Thomas G. Shelton

Carbon dioxide release in Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar): effects of caste, mass, and movement

Movement and carbon dioxide (CO(2)) release of individual Formosan, Coptotermes formosanus Shiraki and Eastern, Reticulitermes flavipes (Kollar) subterranean termites were recorded simultaneously in real time. Worker, soldier, and pre-alate (nymph) caste termites were recorded over 1-h periods at ambient temperature and normoxia in dry, CO(2)-free air. No evidence of discontinuous gas exchange cycles (DGCs) was observed in 344 recordings. Intensity of movement was constant in video tape recordings of termites under respirometry conditions. Duration of movement did not have a significant effect on residuals of &Vdot;(CO(2)) regressed on mass. Thus, movement did not effect &Vdot;(CO(2)) for these two species. Overall CO(2) release values were calculated for all recordings resulting in mean &Vdot;(CO(2)) (ml CO(2) g(-1) h(-1)), and compared among caste, colony, and species with a nested ANOVA. There was significant interaction (P=0.0161) only for species. Mean CO(2) release was significantly greater for R. flavipes (0.507 ml CO(2) g(-1) h(-1)) than C. formosanus (0.310 ml CO(2) g(-1) h(-1)). Mass scaling of termite &Vdot;(CO(2)) was investigated by regressing log(10)&Vdot;(CO(2)) on log(10)mass. The overall model combining species gave a mass scaling coefficient of 0.861(+/-0.0791), which approximates a previously published value for the arthropods as a whole (0.825).

Cyclic carbon dioxide release in the dampwood termite, Zootermopsis nevadensis (Hagen).

Real-time traces of CO(2) release of pseudergates of the dampwood termite, Zootermopsis nevadensis (Hagen) were obtained using flow-through respirometry. Traces were made at each of six temperatures, between 10 and 35 degrees C. Termites released CO(2) in a cyclic pattern at each of the six temperatures. CO(2) release rate (as V(CO(2)) in ml h(-1)) increased significantly with temperature and body mass. Rate of change in V(CO(2)) with temperature (or Q(10)) was 2.11. Degree of cycling in CO(2) traces was estimable using the coefficient of variability. Coefficient of variability for both acyclic and cyclic traces declined exponentially with increasing temperature.

Cyclic CO2 release in Cryptotermes cavifrons Banks, Incisitermes tabogae (Snyder) and I. minor (Hagen) (Isoptera: Kalotermitidae)

CO(2) release patterns of three drywood termite species were investigated using flow-through respirometry techniques. Eight hours of real-time CO(2) release data were recorded for pseudergates of Cryptotermes cavifrons Banks, Incisitermes minor (Hagen), and I. tabogae (Snyder) at 20-40 degrees C. Cyclic release of CO(2) was observed in 20-90% of C. cavifrons, 70-100% of I. tabogae, and 87-100% of I. minor pseudergates. Variability of the recordings (calculated as the coefficient of variability or CV) was used to estimate the level of cycling in each recording. CV ranged from 14.53+/-2.57 (40 degrees C) to 32.33+/-1.12% (30 degrees C) in C. cavifrons, 20.24+/-2.44 (35 degrees C) to 67.3+/-10.3% (20 degrees C) in I. minor, and 15.9+/-1.46 (35 degrees C) to 34.15+/-6.18% (20 degrees C) in I. tabogae. The relationship between temperature and CV for each species was modeled using non-linear regression. CV of both Incisitermes spp. decreased exponentially with temperature, while C. cavifrons CV followed a Gaussian model, indicating an optimal cycling temperature of approximately 30 degrees C. Mean V.CO(2) values were determined for each species as a function of temperature, and ranged from 0.1 ml CO(2) g(-1) h(-1) (I. minor at 20 degrees C) to 0.8 ml CO(2) g(-1) h(-1) (C. cavifrons at 40 degrees C). For all three species, V.CO(2) significantly increased linearly with temperature. Colinearity tests indicated that different models described the V.CO(2) relationship with temperature for both genera. Q(10) values for V.CO(2) over the range of 20-40 degrees C were 1.92 for I. minor, 1.66 for I. tabogae, and 1.62 for C. cavifrons pseudergates.

Cyclic Co2 Release and Water Loss in Alates of the Eastern Subterranean Termite (Isoptera: Rhinotermitidae)

Abstract CO2 release and water loss of unmated alates of Reticulitermes flavipes (Kollar), collected immediately before flight, were examined using flow-through respirometry. Whole body lipid and water content and cuticular permeability were also determined. Two models were used to estimate cuticular surface area for permeability calculation. CO2 release and water loss cycled concurrently in 90.9 and 66.7% of the recordings for males and females, respectively. Level of cycling of the recordings was determined by use of the coefficient of variability of the V˙CO2. Cyclic traces (40.4 ± 3.4 for females and 53.7 ± 2.1% for males) had greater coefficient of variability than acyclic traces (31.7 ± 6.1 and 40.5 ± 3.2%, for females and males, respectively) from both genders. Mean overall V˙CO2 did not vary significantly with alate gender. Lipid content (≈12%) was not significantly different between genders of R. flavipes alates. However, cuticular permeability values varied depending on the model for determining surface area used. Cuticular permeability values calculated using Meeh’s formula were comparable to those reported in the literature (28.3 and 36.1 μg H2O lost cm−2 h−1 mmHg−1, for females and males, respectively).

Cyclic CO2 Release and Water Loss in the Western Drywood Termite (Isoptera: Kalotermitidae)

Abstract CO2 release and water loss patterns of Incisitermes minor (Hagen) pseudergates were investigated using flow-through respirometry techniques. Four hours of real-time CO2 release and water loss data were recorded for pseudergates of I. minor at 20–40°C. Cyclic release, but not traditional DGC, was the CO2 release pattern observed in these pseudergates. Variability of V˙co2 expressed as coefficient of variability (CV) was used to estimate the level of cycling in each recording. CV decreased exponentially with temperature. Mean V˙co2 values ranged from 0.24 ± 0.07 ml CO2 g−1 h−1 at 25°C to 0.89 ± 0.16 ml CO2 g−1 h−1 at 35°C. V˙co2 increased significantly (P = 0.014) with temperature, but was not influenced (P = 0.063) by body mass. Q10 for V˙co2 over the range of 20–40°C was 1.75 for I. minor pseudergates. Water loss cycled coincidently with CO2 release. Water loss rates ranged from 5.22 ± 1.97 mg H2O lost g−1 h−1 at 20°C to 17.96 ± 2.55 mg H2O lost g−1 h−1 at 40°C. Q10 for water loss over the range of 20–40°C was 1.86 for I. minor pseudergates. Daily respiratory water loss represented from 9.23% at 20°C to 4.72% at 25°C of total daily water loss. Cuticular water loss represented from 93.5% at 25°C to 89.1% at 30°C of total daily water loss.

Effects of monitor examination intervals on resource affinity by Reticulitermes spp. (Isoptera: Rhinotermitidae)

Monthly visits to 2 field sites in southern Mississippi were made to determine the influence of monitor examination on feeding site affinity by southeastern native subterranean termites (Reticulitermes spp.). Wooden board monitors were examined once every 30, 60, or 90 days. Presence of live termites and damage to the boards (both binary parameters) were collected for each plot examined over a 3-yr period, along with monthly soil moisture (as percentage of soil saturation) and temperature at 15.24 cm depth. Time to first occurrence of termite presence and/or damage and subsequent occurrences indicated no difference among the treatments, indicating that none of the treatments influenced termite foraging affinity.

CO2 Release in Groups of Reticulitermes virginicus (Isoptera: Rhinotermitidae)

Abstract CO2 release rates were measured from groups of 10 Reticulitermes virginicus Banks workers, soldiers, and nymphs. For workers, Vijco2, (μl·mg−1·h−1) increased linearly with temperature between 16.2 - 30.4°C. Vijco2 recorded at ≈20°C was 0.177 ± 0.005 μl·mg−1·h−1 for soldiers and 0.219 ± 0.027 (μl·mg−1·h−1 tor nymphs. Assuming a similar slope of temperature increase in Vijco2 for all castes, predicted mass-corrected CO2 release values for grouped R. virginicus workers, soldiers and nymphs at 23.6°C were 27, 52 and 27% lower than literature values for the same castes of R. flavipes measured individually at that temperature. CO2 release rate (μl·mg−1·h−1) for R. virginicus nearly doubled over the 20°C to 30°C temperature range (Q10 = 1.91), similar to literature values for Zootermopsis nevadensis (Hagen) over the same range. For all temperatures except 25.2°C, CO2 release rate (in μl·h−1) increased significantly with mass, with coefficients ranging from 0.123 (16.2°C) to 0.599 (30.4°C).