Morphological changes and habitat shifts with growth of endangered floodplain fish: Possible adaptations to fluctuating environments

Abstract

Adaptations that maximise food intake are dependent on food and/or habitat types. However, there have been few studies on the ability of floodplain primary freshwater fish to rapidly change their morphology, especially the internal one, to maximise utilisation efficiency of food resources in response to environmental fluctuations during their life history. We investigated morphological changes of an Acheilognathinae species (Acheilognathus longipinnis) that inhabits creeks in Japan to determine whether body shape variation correlated with environmental characteristics, including water depth, current velocity, vegetation cover and food availability. When shifting from floodwater‐level to low‐water‐level season, the current velocity of the study area increased as the water level decreased, causing a significant increase in periphyton and a significant decline in zooplankton and phytoplankton. Concurrently, during the short period when A. longipinnis grow from the juvenile to the premature stage, changes in internal morphology, that is intestinal elongation, and changes in external morphology such as an increase of body depth were observed. In contrast, intestinal length significantly decreased in the adult stage. Our findings suggest that morphological changes between floodwater‐level and low‐water‐level seasons associated with juvenile to premature development are an adaptation to changes in food availability due to environmental fluctuations. Additionally, the shortening of the intestine from the premature to the adult stage may be an adaptive strategy for reproduction.

Asymmetric expression of homoeologous genes contributes to dietary adaption of an allodiploid hybrid fish derived from Megalobrama amblycephala (♀) × Culter alburnus (♂)

“…Fish can change their behavioral and physiological characteristics, such as food selection, food intake, enzyme production, and alimentary tract development, to adjust to changes in the quality of available food [ 27 , 29 ]. Generally, these adaptive changes are limited by the range of phenotypic plasticity in the short term, and long-term adaptability depends on the evolution of genotype.…”

Morphological Characteristics and Genetic Relationship of Red Snappers (Lutjanus timoriensis, Lutjanus malabaricus, Lutjanus erythropterus) in Papuan Waters

“…Variation in morphological features can be influenced by both environmental and genetic factors. The morphological characteristics of an organism can exhibit variation in response to distinct and diverse environmental conditions (Shuai et al, 2018;Nishio et al, 2019). According to Dunn et al (2020), and Endo and Watanabe (2020), fish commonly exhibit a greater degree of morphological diversity, which can be observed both within and between groups.…”

Effect of logged forests on diet of small characids from Neotropical streams

“…Fish species in small streams exhibit great dietary plasticity associated with seasonal, spatial, and ontogenetic features (Nishio et al, 2020). In this sense, trophic ecology studies are important due to high species diversity (Delariva & Neves, 2020), since fishes are essential components of aquatic food webs, contributing to energy flow and nutrient cycling (López‐Rodríguez et al, 2019).…”

“…Changes in fish diet due to riparian zone modification have been demonstrated for streams in temperate regions (Nakano et al, 1999;Nakano & Murakami, 2001). However, scarce information is available for rainforest streams.Fish species in small streams exhibit great dietary plasticity associated with seasonal, spatial, and ontogenetic features (Nishio et al, 2020). In this sense, trophic ecology studies are important due to high species diversity (Delariva & Neves, 2020), since fishes are essential components of aquatic food webs, contributing to energy flow and nutrient cycling (López-Rodríguez et al, 2019).…”