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Abstract：
Across vertebrates increased maternal investment (via increased pre- and postnatal provisioning) is associated with larger relative brain size, yet it remains unclear how brain organization is shaped by life history and ecology. Here, we tested whether maternal investment and ecological lifestyle are related to variation in brain size and organization across 100 chondrichthyans. We hypothesized that brain size and organization would vary with the level of maternal investment and habitat depth and complexity. We found that chondrichthyan brain organization varies along four main axes according to (1) absolute brain size, (2) relative diencephalon and mesencephalon size, (3) relative telencephalon and medulla size, and (4) relative cerebellum size. Increased maternal investment is associated with larger relative brain size, while ecological lifestyle is informative for variation between relative telencephalon and medulla size and relative cerebellum size after accounting for the independent effects of reproductive mode. Deepwater chondrichthyans generally provide low levels of yolk-only (lecithotrophic) maternal investment and have relatively small brains, predominantly composed of medulla (a major portion of the hindbrain), whereas matrotrophic chondrichthyans-which provide maternal provisioning beyond the initial yolk sac-found in coastal, reef, or shallow oceanic habitats have relatively large brains, predominantly composed of telencephalon (a major portion of the forebrain). We have demonstrated, for the first time, that both ecological lifestyle and maternal investment are independently associated with brain organization in a lineage with diverse life-history strategies and reproductive modes.
摘要：
在脊椎动物中，增加的母体投资（通过增加产前和产后供应）与更大的相对大脑大小有关。然而，目前尚不清楚大脑组织是如何由生活史和生态学形成的。这里,我们测试了产妇投资和生态生活方式是否与100个软骨鱼的大脑大小和组织变化有关。我们假设大脑的大小和组织会随着母亲的投资水平以及栖息地的深度和复杂性而变化。我们发现，根据（1）绝对大脑大小，软骨石的大脑组织沿四个主轴变化，（2）间脑和中脑的相对大小，（3）相对端脑和髓质大小，和(4)相对小脑大小。母亲投资的增加与更大的相对大脑大小有关，而在考虑了生殖模式的独立影响后，生态生活方式可提供有关端脑和髓质相对大小与小脑相对大小之间变化的信息。深水软骨病通常提供低水平的仅蛋黄（卵磷脂营养）母体投资，并且大脑相对较小，主要由髓质（后脑的主要部分）组成，而在沿海发现的母体营养软骨病-提供超过初始卵黄囊的母体供应，珊瑚礁,或者浅海栖息地有相对较大的大脑，主要由端脑（前脑的主要部分）组成。我们已经证明,第一次,生态生活方式和母亲投资都与大脑组织独立相关，具有不同的生活史策略和生殖模式。
