Benthic fluxes of dissolved nutrients, oxygen, dissolved inorganic carbon, and total alkalinity were measured over a 2 yr period in Tomales Bay, California, USA, using in situ incubation chambers. Release of dissolved nutrients from the sediment peaked in late summer and was lowest in winter. The difference between C : N : P flux ratios and composition of suspended particulates indicated the existence of a sink for regenerated N, relative to C and P. Total alkalinity flux revealed that carbon metabolism by net sulfate reduction represented ca one-third of total benthic metabohsm Partitioning net system fluxes into component fluxes suggested that the equivalent of ca 70 to 80 % of the available particulate C, N and P was respired within the water column, while about 20 to 30 O/ O was respired by the benthos. During spring, increasing light resulted in higher water column productivity, followed closely by rising water column respiration. With low delivery of the new organic material to the benthos, and low residual organics in the sediment, benthic respiration remained low. Fallout of particulate material, coinciding with peak water temperature in late summer, resulted in a 'crossover' with benthic respiration temporarily exceeding water column respiration.
A modification of the Euler equation is used to describe a simple parasite life history in which survival decreases with age at a rate determined by mortality of the parasitized host. The advantages of castration of hosts by parasites are discussed using the modified equation in which castration is equivalent to reducing parasite virulence in the host to near zero or zero. It is suggested that castrating parasites can infest a wider range of hosts with higher mortality rates and that within parasite groups having castrating and noncastrating species, the former should infest hosts with higher mortality rates and relatively larger gonads.
A model of colonizing strategy in planktonic larvae of marine invertebrates is proposed in which reproductive efficiency is measured by the frequency of adult habitat patches colonized by a least one larva divided by adult reproductive effort. Conditions leading to alternative energy allocation to either fuel larval habitat search or to support more efficient metamorphosis and post-larval survival are examined. Three predictions emerge: (1) Benthic organisms whose larvae colonize abundant habitat patches should lose larval stages more often than those whose larvae colonize rare patches; (2) prolonged larval life should be assoc~ated with colonization of rare patches; and (3) along clines of increasingly unfavorable conditions for larval survival, energy should be allocated to modifications reducing larval mortality and increasing energy reserves for metamorphosis and early post-larval development. Aspects of larval biology and data needs are discussed.
The "male choice" experimental method was used to test mating preferences of six races of Drosophila paulistorum. The races (number of strains in parentheses) are: Centro-American (3); Amazonian (4); Orinocan (5); Andean-South Brazilian (6); Transitional (4); and Guianan (1).
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