Gerringer M E, Dias A S, von Hagel A A, Orr J W, Summers A P, Farina S
State University of New York at Geneseo, Geneseo, NY, 14454, USA.
Whitman College, Walla Walla, WA, 99362, USA.
Front Zool. 2021 Apr 16;18(1):16. doi: 10.1186/s12983-021-00399-9.
We tested the hypothesis that deep-sea fishes have poorly mineralized bone relative to shallower-dwelling species using data from a single family that spans a large depth range. The family Liparidae (snailfishes, Cottiformes) has representatives across the entire habitable depth range for bony fishes (0 m-> 8000 m), making them an ideal model for studying depth-related trends in a confined phylogeny. We used micro-computed tomography (micro-CT) scanning to test three aspects of skeletal reduction in snailfishes (50 species) across a full range of habitat depths: 1) reduction of structural dimensions, 2) loss of skeletal elements, and 3) reduction in bone density. Using depth data from the literature, we found that with increasing depth, the length of the dentary, neurocranium, and suborbital bones decreases. The ventral suction disk decreases width with increasing maximum habitat depth and is lost entirely in some deeper-living taxa, though not all. Although visual declines in bone density in deeper-living taxa were evident across full skeletons, individual densities of the lower jaw, vertebra, suction disk, hypural plate, and otoliths did not significantly decline with any depth metric. However, pelagic and polar taxa tended to show lower density bones compared to other species in the family. We propose that skeletal reductions allow snailfishes to maintain neutral buoyancy at great depths in the water column, while supporting efficient feeding and locomotion strategies. These findings suggest that changes in skeletal structure are non-linear and are driven not only by hydrostatic pressure, but by other environmental factors and by evolutionary ancestry, calling the existing paradigm into question.
我们利用来自一个跨越较大深度范围的单一鱼类家族的数据，检验了深海鱼类相对于浅海栖息物种骨骼矿化程度较低的假设。狮子鱼科（狮子鱼，鲉形目）在硬骨鱼的整个可栖息深度范围内（0米至8000米）均有代表物种，这使其成为研究特定系统发育中与深度相关趋势的理想模型。我们使用显微计算机断层扫描（micro-CT）对50种狮子鱼在整个栖息地深度范围内骨骼退化的三个方面进行了测试：1）结构尺寸的减小，2）骨骼元素的缺失，以及3）骨密度的降低。利用文献中的深度数据，我们发现随着深度的增加，齿骨、脑颅和眶下骨的长度会减小。腹侧吸盘的宽度随着最大栖息地深度的增加而减小，并且在一些生活在更深水域的分类群中完全消失，不过并非所有分类群都是如此。尽管在整个骨骼中，生活在更深水域的分类群的骨密度明显下降，但下颌、脊椎、吸盘、尾下骨板和耳石的个体密度并未随任何深度指标显著下降。然而，与该家族中的其他物种相比，远洋和极地分类群的骨骼密度往往较低。我们认为，骨骼退化使狮子鱼能够在水柱的深处保持中性浮力，同时支持高效的摄食和运动策略。这些发现表明，骨骼结构的变化是非线性的，不仅受静水压力驱动，还受其他环境因素和进化谱系的影响，这对现有的范式提出了质疑。
