Ghedotti Michael J, DeKay Hannah M, Maile Alex J, Smith W Leo, Davis Matthew P
Department of Biology, Regis University, Denver, Colorado, USA.
Bell Museum of Natural History, University of Minnesota, St. Paul, Minnesota, USA.
J Morphol. 2021 Jun;282(6):820-832. doi: 10.1002/jmor.21349. Epub 2021 Mar 25.
Bacterial bioluminescent organs in fishes have a diverse range of tissues of origin, patterns of compartmentalization, and associated light-conducting structures. The morphology of the perianal, bacterial bioluminescent organ of Aulotrachichthys prosthemius was described previously, but the light organ in other species of slimeheads, family Trachichthyidae, is poorly known. Here, we describe the anatomy of the bioluminescent organs in trachichthyids and places the evolution of this light-producing system in the context of a new phylogeny of the Trachichthyoidei to test the hypothesis that bioluminescence evolved twice in the suborder and that the light-producing component derives from the perianal ectoderm. We use gross and histological examination to provide the first description of the bioluminescent organ of Paratrachichthys and four additional species of Aulotrachichthys. Observations also strongly suggest the presence of a perianal bioluminescent organ in Sorosichthys ananasa. The updated phylogeny of the Trachichthyoidei is the first to combine morphological and DNA-sequence (11-gene fragments) evidence, and supports a monophyletic Trachichthyidae with component subfamilies Hoplostethinae and Trachichthyinae, supporting continued recognition of the family Anoplogastridae. All bioluminescent trachichthyoids share a similar bioluminescent-organ structure with elongate chambers filled with bacteria and connected to collecting ducts that, in turn, connect to superficial ducts that lead to and have lining epithelia continuous with the epidermis. In the context of the phylogeny, the bioluminescent organ of trachichthyids is inferred to have evolved as an elaboration of the proctodeum in the ancestor of Aulotrachichthys, Paratrachichthys, and Sorosichthys independently from the structurally similar cephalic bioluminescent organs in Anomalopidae and Monocentridae.
鱼类的细菌发光器官具有多种不同的组织起源、分隔模式以及相关的导光结构。此前已对前肛软棘鱼（Aulotrachichthys prosthemius）的肛周细菌发光器官形态进行过描述，但对于燧鲷科（Trachichthyidae）其他种类的发光器官却知之甚少。在此，我们描述了燧鲷科鱼类发光器官的解剖结构，并将这种发光系统的进化置于燧鲷亚目（Trachichthyoidei）新系统发育关系的背景下，以检验以下假设：在该亚目中生物发光进化了两次，且发光成分源自肛周外胚层。我们通过大体解剖和组织学检查，首次描述了副燧鲷属（Paratrachichthys）以及另外四种前肛软棘鱼属（Aulotrachichthys）鱼类的发光器官。观察结果还强烈表明，安南索罗斯燧鲷（Sorosichthys ananasa）存在肛周发光器官。更新后的燧鲷亚目系统发育关系首次结合了形态学和DNA序列（11个基因片段）证据，支持燧鲷科为单系群，包含棘燧鲷亚科（Hoplostethinae）和燧鲷亚科（Trachichthyinae），并支持继续承认黑头鱼科（Anoplogastridae）。所有发光的燧鲷类都具有相似的发光器官结构，即有充满细菌的细长腔室，这些腔室与收集管相连，收集管又与通向表皮且上皮与表皮连续的表面导管相连。在系统发育的背景下，推断燧鲷科的发光器官是在Aulotrachichthys、Paratrachichthys和Sorosichthys的祖先中由原肛演化而来，独立于发光鲷科（Anomalopidae）和单角鲀科（Monocentridae）结构相似的头部发光器官。
