Autumnal vs spring hatching in the fairy shrimp Siphonophanes grubii (Dybowski) (Crustacea, Anostraca): diversified bet-hedging strategy ?

Polyphenisms, as opposed to polymorphism, refers to coexistence of several distinct phenotypes having a common genotype. Polyphenism can be selected for in unpredictable environments. Here we document and anlyse a case of siphenism in the north-European fairy shrinp Siphonophanes grubii (Dybowski), in relation to the temporary and unpredictable nature of its habitat. The active part of this species'life cycle usually consists of a single, short-lived, spring cohort. Here we report field observations on autumnal hatching and on a long-lived, overwintering cohort; we show that the winter cohort runs the risk of total failure, due to the pond freezing entirely or drying up during winter. If, however, environmental conditions allow winter survival, animals reach a larger size, reproduce for a longer time, and display higher fecundity, than do animals from the spring cohort. Laboratory experiments support the theory that these differences are purely phenotypic and dependent on temperatur. Using an analytical model adapted from Cohen (1966), we propose that the coexistence of both a winter and a spring cohort in the same ponds can be interpreted as a diversified bet-hedging strategy.

Responsive Management Report, Winter/Spring 2001

Newsletter produced by Iowa Department of Natural Resources.

Differential Gene Expression between Fall- and Spring-Run Chinook Salmon Assessed by Long Serial Analysis of Gene Expression

Of all Pacific salmonids, Chinook salmon Oncorhynchus tshawytscha display the greatest variability in return times to freshwater. The molecular mechanisms of these differential return times have not been well described. Current methods, such as long serial analysis of gene expression (LongSAGE) and microarrays, allow gene expression to be analyzed for thousands of genes simultaneously. To investigate whether differential gene expression is observed between fall- and spring-run Chinook salmon from California's Central Valley, LongSAGE libraries were constructed. Three libraries containing between 25,512 and 29,372 sequenced tags (21 base pairs/tag) were generated using messenger RNA from the brains of adult Chinook salmon returning in fall and spring and from one ocean-caught Chinook salmon. Tags were annotated to genes using complementary DNA libraries from Atlantic salmon Salmo salar and rainbow trout O. mykiss. Differentially expressed genes, as estimated by differences in the number of sequence tags, were found in all pairwise comparisons of libraries (freshwater versus saltwater = 40 genes; fall versus spring = 11 genes: and spawning versus nonspawning = 51 genes). The gene for ependymin, an extracellular glycoprotein involved in behavioral plasticity in fish, exhibited the most differential expression among the three groupings. Reverse transcription polymerase chain reaction analysis verified the differential expression of ependymin between the fall- and spring-run samples. These LongSAGE libraries, the first reported for Chinook salmon, provide a window of the transcriptional changes during Chinook salmon return migration to freshwater and spawning and increase the amount of expressed sequence data.

News, I-74 Iowa-Illinois Corridor Study, Issue 1 Spring 2001

Newsletter updating the corridor study of the Mississippi Bridge project for the states of Iowa and Illinois.

Iowa Aviation Bulletin, Spring 1999

Quarterly newsletter published by the Iowa Department of Transportation's Office of Aviation that contains information of interest to aviation-related persons and organizations.

Iowa Aviation Bulletin, Spring 2002

Quarterly newsletter published by the Iowa Department of Transportation's Office of Aviation that contains information of interest to aviation-related persons and organizations.

Iowa Aviation Bulletin, Spring 2001

Quarterly newsletter published by the Iowa Department of Transportation's Office of Aviation that contains information of interest to aviation-related persons and organizations.

Iowa Aviation Bulletin, Spring 2000

Quarterly newsletter published by the Iowa Department of Transportation's Office of Aviation that contains information of interest to aviation-related persons and organizations.

I-35 Corridor Trade Study Newsletter, Spring 1999

The Federal Highway Administration (FHWA)and the Departments of Transportation in Texas, Oklahoma, Kansas, Missouri, Iowa and Minnesota combined their efforts to conduct The I-35 Trade Corridor Study.

I-35 Corridor Trade Study Newsletter, Spring 1998

The Federal Highway Administration (FHWA)and the Departments of Transportation in Texas, Oklahoma, Kansas, Missouri, Iowa and Minnesota combined their efforts to conduct The I-35 Trade Corridor Study.

Connections, Spring 2001

Newsletter for Iowa Department of Transportation, Office of Public Transit

Resident Spring Turkey Hunting Information, 2006

This six page document outlines the regulations for spring turkey hunting in Iowa.

Nonresident Spring Turkey Hunting Information, 2006

This three page document outlines the regulations for spring turkey hunting in Iowa.

Iowa Aviation Bulletin, Spring 2006

Quarterly newsletter published by the Iowa Department of Transportation's Office of Aviation that contains information of interest to aviation-related persons and organizations.

SmartNews, Spring 2006

News from the Iowa Careers Consortium