Effect of variable and constant thermal conditions on embryonic and early larval development of fish from the genus Leuciscus (Cyprinidae, Teleostei)

Abstract

In recent years, despite a certain deceleration of the process, evident decrease or even extinction of many local populations of the majority of rheophilic fish species including dace Leuciscus leuciscus (L.), ide L. idus (L.), and chub L. cephalus (L.) -the only representatives of the genus Leuciscus in Polish ichthyofauna -has still been observed. Invariably, the major reasons for that situation are ) and chub L. cephalus (L.) were obtained from rivers belonging to the Pasleka River basin (northeastern Poland) and next transported to a hatchery for the purpose of conducting artificial reproduction. The obtained eggs were fertilized and next incubated under a variety of thermal protocols: slow gradual heating of water (M1), rapid increase in temperature at the end of incubation (M2), fluctuating temperature (M3) and two constant temperatures (optimum and sublethal). Variable thermal changes of water were also continued after hatching, up to the yolk sac resorption by larvae. During the study it was shown that relative to incubation at optimal temperatures (12.3°C for dace, 15.7°C for ide and 19.0°C for chub), thermal modifications had no clear influence on a decrease in survival rates (differences among regimes did not exceed 5%) and increase in developmental deformations (differences below 1.0%) observed among the hatched embryos. The duration of egg incubation and developmental rate increased with increasing temperature. In the systems with modified temperature the embryonic development of dace (from fertilisation to commencement of exogenous food intake) took from 9.5 to 22.5 days, for ide from 6.1 to 12 days and for chub from 5.0 to 10.5 days. The yolk sac resorption stage in the particular species occurred from 11.7 to 23 days for dace, 7.5 to 13.2 days for ide and 5.5 to 12.8 days for chub. Different time of hatching was also reflected in the level of ontogeny of hatched embryos. Among the fish hatched at modified temperatures the largest sizes, similar to those characteristic of fish incubated at optimum temperatures, were observed in individuals originating from variants where the temperature fluctuated. The developmental disproportions among the embryos of studied species originating from different thermal regimes observed at the time of leaving the egg shells were definitely larger than during the following development stages. This study also confirmed that the embryos of studied species can adapt to increasing water temperature due to global warming up to 19.0 (dace), 23.0°C (ide) and 27.5°C (chub). The obtained results are very important not only for practical purposes but also from physiological and ecological aspects.

Early development and allometric growth patterns of rheophilic cyprinid common dace Leuciscus leuciscus (Cyprinidae: Leuciscinae)

“…Within a few hours following emergence, free embryos start to swim up to the surface to fill their swim bladder and start active swimming. A similar level of development at hatching is characteristic for few other cyprinids from a group of open substratum early spring spawners, such as ide Leuciscus idus, or asp Aspius aspius, which are able to swim freely soon after emergence (Kupren et al 2011(Kupren et al , 2015aKorzelecka-Orkisz et al 2013). The level of ontogenetic development at hatching is species specific, depends on the reproductive and larval lifestyles, and is highly dependent on environmental conditions, especially water temperature (Sakai 1990;Kamler 1992;Korzelecka-Orkisz et al 2009;Teletchea et al 2009).…”

“…stages of hatching, first free swimming, and first intake of exogenous food). At the moment of hatching, common dace is more advanced in their development than the individuals of majority of teleost fish species (Kennedy 1969;Kupren et al 2008Kupren et al , 2011. The newly hatched common dace have almost a straight body with the head clearly separated from the yolk sac at an advanced stage of absorption.…”

“…The most advanced fish with the largest body lengths and smallest yolk sacs hatch at temperatures within the optimum range. At other temperatures, the individuals that left the egg membranes usually show less advanced ontogenic development (Kokurewicz 1969(Kokurewicz , 1970Kupren et al 2011). The reason for faster hatching of embryos at higher temperatures is their increased mobility in warmer water and earlier excretion of the hatching enzyme (Blaxter 1969(Blaxter , 1992Kamler 1992;Kamler et al 1998;Korwin-Kossakowski 2012).…”

“…Hoda and Tsukahara 1971;Osse et al 1997;van Snik et al 1997). In this paper, we use a multivariate approach to objectively define the transition from larval to juvenile period using morphometric as well as morphological characters and apply this method to common dace Leuciscus leuciscus-a cyprinid characterized by larger eggs and larvae than the common carp (Kennedy 1969;Kupren et al 2011).…”

“…Adult common dace feeds on insects, mollusks, crustaceans, and macrophytes (Mann 1974;Hellawell 1974;Mills et al 1985). Fragmentary descriptions of its early morphological development have been described by Kennedy (1969) and Kupren et al (2008Kupren et al ( , 2011, but none of these studies reported age or size at larval transformation. Moreover, they do not contain information concerning allometric growth.…”