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Mating behavior of Daphnia: impacts of predation risk, food quantity, and reproductive phase of females.

La GH, Choi JY, Chang KH, Jang MH, Joo GJ, Kim HW - PLoS ONE (2014)

Bottom Line: Mating-related behavior involved male-female contact (mating) as well as male-male contact (fighting).Mating frequency increased while unnecessary fighting decreased in the presence of predation risk.In addition, low food concentration reduced fighting between males.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Education, Sunchon National University, Suncheon, Korea.

ABSTRACT
High predation risk and food depletion lead to sexual reproduction in cyclically parthenogenetic Daphnia. Mating, the core of sexual reproduction, also occurs under these conditions. Assessment of the environmental conditions and alteration of mating efforts may aid in determining the success of sexual reproduction. Here, we evaluated the impacts of predation risk, food quantity, and reproductive phase of females on the mating behavior of Daphnia obtusa males including contact frequency and duration using video analysis. Mating-related behavior involved male-female contact (mating) as well as male-male contact (fighting). Mating frequency increased while unnecessary fighting decreased in the presence of predation risk. In addition, low food concentration reduced fighting between males. Males attempted to attach to sexual females more than asexual females, and fighting occurred more frequently in the presence of sexual females. Duration of mating was relatively long; however, males separated shortly after contact in terms of fighting behavior. Thus, assessment of environmental factors and primary sexing of mates were performed before actual contact, possibly mechanically, and precise sex discrimination was conducted after contact. These results suggest that mating in Daphnia is not a random process but rather a balance between predation risk and energetic cost that results in changes in mating and fighting strategies.

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Related in: MedlinePlus

Example of video analysis of the mating process in Daphnia obtusa.Frame numbers of the video from encounter to separation of each contact were converted into time to determine the duration of the contact (black line: trajectory of male; grey line: trajectory of female; dashed line: trajectory of male and female during mating).
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pone-0104545-g001: Example of video analysis of the mating process in Daphnia obtusa.Frame numbers of the video from encounter to separation of each contact were converted into time to determine the duration of the contact (black line: trajectory of male; grey line: trajectory of female; dashed line: trajectory of male and female during mating).

Mentions: To evaluate the impact of predation risk (absence or presence of kairomones), food quantity (low or high), and reproductive phase of females (asexual or sexual) on mating, we conducted a 2×2×2 experimental design (12 replicates for each treatment, total of 96 observations). Small acryl chambers designed for two–dimensional observations were used (length × height × width  = 8.5×7×0.5 cm). The observation chamber was placed in a box made of black panel without a cover or front side. All experiments were conducted during day time and a 20 W fluorescent lamp was placed above the box for illumination. We filled the observation chamber with 30 mL of medium for each treatment (absence or presence of fish kairomones and low or high food) and added 10 males and females (asexual or sexual). Before recording, there was an acclimation period of 10 minutes. We recorded all contact events for 10 minutes under each treatment using a digital camcorder (Sanyo Xacti VPC–SH1, Tokyo, Japan) recording at 30 frames per second. Contact frequency and frame number of the video for initiation and separation of every contact event were recorded (Fig. 1). Total frame numbers of each contact were used to calculate the duration time of contact. Simple collisions (when individuals swam in a different direction immediately without adherence) and contact events occurring before the recording or continued after 10 minutes were excluded.


Mating behavior of Daphnia: impacts of predation risk, food quantity, and reproductive phase of females.

La GH, Choi JY, Chang KH, Jang MH, Joo GJ, Kim HW - PLoS ONE (2014)

Example of video analysis of the mating process in Daphnia obtusa.Frame numbers of the video from encounter to separation of each contact were converted into time to determine the duration of the contact (black line: trajectory of male; grey line: trajectory of female; dashed line: trajectory of male and female during mating).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128813&req=5

pone-0104545-g001: Example of video analysis of the mating process in Daphnia obtusa.Frame numbers of the video from encounter to separation of each contact were converted into time to determine the duration of the contact (black line: trajectory of male; grey line: trajectory of female; dashed line: trajectory of male and female during mating).
Mentions: To evaluate the impact of predation risk (absence or presence of kairomones), food quantity (low or high), and reproductive phase of females (asexual or sexual) on mating, we conducted a 2×2×2 experimental design (12 replicates for each treatment, total of 96 observations). Small acryl chambers designed for two–dimensional observations were used (length × height × width  = 8.5×7×0.5 cm). The observation chamber was placed in a box made of black panel without a cover or front side. All experiments were conducted during day time and a 20 W fluorescent lamp was placed above the box for illumination. We filled the observation chamber with 30 mL of medium for each treatment (absence or presence of fish kairomones and low or high food) and added 10 males and females (asexual or sexual). Before recording, there was an acclimation period of 10 minutes. We recorded all contact events for 10 minutes under each treatment using a digital camcorder (Sanyo Xacti VPC–SH1, Tokyo, Japan) recording at 30 frames per second. Contact frequency and frame number of the video for initiation and separation of every contact event were recorded (Fig. 1). Total frame numbers of each contact were used to calculate the duration time of contact. Simple collisions (when individuals swam in a different direction immediately without adherence) and contact events occurring before the recording or continued after 10 minutes were excluded.

Bottom Line: Mating-related behavior involved male-female contact (mating) as well as male-male contact (fighting).Mating frequency increased while unnecessary fighting decreased in the presence of predation risk.In addition, low food concentration reduced fighting between males.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Education, Sunchon National University, Suncheon, Korea.

ABSTRACT
High predation risk and food depletion lead to sexual reproduction in cyclically parthenogenetic Daphnia. Mating, the core of sexual reproduction, also occurs under these conditions. Assessment of the environmental conditions and alteration of mating efforts may aid in determining the success of sexual reproduction. Here, we evaluated the impacts of predation risk, food quantity, and reproductive phase of females on the mating behavior of Daphnia obtusa males including contact frequency and duration using video analysis. Mating-related behavior involved male-female contact (mating) as well as male-male contact (fighting). Mating frequency increased while unnecessary fighting decreased in the presence of predation risk. In addition, low food concentration reduced fighting between males. Males attempted to attach to sexual females more than asexual females, and fighting occurred more frequently in the presence of sexual females. Duration of mating was relatively long; however, males separated shortly after contact in terms of fighting behavior. Thus, assessment of environmental factors and primary sexing of mates were performed before actual contact, possibly mechanically, and precise sex discrimination was conducted after contact. These results suggest that mating in Daphnia is not a random process but rather a balance between predation risk and energetic cost that results in changes in mating and fighting strategies.

Show MeSH
Related in: MedlinePlus