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Paternal care, filial cannibalism and sexual conflict in the sand goby, Pomatoschistus minutus
Stockholm University, Faculty of Science, Department of Zoology.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Natural and sexual selection and sexual conflict are forces shaping the evolution of reproductive behaviour, while constrained by factors like environment, physiology and life-history trade-offs. Parental care is costly both in terms of time and energy. In fish, filial cannibalism is a strategy for caring males to compensate for some of the energy loss. Human impact like eutrophication also alters the basics for animals living in that environment. It is fundamental to any species to adjust its behaviour to a changing environment. Studying sand goby males, I found trade-offs both regarding parental care allocations, like ventilation vs. predator defence, and investment in present vs. future reproductive success. Paternal sand gobies exposed to water with low oxygen levels increased their fanning effort but did not compensate by eating more eggs, even though an increased current parental effort should affect future reproductive success negatively. Investigating if patterns of filial cannibalism change with time of season, I found no correlation. Theory predicts that it should pay more to eat eggs early, when future mating potential is higher than late in the season. However, as early hatching fry are likely to gain higher fitness through larger size the next breeding season, this may provide an opposing selection pressure. In species with male care the only way a female can affect the level of post-spawning care is by choosing a good mate. A female preference to spawn in nests that already contain eggs of other females has been interpreted as a means to avoid filial cannibalism through a dilution effect or to decrease the costs of search time. Yet, in my study females did not avoid filial cannibalism by preferring large clutches to small ones. Oxygenation of the eggs might be a key factor, since both large and small females preferred spawning in nests with small clutches. Thus, as in most animals, trade-offs clearly govern the reproductive behaviour of sand gobies.

Place, publisher, year, edition, pages
Stockholm: Zoologiska institutionen , 2006. , 100 p.
Keyword [en]
female choice, filial cannibalism, Gobiidae, parental care, Pomatoschistus minutus, sand goby, sexual conflict, sexual selection
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:su:diva-1399ISBN: 91-7155-357-6 (print)OAI: oai:DiVA.org:su-1399DiVA: diva2:190013
Public defence
2007-01-19, sal G, Arrheniuslaboratorierna, Svante Arrhenius väg 14-18, Stockholm, 10:00
Opponent
Supervisors
Available from: 2006-12-06 Created: 2006-12-06Bibliographically approved
List of papers
1. Effects of a low oxygen environment on parental effort and filial cannibalism in the male sand goby, Pomatoschistus minutus: Low oxygen, parental effort, and filial cannibalism in the sand goby
Open this publication in new window or tab >>Effects of a low oxygen environment on parental effort and filial cannibalism in the male sand goby, Pomatoschistus minutus: Low oxygen, parental effort, and filial cannibalism in the sand goby
2003 (English)In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 14, no 3, 374-381 p.Article in journal (Refereed) Published
Abstract [en]

In fish, brood cycling parental males sometimes eat some or all of their eggs, a behavior termed filial cannibalism. We tested predictions of filial cannibalism models related to the cost of parental care in the male sand goby, Pomatoschistus minutus, by increasing the parental effort (fanning expenditure) through reduced levels of dissolved oxygen to 39% in an experimental group, whereas a control group had fully saturated water. Males showed both full-clutch cannibalism and partial-clutch cannibalism in both treatments. Giving the males one to three females to spawn with, we found that small clutches were completely eaten more often than were larger ones, whereas partial-clutch cannibalism was not affected by clutch size. Although treatment did not affect filial cannibalism, it did affect a male's energy state such that males in the low oxygen treatment lost more body fat, indicating a greater fanning effort. This shows that males in the low oxygen treatment allocated more energy to the present brood, potentially at the expense of future reproductive success. Our study strongly suggests that filial cannibalism in male sand gobies represents a strategic life-history decision as an investment in future reproductive success, and is not triggered by a proximate need for food necessary for the male's own survival. Furthermore, males in the low oxygen treatment built nests with larger entrances, and were less likely to rebuild their nests after destruction. Presumably, this makes fanning easier but the nest more vulnerable to predators, suggesting a trade-off between fanning and nest defense.

National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-23056 (URN)374-381 10.1093/beheco/14.3.374 (DOI)
Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2014-01-08Bibliographically approved
2. Ventilation or nest defence – Parental care trade-offs in a fish with male care
Open this publication in new window or tab >>Ventilation or nest defence – Parental care trade-offs in a fish with male care
2006 (English)In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 60, no 6, 864-873 p.Article in journal (Refereed) Published
Abstract [en]

Brood guarding animals face many critical trade-offs. Sand goby males (Pomatoschistus minutus) build nests with larger openings during low oxygen conditions, presumably to enhance ventilation. However, this may make the nest easier for egg predators to detect and harder for guarding males to defend. Manipulating oxygen level and predator presence (a small crab) for small and large males, we found support for a parental trade-off between fanning and nest defense. An increased fanning activity resulted in less time for guarding. Small males and males in low oxygen showed a higher fanning expenditure than large males and males in high oxygen, but surprisingly, filial cannibalism did not differ between these groups. Males built larger nest openings in low than high oxygen. However, males in both high and low oxygen treatments reduced their nest opening size in the presence of a predator, again indicating an important trade-off between ventilation and nest defense.

National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-23057 (URN)
Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2014-01-08Bibliographically approved
3. Does time of the season influence filial cannibalism in the sand goby, Pomatoschistus minutus?
Open this publication in new window or tab >>Does time of the season influence filial cannibalism in the sand goby, Pomatoschistus minutus?
2007 (English)In: Environmental Biology of Fishes, ISSN 0378-1909, E-ISSN 1573-5133, Vol. 80, no 1, 69-75 p.Article in journal (Refereed) Published
Abstract [en]

According to life-history theory, filial cannibalism by fish that breed over one season only should be more beneficial early than late in the season if they eat eggs to invest energy into later clutches. Also, filial cannibalism may be more costly late in the season if finding ripe females for replacing eaten eggs is harder then. On the other hand, offspring hatching early may have a competitive advantage over fry hatching late and hence provide higher fitness to the parent. Using data collected over three successive years, I tested if sand goby males are more prone to eat of their eggs early than late in the reproductive season. I found no difference in the amount of eggs eaten or in the frequency of males eating the whole clutch between early and late in the season. Furthermore, there was no difference in the frequency of males who ate parts of their clutches, early compared to late. This might reflect a tradeoff between quality (early hatching offspring) and quantity (producing as many offspring as possible over a long reproductive season). If so, the lack of seasonal pattern of filial cannibalism found in sand gobies might be the result of opposing selection pressures.

Place, publisher, year, edition, pages
Springer, 2007
Keyword
Filial cannibalism, Operational sex, ratio, Parental investment, Pomatoschistus miniutus, Reproductive season
National Category
Zoology
Identifiers
urn:nbn:se:su:diva-23058 (URN)10.1007/s10641-006-9117-1 (DOI)000249012100007 ()
Note
Part of urn:nbn:se:su:diva-1399Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2011-01-19Bibliographically approved
4. Are small females choosier than large? – Implications for female reproductive success in a fish with paternal care and filial cannibalism
Open this publication in new window or tab >>Are small females choosier than large? – Implications for female reproductive success in a fish with paternal care and filial cannibalism
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-23059 (URN)
Note
Part of urn:nbn:se:su:diva-1399Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2010-01-13Bibliographically approved

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