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| Author(s): |
Paula Kasten
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Ribeirão Preto. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC) |
| Defense date: | 2011-11-18 |
| Examining board members: |
Augusto Alberto Valero Flores;
Luiz Silveira Menna Barreto;
Rubens Mendes Lopes
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| Advisor: | Augusto Alberto Valero Flores |
| Abstract | |
Synchronized reproduction is common among marine invertebrates, and intertidal organisms make use of exogenous cues, such as environmental cycles generated by the movements of the Earth and Moon, to synchronize their biological clocks in phase with such oscillations, at least in one stage of the reproductive cycle. In previous reports on barnacle rhythms, some studies have stressed a clear relationship between larval emission and high phytoplankton production, while others indicate a close relationship with the regimes of tide and moon phases. In this project we intended to detect environmental variables associated with the rhythmic larval release activity in the barnacle Chthamalus bisinuatus, both in constant laboratory conditions, allowing the detection of an endogenous component associated with such activity, and in the field, by monitoring larval release and other environmental conditions that might influence the reproductive cycle. For such purposes, populations were tested in constant laboratory conditions, where the variables temperature, photoperiod and time of immersion were tested both alone and combined in pairs, and in the field, by monitoring reproductive activity in populations of these cirripedes for 32 days, together with temperature, water flow, and chlorophyll-a concentration, as to establish relationships between larval release and these variables. The results indicate the existence of an endogenous component setting the rhythm of emission and larval molt activity synchronized with the cycle of tidal range (14.4 days), and the use of tides and daily fluctuations in temperature as cues in the synchronization of ultradian release activities. In the field, extremes of temperature, peaks of chlorophyll-a concentration (a proxy of food availability for adults) and water flow, triggered naupliar release 1 and 6 days ahead, for the first two variables, and 1 and 3 days before for the last one, thus proving to be important variables in determining the time of larval emission. Therefore, it is concluded that endogenous tidal-amplitude rhythms may partly explain sharp fortnight patterns centered at neap-tide periods in populations examined elsewhere, but, as shown herein, such rhythmicity may be disrupted by variations of temperature, food availability and intense water flow. It is argued that the first effect may be related to a physiological mechanism ensuring reproduction in individuals at a higher mortality risk, and that food is a limiting resource for reproduction in the study population. In a shorter time scale, endogenous rhythmicity, entrained by the combined control of temperature and immersion time, favors high-tide larval release. In the absence of other environmental release-inducing factors, endogenous timing would lead to high-tide release during neap periods, which would favor coastal retention and minimize stranding risk. (AU) | |
| FAPESP's process: | 09/12645-0 - Rhythmicity in the emission of propagules in Chthamalus bisinuatus (Pilsbry, 1916): endogenous and exogenous components |
| Grantee: | Paula Kasten |
| Support Opportunities: | Scholarships in Brazil - Master |