The significance of droughts for hyporheic dwellers: evidence from freshwater crayfish

Abstract

Freshwater biodiversity is globally threatened by various factors while severe weather events like long-term droughts may be substantially devastating. In order to remain in contact with the water or stay in a sufficiently humid environment at drying localities, the ability to withstand desiccation by dwelling in the hyporheic zone, particularly through vertical burrowing is crucial. We assessed the ability of three European native and five non-native crayfish as models to survive and construct vertical burrows in a humid sandy-clayey substrate under a simulated one-week drought. Three native species (Astacus astacus, A. leptodactylus, and Austropotamobius torrentium) suffered extensive mortalities. Survival of non-native species was substantially higher while all specimens of Cherax destructor and Procambarus clarkii survived. The native species and Pacifastacus leniusculus exhibited no ability to construct vertical burrows. Procambarus fallax f. virginalis and P. clarkii constructed bigger and deeper burrows than C. destructor and Orconectes limosus. In the context of predicted weather fluctuations, the ability to withstand desiccation through constructing vertical burrows into the hyporheic zone under drought conditions might play a significant role in the success of particular crayfish species, as well as a wide range of further hyporheic-dwelling aquatic organisms in general.

High air humidity is sufficient for successful egg incubation and early post‐embryonic development in the marbled crayfish (Procambarus virginalis)

“…When transferred to aquatic conditions, they moulted to the third developmental stage in the course of several days and further progressed normally. This survival trait enables marbled crayfish to spread into a wide range of habitats that experience situations of water scarcity that might otherwise be unsuitable for other, less adapted crayfish species as well as other aquatic taxa (Feria & Faulkes, ; Kouba et al., ). However, we expect that other crayfish species such as the primary burrowers and perhaps some secondary burrowers, especially the highly invasive P. clarkii, are also capable of maintaining ontogeny to some degree without free standing water under humid conditions in a burrow.…”

“…Thus, the capacity of adaptations such as that described here will probably be of key importance as climatic drying progresses, possibly eliminating species that lack adaptations that maintain reproduction during prolonged drying (Johnston & Robson, ; Robson et al., ). Such drying events may also occur in previously unexpected places (Kouba et al., ), which requires further knowledge of the effects of drying conditions on macroinvertebrate communities (Robson et al., ).…”

“…In cases of burrows above the water table, water present in the burrows is most likely to be perched from the time of their construction and settlement, or perhaps periodically refreshed from seepage or percolation from rainfall. Chimney‐like structures built by many species from the genera Cambarus , Engaeus , and Geocharax (Grow & Merchant, ; Horwitz et al., ; March & Robson, ; Noro, Fonseca, Buckup, & Bond‐Buckup, ; Suter & Richardson, ) or closing of the burrow entrance by a mud plug, particularly in females (Barbaresi & Gherardi, ; Correia & Ferreira, ; Kouba et al., ), help in maintaining suitable living condition inside. Aestivation chambers to maintain humidity during desiccation in streambeds are built by adult Geocharax sp.…”

“…Crayfish have evolved to construct or use burrows not only to survive under fluctuating aquatic habitats, but perhaps also to reproduce W10d-stage 1 10 11.5 ± 0.5 a 27.1 (21.5 + 5.6) ± 1.1 a 33.3 (27.1 + 6.2) ± 1.0 a W10d-stage 2 10 11.5 ± 0.5 a 27.4 (21.5 + 5.9) ± 1.2 a 35.3 (27.4 + 7.9) ± 3.7 a W10d-stage 3 10 11.5 ± 0.5 a 28.0 (21.5 + 6.5) ± 2.9 a NA (Feria & Faulkes, 2011;Kouba et al, 2016).…”

“…While it is becoming more obvious that oviposition in crayfish is hampered or delayed in burrows lacking free standing water, the effects of high humidity on embryogenesis is largely unknown (McClain, 2013;Niksirat, Kouba, & Kozák, 2014, 2015. However, survival and reproduction of crayfish individuals in burrows over extended periods of time without free water have been demonstrated (Jordan, Babbitt, McIvor, & Miller, 2000;Kouba et al, 2016;McClain, 2013;McClain & Romaire, 2004). Due to its exclusively parthenogenetic mode of reproduction, burrowing behaviour and potential invasive abilities (Gutekunst et al, 2018;Scholtz et al, 2003), P. virginalis is a suitable model species to study the effect of seasonal water level fluctuations on the early life-history traits of crayfish living in intermittent aquatic environments (Hossain, Patoka, Kouba, & Buřič, 2018).…”