Age and Growth of Predatory Mesopelagic Fishes in a Low-Latitude Oceanic Ecosystem

Mesopelagic and bathypelagic fishes provide important global ecosystem services, such as carbon sequestration via the biological pump and provision of food for economically important (billfishes and tuna) and federally protected (cetaceans and seabirds) species. These attributes are becoming increasingly recognized, while simultaneously mesopelagic fisheries are becoming of interest for direct harvest as coastal fisheries have become overexploited. Additionally, climate change, ocean acidification, and seabed mining threaten deep-sea fishes. With increasing interest in deep-sea fisheries and anthropogenic threats, age and growth information on these fishes is necessary for management and conservation. Currently ecosystem models lack data such as sexual maturity and lifespan on deep-pelagic fishes, hindering our ability to quantify production rates and resilience to disturbance. Here we examine four numerically dominant predatory fishes from the Gulf of Mexico exhibiting a range of trophic ecologies and vertical distributions: Lampanyctus lineatus (Myctophidae), Omosudis lowii (Omosudidae), Stomias affinis (Stomiidae), and Chauliodus sloani (Stomiidae). In this thesis, the otoliths (‘ear stones’) of each species were examined in order to estimate age and duration of specific life history stages (e.g. juvenile, intermediate, and adult) and landmarks (e.g., sexual maturity and determine longevity). Given that otolith ring validation was not possible (these fishes cannot be kept alive, marked and recaptured, and hourly sampling is not possible for species living at great depths), we present putative minimum and maximum estimates at landmarks based on two scenarios: 1) total rings = days of life; and 2) major (darkest) otolith increments = years of life). Comparing both estimates to available validated ages of their prey, we conclude that the maximum age scenario is most appropriate. Results of this study suggest that the deep-living myctophid species and higher-level predators investigated have relatively long generation times (L. lineatus one year, C. sloani 9 - 17 years, and S. affinis 10 – 19 years until sexual maturity), and thus likely have low resilience to population level-perturbation

Microscopic and Genetic Characterization of Bacterial Symbionts With Bioluminescent Potential in Pyrosoma atlanticum

The pelagic tunicate pyrosome, Pyrosoma atlanticum, is known for its brilliant bioluminescence, but the mechanism causing this bioluminescence has not been fully characterized. This study identifies the bacterial bioluminescent symbionts of P. atlanticum collected in the northern Gulf of Mexico using several methods such as light and electron microscopy, as well as molecular genetics. The bacteria are localized within the pyrosome light organs. Greater than 50% of the bacterial taxa present in the tunicate samples were the bioluminescent symbiotic bacteria Vibrionaceae as determined by utilizing current molecular genetics methodologies. A total of 396K MiSeq16S rRNA reads provided total pyrosome microbiome profiles to determine bacterial symbiont taxonomy. After comparing with the Silva rRNA database, a Photobacterium sp. r33-like bacterium (which we refer to as “Photobacterium Pa-1”) matched at 99% sequence identity as the most abundant bacteria within Pyrosoma atlanticum samples. Specifically designed 16S rRNA V4 probes for fluorescence in situ hybridization (FISH) verified the Photobacterium Pa-1 location as internally concentrated along the periphery of each dual pyrosome luminous organ. While searching for bacterial lux genes in two tunicate samples, we also serendipitously generated a draft tunicate mitochondrial genome that can be used for Pyrosoma atlanticum identification. Scanning (SEM) and transmission (TEM) electron microscopy confirmed the presence of intracellular rod-like bacteria in the light organs. This intracellular localization of bacteria may represent bacteriocyte formation reminiscent of other invertebrates

On the Age and Growth of Mesopelagic Fishes, With Case Studies of Four Ecologically Important Species From the Gulf of Mexico

Mesopelagic fishes provide important ecosystem services, such as carbon sequestration via the biological pump and provision of food for economically important (billfishes and tuna) and federally protected (cetaceans and seabirds) species. These attributes are becoming increasingly recognized, while simultaneously mesopelagic fisheries are becoming of interest as coastal fisheries have become overexploited. Additionally, climate change, ocean acidification, and seabed mining threaten deep-sea fishes. With increasing interest in deep-sea fisheries and anthropogenic threats, age and growth information on these fishes is a necessity for management. A serious constraint for conservation and management of these resources is that very few age estimations of mesopelagic fishes have been validated. In order to address information gaps, age estimations and otolith shape and microincrement descriptions linked to life histories will be presented for the meso/bathypelagic fish species Lampanyctus lineatus (lanternfish), Omosudis lowii (hammerjaw), Stomias affinis (dragonfish), and Chauliodus sloani (viperfish). These fishes were collected during seven research cruises from 2010 - 2011, as part of the DWHOS NRDA, and during six research cruises from 2015 - 2018, as part of the GOMRI-supported DEEPEND Consortium. We found that Stomias affinis grow exponentially, with a slow initial growth followed by a rapid increase in growth with time. Chauliodus sloani exhibits logistic growth, with a gradual increase in growth at first followed by period of rapid growth and then a decrease in growth. Osmodus lowii and Lampanyctus lineatus grow isometrically, which is the normal growth pattern for most fishes. These are the first growth curves produced of these species for the Gulf of Mexico, which serves as an analog for the world’s low-latitude, oligotrophic domain

On the Age and Growth of Meso-Bathypelagic Fishes, with Case Studies of Omosudis lowii, Stomias affinis and Lampanyctus lineatus from the Gulf of Mexico

Mesopelagic fishes provide important ecosystem services, such as carbon sequestration via the biological pump and provision of food for economically important (billfishes and tuna) and federally protected (cetaceans and seabirds) species. These attributes are becoming increasingly recognized, while simultaneously mesopelagic fisheries are becoming of interest as coastal fisheries have become overexploited. Additionally, climate change, ocean acidification, and seabed mining threaten deep-sea fishes. With increasing interest in deep-sea fisheries and anthropogenic threats, age and growth information on these fishes is a necessity for management. With increasing threats, age and growth information on deep-pelagic fishes is needed for management. A limitation for deep-pelagic research, conservation, and management is that very few age estimations of fishes have been validated. Additionally, the majority of age and growth studies have been performed on the family Myctophidae (lanternfishes) due to their presumed importance in food chains via vertical migration; most other taxa remain relatively uninvestigated. In order to address these information gaps, age estimations and otolith shape and microincrement descriptions linked to life histories will be presented for the meso/bathypelagic fish species Omosudis lowii, Stomias affinis, and Lampanyctus lineatus These fishes were collected during seven research cruises from 2010 – 2011, as part of the NOAA supported Offshore Nekton Sampling and Analysis Program, and during six research cruises from 2015 – 2018, as part of the GOMRI-supported Deep Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND). We found that the dragonfish Stomias affinis grows exponentially, with a slow initial growth followed by a rapid increase in growth with time. The hammerjaw Omosudis lowii and the deep-living lanternfish Lampanyctus lineatus grow isometrically, which is the normal growth pattern for most fishes. These are the first growth curves produced of these species for the Gulf of Mexico, which serves as an analog for the world’s low-latitude, oligotrophic domain

Akkermansia muciniphila induces intestinal adaptive immune responses during homeostasis

Intestinal adaptive immune responses influence host health, yet only a few intestinal bacteria species that induce cognate adaptive immune responses during homeostasis have been identified. Here, we show that Akkermansia muciniphila, an intestinal bacterium associated with systemic effects on host metabolism and PD-1 checkpoint immunotherapy, induces immunoglobulin G1 (IgG1) antibodies and antigen-specific T cell responses in mice. Unlike previously characterized mucosal responses, T cell responses to A. muciniphila are limited to T follicular helper cells in a gnotobiotic setting, without appreciable induction of other T helper fates or migration to the lamina propria. However, A. muciniphila-specific responses are context dependent and adopt other fates in conventional mice. These findings suggest that, during homeostasis, contextual signals influence T cell responses to the microbiota and modulate host immune function