Department of Biology, University of Southern Denmark, Odense, Denmark.
Eurofins Miljø A/S, Vejen, Denmark.
J Fish Biol. 2023 Sep;103(3):684-694. doi: 10.1111/jfb.15477. Epub 2023 Jun 29.
Bipartite life histories involve a suite of morphological changes that support the pelagic to demersal transition and an expanded range of prey options and microhabitats. Pelagic individuals are thought to shift (settle) to their preferred benthic habitat at the earliest opportunity once they have attained a minimum level of morphological competency to access their new environment. In theory, early changes in larval morphology (collectively termed 'metamorphosis'), habitat and diet-a measure of habitat-use-ought to be synchronous. Yet relationships may be decoupled by factors linked to behaviour, prey availability or morphological complexity, and few descriptions exist to allow such synchrony to be assessed. The sand goby, Pomatoschistus minutus, is a common coastal fish across north-western Europe, with a size at larval metamorphosis and settlement of around 10 and 16-18 mm standard length (SL), respectively. We sampled shoreline larval and juvenile populations to examine relationships between morphology, diet and life stage. Prey diversity increased with body length; however, dietary change was clearest at 16-18 mm SL, with a reduction in calanoid copepods and shift to larger prey such as Nereis polychaetes and mysid and amphipod crustacea. Early growth in five prey capture and processing morphologies was rapid. Four of these showed a subsequent marked shift to slower growth, but none of these changes were aligned with size at metamorphosis and only that of mouth width coincided with body size at settlement. Early life history in P. minutus appears geared towards a protracted morphological reorganization prior to demersal life and an alternative suite of prey resources. Larval metamorphosis seems to be of limited consequence in this regard. Comparable studies of other Baltic Sea fishes would confirm whether these dynamics relate to shared environmental pressures or to factors intrinsic to P. minutus biology.
二相生活史涉及一系列形态变化，支持从浮游到底栖的过渡以及更广泛的猎物选择和微生境。一旦浮游个体获得进入新环境的最低形态能力，它们就会被认为会尽早（定居）转移到它们首选的底栖栖息地。理论上，幼虫形态（统称为“变态”）、栖息地和饮食的早期变化——衡量栖息地利用的一种方法——应该是同步的。然而，由于与行为、猎物可用性或形态复杂性相关的因素，这些关系可能会脱钩，而且很少有描述可以评估这种同步性。沙鲷，Pomatoschistus minutus，是欧洲西北部常见的沿海鱼类，其幼虫变态和定居的大小分别约为 10 毫米和 16-18 毫米标准体长 (SL)。我们采样了海岸线幼虫和幼鱼种群，以研究形态、饮食和生活阶段之间的关系。猎物多样性随体长增加而增加；然而，饮食变化在 16-18 毫米 SL 时最为明显，桡足类减少，转向更大的猎物，如多毛类 Nereis 和糠虾和磷虾甲壳类。五种猎物捕捉和处理形态的早期生长迅速。其中四种表现出随后明显的生长减缓，但这些变化都没有与变态大小对齐，只有口宽的变化与定居时的体型大小对齐。P. minutus 的早期生活史似乎是为了在底栖生活之前进行长期的形态重组和替代的猎物资源。幼虫变态在这方面似乎没有什么影响。对其他波罗的海鱼类的类似研究将证实这些动态是与共同的环境压力有关，还是与 P. minutus 生物学的内在因素有关。
