Browsing by Author "Pörtner, HO"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Full time mothers
    (2002) Ruiz-Tagle, N; Fernández, M; Pörtner, HO
    Daily rhythms in activity have been reported for marine and terrestrial organisms, including brooding behaviors which supply oxygen to the embryos of marine invertebrates. Considering that oxygen is a limiting factor in embryo masses of Brachyuran crabs and that female crabs play a critical role in supplying oxygen to the embryos, we studied and compared daily patterns of (1) brooding and nonbrooding behaviors in brooding females, (2) behaviors in nonbrooding females, and (3) oxygen provision to the embryos in a Xanthid crab (Homalaspis plana). We also experimentally evaluated whether daily patterns of nonbrooding behaviors were related to food intake. Behaviors were identified using video recordings and correlated with oxygen analyses in the center of the egg masses by use of microoptodes. According to PO2 recordings abdominal flapping was identified as the single, most important behavior supplying oxygen to the center of the egg mass, maintained at a constant rate during both day and night. Furthermore, the lack of a daily pattern in oxygen availability in the center of the embryo mass is consistent with the lack of daily pattern in abdominal flapping. In contrast, locomotor activity (walking) and maxilliped movements remained unrelated to PO2 oscillations and showed a pronounced diurnal pattern, increasing during the night. This strong diurnal rhythmicity in walking behavior decreased as embryos developed. The frequency of locomotor activity and egg ventilation increased as embryo development progressed. The increase in egg ventilation throughout embryo development may be a response to the increase in embryonic oxygen demand during development. The change in locomotor activity was unrelated to feeding activity, but may serve to make the ventilation process more efficient. These findings emphasize that oxygen is a crucial factor during early development, affecting the normal rate of development of embryos. In consequence, females permanently provide oxygen to the brood despite daily cycles in other behaviors. (C) 2002 Elsevier Science B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Reproductive investment in the crab Cancer setosus along a latitudinal cline
    (2003) Brante, A; Fernández, M; Eckerle, L; Mark, F; Pörtner, HO; Arntz, W
    Reproductive output (RO) is commonly used as a proxy for reproductive effort (RE) among Brachyuran crabs and other marine invertebrates, and so far no attempt has been made to incorporate the cost of brooding into RE to obtain a more reliable estimate of reproductive investment, nor to compare it along a temperature (latitudinal) gradient. We compared RO among 3 sites (ca. 20, 30 and 40degrees S, reflecting mean annual sea-surface temperatures of 18, 14 and 10degreesC, respectively), and the cost of brooding (oxygen provision) at those temperatures, in order to obtain a more reliable pattern of reproductive investment along an extended latitudinal gradient. A total of 187 brooding females of Cancer setosus were collected to estimate RO. Fecundity, volume and weight of the embryos, and embryo losses were also estimated. Laboratory experiments were carried out at the characteristic temperatures of those sites (acclimating females from central Chile) to determine (1) patterns of oxygen provision to the embryos, (2) patterns of brooding behavior, and (3) to quantify the cost of embryo ventilation. Optic fibers, video recording and respiration chambers were used to meet these goals. Results showed that (1) RO, (2) fecundity, and (3) volume and weight of embryos varied with latitude, and that temperature affects (1) period of embryo ventilation (oxygen provision) events, (2) flapping frequency, (3) embryo losses throughout the brooding period, and (4) cost of embryo ventilation per unit of time. While RO increased with latitude, the cost of embryo ventilation decreased with temperature, suggesting a trade-off between investment in eggs and the cost of providing oxygen to the embryos at different temperatures (latitudes). This pattern may not be exclusive to Brachyuran crabs, but may also apply to other marine invertebrates since oxygen limitation during early development occurs in other brooding species.
  • No Thumbnail Available
    Item
    The cost of being a caring mother
    (2000) Fernández, M; Bock, C; Pörtner, HO
    Investment in reproduction ranges from gamete production to active parental care, and marine invertebrates span this range. However, the cost of parental care has not yet been systematically quantified, nor incorporated into life history studies of marine invertebrates, in contrast to most other animal taxa. Since oxygen is a limiting factor in egg masses of marine invertebrates, we studied patterns of oxygen partial pressure over time in embryo masses of Brachyuran crabs, and correlated these results with the cost of providing oxygen to the embryos. We found that: (1) oxygen is limiting in the embryo masses, (2) female crabs show an active brooding behaviour that we think helps to provide oxygen to the embryo mass, and (3) there is a substantial parental investment associated with brooding behaviours. Oxygen limitation and parental investment seem to be associated in many taxa of marine invertebrates, and we suggest that oxygen provision to the embryos may be a critical factor determining parental investment in this group.