Taft Natalia K
Department of Organismic and Evolutionary Biology, 319 Morrill Science Center South, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
J Morphol. 2011 Sep;272(9):1144-52. doi: 10.1002/jmor.10970. Epub 2011 May 27.
In this study, I compare the morphology from the pectoral fin rays from the benthic longhorn sculpin (Myoxocephalus octodecimspinosus) to those from a species that does not use its fins for substrate contact, the yellow perch (Perca flavescens). I use CT scanning technology to compare the shape and structure of the paired hemitrichia that make up the pectoral fin rays between these species. I found that the structure of hemitrichia of the fin rays in yellow perch is consistent with previous descriptions for pelagic fishes. They are almost completely segmented, have a crescent shape in cross section, and are branched distally. In contrast, longhorn sculpin hemitrichia exhibit morphological regionalization along the proximo-distal length of the ray. The most proximal 20-50% of the length of the hemitrichia is unsegmented and cylindrical in cross section. Distally, the fin rays of longhorn sculpin are segmented and crescent-shaped but do not branch. I measured the second moment of area of the hemitrichia at distances of 10%, 30%, 50%, and 70% distance along the length of the fin rays. The cylindrical regions of the sculpin hemitrichia had a higher second moment of area than the crescent-shaped regions in either species. I hypothesize that that this regionalization of individual fin rays provides resistance to bending proximally and flexibility distally, features that may be useful during substrate contact. This combination of an elongate, unsegmented proximal region and segmented distal region in fin rays has not yet been described among extant ray-finned fishes. However, this structure is reminiscent of that of the elongate cylindrical region found in the fossil sarcopterygian fish Eusthenopteron.
在本研究中，我将底栖长角杜父鱼（Myoxocephalus octodecimspinosus）胸鳍鳍条的形态与另一种不利用其鳍与底物接触的物种——黄斑鲈（Perca flavescens）的胸鳍鳍条形态进行了比较。我使用CT扫描技术来比较这两个物种中构成胸鳍鳍条的成对半鳍条的形状和结构。我发现，黄斑鲈鳍条的半鳍条结构与之前对远洋鱼类的描述一致。它们几乎完全分节，横截面呈月牙形，并且在远端分支。相比之下，长角杜父鱼的半鳍条在鳍条的近端到远端长度上呈现出形态区域化。半鳍条长度最近端的20 - 50%不分节，横截面呈圆柱形。在远端，长角杜父鱼的鳍条分节且呈月牙形，但不分支。我在沿着鳍条长度的10%、30%、50%和70%距离处测量了半鳍条的面积惯性矩。杜父鱼半鳍条的圆柱形区域比这两个物种中任何一个的月牙形区域具有更高的面积惯性矩。我推测，单个鳍条的这种区域化在近端提供抗弯曲能力，在远端提供灵活性，这些特征在与底物接触时可能是有用的。鳍条中这种细长的、不分节的近端区域和分节的远端区域的组合在现存的辐鳍鱼类中尚未被描述过。然而，这种结构让人联想到在化石肉鳍鱼类真掌鳍鱼中发现的细长圆柱形区域的结构。
