Live fast, die young in the Amazon: testing life history predictions for the Amazon's smallest vertebrates through international collaboration between TAMU and UFSCar

Abstract

The Amazon River drainage harbors the most diverse assemblage of freshwater fishes on the planet. Knowledge of this hyper-diverse aquatic fauna is still rudimentary, with information on life history and ecology available for only a fraction of species and heavily biased towards larger-bodied species of commercial importance or of conservation concern. In the majority of cases, the reproductive cycle of these larger-bodied species has been shown to be seasonal and tied to the wet/dry annual cycle of floodplain or forest inundation. Information on the life history of Amazon freshwater fishes that occupy the lower end of the body size spectrum (e.g., miniature species) is scant and in the absence of data to the contrary is often inferred to be seasonal. Based on life history theory we would expect these miniature species to maximize reproductive output by spawning early in their life (via progenesis) and frequently (i.e., continuous spawning), resulting in a lifecycle that is decoupled from the wet/dry annual cycle. We have established an interdisciplinary research team that unites faculty from TAMU (PI Conway and Co-PI Perkin) and UFSCar/FAPESP (PI Mattox) with expertise in the ecology, anatomy, and taxonomy of freshwater fishes to test life history predictions about miniature Amazonian fishes centered around a recently discovered and diverse assemblage of miniature taxa in the Lower Amazon in Rio Jacundá, State of Pará. At the core of our proposal is fieldwork to this locality during the wet season to collect samples that will compliment those already available from the dry season and collected as part of an active FAPESP project lead by PI Mattox (FAPESP Proc. 2017/01970-4). We will utilize a combination of anatomical/histological analyses of gonad maturation and otolith analyses to answer questions concerning growth and maturation in miniature fishes collected during both dry and wet seasons. We will strengthen ties between TAMU and UFSCar/FAPESP through reciprocal research seminars and faculty lead workshops, including two at UFSCar (one focused on otolith preparation and analysis and another on the statistical software R) and one at TAMU (centered around the collection of Neotropical fishes in the Biodiversity Research and Teaching Collections at TAMU). PI Mattox will also receive training in histological techniques at TAMU. (AU)