Peterson R D, Evans A J, Hernandez L P
Department of Biological Sciences, The George Washington University, Washington DC 20052, USA.
Integr Org Biol. 2023 Jan 20;5(1):obad001. doi: 10.1093/iob/obad001. eCollection 2023.
Mormyridae is an early diverging family of Teleostean fishes that produce an electric field for navigation and communication using an electric organ. This clade has a diverse array of soft-tissue rostral appendages, such as the chin-swelling, the Schnauzenorgan, and the tubesnout combined with a Schnauzenorgan, that have evolved multiple times. Here we assess if macroscopically convergent, soft-tissue rostral appendages are also histologically convergent. Further, we investigate how the histology of these appendages can inform their function. We sampled independent gains of the chin-swelling and Schnauzenorgan to understand similarities and differences in their anatomies. We show that macroscopically convergent rostral appendages are also convergent at a histological level, and different types of rostral appendages share a similar anatomy; that said, minor differences likely relate to their specific functions. Based on a comparison of the skeletal muscle distribution and the differing attachment shapes of each appendage to the dentary, we conclude that the Schnauzenorgan is capable of a wider range of movements than the chin swelling. Furthermore, the anatomy suggests that these soft-tissue rostral appendages likely function as electrosensory foveas (i.e., an appendage that focuses a sensory system). Lastly, these histological data support the hypothesis that the chin swelling may be a precursor to the Schnauzenorgan.
长颌鱼科是硬骨鱼中一个早期分化的家族，它们利用电器官产生电场用于导航和交流。该类群有各种各样的软组织吻部附属结构，如颏隆凸、鼻器官以及与鼻器官结合的管吻，这些结构已经多次进化。在这里，我们评估宏观上趋同的软组织吻部附属结构在组织学上是否也趋同。此外，我们研究这些附属结构的组织学如何揭示它们的功能。我们对颏隆凸和鼻器官的独立演化进行采样，以了解它们解剖结构的异同。我们表明，宏观上趋同的吻部附属结构在组织学水平上也是趋同的，不同类型的吻部附属结构具有相似的解剖结构；也就是说，微小的差异可能与它们的特定功能有关。基于对骨骼肌分布以及每个附属结构与齿骨不同附着形状的比较，我们得出结论，鼻器官比颏隆凸能够进行更广泛的运动。此外，解剖结构表明这些软组织吻部附属结构可能起到电感觉中央凹（即一种集中感觉系统的附属结构）的作用。最后，这些组织学数据支持了颏隆凸可能是鼻器官前身的假说。
