Passive sinking into the snow as possible survival strategy during the off-host stage in an insect ectoparasite

Abstract

Abiotic and biotic factors determine success or failure of individual organisms, populations and species. The early life stages are often the most vulnerable to heavy mortality due to environmental conditions. The deer ked (Lipoptena cervi Linnaeus, 1758) is an invasive insect ectoparasite of cervids that spends an important period of the life cycle outside host as immobile pupa. During winter, dark-coloured pupae drop off the host onto the snow, where they are exposed to environmental temperature variation and predation as long as the new snowfall provides shelter against these mortality factors. The other possible option is to passively sink into the snow, which is aided by morphology of pupae. Here, we experimentally studied passive snow sinking capacity of pupae of L. cervi. We show that pupae have a notable passive snow sinking capacity, which is the most likely explained by pupal morphology enabling solar energy absorption and pupal weight. The present results can be used when planning future studies and when evaluating possible predation risk and overall survival of this invasive ectoparasite species in changing environmental conditions.

Hippobosca equina L. (Hippoboscidae: Hippobosca)—An Old Enemy as an Emerging Threat in the Palearctic Zone

“…In the above-mentioned representatives of Hippoboscidae, the survival of juveniles during the off-host stage is also facilitated by higher temperatures. Moreover, numerous adaptations to unfavorable environmental conditions can be observed in Hippoboscidae during the non-parasitic phase of the life cycle [ 88 , 89 , 90 ]. Predictions for an increase in ambient temperature will probably contribute to the territorial expansion of ectothermic species belonging to Hippoboscidae [ 84 ].…”

Summer time predation on the obligatory off-host stage of an invasive ectoparasite

“…For the predation experiments, we collected L. cervi pupae from the winter bedding sites of the moose (Alces alces), from March to April 2010, in five Finnish communes: Siikalatva (64°30′20″N, 25°39′ 00″E), Kontiolahti (62°88′58″N, 29°68′95″E), Liperi (62°48′82″N, 29°23′84″E), Vimpeli (63°11′94″N, 23°86′32″E) and Alajärvi (63°05′22″N, 24°21′20″E). Pupae (n = 1710) were collected from the winter bedding sites of the moose, as the moose is the main host of the species in Finland and because black pupae can be easily detected against snow on recently laid bedding sites (Kaunisto et al 2009(Kaunisto et al , 2015b. Pupae are of oval shape and usually circa 3 mm long (Kaunisto et al 2015b).…”

“…Pupae (n = 1710) were collected from the winter bedding sites of the moose, as the moose is the main host of the species in Finland and because black pupae can be easily detected against snow on recently laid bedding sites (Kaunisto et al 2009(Kaunisto et al , 2015b. Pupae are of oval shape and usually circa 3 mm long (Kaunisto et al 2015b). After collections, all diapausing pupae (n = 1710) were kept in a cold room (+3°C) to mimic late winter temperatures.…”

Effect of snow cover on the off-host survival of Dermacentor variabilis (Acari: Ixodidae) larvae

“…A recent study by Volk et al (2022) found that snow cover plays an important role in the overwinter survival of nymphs of Ixodes scapularis Say, while the overwinter survival of nymphs of Ixodes ricinus L. also appears to be greater when a snow cover is present (Vollack et al 2017). Snow cover is also important for the survival of many insects during winter (Aitchison 2001, Bale and Hayward 2010, Marshall and Sinclair 2012, Kaunisto et al 2015, Huang 2016). Continuous snow cover on the ground maintains a high relative humidity and decreases the variation in temperature at the soil surface-litter layer interface (i.e., tick refuge site), the later reducing the chance of inoculative freezing (Lindsay et al 1995, Burks et al 1996a, Zhang 2005, Templer et al 2012), and potentially enhancing tick survival.…”