Wainwright Peter C, Turingan Ralph G
Department of Biological Science, Florida State University, Tallahassee, Florida, 32306-3050.
Evolution. 1997 Apr;51(2):506-518. doi: 10.1111/j.1558-5646.1997.tb02438.x.
The evolution of the extraordinary inflation mechanism of pufferfishes was studied in the light of an independently derived phylogenetic hypothesis of tetraodontiform fishes. Inflation behavior is found in all members of the puffer sister taxa Tetraodontidae and Diodontidae. However, most other tetraodontiform fishes exhibit two functionally similar behaviors. All taxa exhibit a "coughing" behavior and, with the exception of the sister-group to all other tetraodontiforms, represented by the Triacanthidae, all lineages "blow" strong jets of water out of their mouth to excavate prey. Functional specializations associated with the three behaviors were identified from anatomical analyses and electromyographic recordings of muscle activity in representatives of the major lineages of the order. The phylogenetic distribution of the three buccal compression behaviors and their functional bases indicates the following: (1) the evolution of inflation behavior involved major structural modifications of the head that function in a novel mechanism that links depression of the floor of the mouth to posterior expansion of the buccal cavity; (2) the contraction patterns of four key head muscles used in the three behaviors are generally similar both across behaviors and taxa; (3) however, the distribution of the two significant modifications of muscle activity are consistent with the hypothesis that the three behaviors represent a transformation series from coughing to water blowing to inflation. The motor pattern for water blowing is a slightly modified version of that seen in coughing, and the inflation motor pattern retains the blowing specialization and adds a single additional modification. The convergent evolution of a poorly developed inflation behavior in at least one genus of filefish provides evidence that tetraodontiform fishes are predisposed to the evolution of this unusual defensive behavior. The presence of a well developed water-blowing behavior in most tetraodontiform lineages may represent an intermediate functional specialization that increased the probability of the evolution of inflation.
根据独立推导得出的四齿鲀形目鱼类系统发育假说，对河豚独特的膨胀机制的演化进行了研究。在河豚的姐妹分类群四齿鲀科和二齿鲀科的所有成员中都发现了膨胀行为。然而，大多数其他四齿鲀形目鱼类表现出两种功能相似的行为。所有分类群都表现出一种“咳嗽”行为，并且除了以三刺鲀科为代表的所有其他四齿鲀形目的姐妹群外，所有谱系都会从口中喷出强力水流以挖掘猎物。通过解剖分析和该目主要谱系代表的肌肉活动肌电图记录，确定了与这三种行为相关的功能特化。这三种颊部压缩行为的系统发育分布及其功能基础表明：（1）膨胀行为的演化涉及头部的重大结构改变，这些改变在一种新机制中发挥作用，该机制将口腔底部的下压与颊腔的向后扩张联系起来；（2）三种行为中使用的四块关键头部肌肉的收缩模式在行为和分类群之间总体上相似；（3）然而，肌肉活动的两个显著改变的分布与以下假设一致，即这三种行为代表了从咳嗽到喷水再到膨胀的转变系列。喷水的运动模式是咳嗽中所见模式的轻微修改版本，而膨胀运动模式保留了喷水特化并增加了一个额外的修改。至少一种单角鲀属鱼类中发育不良的膨胀行为的趋同演化提供了证据，表明四齿鲀形目鱼类易于演化出这种不寻常的防御行为。大多数四齿鲀形目谱系中存在发育良好的喷水行为可能代表了一种中间功能特化，增加了膨胀演化的可能性。
