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    Ichthyology IV

    2021-07-23   10:45 - 12:15

    Moderator: Ben Frable

    1.  10:45  IN-PERSON    A New Deep-sea Eelpout Associated With a “Hydrothermal Seep” on the Pacific Margin of Costa Rica. Benjamin Frable*, Marine Vertebrate Collection, Scripps Institution of Oceanography; Charlotte Seid, Benthic Invertebrate Collection, Scripps Institution of Oceanography; Peter Rask Møller, Natural History Museum of Denmark

    During five interdisciplinary research cruises by the R/VAtlantisand R/VFalkorto the Pacific margin of Costa Rica, an unknown zoarcid species was observed and collected from the “hydrothermal seep” environment at Jaco Scar. Four specimens were collected at 1800 m depth among colonies of the tubewormLamellibrachia barhamiaround a unique seep with vent-like characteristics, such as temperatures around 6ºC. The specimens are members of the subfamily Lycodinae and possess pelvic fins, lack scales and a lateral line. They have gelatinous flesh, a relatively long preanal length, and a low vertebral count. This places them in the recently described genusPyrolycus, previously known from only two species occurring on hydrothermal vents in the western Pacific. Molecular sequences of COI are provided and are the first for the genus. This is the first vertebrate species known from this composite reducing ecosystem and is the fourth hydrothermally-associated zoarcid from the Eastern Pacific.

    2.  11:00  IN-PERSON    The Hidden Biodiversity of Coral Reefs: Cryptobenthic Fishes from the Coral Sea. Christopher Goatley*, University of New England

    Coral reef fish communities are dominated by small, cryptobenthic fishes. This suite of species, share small body sizes, highly efficient reproductive strategies and very short life expectancies. When combined with their abundance on coral reefs, these life-history characteristics result in cryptobenthic fishes performing vital ecosystem functions as a source of rapidly replenishing prey for larger reef organisms. Unfortunately, due to their small size, cryptic coloration and behavior, studying cryptobenthic fish communities demands special collection techniques, and as such, these important fishes have often been overlooked on coral reefs. In this talk, I will present data from a recent series of research cruises to remote oceanic reefs in the Coral Sea, during which we conducted detailed surveys of the cryptobenthic fish community. I will focus on broad patterns of community structure among these remote reefs, comparing patterns for large and cryptic reef fishes. I will then focus on the taxonomic composition of Coral Sea cryptobenthic fish communities, revealing an abundance of new species records and potentially new species discovered in this region. With such a scarcity of detailed studies of cryptobenthic fish communities around the world, this presentation will highlight that coral reefs may host a treasure trove of new cryptic species for future study.

    3.  11:15  IN-PERSON    Tu-be Or Not Tu-be a Blenny: Deciphering The Evolutionary History Of The Enigmatic Genus Stathmonotus. Carmen Pedraza-Marrón*, University of Oklahoma; Philip Hastings, SCRIPPS Institution of Oceanography; Peter Hundt, University of Minnesota; Lily Hughes, The University of Chicago; Carole Baldwin, Smithsonian Institution; Omar Domínguez-Domínguez, Universidad Michoacana de San Nicolás de Hidalgo; Guillermo Ortí, The George Washington University; Dahiana Arcila, University of Oklahoma; Ricardo Betancur-R., University of Oklahoma

    For a long time, evolution has been perceived as a bifurcating process (i.e., one parent species giving rise to two daughter species), where cases of hybridization, if any, are thought to simply slowdown speciation. Recent studies have revealed that speciation can occur in the face of gene flow; hence, evolutionary relationships are in some cases better depicted by reticulated networks that depart from more typical bifurcating trees. Ancient reticulation events can take place either among terminal species or between internal nodes (deep time reticulation or DTR) as a result of horizontal gene transfer or across-lineage hybridization. New world worm-blennies (Stathmonotus spp.) in the Atlantic and the eastern Pacific provide a great opportunity to test for DTR. They represent a major lineage of blenniiform fishes whose classification and phylogenetic relationships among other families in the order has been contentious. While worm-blennies have been included within the tube-blennies (Chaenopsidae) on the basis of cranium traits, molecular phylogenetic analyses using a scant sampling of genes have placed the genus within Labrisomidae. These conflicting data fueled the hypothesis of a DTR origin of worm-blennies via ancient hybridization between ancestral chaenopsid and labrisomid lineages. We address this controversy by using a genome-wide dataset, consisting of 1061 exons sequenced for 222 species (25%) representing all six families of Blenniformes, and body shape data obtained with geometric morphometrics. While analyses of ancient hybridization and DTR are underway, preliminary phylogenetic results strongly place worm-blennies within labrisomids, suggesting that morphological similarity with tube-blennies may stem from convergent evolution.

    4.  11:30  VIRTUAL    A new species of extinct symmoriiform and a phylogeny of early chondrichthyans. Allison Bronson*, Humboldt State University; Alan Pradel, Muséum national d'histoire naturelle; John Denton, University of Florida; John Maisey, American Museum of Natural History

    We introduce a new genus of symmoriiform chondrichthyan from the Late Mississippian Fayetteville Shale of Arkansas, with elongate cartilaginous rays extending posteriorly from the gill arches. These rays appear to form an operculate structure that covers at least two of the branchial arches farther posteriorly. Although presence of a ‘hyoid operculum’ has been postulated in at least two unrelated Paleozoic sharks, these earlier inferences were not supported by subsequent analyses, which means this new taxon represents the first evidence of an operculum formed by pharyngeal arch rays in a symmoriiform. We also performed a phylogenetic analysis of early chondrichthyans, based on 222 morphological characters. This phylogeny places this taxon within the Symmoriiformes and recovers the order as part of the stem chondrichthyans, rather than allied with the holocephalans (ratfishes and chimaeras) or elasmobranchs.

    5.  11:45  IN-PERSON    What’s Up Front: Mating Territory Location Drives Mating Success by Male Wrasses (Labridae) at a Resident Spawning Aggregation Site. Terry Donaldson*, University of Guam Marine Laboratory

    An increasing number of reef fish species have been shown to form spawning aggregations. These aggregations occur at predictable times and places with participants utilizing single or mixed mating systems. In a lek-like mating system, males establish temporary courtship territories that they defend against rival males while attracting females to spawn. The location of these territories often contributes towards differential mating success. Males holding territories deemed “desirable” by females, because of the physical attributes of their location, attract more females and secure greater mating opportunities compared to those males that defend territories elsewhere within the spawning aggregation site. Presumably, females favor locations where newly spawned eggs may be carried away from potential predators more effectively. Thus, males holding territories located at the outer edge of the site in an area exposed to water currents running parallel to the reef face have far greater mating success than those males that hold territories found on inner or middle sections of the site where currents are less pronounced. This pattern is consistent across a range of taxa within the family Labridae co-occurring at a multispecies spawning aggregation site on a coral reef at Guam, Western Pacific.

    6.  12:00  IN-PERSON    Genomic Assessment of two imperiled Rio Grande basin endemics, Rio Grande Shiner and Speckled Chub. Megan Osborne*, University of New Mexico; David Portnoy, Texas A&M University; Andrew Fields, Texas A&M University; Megan Bean, Texas Parks and Wildlife Department; Christopher Hoagstrom, Weber State University; Kevin Conway, Texas A&M University

    The Rio Grande drainage of the southwestern United States and Mexico has been severely altered by anthropogenic changes. Two Rio Grande endemic pelagophils; the co-occurring Rio Grande Shiner (Notropis jemezanus) and Speckled Chub (Macrhybopsis aestivalis), have experienced dramatic recent range-wide declines yet have slipped under the radar of conservation efforts. Using multiple molecular markers(SNPs, microsatellites and mtDNA) we evaluated the genetic status of N. jemezanusand M. aestivalis in the Rio Grande and Pecos River. Genetic evidence revealed divergence between Rio Grande and Pecos Riverpopulations of both species. Additionally, 159 outlier loci were identified in M. aestivalis suggesting possible local adaptation in the Rio Grande and Pecos River populations. Though range-wide genetic data are limited,N. jemezanus populations in both rivers harbor considerable genetic diversity. Mitochondrial data from both taxa are consistent with a history of secondary contact between formerly isolated populations with deeply divergent haplotypes found within the Rio Grande and Pecos River populations of N. jemezanus and within the Rio Grande population of M. aestivalis. Extensive survey efforts in the lower Rio Grande and its tributaries in Texas document significant range contraction and near extirpation of N. jemezanusfrom this part of the basin; highlighting the need for immediate action to protect the species.

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