The influence of temperature on the survival, development, growth, and chromosome preparation quality of the EFG/C, ACD, and AA cytotypes of the Simulium venustum–verecundum complex (Diptera: Simuliidae)

Abstract

The influence of temperature on survival, development, and growth of simuliid larvae of the EFG/C cytotype and of a mixed population of ACD–AA cytotypes was examined, employing a stir bar rearing system. The EFG/C type completed larval development from 5 to 30 °C, with maximum survival between 15 and 20 °C (68.0–73.5%). The ACD–AA types completed development between 5 and 25 °C, with maximum survival between 15 and 25 °C (55.3–61.0%). The temperature–survivorship curve of EFG/C was significantly different from the ACD–AA one. Using regression analysis, threshold temperature was determined to be 0 °C. Mean degree-days required to complete larval development varied depending on temperature, cytotype, and sex. Degree-day determination in the laboratory agreed well with field data. Final larval instars of EFG/C and ACD were largest at 10–15 °C. The results are compared with those of previous studies and discussed in relation to "optimal temperature" and fitness. The size and band discrimination of the salivary gland polytene chromosomes used to identify the above cytotypes were found to vary with rearing conditions. We suggest that larvae reared at 15 °C and fed Tetra, at a dosage of ≥ 0.3 mg/larva per day, will provide good-quality chromosome preparations.