Paying the piper: how two fish species adjust calcium cycling for different mating calls

在一些种类的鱼中，雄性鱼以100赫兹到250赫兹的频率收缩和放松围绕充满气体的泳囊的肌肉，以产生交配叫声。钙(钙)，肌肉收缩的开关，在每次刺激时从肌浆网释放并泵回肌浆网。这种快速的收缩似乎需要惊人的钙泵速率。然而，钙离子泵的速度并不是很快。蟾鱼通过两种方式解决钙离子问题：(1)蟾鱼减少每个刺激物释放的钙离子，因此需要更少的抽水。(2)ToadFish不会连续呼叫，它们会发出400ms的呼叫，然后是较长的5-15秒呼叫间间隔(即3-8%的占空比呼叫)。蟾鱼体内有一种蛋白质，小白蛋白(Parv)，浓度很高，它能结合在一次叫声中释放的70%-80%的钙离子。然后，在漫长的呼叫间隔期间，PARV缓慢地释放钙离子，并以适度的速度将其泵回。另一种鱼类，海军学员，发出100%的值班呼叫，一次呼叫可以持续1个小时。如果没有呼叫间间隔来卸载钙离子，PARV就没有用处了。因此，海军学员只有1/7的Parv是蟾鱼。这就留下了一个问题：海军少校怎么打电话？这项研究项目将检测每个刺激释放多少钙，呼叫过程中钙水平如何变化，以及学员是否拥有一种执行机械工作的方法，几乎不释放和重新吸收钙-利用在昆虫中观察到的、但在脊椎动物肌肉中从未见过的一种机制(异步收缩)。这项工作将利用创新的能量分析、高速细胞内钙离子和高速力学/视频技术(20,000帧/S)。蟾鱼和学员与鸟类和哺乳动物分享神经机制，因此这项工作将提高我们对声音交流如何进化的理解。此外，极端功能通常包括极端的修改，因此对这些极端肌肉的研究将揭示正常肌肉中看不到的新机制。该项目将包括通过伍兹霍尔MBL的REU项目指导未被充分代表的少数族裔本科生。此外，来自PI生理学和高级肌肉/生物力学课程的1到2名本科生将有机会在费城和伍兹霍尔从事该项目。

In some species of fish, males contract and relax muscles which surround the gas-filled swimbladder at 100 Hz and up to 250 Hz to produce a mating call. Calcium (Ca2+), the switch for muscle contraction, is released from and pumped back into the sarcoplasmic reticuluum on each stimulus. The rapid contractions would seem to require a prodigious Ca2+ pumping rate. However the Ca2+ pumps are not very fast. Toadfish solve the Ca2+ problem in two ways: (1) Toadfish reduce the amount of Ca2+ released per stimulus and thus require less pumping. (2) Toadfish do not call continuously, they make 400 ms calls followed by a long 5-15 second intercall interval (i.e., 3-8% duty cycle calls). Toadfish possess a protein, parvalbumin (Parv), in very high concentrations which binds 70-80% of the Ca2+ released during a call. Parv then releases the Ca2+ slowly during the long intercall interval and it is pumped back at a modest rate. Another fish species, the midshipman, make a 100% duty cycle call and a single call can last 1 hour. Without the intercall interval to unload Ca2+, Parv cannot be useful. Accordingly, midshipman have only 1/7 of the Parv as toadfish. This leaves the problem: how can midshipman call? This research project will examine how much Ca2+ is released per stimulus, how the Ca2+ level changes during calling, and whether midshipman possess a means of performing mechanical work with little release and reuptake of Ca2+-utilizing a mechanism (asynchronous contraction) observed in insects, but never before seen in vertebrate muscle. The work will utilize innovative energetic analyses, high speed intracellular Ca2+ and high speed mechanics/video techniques (20,000 frames/s) developed by the collaborators. Toadfish and midshipman share neural mechanisms with birds and mammals and thus this work will improve our understanding of how vocal communication evolved. Also, extreme function usually involves extreme modifications, and thus studies of these extreme muscles will reveal new mechanisms that are not visible in normal muscle. This project will include mentoring underrepresented minority undergraduates through a REU program at the MBL in Woods Hole. In addition 1 or 2 undergraduate students from the PI's physiology and advanced muscle/biomechanics class will be given the opportunity to work on the project in Philadelphia and Woods Hole.