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

在某些种类的鱼类中，雄性鱼会以100赫兹到250赫兹的频率收缩和放松充满气体的鳔周围的肌肉，从而发出求偶的声音。钙（Ca2+），肌肉收缩的开关，在每次刺激下从肌浆网释放并泵回肌浆网。快速收缩似乎需要惊人的Ca2+泵送速率。然而Ca2+泵不是很快。Toadfish通过两种方式解决Ca2+问题：(1)Toadfish减少每次刺激释放的Ca2+量，因此需要更少的泵送。(2)蟾蜍鱼不会连续鸣叫，它们会发出400毫秒的鸣叫，然后是5-15秒的鸣叫间隔（即3-8%的占空比）。蟾鱼体内有一种名为Parv的蛋白质，其浓度非常高，可以结合叫声中释放的70-80%的Ca2+。然后Parv在长间隔内缓慢释放Ca2+，并以适度的速率泵回。另一种鱼，海军军官候补生，发出100%的工作周期呼叫，一次呼叫可以持续1小时。如果没有调用间间隔来卸载Ca2+， Parv就无法发挥作用。因此，海军军官候补生只有七分之一的人数是蟾蜍鱼。这就留下了一个问题：海军军官候补生怎么打电话？该研究项目将研究每次刺激释放多少Ca2+， Ca2+水平在呼叫过程中如何变化，以及midshipman是否具有一种执行机械工作的方法，很少释放和再摄取Ca2+-利用在昆虫中观察到的机制（异步收缩），但从未在脊椎动物肌肉中看到。这项工作将利用创新的能量分析、高速细胞内Ca2+和由合作者开发的高速力学/视频技术（20,000帧/秒）。Toadfish和midshipman与鸟类和哺乳动物共享神经机制，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，极端的功能通常涉及极端的改变，因此对这些极端肌肉的研究将揭示在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项目指导代表性不足的少数民族本科生。此外，PI生理学和高级肌肉/生物力学课程的1或2名本科生将有机会在费城和伍兹霍尔进行项目工作。

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.