Population structure, recruitment and distribution patterns of Patella depressa Pennant, 1777 on the central Portuguese coast (original) (raw)
Related papers
Reproduction of" Patella depressa" Pennant, 1777 on the central Portuguese coast
2003
The reproductive cycle and the sex ratio of the limpet Patella depressa Pennant, 1777 were studied on two rocky shores of the central coast of the Portugal, over a period of one year. The gonads were examined and their stage of development was assessed. The gonads of P. depressa were found to develop mainly from August the gonads seem to go into a resting phase. In P. depressa the sex proportions seem to be approximately equal, suggesting the absence of sex reversal in these limpets. High wind speed under optimum conditions of air temperatures appears to induce spawning in this species.
Samples of Patella vulgata were collected along the Portuguese continental and the southern Spanish coast. Specimens were identified using shell and radula characteristics. Patella vulgata was abundant at sites north of the river Douro whereas, to the south, its abundance decreased markedly. Patella vulgata was not observed at Portinho da Arrábida; however, near Cape São Vicente, at Ponta Ruiva and Telheiro, the species was again abundant. Passing Cape São Vicente, the species became scarce. The last significant population was observed at Ingrina, and the last specimen at Rocha. It was proposed that these sites constitute the present day limit of distribution of P. vulgata, replacing Odeceixe, reported in the literature fifty years ago. The distribution of P. vulgata is not a simple function of the maximum or minimum seawater surface temperature, but appears to depend directly on the temperature in May, the species being absent when the temperature is higher than ca. 18°C. Two hypotheses were formulated to explain the influence of seawater temperature in May on the distribution of P. vulgata:
The southern limit of distribution of Patella vulgata
Iberus, 2007
Samples of Patella vulgata were collected along the Portuguese continental and the southern Spanish coast. Specimens were identified using shell and radula characteristics. Patella vulgata was abundant at sites north of the river Douro whereas, to the south, its abundance decreased markedly. Patella vulgata was not observed at Portinho da Arrábida; however, near Cape São Vicente, at Ponta Ruiva and Telheiro, the species was again abundant. Passing Cape São Vicente, the species became scarce. The last significant population was observed at Ingrina, and the last specimen at Rocha. It was proposed that these sites constitute the present day limit of distribution of P. vulgata, replacing Odeceixe, reported in the literature fifty years ago. The distribution of P. vulgata is not a simple function of the maximum or minimum seawater surface temperature, but appears to depend directly on the temperature in May, the species being absent when the temperature is higher than ca. 18°C. Two hypotheses were formulated to explain the influence of seawater temperature in May on the distribution of P. vulgata: 1. Inhibition of the beginning of gametogenesis due to high temperature stress during the resting period. 2. Death of the spat due to high temperature stress, with concomitant failure of the settlement of new generations on the substrates. In addition, the absence of upwelling waters in the eastern part of the Algarve coast could hinder the larval stage of P. vulgata, and severe competition with Patella intermedia and Patella ulyssiponensis could prevent the establishment of those few individuals of the spat that survived. Tonel, Mareta, Martinhal, Barranco and Ingrina sites are candidates to be used as reference points to follow future changes in seawater surface temperature.