Bass A H, Horvath B J, Brothers E B
Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853-6401, USA.
J Neurobiol. 1996 Aug;30(4):493-504. doi: 10.1002/(SICI)1097-4695(199608)30:4<493::AID-NEU5>3.0.CO;2-Z.
Midshipman fish, Porichthys notatus, have two male reproductive morphs: type 1 males generate long duration advertisement calls ("hums") to attract females to a nest; type II males sneak-spawn and, like females, do not produce mate calls but generate short duration agonistic calls. A vocal pacemaker circuit includes: motoneurons in the caudal brain stem and rostral spinal cord that innervate vocal/sonic muscles; pacemaker neurons that are located ventrolateral to motoneurons and establish their fundamental discharge frequency; and a ventral medullary nucleus that couples the motoneuron-pacemaker circuit bilaterally. Transneuronal biocytin transport identified morph-specific developmental trajectories for the vocal circuit. Among nonreproductive, juvenile type I males, motoneuron soma size and motor nucleus volume increase most during a stage prior to sexual maturation. An additional increase in motoneuron size and nucleus volume is coupled to the greatest increase in pacemaker soma size at a stage coincident with the onset of sexual maturity; ventral medullary neurons show similar growth increments during both stages. Type II males (and females) mature with no or little change in cell size or motor nucleus volume. The results indicate that alternative mating tactics are paralleled by alternative developmental trajectories for the neurons that determine tactic-specific behaviors, in this case vocalizations. Together with aging data based on otolith growth, the results support the hypothesis that alternative male morphs in midshipman fish adopt nonsequential, mutually exclusive life history tactics.
军曹鱼（Porichthys notatus）有两种雄性生殖形态：1型雄性发出持续时间长的求偶叫声（“嗡嗡声”）以吸引雌性到巢穴；2型雄性偷情产卵，并且像雌性一样，不发出求偶叫声，但会发出持续时间短的争斗叫声。一个发声起搏器回路包括：位于尾端脑干和吻端脊髓的运动神经元，它们支配发声/声波肌肉；位于运动神经元腹外侧并确定其基本放电频率的起搏器神经元；以及一个双侧连接运动神经元-起搏器回路的腹侧髓核。跨神经元生物素转运确定了发声回路的形态特异性发育轨迹。在未成熟的1型雄性幼鱼中，运动神经元的胞体大小和运动核体积在性成熟前的一个阶段增加最多。在与性成熟开始同时的一个阶段，运动神经元大小和核体积的额外增加与起搏器胞体大小的最大增加相关联；腹侧髓核神经元在这两个阶段都显示出类似的生长增加。2型雄性（和雌性）成熟时细胞大小或运动核体积没有变化或变化很小。结果表明，替代交配策略与决定策略特异性行为（在这种情况下是发声）的神经元的替代发育轨迹并行。结合基于耳石生长的衰老数据，结果支持了军曹鱼中替代雄性形态采用非顺序、相互排斥的生活史策略这一假设。
