Capacity for extended egg diapause in six Isogenoides Klapalek species (Plecoptera: Perlodidae)

• Published in: Transactions of the American Entomological Society (1890) 2004-12, Vol.130 (4), p.411-423
• Main Authors: Sandberg, J.B, Stewart, K.W
• Format: Article
• Language: English
• Subjects: Diapause; duration; egg hatchability; Egg masses; Eggs; embryogenesis; extended diapause; Female animals; Fluvial deposition; Hatching; Incubation; Insect eggs; insect reproduction; Isogenoides; Nymphs; ova; Perlodidae; Streams; temperature
• ISSN: 0002-8320; 2162-3139

The eggs of six Isogenoides species have been incubated at a single, approximately simulated, San Miguel River, Colorado, seasonal temperature regime for 2-5 years. Eggs were collected from reared, laboratory-mated females of I. colubrinus, I. doratus, I. elongatus, I. frontalis, I. varians, and I. zionensis. Eggs were held in 8 ml containers and visually examined usually weekly for development and hatch. Only some I. zionensis eggs from a combined first and second mass of a Leopard Creek, Colorado population hatched directly within two weeks, continuing until late September, and resuming mainly May-June the following year; one and two eggs hatched in 2002 and 2004, respectively. I. doratus and I. varians experienced hatch only after an over-summer, 3-4 month diapause, and I. varians again in late August-September during the second year. Populations of I. colubrinus, I. elongatus, I. frontalis and a San Miguel River, Colorado population of I. zionensis began hatching only in the year following deposition, after a 10-12 month diapause. Some hatching of these four species occurred at spring-summer temperatures in subsequent years (2nd, 3rd, 3rd, and 4th years, respectively), with no intervening hatch at winter temperatures. The study confirms extended, usually asynchronous diapause and hatching for from 3 months to 4 years, probably genetically controlled, in the six species, and a great degree of adaptive capacity for diapause in the genus Isogenoides.