Freshwater microturbellarians (Platyhelminthes) from Rio Grande do Sul, Brazil

Freshwater microturbellarians (Platyhelminthes) from Rio Grande do Sul, Brazil

Jacinto Gamo^I; Ana Maria Leal-Zanchet^II

^IDepartamento de Biología Animal, Universidad de Alcalá. Ctra. N-II, Km 33,6, 28871 Alcalá de Henares, Madrid, Spain. E-mail: [e-mail] ^IIInstituto de Pesquisas de Planárias, Universidade do Vale do Rio dos Sinos. Avenida Unisinos 950, 93022-000 São Leopoldo, Rio Grande do Sul, Brasil. E-mail: [e-mail]

ABSTRACT

Ten species of freshwater microturbellarians of three ordens, Catenulida, Macrostomida and Rhabdocoela, were collected in seven sites situated in the Northeast region of Rio Grande do Sul, Brazil. Two species, Macrostomum johni Young, 1972 and Mesostoma productum (Schmidt, 1848), are cited for the first time for Brazil, the citation of M. johni being also the first one for the Neotropical Region. All species are cited for the first time for the state of Rio Grande do Sul.

Key words: Neotropical, new records.

RESUMO

Dez espécies de microturbelários dulciaqüícolas, pertencentes a três ordens, Catenulida, Macrostomida e Rhabdocoela, foram coletados em sete localidades situadas no Nordeste do estado do Rio Grande do Sul, Brasil. Duas dessas espécies, Macrostomum johni Young, 1972 e Mesostoma productum (Schmidt, 1848), são registradas pela primeira vez para o Brasil, sendo o registro de M. johni o primeiro também para a Região Neotropical. Todas as espécies são registradas pela primeira vez para o estado do Rio Grande do Sul.

Palavras chave: Neotropical, novos registros.

Compared to other geographical regions, the diversity and distribution of continental turbellarians from the Neotropical Region are poorly known. Besides, most of these studies focused, however, on macroturbellarians of the order Tricladida, suborders Paludicola and Terricola (see KAWATSU et al. 1992, SEITENFUS & LEAL-ZANCHET in press). Referring to freshwater Neotropical microturbellarians, the studies are scarcer, the MARCUS' studies (1943, 1944, 1945a, b, 1946, 1949) being very important. More recently, PONCE DE LEÓN (1984, 1986), NOREÑA-JANSSEN (1995), NOREÑA-JANSSEN & FAUBEL (1996) and BRUSA et al. (2003), among others, have increased the knowledge on the diversity and distribution of this group in South-America as showed by NOREÑA et al. (2003).

The main purpose of the present work is to report on the results of the first survey of freshwater microturbellarians from Southern Brazil (state of Rio Grande do Sul, Brazil).

MATERIAL AND METHODS

The sample sites (Fig. 1, Tab. I) were visited once between March and April 2003. Turbellarians were collected by means of a conical hand net (mesh width 335 µm), which was used to sweep through vegetation of the margins of the water bodies. In the laboratory, samples were examined and the microturbellarians were extracted for observations in vivo by the method of progressive squash (GAMO 1987a). If necessary for species determination, part of the material was fixed with neutral formaline or Bouin (ROMEIS 1989), embedded in Paraplast (Sigma) and sectioned at 5 µm. Sections were stained with Mallory/Cason (ROMEIS 1989).

The material was determined based on the taxonomic keys of GAMO (1987b) and YOUNG (2001) as well as by comparison with the material described by FARÍAS et al. (1995), GAMO & SCHWANK (1987), GAMO & NOREÑA-JANSSEN (1998), LUTHER (1955, 1960, 1963), MARCUS (1945a, b, 1946) and NOREÑA-JANSSEN (1995).

RESULTS AND DISCUSSION

All species herein reported are cited for the first time for the state of Rio Grande do Sul, Brasil. Two citations, Macrostomum johni Young, 1972 and Mesostoma productum (Schmidt, 1848), are the first ones for Brazil, the citation of M. johni being also the first one for the Neotropical Region.

Catenulida Meixner, 1924

Catenulidae Graff, 1905

Catenula lemnae Dugés, 1832

Numerous individuals (more than 100) formed by chains of up to 20 zooids (Fig. 2) were collected in one site only (Tab. II). The species was previously recorded by MARCUS (1945a) for the city of São Paulo and vicinities, state of São Paulo, and the vicinities of Curitiba, state of Paraná, Brazil, and by NOREÑA-JANSSEN (1995) for Santa Fé, Argentina. This is the fourth record for the Neotropical Region and the third one for Brazil.

Stenostomidae Vejdovsky, 1880

Stenostomum bicaudatum Kennel, 1888

In all four collection sites (Tab. II) more than five individuals were collected. They were constituted by one or two zooids (Figs 3-4) between 1 to 2 mm long. All collected individuals show four spherules in the third pair of light refracting organs instead of two spherules as in the case of the specimens studied by MARCUS (1945a).

The species was previously registered by MARCUS (1945a) for the city of São Paulo, Brazil, and by NOREÑA-JANSSEN (1995) for Santa Fé, Argentina. This is the third record for the Neotropical Region and the second one for Brazil.

Stenostomum grande Child, 1902

In the three collection sites (Tab. II), where S. grande was registered, more than five individuals were collected, which are constituted almost always by two zooids (Fig. 5) with length between 1.7 to 2.0 mm long. The species was previously recorded by MARCUS (1945a) for the city of São Paulo as well as for Curitiba, state of Paraná, Brazil, the present record being the third one for the Neotropical Region and Brazil.

Stenostomum leucops leucops (Dugés, 1828)

In all four collection sites (Tab. II) more than five individuals were collected. They are constituted by two zooids (Fig. 6) with length between 1.5 and 2.0 mm. The species was registered by MARCUS (1945a), as Stenostomum tenuicauda Graff, 1912, for the city of São Paulo, and as Stenostomum amphotum Marcus, 1945, for the cities of São Paulo and Campinas, state of São Paulo, both having been synonymised by LUTHER (1960) with S. leucops leucops. The present record is the fourth one for the Neotropical Region and Brazil.

Macrostomida Meixner, 1924

Macrostomidae Beneden, 1870

Macrostomum johni Young, 1972

Two individuals of M. johni were collected in one site only (Tab. II). They are 0.6 and 0.7 mm long showing penis stylet with a length of 40 and 45 µm, respectively (Figs 7-8). In England, the individuals of M. johni, that have a length of up to 1.3 mm, show a penis stylet measuring 86 µm long (YOUNG 1972). This is the first record for the Neotropical Region.

Macrostomum tuba (Graff, 1882)

One specimen in each collection site (Tab. II) was registered; a 1.3 mm long adult (Fig. 9) in Nova Petrópolis and a 0.6 mm long juvenile specimen in São Leopoldo. The adult showed a penis stylet 155 µm long (Fig. 10). However, the length of the stylet registered for the species varies between 280 and 420 µm (YOUNG 2001). The species was previously registered by MARCUS (1946), as Macrostomum gigas Okugawa, 1930, having been synonymised by HYMAN (1955) with M. tuba, for the city of São Paulo and vicinities, and by HYMAN (1955) for Cabagua Island, near Venezuela. The present record is the third one for the Neotropical Region and the second one for Brazil.

Rhabdocoela Meixner, 1925

Dalyellioida Bresslau, 1928-34

Dalyelliidae Graff, 1903

Gieysztoria ornata Hofsten, 1907

Two specimens were collected in only one collection site (Tab. II, Figs 11-12), presenting lengths of 0.5 and 0.6 mm with penis stylet of 25 and 30 µm long, respectively, that are close to the length for the species registered by LUTHER (1955) for specimens from Brännskär and Tümpel (Northern Europe) (between 0.8 and 1.0 mm), and by MARCUS (1946) for specimens from the city of São Paulo (0.8 mm). The present record is the second one for the Neotropical Region and Brazil.

Gieysztoria trisolena Marcus, 1946

Two 0.6 mm long individuals were collected in only one collection site (Tab. II, Figs 13-14), which correspond very well with the description given by MARCUS (1946) for the specimens from the city of São Paulo, being smaller than Marcus' specimens (up to 2.0 mm). This is the second record of G. trisolena for the Neotropical Region and Brazil.

Typhloplanoida Bresslau, 1933

Typhloplanidae Graff, 1905

Mesostominae Luther, 1904

Mesostoma ehrenbergii (Focke, 1836)

Two juvenile specimens were collected in Lomba Grande and an adult in Nova Tramandaí (Tab. II, Fig. 15), which are 3 mm, 4 mm and 6 mm long, respectively. Such measurements contrast with the 12-14 mm long adult specimens from Europe as well as with those from São Paulo (15mm long), but are closer to the length (8-10 mm) of the specimens from Argentina (NOREÑA-JANSSEN 1995). The adult specimen showed 17 subtaneous eggs, each with a developing embryo. This world-wide distributed species was previously registered for São Paulo (MARCUS 1946), Sauce, Uruguai (PONCE DE LEÓN 1984), Lake Titicaca, Peru (BEAUCHAMP 1939), Santa Fé and San Carlos de Bariloche, Argentina (NOREÑA-JANSSEN 1995), the present record being the sixth one for the Neotropical Region, the second one for Brazil.

Mesostoma productum (Schmidt, 1848)

Ten individuals were collected, two in Nova Petrópolis, three in Nova Tramandaí and five in São Leopoldo (Tab. II). They are between 0.6 and 0.8 mm long (Figs 16-18). The species was previously registered by NOREÑA-JANSSEN (1995) for Santa Fé, Argentina, the description and measurements of which coincide with those of the present study. This is the second record for the Neotropical Region and the first one for Brazil.

ACKNOWLEDGMENTS

We dedicate this work to the founder of the Instituto de Pesquisas de Planárias, Prof. Dr. Josef Hauser S.J. (1920-2004), who devoted his scientific life to encourage the knowledge enhancing of morphology, taxonomy and biology of invertebrates in Rio Grande do Sul. The present study has been done during the stay of the senior author at IPP/UNISINOS, who received financial support from the Fundação de Amparo à Pesquisa do Rio Grande do Sul (FAPERGS), proc. nr. APV 02/16517, and whishes to thank the IPP team for its warm welcome. Thanks are also due to the laboratorial technicians Welcy H. Santos for her help with the collecting of specimens, and Letícia A. Guterres for sections preparation.

Received in 22.III.2004; accepted in 11.XI.2004.

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Publication Dates

• Publication in this collection
  27 Apr 2006
• Date of issue
  Dec 2004

History

• Received
  22 Mar 2004
• Accepted
  11 Nov 2004