| 1. |
- Lissaker, M., et al.
(författare)
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Effects of a low oxygen environment on parental effort and filial cannibalism in the male sand goby, Pomatoschistus minutus
- 2003
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 14:3, s. 374-381
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Svensson, Ola, 1971-, et al.
(författare)
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Costly courtship or dishonest display? Intensely displaying sand goby males have lower lipid content
- 2004
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 64:5, s. 1425-1429
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Tidskriftsartikel (refereegranskat)abstract
- Intensely displaying sand goby Pomatoschistus minutus males had lower lipid content, indicating that signalling increased energy expenditure, or that low condition males increased their signalling effort. Display intensity correlated positively with nest-defence and tended to correlate positively with filial cannibalism. (C) 2004 The Fisheries society of the British Isles.
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| 3. |
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| 4. |
- Svensson, Ola, 1971-, et al.
(författare)
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Male mating success in relation to food availability in the common goby
- 2003
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 62:5, s. 1217-1221
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Tidskriftsartikel (refereegranskat)abstract
- In a feeding experiment with the common goby Pomatoschistus microps, there was no female preference for well-fed males, although these males had a higher mating success. This suggests that care should be taken about drawing conclusions regarding mate choice and mating success based on mate preference tests alone. (C) 2003 The Fisheries Society of the British Isles.
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| 5. |
- Svensson, Ola, 1971-
(författare)
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Sexual selection in Pomatoschistus – nests, sperm competition, and paternal care
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sexual selection arises through variation in reproductive success. This thesis investigates different aspects important in sexual selection, namely nest building, sperm competition, paternity and paternal care, and their mutual interrelationships. In the studied species, the sand goby (Pomatoschistus minutus) and the common goby (Pomatoschistus microps), sperm competition did arise when small males, so called sneakers, sneaked into other males nests and released sperm. They seemed to use female behaviour as their prime cue for a sneaking opportunity. However, also nest-holders, both with and without eggs, were found to fertilize eggs in the nests of other males.Clearly, nest-holding males tried to prevent other males from spreading their sperm in their nests, since they showed aggression towards such males. A nest building experiment indicated that the small nest-openings found in the sneaker male treatment were sexually selected through protection against sneaking or by female choice. Yet, no behavioural or genetical support for the hypothesis that the nest functions as a physical or visual defence, or that sneaker males prefer to sneak upon nests with wide nest-openings, were found in the other studies. Still, individual nest-holding males showed a higher mucus preparation effort inside the nest in the presence of a sneaker male than when alone. In close relatives, such mucus contains sperm, suggesting an importance in sperm competition. However, the mucus may also have pheromone and anti-bacterial functions and may constitute a mating effort, as found in other gobies. Both a behavioural and a mate choice experiment suggested that the males were not less eager to spawn in the presence of a sneaker male.Sneak intrusion did not affect nest defence, fanning or filial cannibalism, nor had paternity an effect on filial cannibalism. This and various life history aspects, together with the fact that the parasitic male only fertilized a fraction of the clutches, would predict females to ignore sneaker males. This was also the case, as the presence of sneaker males was found not to affect female spawning decision. Still, several females spawned in two nests, which coincided with parasitic spawnings, suggesting a cost of disturbance for the females and thus a substantial cost to the nest-holding males in terms of lost mating success. However, females paid attention to other traits in their choice of mate since spawning was associated with sand volume of the nest, but not with nest-opening width. Also, female (but not male) courtship was correlated with partial clutch filial cannibalism, indicating that females are able to anticipate future male cannibalism.In a partial correlation of nest opening, sand volume, male courtship display, displacement fanning and male size, a large number of traits were correlated both positively and negatively with regard to how we may expect them to be appreciated by females. For instance, males which fan well also build large nests or display intensely (but not both). Together with all the other results of this thesis, this shows the entangled selection pressures working on breeding animals, as well as the different male and female tactics employed to maximize their reproduction.
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| 6. |
- Svensson, Ola, 1971-, et al.
(författare)
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Sexually selected nest-building - Pomatoschistus minutus males build smaller nest-openings in the presence of sneaker males
- 2003
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 16:5, s. 896-902
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Tidskriftsartikel (refereegranskat)abstract
- Both natural selection and sexual selection may act on nest-building. We tested experimentally how different regimes of egg-predation and male-male competition influence nest-building before mating, using the marine fish sand goby, Pomatoschistus minutus. Males with sneaker males present built the smallest nest-openings, smaller than males held alone or with Pomatoschistus microps males (which may predate eggs and compete over nest-sites but not compete over fertilizations). Males with visual access to other nest-building males tended also to build smaller openings than males held alone or with P. microps. Males with egg-predators present built nests with openings not differing significantly from any other treatment. Our results indicate that the small nest-openings found in the sneaker male treatment are sexually selected through protection against sneaking or by female choice. Across treatments, time span before a male started to build his nest also explained variation in nest-opening width; males starting late built larger nest-openings.
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