How are little flatworms colored? A Geoplana vaginuloides analysis

by Piter Kehoma Boll

ResearchBlogging.org As you already know, I work with land planarians, so there’s nothing more natural than seeing me talking about them. Today I’ll make a brief comment about the type species of the genus Geoplana which gives name to the family Geoplanidae (the land planarians themselves).

Geoplana vaginuloides was originally described by Charles Darwin in 1844 under the name Planaria vaginuloides. His description was based only on external morphology, which today is considered insufficient to describe correctly a land planarian. Later Stimpson (1857) moved it to his new genus Geoplana, but still only external features were used. By that time, no type species had been assigned to the genus and E. M. Froehlich (1955) decided to choose Geoplana vaginuloides (Darwin, 1844) as the type species for being the first one found by Darwin and one of the species put in the genus Geoplana by Stimpson when he described it.

It was only in 1990 that a good revision of land planarians was made by Ogren and Kawakatsu and the internal morphology, especially that of the copulatory apparatus, started to have a greater importance in describing a species correctly. Based on Geoplana vaginuloides, they defined the genus Geoplana as follows:

“Geoplanidae of elongate body form; creeping sole broader than a third of the body width; strong cutaneous longitudinal muscles; mc:h value from 4%-8%; parenchymal longitudinal musculature weak or absent, not in a ring zone; testes are dorsal; penis papilla present; female canal enters genital antrum dorsally; cephalic glandulo-muscular organs, sensory papillae and adenodactyls absent.” (Ogren & Kawakatsu, 1990).

As noticed by Riester (1938), G. vaginuloides possesses a very long penis papilla invading the female antrum, as well as other peculiar features. These aspects were important to consider a land planarian found by Marcus in 1951 as belonging to this species, even though it had external colors almost inverted when compared to the specimen described by Darwin.

Using the internal morphology to assure that all the following descriptions of land planarians belong to a single species, Geoplana vaginuloides, we can find at least 4 different external color patterns to this species:

  •  Darwin 1844:  “Ocelli numerous, placed at regular intervals on the anterior extremity; irregularly, round the edges of the foot. […] Sides of the 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; these stripes become narrow towards both extremities.”
    Locality: Rio de Janeiro, Brazil
  •  Riester, 1938: “Unterseite und Körperänder weinrot, dann zwei schmale gelbe Streifen und in der Rückenmitte ein tief Schwarz glänzendes breites Band.” (Underside and body edges wine red, then two narrow yellow stripes and in the middle of the back a deep black shiny broad band.)
    Locality: Teresópolis/Guapimirim, Rio de Janeiro, Brazil
  • Marcus, 1951: “A faixa mediana é ocre, na maior parte da extensão. Anterior e posteriormente é preta. Flanqueiam-na faixas amarelas claras, cada uma tão larga quão a mediana. As zonas dorso-laterais são pretas com pontinhos claros, que não são olhos. O ventre é claro.” (The median band is ochre in most of its length. Anteriorly and posteriorly it’s black. Light yellow bands flank it, each one as broad as the median one. The dorsolateral zones are black with white spots, which aren’t eyes. The venter is light.)
    Locality: Eldorado, São Paulo, Brazil
  • C. G. Froehlich, 1958: “The colour pattern is similar to type C of Marcus (1952, pp. 76-77, pl. 23 fig. 136) but the median reddish stripe is broader (about 1 mm. across, just in front of the pharynx), and both the black and the white stripes that follow on each side are narrower (about 0.2 to 0.3 mm broad each, in the same region). The median stripe begins at 2.5 mm from the anterior tip. The creeping sole is greyish white.”
    Locality: Itanhaém, São Paulo, Brazil

Different color patterns in Geoplana vaginuloides according do Darwin, 1844 (1), Riester, 1938 (2), Marcus, 1951 (3) and C. G. Froehlich, 1958 (4)

Location of the 4 morphotypes seen in the picture above. Image made on Google Earth.

Along with those descriptions, Prudhoe (1949), found an animal in Trinidad with the same external description given by Darwin, but its internal structure was very different from Riester (1938). So it was probably a different species.

About photographs of this species, I found only the three seen below. They all belong to specimens with a color pattern close to those described by Marcus and Froehlich. It would be interesting to find an animal with the color pattern from the original description by Darwin!

Geoplana vaginuloides (Darwin, 1844). Photo by Fernando Carbayo. Extracted from each.uspnet.usp.br/planarias/

Geoplana vaginuloides (Darwin, 1844). Photo by Fernando Carbayo. Extracted from each.uspnet.usp.br/planarias/

Geoplana vaginuloides (Darwin, 1844). Notice that this one doesn’t have the black border flanking the median orange band. Photo by Instituto Rã-Bugio. Extracted from http://www.ra-bugio.org.br

– – –

References:

Darwin, C. 1844. Brief Description of several Terrestrial Planariae, and of some remarkable Marine Species, with an Account of their Habits. Annals and Magazine of Natural History, Annales des Sciences Naturelles, 14, 241-251

Froehlich, E. M. 1955. Sobre Espécies Brasileiras do Gênero Geoplana. Boletim da Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, Série Zoologia, 19, 289-339

Froehlich, C. G. 1958. On a Collection of Brazilian Land Planarians. Boletim da Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, Série Zoologia, 21, 93-121

Marcus, E. 1951. Turbellaria Brasileiros. Boletim da Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, Série Zoologia, 16, 5-215

Ogren, R. E. & Kawakatsu, M. 1990. Index to the species of the family Geoplanidae (Turbellaria, Tricladida, Terricola) Part I: Geoplaninae. Bulletin of Fuji Women’s College, 28, 79-166

Prudhoe, S. 1949. Some roundworms and flatworms from the West Indies and Surinam. – IV. Land Planarians. Journal of the Linnean Society of London, Zoology, 41 (281), 420-433 DOI: 10.1111/j.1096-3642.1940.tb02415.x

Riester, A. 1938. Beiträge zur Geoplaniden-Fauna Brasiliens. Abhandlungen der senkenbergischen naturforschenden Gesellschaft, 441, 1-88

Stimpson, W. 1857. Prodromus descriptionis animalium evertebratorum quæ in Expeditione ad Oceanum, Pacificum Septentrionalem a Republica Federata missa, Johanne Rodgers Duce, observavit er descripsit. Pars I. Turbellaria Dendrocœla. Proceedings of the Academy of Natural Sciences of Philadelphia, 19-31

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