1. Anatomy and evolution of bioluminescent organs in the slimeheads (Teleostei: Trachichthyidae).
Ghedotti MJ, DeKay HM, Maile AJ, Smith WL, Davis MP
Journal of morphology J Morphol Anatomy and evolution of bioluminescent organs in the slimeheads (Teleostei: Trachichthyidae). 10.1002/jmor.21349 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. © 2021 Wiley Periodicals LLC. Ghedotti Michael J MJ https://orcid.org/0000-0003-3240-6382 Department of Biology, Regis University, Denver, Colorado, USA. Bell Museum of Natural History, University of Minnesota, St. Paul, Minnesota, USA. DeKay Hannah M HM Department of Biology, Regis University, Denver, Colorado, USA. Maile Alex J AJ Department of Biological Sciences, St. Cloud State University, St. Cloud, Minnesota, USA. Smith W Leo WL Department of Ecology and Evolutionary Biology and Biodiversity Institute, University of Kansas, Lawrence, Kansas, USA. Davis Matthew P MP Department of Biological Sciences, St. Cloud State University, St. Cloud, Minnesota, USA. eng MJG2018 Regis University, University Research and Scholarship Council Faculty Grant DEB1258141 United States National Science Foundation DEB1543654 United States National Science Foundation GRF 2105077 University of Kansas Journal Article 2021 03 17 United States J Morphol 0406125 0022-2887 IM Aulotrachichthys Paratrachichthys Sorosichthys bacteria histology 2021 03 11 2021 01 25 2021 03 14 2021 3 19 6 0 2021 3 19 6 0 2021 3 18 7 5 aheadofprint 33733466 10.1002/jmor.21349 REFERENCES, 2021