School of Life Sciences, University of Nevada, Las Vegas, 4505 S, Maryland Parkway, Las Vegas, Nevada 89154-4004, USA.
BMC Evol Biol. 2013 Sep 14;13:197. doi: 10.1186/1471-2148-13-197.
Life history tradeoffs may result from temporal and physiological constraints intrinsic to an organism. When faced with limited time and energy, compromises occur and these resources are allocated among essential activities, such as body growth, maintenance, foraging, mating, and offspring care. We investigated potential tradeoffs that may occur between reproductive activities and feeding performance in female Arizona Bark Scorpions (Centruroides sculpturatus) by comparing the time taken to capture prey between non-reproductive and reproductive females (gravid females and females exhibiting maternal care, i.e. carrying offspring on their backs).
Gravid females were as efficient at catching prey as non-gravid females. To control for variation in the duration of the maternal care period, we removed all offspring from all post-parturient females after 5 days. Brooding females and females 24 hours following offspring removal (FOR) did not successfully capture prey within the 900-second trial period. Twenty-eight days FOR, females caught prey faster than females displaying maternal care and females 24 hours FOR, but were not as efficient at catching prey as non-gravid and gravid females. When pursuing prey, C. sculpturatus exhibiting maternal care used an active foraging strategy more frequently than non-gravid, gravid, and females 28 days FOR. In contrast, non-gravid, gravid, and females 28 days FOR used active and ambush foraging with similar frequency.
Our data suggest that reproduction does not significantly reduce the predatory efficiency of gravid C. sculpturatus, and that these females can cope with increasing body mass and the physiological costs of gestation. However, the observation that brooding females and females 24 hours FOR did not catch prey within the trial period indicates that maternal care significantly reduces predatory efficiency in these scorpions. Females 28 days FOR were still not as efficient at catching prey as non-gravid and gravid females, suggesting that reproductive costs extend for at least 4 weeks after the end of the maternal care period. Preferential use of an active foraging strategy by brooding females may increase prey encounter rates, allowing the scorpions to more rapidly replenish energy reserves depleted during reproduction. However, active foraging may be energetically costly and increase predation risk for brooding females. Our findings regarding antagonistic interactions between reproduction and feeding in female C. sculpturatus demonstrate the pervasive nature of reproductive costs for viviparous females, and may provide insight on factors that influence the diversity of reproductive strategies observed in nature.
生活史权衡可能是由于生物体内在的时间和生理限制造成的。当面临有限的时间和精力时，就会出现妥协，这些资源会在身体生长、维持、觅食、交配和照顾后代等基本活动之间进行分配。我们通过比较非繁殖期和繁殖期雌性（怀孕雌性和表现出母性照顾的雌性，即背着后代）捕捉猎物所需的时间，研究了雌性亚利桑那树皮蝎子（Centruroides sculpturatus）繁殖活动与摄食表现之间可能发生的潜在权衡。
怀孕雌性与非怀孕雌性捕捉猎物的效率相同。为了控制母性照顾期持续时间的变化，我们在产后 5 天从所有产后的雌性身上取下所有的后代。育雏雌性和产后 24 小时（FOR）的雌性在 900 秒的试验期内未能成功捕获猎物。产后 28 天的雌性比表现出母性照顾的雌性和产后 24 小时的雌性捕捉猎物更快，但捕捉猎物的效率不如非怀孕和怀孕的雌性。当追逐猎物时，表现出母性照顾的 C. sculpturatus 比非怀孕、怀孕和产后 28 天的雌性更频繁地使用主动觅食策略。相比之下，非怀孕、怀孕和产后 28 天的雌性以类似的频率使用主动和伏击觅食策略。
我们的数据表明，繁殖并没有显著降低怀孕的 C. sculpturatus 的捕食效率，并且这些雌性能够应对体重增加和妊娠的生理成本。然而，育雏雌性和产后 24 小时的雌性在试验期内未能捕获猎物的观察结果表明，母性照顾显著降低了这些蝎子的捕食效率。产后 28 天的雌性在捕捉猎物方面仍然不如非怀孕和怀孕的雌性有效，这表明繁殖成本至少会在母性照顾期结束后的 4 周内持续存在。育雏雌性更倾向于使用主动觅食策略可能会增加猎物遭遇率，使蝎子能够更快地补充繁殖期间消耗的能量储备。然而，主动觅食可能是能源密集型的，并增加育雏雌性的捕食风险。我们关于雌性 C. sculpturatus 繁殖与摄食之间的拮抗相互作用的研究结果表明，繁殖对胎生雌性的影响是普遍存在的，这可能为理解影响自然中观察到的生殖策略多样性的因素提供了线索。
