Geoplana, Schultze & Muller, 1857

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 : 60-61

MORPHOLOGICAL DISTINCTION OF THE SPECIES OF

GEOPLANA

A total of five species are distinguished from the remaining congeners in the chromatic pattern of the dorsum, namely G. vaginuloides (median black band,

white-yellow para-median stripes externally bordered by black lines, and lateral reddish-iron bands), G. apua (median luminous orange band, bounded on either side by a black stripe, externally to which is a greenishyellow stripe, and this again is bordered externally by a marginal black band), G. mogi (median orange-ochre band, bounded on either side by a thin whitish stripe, and in turn this is bordered externally by a thin black line, externally to which is a grey band with dense white mottling, externally to which is a thin marginal black line), G. iporanga (median melon yellow band, bounded on either side by a black band, externally to which is a white band divided longitudinally in half by a black line), and G. pulchella (anterior third of dorsal body pure orange; remaining dorsal side constituted by a median light grey band, bordered on either side by a black band; entire dorsum sprinkled with conspicuous whitish specks).

There are six pairs of species that are indistinguishable by means of only either the external aspect ( G. piratininga – G. ibiuna , G. chita – G. boraceia , G. caraguatatuba – G. cananeia and G. cambara – G. paranapiacaba ) or the internal organs ( G. cambara – G. chita and G. mogi – G. boraceia ). Their profound similarity means that we rely on a combination of both external and internal atributes to recognize every species.

The dorsum of G. piratininga and G. ibiuna is very alike (median traffic red or orange-ochre band, bounded on either side by a black stripe, externally to which is a white stripe, and in turn this is externally bordered by a black band, externally to which is a thin marginal white line). However, their copulatory apparatus differs in that in G. piratininga the penis papilla is as long as five times its diameter, and the femaleto-male atrial length ratio is 2.0, whereas in G. ibiuna the penis papilla is as long as seven times its diameter, and the female-to-male atrial length ratio is 1.0.

The dorsum of G. chita and G. boraceia is also indistinguishable from each other (median mustard-coloured band, bounded on either side by a black band; entire dorsum sprinkled with conspicuous whitish specks). The internal most conspicuous difference between them is that the diameter of the muscular cylinder around the ejaculatory duct is equivalent to ten times the diameter of this duct in G. chita , whereas in G. boraceia it is equivalent to 1.5 times.

Geoplana caraguatatuba and G. cananeia present a dorsal colour pattern also very alike (median orangeochre or yellow-orange band, 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 stripe that merges into a grey band with white mottling, which fades gradually towards its outer margin, whereas this margin is bordered by a black stripe). However, the penis papilla of G. caraguatatuba is pointed, the female atrium presents smooth walls, and female-to-male atrial length ratio is 2.0, whereas in G. cananeia the penis papilla is blunt, the posterior half of the female atrium has a richly folded wall and the female-to-male atrial length ratio is 1.0. Additionally, in the latter species the stroma of the penis papilla presents necks of glands gathered in gross bundles.

The pair of species G. cambara – G. paranapiacaba are externally very alike (median stripe of orange or orange-ochre, bounded on either side by a black line, externally to which is a broader white line, and in turn this is externally bordered by a thin black line, externally to which is a grey band with dense white mottling, bordered by a thin marginal black line). Internally, they can be distinguished in that the longitudinal parenchymal muscle fibres are disposed around intestine as a loose muscular cylinder in G. cambara , whereas in G. paranapiacaba the muscle fibres are positioned only dorsally and ventrally to the intestine. Furthermore, in G. cambara the diameter of the muscular cylinder around the ejaculatory duct is equivalent to 12 times the diameter of this duct, whereas in G. paranapiacaba it is equivalent to 2.5 times.

Finally, the species of each of two pairs of species ( G. cambara – G. chita and G. mogi – G. boraceia ) cannot be differentiate from each other with regard to the internal organs, especially the copulatory apparatus. However, the chromatic pattern of G. cambara is constituted by a median orange stripe plus five pairs of lines (lateralmost lines are difficult to discern) either black, white or grey, whereas the dorsum of G. chita displays a median mustard-coloured band, bounded on either side by a black band, with entire dorsum sprinkled with conspicuous whitish specks.

The internal organs of G. mogi and G. boraceia are also very similar to each other, but the dorsum in G. mogi is constituted by a median orange-ochre band plus four pairs of whitish, black or grey lines, whereas in G. boraceia the median mustard-coloured band is bounded on either side by a black band; with the entire dorsum sprinkled with conspicuous whitish specks.