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• Bol. Inst. Oceanogr. 4 (1-2) • Dez 1953 • https://doi.org/10.1590/S0373-55241953000100003   copiar

Notas biológicas: II. sobre Embletonia mediterranea (Costa), nudibranquio da região lagunar de Cananéia

Resumos

1) - Foram estabelecidas em S. Paulo algumas colónias de E. mediterranea proveniente das águas salobras da região de Cananéia afim de completar as observações realisadas in loco. 2) - São apresentadas tanto a descrição como a classificação, incluindo uma rápida comparação com quase todas as outras espécies desse gênero que foram até hoje descritas. 3) - Descreve-se o ciclo completo desde a desova até a postura da geração seguinte. Não foi feito o estudo embriológico detalhado. 4) - Foram anotados o habitat e a alimentação, e verificada a ausência de cnidocistos em animais não alimentados com hidrozoários. 5) - Foram estabelecidas as temperaturas letais e a duração das principais fases do desenvolvimento em temperaturas diferentes. 6) - Foi feita a comparação com o ciclo de E. pallida, otimamente descrito e figurado por Rasmussen (1944). 7) - Foi verificada in loco a ausência de migrações. 8) - Considera-se essa espécie, sem dúvida eurihalina, um ótimo material para o estudo das relações entre o meio interno e a pressão osmótica externa.

A rich colony of the cladohepatic nudibranchiate mollusk Embletonia mediterranea was studied from the lagoon region of Cananéia, from March to July (end of summer through winter). To the author's knowledge this species is here redescribed for the first time since its description by Costa (1866), fulfilling some omissions present in the original paper. A comparison is here made with 4 out of the remaining 8 species of the genus. All the species are closely allied, two of the species which were not compared for lack of the necessary bibliography, are probably only a variety of E. pallida which is known to the authors. These are: E. juscata and E. remigata. E. minuta, also not compared, may be a synonim of E. pulchra. The fourth uncompared species: E. pygmex is the only one totally unknown to the authors. The colony became well established in aquaria in S. Paulo where the animals reproduced freely. The whole individual cycle was observed from spawning of a generation to spawning of the following one. The egg masses are lump-shaped, they contain an average of 11 eggs; each full-size animal lays about 16 to 17 eggs in 24 hours. Spawning begins in animals about one third full length. The whole development, from spawning to hatching takes from 48 h to 60 h in temperatures from 20º C to 25º C. Few days after hatching the veligers settle to the bottom and after 24 h to 48 h the young ones abandon the nautiloid shell yet with no cerata neither rhinophores and with reduced cephalic expansions. A comparison is made with the development of E. pallida, described and wonderfully portrayed by Rasmussen (1944). This species is closely associated to Bougainvillia on which were always found numerous egg-masses and adults and on which the animals feed. On the athecate hydroid, are usually found several cauli of Obelia bidentata. Animals reared out of reach of living hydroids had cerata entirely devoid of cnidocysts. In spite of its natural association to the mentioned hydroids, the species is euryphagous since it thrives well in captivity feeding on detritus and perhaps diatoms, small ciliates and suctorians. There is no annual cycle, the species having been found active continuously from summer through the coldest months. No migrations have been recorded and the population seems to be stationary the year round. Finally it was pointed out that this species seems to be a suitable material to study the problems of the relation between the internal medium and the external osmotic pressure.

Notas biológicas. II. Sobre Embletonia mediterranea (Costa), nudibranquio da região lagunar de Cananéia

M. Vannucci; K. Hosoe

RESUMO

1) - Foram estabelecidas em S. Paulo algumas colónias de E. mediterranea proveniente das águas salobras da região de Cananéia afim de completar as observações realisadas in loco.

2) - São apresentadas tanto a descrição como a classificação, incluindo uma rápida comparação com quase todas as outras espécies desse gênero que foram até hoje descritas.

3) - Descreve-se o ciclo completo desde a desova até a postura da geração seguinte. Não foi feito o estudo embriológico detalhado.

4) - Foram anotados o habitat e a alimentação, e verificada a ausência de cnidocistos em animais não alimentados com hidrozoários.

5) - Foram estabelecidas as temperaturas letais e a duração das principais fases do desenvolvimento em temperaturas diferentes.

6) - Foi feita a comparação com o ciclo de E. pallida, otimamente descrito e figurado por Rasmussen (1944).

7) - Foi verificada in loco a ausência de migrações.

8) - Considera-se essa espécie, sem dúvida eurihalina, um ótimo material para o estudo das relações entre o meio interno e a pressão osmótica externa.

SUMMARY

A rich colony of the cladohepatic nudibranchiate mollusk Embletonia mediterranea was studied from the lagoon region of Cananéia, from March to July (end of summer through winter). To the author's knowledge this species is here redescribed for the first time since its description by Costa (1866), fulfilling some omissions present in the original paper. A comparison is here made with 4 out of the remaining 8 species of the genus. All the species are closely allied, two of the species which were not compared for lack of the necessary bibliography, are probably only a variety of E. pallida which is known to the authors. These are: E. juscata and E. remigata. E. minuta, also not compared, may be a synonim of E. pulchra. The fourth uncompared species: E. pygmex is the only one totally unknown to the authors.

The colony became well established in aquaria in S. Paulo where the animals reproduced freely. The whole individual cycle was observed from spawning of a generation to spawning of the following one. The egg masses are lump-shaped, they contain an average of 11 eggs; each full-size animal lays about 16 to 17 eggs in 24 hours. Spawning begins in animals about one third full length. The whole development, from spawning to hatching takes from 48 h to 60 h in temperatures from 20º C to 25º C. Few days after hatching the veligers settle to the bottom and after 24 h to 48 h the young ones abandon the nautiloid shell yet with no cerata neither rhinophores and with reduced cephalic expansions.

A comparison is made with the development of E. pallida, described and wonderfully portrayed by Rasmussen (1944). This species is closely associated to Bougainvillia on which were always found numerous egg-masses and adults and on which the animals feed. On the athecate hydroid, are usually found several cauli of Obelia bidentata. Animals reared out of reach of living hydroids had cerata entirely devoid of cnidocysts. In spite of its natural association to the mentioned hydroids, the species is euryphagous since it thrives well in captivity feeding on detritus and perhaps diatoms, small ciliates and suctorians.

There is no annual cycle, the species having been found active continuously from summer through the coldest months.

No migrations have been recorded and the population seems to be stationary the year round. Finally it was pointed out that this species seems to be a suitable material to study the problems of the relation between the internal medium and the external osmotic pressure.

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BIBLIOGRAFIA

  • ALDER, J. & HANCOCK, A. 1844. Descriptions of Pterochilus, a new species of Nudibranchiate Mollusca, and two new species of Doris. Ann. Mag. Nat. Hist. Vol. 14, p. 329-331.
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  • RASMUSSEN, E. 1944. Faunistic and Biological notes on marine invertebrates. I. The eggs and larvae of . . . . . and Embletonia pallida (Alder & Hancock). - (Gastropoda marina). Vidensk. Meddel. Dansk. Naturhist. Foren. Copenhagen. Vol. 107, p. 207-233.
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  • WEIL, E. & PANTIN, C. F. A. 1931. The Adaptation of Gunda ulvæ to Salinity. II. The Water Exchange. J. Exp. Biol. Vol. 8, p. 82-94.

Datas de Publicação

  • Publicação nesta coleção
    15 Jun 2012
  • Data do Fascículo
    Dez 1953
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