The effect of temperature and substrates on polyp settlement of the spotted tellyfish, phyllorhiza punctata (Von Lendenfeld, 1884)

• Autor(a) principal: Pinto, Carlos Daniel Carvalho
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.8/6230
• topic: Scyphozoa; Warming; Substrate selectivity; Benthic life stage; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

In recent decades, human activity has been known to influence Earth’s marine ecosystems in a multitude of different ways, such as through global warming, overfishing, coastal or marine construction, pollution, among others. These impacts will then produce different effects on the affected organism populations. One of these groups is the gelatinous one, which has gained a lot of scientific interest due to the increased frequency and abundance jellyfish populations worldwide. It is speculated that human activities may have an impact on the development and reproduction of these species. Therefore, the aim of this work was to evaluate the effect of temperature, and different substrates on the asexual reproduction and polyp settlement of the jellyfish species Phyllorhiza punctata (Von Lendenfeld, 1884). Polyps of P. punctata were subjected to two different experiments. In the first experiment, the polyps were exposed to four different temperatures (22, 24, 26, and 28 ºC), and provided with five different substrate types (glass, rock, shell, plastic (PVC), and fishing net). After 60 days, the total number of polyps for each substrate and temperature was observed. In the second experiment, a different group of polyps was exposed to the same five substrates at the temperature of 24 ºC, and after 60 days, the total number of polyps, and their preferred distribution were compared. The results showed significant differences between the temperatures of 22 and 26 ºC, showing that higher temperatures have a positive effect on polyp asexual reproduction. It was also verified that a lower number of polyps was obtained at 28 ºC when compared with to 26 ºC, which indicates that this temperature may be outside the optimal range for P. punctata polyps, and therefore might restrict polyp reproduction instead. This leads us to believe that slight warming may benefit polyp asexual reproduction of P. punctata, but only within the limits supported by the species. Furthermore, polyp settlement occurred in all the provided substrates, although significant differences were observed between the plastic and the glass, rock, and shell substrates, being the later three significantly preferred over the first one. It was also possible to perceive a higher preference by the polyps to positions further away from the bottom of the goblet (negative geotaxis). In conclusion, marine-bound human activities appear to influence gelatinous organisms, and as such, further studies are required to better understand their influence on these organisms.