This paper compares two reef sites near Discovery Bay, Jamaica, Dairy Bull and Dancing Lady, from 2000 to 2015. At Dairy Bull reef, with low macroalgal cover (8% in 2002 falling to 1% in 2015) and significant number o...This paper compares two reef sites near Discovery Bay, Jamaica, Dairy Bull and Dancing Lady, from 2000 to 2015. At Dairy Bull reef, with low macroalgal cover (8% in 2002 falling to 1% in 2015) and significant number of Diadema antillarum urchins (c. 5 m<sup>-2</sup>), live coral cover increased from 13% ± 5% in 2006 after the bleaching event in 2005, to 31% ± 7% in 2008, while live Acropora cervicornis increased from 2% ± 2% in 2006 to 28% ± 5% in 2015. Coral cover levels were at least maintained until 2015, owing mostly to a slight increase in A. cervicornis. Dancing Lady reef however was dominated by macroalgae throughout this period (cover of c. 76% ± 7%), with no D. antillarum and showed little decrease in the already low (6% ± 1%) coral cover in 2005. Growth rates for Siderastrea siderea were similar for both sites (7 mm·yr<sup>-1</sup>), while growth rates of A. cervicornis and A. palmata were 120.0 ± 30 mm·yr<sup>-1</sup> and 71.0 ± 29 mm·yr<sup>-1</sup> respectively at Dairy Bull in 2015. At Dancing Lady reef, A. cervicornis colonies which were present from 2003 to 2005 had disappeared in 2006, possibly as a result of the mass bleaching event. It appears that A. cervicornis was the most impacted species during the 2005 bleaching event, but was also the species that recovered fastest after its decline at Dairy Bull.展开更多
Social conditions experienced prior to sexual maturity influence reproduction later in life in many animals. In simulta- neous hermaphrodites, variation in mating group size influences reproductive investment. As the ...Social conditions experienced prior to sexual maturity influence reproduction later in life in many animals. In simulta- neous hermaphrodites, variation in mating group size influences reproductive investment. As the mating group size increases, re- productive resources devoted to the female function decrease in favor of the male function. Prior to sexual maturity, many her- maphrodites have a protandrous phase during which they produce sperm and can fertilize hermaphrodites＇ eggs. In the simulta- neously hermaphroditic polychaete worm Ophryotrocha diadema, the cost of male reproduction during adolescence is spread over the whole energy budget of worms as shown by a reduced growth rate, a delayed age at sexual maturity and the shortening of life span compared to protandrous males that do not reproduce. Little is known on whether social conditions experienced dur- ing development affect reproductive investment of immature individuals. We investigated whether social conditions affected the length of the protandrous phase, body size and also the subsequent female fecundity of same-age protandrous individuals of O. diadema, which did not had to face competition for egg fertilization. Results show that in large group sizes protandrous males lengthened their protandrous phase, slowed down body growth and decreased their individual investment at the first egg laying compared to protandrous males that were reared in isolation. In the successive egg layings worms adjusted their egg output to the current social conditions. We interpreted these results as an indication that early social conditions represent a social stress result- ing in a reduction of the overall reproductive resources up to the first egg laying .展开更多
Sex allocation theory applied to hermaphrodites assumes that there is a trade off between the alloca- tion of resources to male and female functions, within a fixed reproductive resource budget. Charnov＇s classic res...Sex allocation theory applied to hermaphrodites assumes that there is a trade off between the alloca- tion of resources to male and female functions, within a fixed reproductive resource budget. Charnov＇s classic resource allocation model predicts a more female-biased sex allocation when competition among different sperm donors is low due to diminishing fitness returns for male investment. By manipulating the social group size, one automatically changes the population density at which individ- uals live. Increasing population density may affect reproductive allocation, leading to resource compe- tition and/or to increased concentration of harmful metabolites. This could lead to an over- or under- estimation of the individual adjustment of sex allocation responses to mating opportunities. In this article, we tested the effects of density and social group size separately on female investment and body growth （considered as proxy of the overall energy budget） in the simultaneously hermaphroditic polychaete worm Ophryotrocha diadema. We manipulated social group size （i.e., monogamous and promiscuous regimes） and density （i.e., 4 levels） using a full-factorial design, to identify the underlying factor affecting female allocation （in terms of egg production） and body growth. In contrast to findings of previous experiments, we found that an increase in population density reduced body growth and egg production of hermaphrodites irrespective of social group size. We advance the hypothesis that the increase of catabolites and oxygen consumption in high-density conditions reduces the overall resource budget and this could obscure group size effects on female fecundity.展开更多
文摘This paper compares two reef sites near Discovery Bay, Jamaica, Dairy Bull and Dancing Lady, from 2000 to 2015. At Dairy Bull reef, with low macroalgal cover (8% in 2002 falling to 1% in 2015) and significant number of Diadema antillarum urchins (c. 5 m<sup>-2</sup>), live coral cover increased from 13% ± 5% in 2006 after the bleaching event in 2005, to 31% ± 7% in 2008, while live Acropora cervicornis increased from 2% ± 2% in 2006 to 28% ± 5% in 2015. Coral cover levels were at least maintained until 2015, owing mostly to a slight increase in A. cervicornis. Dancing Lady reef however was dominated by macroalgae throughout this period (cover of c. 76% ± 7%), with no D. antillarum and showed little decrease in the already low (6% ± 1%) coral cover in 2005. Growth rates for Siderastrea siderea were similar for both sites (7 mm·yr<sup>-1</sup>), while growth rates of A. cervicornis and A. palmata were 120.0 ± 30 mm·yr<sup>-1</sup> and 71.0 ± 29 mm·yr<sup>-1</sup> respectively at Dairy Bull in 2015. At Dancing Lady reef, A. cervicornis colonies which were present from 2003 to 2005 had disappeared in 2006, possibly as a result of the mass bleaching event. It appears that A. cervicornis was the most impacted species during the 2005 bleaching event, but was also the species that recovered fastest after its decline at Dairy Bull.
文摘Social conditions experienced prior to sexual maturity influence reproduction later in life in many animals. In simulta- neous hermaphrodites, variation in mating group size influences reproductive investment. As the mating group size increases, re- productive resources devoted to the female function decrease in favor of the male function. Prior to sexual maturity, many her- maphrodites have a protandrous phase during which they produce sperm and can fertilize hermaphrodites＇ eggs. In the simulta- neously hermaphroditic polychaete worm Ophryotrocha diadema, the cost of male reproduction during adolescence is spread over the whole energy budget of worms as shown by a reduced growth rate, a delayed age at sexual maturity and the shortening of life span compared to protandrous males that do not reproduce. Little is known on whether social conditions experienced dur- ing development affect reproductive investment of immature individuals. We investigated whether social conditions affected the length of the protandrous phase, body size and also the subsequent female fecundity of same-age protandrous individuals of O. diadema, which did not had to face competition for egg fertilization. Results show that in large group sizes protandrous males lengthened their protandrous phase, slowed down body growth and decreased their individual investment at the first egg laying compared to protandrous males that were reared in isolation. In the successive egg layings worms adjusted their egg output to the current social conditions. We interpreted these results as an indication that early social conditions represent a social stress result- ing in a reduction of the overall reproductive resources up to the first egg laying .
文摘Sex allocation theory applied to hermaphrodites assumes that there is a trade off between the alloca- tion of resources to male and female functions, within a fixed reproductive resource budget. Charnov＇s classic resource allocation model predicts a more female-biased sex allocation when competition among different sperm donors is low due to diminishing fitness returns for male investment. By manipulating the social group size, one automatically changes the population density at which individ- uals live. Increasing population density may affect reproductive allocation, leading to resource compe- tition and/or to increased concentration of harmful metabolites. This could lead to an over- or under- estimation of the individual adjustment of sex allocation responses to mating opportunities. In this article, we tested the effects of density and social group size separately on female investment and body growth （considered as proxy of the overall energy budget） in the simultaneously hermaphroditic polychaete worm Ophryotrocha diadema. We manipulated social group size （i.e., monogamous and promiscuous regimes） and density （i.e., 4 levels） using a full-factorial design, to identify the underlying factor affecting female allocation （in terms of egg production） and body growth. In contrast to findings of previous experiments, we found that an increase in population density reduced body growth and egg production of hermaphrodites irrespective of social group size. We advance the hypothesis that the increase of catabolites and oxygen consumption in high-density conditions reduces the overall resource budget and this could obscure group size effects on female fecundity.
