Simulated winter to summer transition in diapausing adults of the lady beetle ( Hippodamia convergens ): supercooling point is not indicative of cold‐hardiness

Abstract

Adults of Hippodumiu convergens Guerin-Meneville (Coleoptera: Coccinellidae) form massive overwintering aggregations in the Sierra Nevada Mountains of California. These diapausing pre-reproductive adults may remain in the aggregations for up to 10 months. Beetles were collected from overwintering sites in Nevada County, California, and held at 4°C for 6 weeks. In order to simulate the winter to summer transition, the beetles were transferred to 20°C and 68% r.h. under a LD 12:12 h cycle. Supercooling points increased slightly from -16°C on day 0 to -12.9"C on day 21. In contrast, low temperature tolerance decreased markedly within 2 weeks. On day 0 nearly all beetles survive 2 h of exposure to -5"C, whereas only 50% survived this treatment on day 4. These data demonstrate the general lack of correlation between the supercooling point and the lower lethal temperature in warm-acclimated beetles. Within 1 day of transfer to 20"C, oxygen consumption decreased by 26%. This decrease continued through day 14 when the rate of oxygen consumption had decreased to 40% of initial values. Beetles acclimated to 20°C selected temperatures significantly higher than cold-acclimated beetles. The parametric shifts observed in this study are consistent with a physiological transition from cold-hardiness and energy conservation during winter to one of dispersal, feeding and reproduction in summer beetles.

Freeze tolerance of a beneficial lady beetle, Hippodamia convergens

“…Our H. convergens supercooled to approximately −15°C and survived brief exposures to temperatures close to −15°C as long as they did not freeze, which is consistent with previous work on these beetles (Bennett and Lee, 1989). Freeze avoidance via supercooling point depression is a common cold tolerance strategy among lady beetles, including H. variegata (Hamedi and Moharramipour, 2013; Khabir et al, 2023), Hippodamia quinquesignata (Harper and Lilly, 1982), and H. axyridis (Berkvens et al, 2010; Koch et al, 2004).…”

“…The metabolites we detected in the fat body of H. convergens included common cryoprotectants such as glycerol, proline, myo-inositol, and trehalose, but we did not detect sorbitol or mannitol. Our concentrations (less than 10 µmol/g wet mass) were generally low or moderate, consistent with earlier work on H. convergens showing that none of glycerol, sorbitol, trehalose, or mannitol were present in tissue homogenates at concentrations greater than 1 mM (Bennett and Lee, 1989). Our results are also similar to studies on overwintering H. variegata collected in Iran, which had concentrations of myo-inositol, glucose, glycerol, and trehalose on a similar order of magnitude (e.g., 5 -10 µmol/g wet mass) to our study (Hamedi et al, 2013;Khabir et al, 2023).…”

“…The ability of H. convergens to survive inoculative freezing is similar to the firebug Pyrrhocoris apterus , which is typically classified as freeze-avoidant (or freeze-intolerant) but is freeze-tolerant when inoculatively frozen by contact with external ice at high subzero temperatures (e.g., −2.5°C) for durations similar to our experiment (Rozsypal and Koštál, 2018). Thus, although prior work describes H. convergens as freeze-intolerant (Bennett and Lee, 1989; Lee, 1980), we show that they can survive freezing under mild conditions such as exposure to −3°C or −4°C, and that gut contents can potentially stimulate survivable freezing in post-diapause beetles. In addition, higher proportions of beetles were inoculatively frozen at lower temperatures (43% at −3°C vs. 87% at −8°C; Table 1), suggesting it becomes more challenging to resist inoculative freezing by contact with external ice as temperatures decrease.…”

Freeze tolerance of a beneficial lady beetle, Hippodamia convergens

“…Our H. convergens supercooled to approximately −15°C and survived brief exposures to temperatures close to −15°C as long as they did not freeze, which is consistent with previous work on these beetles (Bennett and Lee, 1989). Freeze avoidance via supercooling point depression is a common cold tolerance strategy among lady beetles, including H. variegata (Hamedi and Moharramipour, 2013; Khabir et al, 2023), Hippodamia quinquesignata (Harper and Lilly, 1982), and H. axyridis (Berkvens et al, 2010; Koch et al, 2004).…”

“…The metabolites we detected in the fat body of H. convergens included common cryoprotectants such as glycerol, proline, myo-inositol, and trehalose, but we did not detect sorbitol or mannitol. Our concentrations (less than 10 µmol/g wet mass) were generally low or moderate, consistent with earlier work on H. convergens showing that none of glycerol, sorbitol, trehalose, or mannitol were present in tissue homogenates at concentrations greater than 1 mM (Bennett and Lee, 1989). Our results are also similar to studies on overwintering H. variegata collected in Iran, which had concentrations of myo-inositol, glucose, glycerol, and trehalose on a similar order of magnitude (e.g., 5 -10 µmol/g wet mass) to our study (Hamedi et al, 2013;Khabir et al, 2023).…”

“…The ability of H. convergens to survive inoculative freezing is similar to the firebug Pyrrhocoris apterus , which is typically classified as freeze-avoidant (or freeze-intolerant) but is freeze-tolerant when inoculatively frozen by contact with external ice at high subzero temperatures (e.g., −2.5°C) for durations similar to our experiment (Rozsypal and Koštál, 2018). Thus, although prior work describes H. convergens as freeze-intolerant (Bennett and Lee, 1989; Lee, 1980), we show that they can survive freezing under mild conditions such as exposure to −3°C or −4°C, and that gut contents can potentially stimulate survivable freezing in post-diapause beetles. In addition, higher proportions of beetles were inoculatively frozen at lower temperatures (43% at −3°C vs. 87% at −8°C; Table 1), suggesting it becomes more challenging to resist inoculative freezing by contact with external ice as temperatures decrease.…”

Seasonal variation in generation time, diapause and cold hardiness in a central Ohio population of the flesh fly, Sarcophaga bullata

“…We previously reported that the supercooling point is not a good indicator of cold tolerance in flesh flies (Lee & Denlinger,198S), and similar observations have now been reported for several species (Bale, 1987;Bennett & Lee, 1989). In this study we found that diapausing pupae of various ages and nondiapausing pupae all had supercooling points around -21°C.…”

Seasonal Change in Cold Tolerance of the House Spider, Achaearanea tepidariorum (Araneae: Theridiidae).

“…Such differential performance of SCP and LLT 50 may imply that the changes in the supercooling capacity and the chilling tolerance are caused by separate processes. The independence of SCP from LLT 50 or other parameters of the chilling tolerance has been also reported in other arthropod species (LEE & DENLINGER, 1985;BENNETT & LEE, 1989;CHEN et al, 1991;PULLIN et al, 1991;TANAKA & UDAGAWA, in press).…”

Freeze tolerance of a beneficial lady beetle, Hippodamia convergens

“…Our H. convergens supercooled to approximately −15°C and survived brief exposures to temperatures close to −15°C as long as they did not freeze, which is consistent with previous work on these beetles (Bennett and Lee, 1989). Freeze avoidance via supercooling point depression is a common cold tolerance strategy among lady beetles, including H. variegata (Hamedi and Moharramipour, 2013; Khabir et al, 2023), Hippodamia quinquesignata (Harper and Lilly, 1982), and H. axyridis (Berkvens et al, 2010; Koch et al, 2004).…”

“…The metabolites we detected in the fat body of H. convergens included common cryoprotectants such as glycerol, proline, myo-inositol, and trehalose, but we did not detect sorbitol or mannitol. Our concentrations (less than 10 µmol/g wet mass) were generally low or moderate, consistent with earlier work on H. convergens showing that none of glycerol, sorbitol, trehalose, or mannitol were present in tissue homogenates at concentrations greater than 1 mM (Bennett and Lee, 1989). Our results are also similar to studies on overwintering H. variegata collected in Iran, which had concentrations of myo-inositol, glucose, glycerol, and trehalose on a similar order of magnitude (e.g., 5 -10 µmol/g wet mass) to our study (Hamedi et al, 2013;Khabir et al, 2023).…”

“…The ability of H. convergens to survive inoculative freezing is similar to the firebug Pyrrhocoris apterus , which is typically classified as freeze-avoidant (or freeze-intolerant) but is freeze-tolerant when inoculatively frozen by contact with external ice at high subzero temperatures (e.g., −2.5°C) for durations similar to our experiment (Rozsypal and Koštál, 2018). Thus, although prior work describes H. convergens as freeze-intolerant (Bennett and Lee, 1989; Lee, 1980), we show that they can survive freezing under mild conditions such as exposure to −3°C or −4°C, and that gut contents can potentially stimulate survivable freezing in post-diapause beetles. In addition, higher proportions of beetles were inoculatively frozen at lower temperatures (43% at −3°C vs. 87% at −8°C; Table 1), suggesting it becomes more challenging to resist inoculative freezing by contact with external ice as temperatures decrease.…”

Seasonal variation in generation time, diapause and cold hardiness in a central Ohio population of the flesh fly, Sarcophaga bullata

“…We previously reported that the supercooling point is not a good indicator of cold tolerance in flesh flies (Lee & Denlinger,198S), and similar observations have now been reported for several species (Bale, 1987;Bennett & Lee, 1989). In this study we found that diapausing pupae of various ages and nondiapausing pupae all had supercooling points around -21°C.…”

Seasonal Change in Cold Tolerance of the House Spider, Achaearanea tepidariorum (Araneae: Theridiidae).

“…Such differential performance of SCP and LLT 50 may imply that the changes in the supercooling capacity and the chilling tolerance are caused by separate processes. The independence of SCP from LLT 50 or other parameters of the chilling tolerance has been also reported in other arthropod species (LEE & DENLINGER, 1985;BENNETT & LEE, 1989;CHEN et al, 1991;PULLIN et al, 1991;TANAKA & UDAGAWA, in press).…”

Freeze tolerance of a beneficial lady beetle, Hippodamia convergens

“…Our H. convergens supercooled to approximately −15°C and survived brief exposures to temperatures close to −15°C as long as they did not freeze, which is consistent with previous work on these beetles (Bennett and Lee, 1989). Freeze avoidance via supercooling point depression is a common cold tolerance strategy among lady beetles, including H. variegata (Hamedi and Moharramipour, 2013; Khabir et al, 2023), Hippodamia quinquesignata (Harper and Lilly, 1982), and H. axyridis (Berkvens et al, 2010; Koch et al, 2004).…”

“…The metabolites we detected in the fat body of H. convergens included common cryoprotectants such as glycerol, proline, myo-inositol, and trehalose, but we did not detect sorbitol or mannitol. Our concentrations (less than 10 µmol/g wet mass) were generally low or moderate, consistent with earlier work on H. convergens showing that none of glycerol, sorbitol, trehalose, or mannitol were present in tissue homogenates at concentrations greater than 1 mM (Bennett and Lee, 1989). Our results are also similar to studies on overwintering H. variegata collected in Iran, which had concentrations of myo-inositol, glucose, glycerol, and trehalose on a similar order of magnitude (e.g., 5 -10 µmol/g wet mass) to our study (Hamedi et al, 2013;Khabir et al, 2023).…”

“…The ability of H. convergens to survive inoculative freezing is similar to the firebug Pyrrhocoris apterus , which is typically classified as freeze-avoidant (or freeze-intolerant) but is freeze-tolerant when inoculatively frozen by contact with external ice at high subzero temperatures (e.g., −2.5°C) for durations similar to our experiment (Rozsypal and Koštál, 2018). Thus, although prior work describes H. convergens as freeze-intolerant (Bennett and Lee, 1989; Lee, 1980), we show that they can survive freezing under mild conditions such as exposure to −3°C or −4°C, and that gut contents can potentially stimulate survivable freezing in post-diapause beetles. In addition, higher proportions of beetles were inoculatively frozen at lower temperatures (43% at −3°C vs. 87% at −8°C; Table 1), suggesting it becomes more challenging to resist inoculative freezing by contact with external ice as temperatures decrease.…”

Seasonal variation in generation time, diapause and cold hardiness in a central Ohio population of the flesh fly, Sarcophaga bullata

“…We previously reported that the supercooling point is not a good indicator of cold tolerance in flesh flies (Lee & Denlinger,198S), and similar observations have now been reported for several species (Bale, 1987;Bennett & Lee, 1989). In this study we found that diapausing pupae of various ages and nondiapausing pupae all had supercooling points around -21°C.…”

Seasonal Change in Cold Tolerance of the House Spider, Achaearanea tepidariorum (Araneae: Theridiidae).

“…Such differential performance of SCP and LLT 50 may imply that the changes in the supercooling capacity and the chilling tolerance are caused by separate processes. The independence of SCP from LLT 50 or other parameters of the chilling tolerance has been also reported in other arthropod species (LEE & DENLINGER, 1985;BENNETT & LEE, 1989;CHEN et al, 1991;PULLIN et al, 1991;TANAKA & UDAGAWA, in press).…”