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The Azores hydroid fauna and its origin, with discussion of rafting and medusa suppression
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Abstract(s)
Um estudo internacional do benthos costeiro dos Açores, especialmente daquele ao redor da ilha Faial, permitiu adicionar dez novas espécies de hidróides à lista faunística, a qual totaliza agora setenta espécies dependendo da linha taxonómica adotada. As novas ocorrências regionais são: Tubularia crocea, T. indivisa, Eudendrium sp., Bougainvillia sp., Silhouetta uvacarpa, Laomedea calceolifera, Amphisbetia operculata, Diphasia cf. attenuata, Ventromma halecioides e Aglaophenia picardi. A natureza e a origem zoogeográfica da limitada fauna de hidróides e de hidromedusas são discutidas em relação às correntes oceânicas e a outros fatores ambientais.
A fauna de águas rasas tem uma alta proporção de espécies de hidróides nas quais a fase de medusa está ausente. É provável que o seu recrutamento para os Açores tenha ocorrido através de deriva trans-oceânica. Além disso, a maioria dos hidróides reportados para o local, que possuem uma fase de medusa, derivam. Possivelmente, nenhum hidróide açoriano de águas rasas se estabeleceu no Arquipélago através de um estado de medusa proveniente da zona costeira continental.
As tempestades de Inverno e o facto de serem alimento dos peixes da região infralitoral são considerados importantes factores na limitação das populações dos hidróides açorianos.
Um grupo reconhecido de espécies de hidróides derivantes, alguns com e outros sem o
estado de medusa, ocorre em ilhas oceânicas ao redor do mundo. O conceito de "species
club" é introduzido para explicar este fenômeno.
ABSTRACT: An international study of Azorean coastal benthos, especially of that around Faial Island, has added ten hydroid species ta the faunal list, which now totals about 70 species depending on taxonomic opinion. The species newly recorded are Tubularia crocea, T. indivisa, Eudendrium sp., Bougainvillia sp., Silhouetta uvacarpa, Laomedea calceolifera, Amphisbetia operculata, Diphasia cf. attenuata, Ventromma halecioides e Aglaophenia picardi. The nature and zoogeograpbic origin of this limited hydroid and hydromedusa fauna are discussed in relation to ocean currents and other environmental factors. The shallow-water fauna has a high proportion of hydroid species lacking a medusa stage. Their recruitment to the Azores is likely to have been through trans-oceanic rafting. Further, most of the locally recorded hydroids, which do have a medusa stage, are known to raft. Possibly no shallow-water Azorean hydroid has become established in the archipelago by means of a medusa stage liberated on a mainland continental coast. Winter storms and browsing by subtidal fish are considered important factors in limiting Azorean hydroid populations. A recognisable group of rafting hydroid species, some having and some lacking a medusa stage, occurs on oceanic islands around the world. The concept of "species club" is introduced to embrace this phenomenon.
ABSTRACT: An international study of Azorean coastal benthos, especially of that around Faial Island, has added ten hydroid species ta the faunal list, which now totals about 70 species depending on taxonomic opinion. The species newly recorded are Tubularia crocea, T. indivisa, Eudendrium sp., Bougainvillia sp., Silhouetta uvacarpa, Laomedea calceolifera, Amphisbetia operculata, Diphasia cf. attenuata, Ventromma halecioides e Aglaophenia picardi. The nature and zoogeograpbic origin of this limited hydroid and hydromedusa fauna are discussed in relation to ocean currents and other environmental factors. The shallow-water fauna has a high proportion of hydroid species lacking a medusa stage. Their recruitment to the Azores is likely to have been through trans-oceanic rafting. Further, most of the locally recorded hydroids, which do have a medusa stage, are known to raft. Possibly no shallow-water Azorean hydroid has become established in the archipelago by means of a medusa stage liberated on a mainland continental coast. Winter storms and browsing by subtidal fish are considered important factors in limiting Azorean hydroid populations. A recognisable group of rafting hydroid species, some having and some lacking a medusa stage, occurs on oceanic islands around the world. The concept of "species club" is introduced to embrace this phenomenon.
Description
Keywords
Fauna Marinha Hidróide Bentónico Açores Coastal Benthos Marine Fauna Azores
Citation
CORNELIUS, Paul F.S. (1992). The Azores hydroid fauna and its origin, with discussion of rafting and medusa suppression. "Arquipélago. Boletim da Universidade dos Açores: Ciências da Natureza", 10: 75-99.