Not All Offspring Are Created Equal: Variation in Larval Characteristics in a Serially Spawning Damselfish

<div><p>The way organisms allocate their resources to growth and reproduction are key attributes differentiating life histories. Many organisms spawn multiple times in a breeding season, but few studies have investigated the impact of serial spawning on reproductive allocation. This study investigated whether resource allocation was influenced by parental characteristics and prior spawning history in a serial spawning tropical damselfish (<em>Pomacentrus amboinensis</em>). The offspring attributes of isolated parents of known characteristics were monitored over a 6-week breeding period in the field. Smaller females produced larvae of longer length and larger energy reserves at hatching. This finding is contrary to several other studies that found larger females produce offspring of greater quality. We found that resource allocation in the form of reproductive output was not influenced by the number of spawning events within the breeding season, with larger females producing the greatest number of offspring. Larval characteristics changed as spawning progressed. There was a general decline in length of larvae produced, with an increase in the size of the larval yolk-sac, for all females regardless of size as spawning progressed. This trend was accentuated by the smallest females. This change in larval characteristics may reflect a parental ability to forecast unfavourable conditions as the season progresses or a mechanism to ensure that some will survive no matter what conditions they encounter. This study highlights the importance of accounting for temporal changes in reproductive allocation in studies of reproductive trade-offs and investigations into the importance of parental effects.</p> </div

Mean (± SE) larval total length (mm) at hatching from different size females through six successive spawns.

<p>Both female size and clutch number had a significant influence on larval length (RM ANOVA; F_{10, 435} = 32.061, p = 0.0001). Filled triangle represent the small sized females (47–52 mm n = 5), filled square represents the medium sized female (55–60 mm n = 5), and filled circle represents the large sized females (63–68mm n = 5).</p

Comparison of the mean (± SE) number eggs produced per clutch between females of different size for six successive clutches.

<p>Female size had a significant influence on the number of offspring produced. C1-C6 represents six successive clutches from the same females. Dark grey bar represents the small sized females (47–52 mm; n = 5), light grey bar represents the medium sized females (55–60 mm; n = 5), and white bar represents the large sized females (63–68 mm; n = 5).</p

Mean (± SE) yolk sac area (mm²) at hatching from different size females through six successive spawns.

<p>Both female size and clutch number had a significant influence on larval yolk sac area (RM ANOVA; F_{10, 435} = 17.610, p = 0.0001). Filled triangle represent the small sized females (47–52 mm n = 5), filled square represents the medium sized female (55–60 mm n = 5), and filled circle represents the large sized females (63-68 mm n = 5).</p