parnaíba/SP, Brazil (23°26′57.2″S, 047°00′43.8″W). F. Carbayo coll., 12 December 2015. Pharynx and copulatory apparatus (underdeveloped): sagittal sections on 17 slides.

Paratype MZUSP PL 2088 (field number F6999): Pico do Jaraguá, São Paulo/SP, Brazil (23°27′28.7″S, 046°45′49.9″W). E. M. Froehlich coll. 15 August 1951. Ovarian region: horizontal sections on 18 slides; prepharyngeal region: transverse sections on 12 slides; copulatory apparatus: sagittal sections on 43 slides.

Distribution

Secondary Atlantic forest in the municipalities of Ibiúna and Santana de Parnaíba, state of São Paulo, Brazil.

Etymology

The specific epithet refers to the Tupi-Guarani (indigenous Brazilian tribe) name of one of the municipalities where the type material was collected.

Diagnosis

Dorsal colour pattern constituted by a median orangeochre stripe, bounded on either side by a black stripe, externally to which is a white stripe, and this in turn is externally bordered by a black band, externally to which is a thin marginal white line. Dorsal insertion of penis papilla strongly displaced anteriorly and very ventrally. Posterior wall of female atrium richly folded. Female-to-male atrial length ratio, 1.0.

External aspect

Live animals 40–50 mm long and 3 mm wide. Body margins nearly parallel; anterior end rounded, posterior pointed. Dorsum convex, ventral side slightly convex. Dorsal body surface constituted by a median orange-ochre band, varying from one-quarter to oneseventh of body width, that grades into the black of the cephalic region (one-ninth of body length) and posterior end, bounded on either side by a black stripe (onefifth), which merge posteriorly, externally to which is a white stripe (one-quarter), and this is bordered externally by a black band (one-third), externally to which is a thin marginal white line ( Fig. 16A ). Ventral surface of the body whitish. In preserved specimens, the dorsal colour remained unchanged. Two types of eyes: a conical type, 100 µm high and 35 µm in width; and a cup-shaped type, 40 µm in diameter. The former contour the anterior end of the body. Cup-shaped-type eyes spread onto the dorsum, reaching whitish stripes all along the body. Sensory pits located ventromarginally in a single row, from the very anterior end up to the end of first quarter of body. Relative position mouth-to-body length, 50–58%. Relative position gonopore-to-body length, 64–71%.

Internal morphology

Creeping sole 82% of body width. Glandular margin absent. Three typical geoplaninid cutaneous muscle layers present, being as thick as 6–8% of body height. Muscle fibres of the longitudinal, innermost layer (30 µm thick) arranged into bundles with 15–25 fibres each. Three parenchymal muscle layers present: dorsal layer of decussate diagonal fibres, supraintestinal layer of transverse and longitudinal fibres, and subintestinal layer with transverse and longitudinal fibres. Longitudinal fibres around intestine constituting a loose tube whose fibres mix up with transverse ones. Ventral nerve plate present.

Mouth situated at a distance from root of the pharynx equivalent to 42–59% of pharyngeal pocket length. Pharynx cylindrical ( Fig. 16B ). Oesophagusto-pharynx ratio, 17%. Outer pharyngeal musculature consisting of a subepithelial layer (8 µm) of longitudinal muscle, followed by a layer (85 µm) of intermingled circular and longitudinal muscle fibres. Inner pharynx musculature consisting of a thin (5 µm) subepithelial layer of longitudinal muscle, followed by a layer (75 µm) of circular fibres and an innermost layer (12 µm) of longitudinal fibres ( Fig. 16C ).

Testes dorsally located between supraintestinal parenchymal muscle layer and intestine; anteriormost testes behind ovaries, at a distance roughly equivalent to 10% of body length; posteriormost follicles slightly anterior to root of pharynx. Penis bulb elongated, extending anteriad ~0.3 mm anterior to penis papilla; in the dorsal portion of the body, the penis bulb extends posteriorly to the level of the gonopore; in the ventral body region, the penis bulb extends posteriorly only to about halfway between the root of the penis papilla and the gonopore. The bulb is strongly developed, consisting of tightly packed muscle fibres variously orientated. Penis bulb muscle more densely packed dorsally than ventrally ( Fig. 16D, E ). Bulb fibres on the right side run obliquely downwards to embrace ventrally the anterior portion of the female atrium, subsequently anchoring presumably on ventral epidermis. Sperm ducts run dorsolaterally to the ovovitelline ducts. Posteriorly to level of insertion of penis papilla, sperm ducts bend anteriorly and medially and then penetrate penis bulb ventrolaterally. The ducts subsequently recurve and join to form the ejaculatory duct. Extrapapillar portion of this duct considerably sinuous; traversing penis papilla centrally to open at its tip. Sperm present in distal portion of sperm duct, along its course both outside and inside penis bulb. Sperm ducts lined with a cuboidal, ciliated epithelium and surrounded by a 20-µm-thick layer of circular muscles. Anterior portion of ejaculatory duct lined with squamous-to-cuboidal, ciliated epithelium pierced by numerous gland cells producing erythrophil granules and surrounded by a coat of circular muscle fibres constituting a muscular cylinder with a diameter equivalent to three times the diameter of this duct.

Penis papilla long, horizontal and progressively thinner towards its tip; this tip very thin. Dorsal insertion strongly displaced anteriorly and very ventrally, so that it projects from anteroventral portion of male atrium. Penis papilla completely fills male atrium and a variable part of the female atrium, probably owing to fixation artefacts. Total length of papilla equal to six to seven times its greatest diameter. Penis papilla covered with a cuboidal epithelium, pierced by gland cells producing fine erythrophil granules. Necks of these glands fill a moderate space immediately beneath epithelium of second third of penis papilla. Subepithelial musculature consisting of dense 45-µm-thick layer of circular muscle, followed by a 30-µm-thick layer of longitudinal muscle.

Male atrium ample, not folded ( Fig. 16D, E ), lined with a low epithelium and underlain by a 5-µm-thick layer of decussate muscles. Circular muscle fibres surround both innermost portion of gonopore canal and nearby atrium.

Ovaries oval shaped, 400 µm in length in longitudinal body axis and situated at a distance from anterior end equivalent to one-fifth of body length. Ovovitelline ducts emerge from dorsolateral aspect of ovaries. The oviducts run laterally to posterior portion of female atrium, then curve medially and join to form common glandular ovovitelline duct. This duct is as long as one-sixth of female atrium length and communicates with female genital duct; the latter is a very narrow projection of the posterior region of female atrium, lined with a 6-µm-tall ciliated epithelium and surrounded by a small but distinct sphincter made up of circular muscle fibres.

Female atrium narrow and long, somewhat funnel shaped; as long as male atrium ( Fig. 16D, E ). Atrial wall very richly folded, either along anterior half or along almost all posterior half, thus narrowing its lumen. Lining epithelium mostly cuboidal, 12 µm high, posteriormost portion tall, 40 µm and with stratified aspect. Two types of gland cells pierce epithelium, producing cyanophil granules and erythrophil substance, respectively. Female atrium surrounded by a 5-µm-thick layer of longitudinal muscle fibres, which do not occur on the posterior portion, followed by a 40-µm-thick layer of decussate fibres. A loose muscle coat of thick (10 µm) longitudinal fibres envelopes this atrium.

Figures

Figure 16. Geoplana ibiuna Almeida & Carbayo sp. nov. A, dorsal view of the living specimen MZUSP PL 2081, 50 mm in length. B, photomicrograph of a sagittal section of the pharynx of specimen MZUSP PL 2081. C, photomicrograph of a sagittal section of the inner pharyngeal epithelium showing its three muscle layers (each indicated with an arrowhead) of specimen MZUSP PL 2066. D, diagrammatic representation of the copulatory apparatus of specimen MZUSP PL 2066 from sagittal sections. Arrowhead points to the sphincter embracing posterior portion of female atrium. E, photomicrograph of a sagittal section of the copulatory apparatus of specimen MZUSP PL 2066.