Different thermal stimuli initiate hatching of Daphnia diapausing eggs originating from lakes and temporary waters

Abstract

The simultaneous hatching of Daphnia resting eggs from a number of different lakes and ponds using one set of hatching cues can be difficult to achieve as environmental conditions differ considerably between water bodies. Therefore, optimal hatching conditions for ephippial eggs originating from shallow temporary waters may differ from those found in large lakes. The aim of our study was to compare the optimal thermal conditions for hatching ephippial eggs of Daphnia found in permanent lakes and those from shallow temporary ponds. We used ephippial eggs of Daphnia from the longispina species complex originating from two temporary city ponds and two deep lakes in Poland. The ephippia were protected against overheating at all stages of the field and laboratory work to prevent activation or killing of the eggs. After a refractory period (imposed storage in cool and dark conditions), ephippia were incubated at six different temperatures (6, 9, 12, 15, 18 and 21°C) under a 16:8 L:D light regime. Our results indicate that hatching of resting eggs of Daphnia that inhabit lakes or ponds may require different thermal conditions. The hatching success of ephippial eggs originating from temporary waters was relatively high (30-56%) at all tested incubation temperatures, while for the ephippial eggs from the deep lakes it was lower (7-37%) and inversely related to water temperature. The divergent hatching responses of the ephippial eggs originating from temporary pools and lakes may reflect the typical thermal conditions during hatching in their native habitats. While in the deep lakes of the temperate zone Daphnia hatching typically occurs during the low water temperatures of early spring, in shallow ponds Daphnia hatching may occur throughout the year at varying water temperatures, from a few to over a dozen degrees Celsius.

Recovery from drought: Viability and hatching patterns of hydrated and desiccated zooplankton resting eggs

“…In addition, after favorable environmental conditions resume, not all resting eggs hatch. Different species and populations may require different cues to break dormancy and terminate diapause (García‐Roger, Armengol‐Díaz, Carmona, & Serra, ; Radzikowski, Krupińska, & Ślusarczyk, ). Moreover, some populations display bet‐hedging strategies, implying that only fractions of the resting eggs hatch when exposed to favorable conditions (Pinceel, Vanschoenwinkel, Hawinkel, Tuytens, & Brendonck, ).…”

Light quantity, not photoperiod terminates diapause in the crustacean Daphnia

“…A subsample of Eppendorf vials with ephippia was randomly transferred from the dark, cold room into six hatching chambers set up with unique photoperiods, 8 vials per incubation chamber (15 ephippia per vial). All hatching chambers were placed in a common water bath of controlled water temperature 20 C AE 0.2 C. In our previous study, we found that ephippial eggs of Daphnia inhabiting urban ponds hatch at comparable proportions in a wide range of tested temperatures (6-21 C), unlike the resting eggs originating from deep lakes, which hatched most readily at low temperatures (Radzikowski et al 2018). The applied temperature of 20 C made the hatching tests shorter but equally effective compared to cooler thermal conditions (Radzikowski et al 2018).…”

“…All hatching chambers were placed in a common water bath of controlled water temperature 20 C AE 0.2 C. In our previous study, we found that ephippial eggs of Daphnia inhabiting urban ponds hatch at comparable proportions in a wide range of tested temperatures (6-21 C), unlike the resting eggs originating from deep lakes, which hatched most readily at low temperatures (Radzikowski et al 2018). The applied temperature of 20 C made the hatching tests shorter but equally effective compared to cooler thermal conditions (Radzikowski et al 2018). Each incubator was made of a lightproof plastic toolbox supplied with a 8 W white, cool fluorescent lamp (Narva LT8W T5 640-020) attached to the lower side of the toolbox lid.…”

An efficient method for hatching diapausing embryos of Daphnia pulex species complex (Crustacea, Anomopoda)

“…Several previous studies (Davison, ; Paes, Rietzler, & Maia‐Barbosa, ; Pancella & Stross, ; Radzikowski et al, ; Schwartz & Hebert, ; Vandekerkhove et al, ) investigated the environmental conditions conducive for diapausing embryo hatching in Daphnia , providing insight into how to hatch these embryos in a laboratory setting (Table ). The set of suitable conditions, which largely simulate the seasonal environmental changes in spring, is reflected in the common practice seen in recent literature (e.g., Heier & Dudycha, ; Innes & Hebert, ).…”

“…For example, Vandekerkhove et al () suggested that an optimal temperature for hatching is 15°C for a wide range of cladoceran species. Moreover, Radzikowski et al () showed that diapausing embryos of Daphnia species inhabiting temporary waters can hatch over a broader range of temperatures compared with species living in lakes where hatching success is inversely related to temperature.…”