Jessica Masterman

Within the highly productive Northern California Current (NCC) ecosystem, the ctenophore Pleurobrachia bachei is common, yet its trophic role remains unclear. Samples of P. bachei were collected from the NCC in 2018–2019 at two latitudes, including the Newport Hydrographic Line and Trinidad, during two seasons (summer and winter). Samples were dissected for gut contents and analyzed for fatty acid concentrations. The three most abundant prey categories found within P. bachei guts were consistently adult copepods, copepod eggs, and invertebrate eggs, although the relative contribution of these and other prey varied significantly between seasons and latitudes. Essential fatty acids, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) together made up nearly half of P. bachei fatty acid content. While this sum was consistent through space and time, EPA and DHA individually varied. Patterns in both P. bachei predation and fatty acid content track seasonal and latitudinal variability in this highly dynamic eastern boundary upwelling system, with seasons driving slightly larger differences. Our analyses suggest that P. bachei in the NCC acts as both an influential predator and an important prey source, highlighting the need to include P. bachei and other underappreciated gelatinous zooplankton in modeling of pelagic food webs.

Many metazoans contain molecules capable of fluorescence, the absorption and re-emission of light. Since the anatomical distribution, or patterning, of these molecules is variable across taxa, patterns of fluorescence may serve as a powerful diagnostic tool in taxonomy and ecology. However, species-specific fluorescence patterns among marine invertebrates are poorly understood. Here, we show that hydrozoans have diverse fluorescence patterns, which may result from molecules that are produced intrinsically or obtained from dietary sources. We surveyed hydrozoans including siphonophores, hydromedusae, and hydroids across 5 orders from pelagic and benthic marine environments in Bocas del Toro, Panama. Our findings show that fluorescence patterns are highly prevalent and may vary across hydrozoan species and throughout development. Most of the examined hydrozoan taxa exhibited some form of fluorescence, with variation observed between life stages and body parts. Fluorescence was documented in 88% of hydromedusae (Leptothecata, Anthoathecata, Limnomedusae and Narcomedusae), 50% of hydroid, and 75% of siphonophore taxa that were observed in this study. Our results illustrate how fluorescence patterns may serve as a useful diagnostic tool to explore marine biodiversity, highlighting the need for further documentation of fluorescence patterns across marine diversity and research into the molecules that underlie this phenomenon. Muchos metazoos contienen moléculas capaces de fluorescencia, absorción y reemisión de luz. Dado que la distribución anatómica, o el patrón, de estas moléculas es variable entre taxones, los patrones de fluorescencia pueden servir como una poderosa herramienta diagnóstica en taxonomía y ecología. Sin embargo, los patrones de fluorescencia específicos de especie entre invertebrados marinos están poco comprendidos. Aquí, mostramos que los hidrozoos tienen diversos patrones de fluorescencia, que pueden ser el resultado de moléculas producidas intrínsecamente u obtenidas de fuentes dietéticas. Estudiamos hidrozoos, incluidos sifonóforos, hidromedusas e hidroides, en 5 órdenes de ambientes marinos pelágicos y bentónicos en Bocas del Toro, Panamá. Nuestros hallazgos muestran que los patrones de fluorescencia son muy prevalentes y pueden variar entre especies de hidrozoos y a lo largo del desarrollo. La mayoría de los taxa de hidrozoos examinados exhibieron alguna forma de fluorescencia, con variación observada entre las etapas de vida y las partes del cuerpo. Se documentó fluorescencia en el 88% de las hidromedusas (Leptothecata, Anthoathecata, Limnomedusae y Narcomedusae), el 50% de los hidroides y el 75% de los sifonóforos que se observaron en este estudio. Nuestros resultados ilustran cómo los patrones de fluorescencia pueden servir como una herramienta diagnóstica útil para explorar la biodiversidad marina, resaltando la necesidad de una mayor documentación de los patrones de fluorescencia en la diversidad marina y de investigar las moléculas que subyacen a este fenómeno.