Screening California surface waters for estrogenic endocrine disrupting chemicals (EEDC) with a juvenile rainbow trout liver vitellogenin mRNA procedure.

Concern regarding the occurrence of chemicals that disrupt endocrine system functions in aquatic species has heightened over the last 15 years. However, little attention has been given to monitoring for estrogenic endocrine disrupting chemicals (EEDCs) in California's freshwater ecosystems. The objective was to screen surface water samples for estrogenic activity using vitellogenin (Vtg) mRNA quantification in livers of juvenile rainbow trout by real-time reverse transcriptase polymerase chain reaction (Q-RT PCR). Vtg mRNA analysis of livers from fish exposed to 113 ambient water samples collected from surface waters in California's Central Valley and northern area indicated that six samples (5% of total) may have contained EEDCs. The six samples induced marginal, but statistically significant, increases of Vtg mRNA. No ambient water sample evoked Vtg mRNA responses equivalent to those in positive controls (all responses were less than 2% of the positive control response). Thus, EEDC concentrations in these samples were low (at or near the threshold for the procedure) or results may have included false positives. To establish a more definitive assessment of EEDC occurrence, follow-up screening at sites where statistically significant, but weak, estrogenic activity was observed is recommended. Overall, results reveal that a majority of the California surface waters tested were below EEDC detection threshold concentration for the screening procedure utilized.

Irrigation runoff insecticide pollution of rivers in the Imperial Valley, California (USA).

The Alamo and New Rivers located in the Imperial Valley, California receive large volumes of irrigation runoff and discharge into the ecologically sensitive Salton Sea. Between 1993 and 2002 we conducted a series of studies to assess water quality using three aquatic species: a cladoceran (Ceriodaphnia dubia), a mysid (Neomysis mercedis), and a larval fish (Pimephales promelas). Although no mortality was observed with the P. promelas, high-level toxicity to the invertebrate species was documented in samples from both rivers during many months of each year. Toxicity identifications and chemical analyses identified the organophosphorus insecticides (OP), chlorpyrifos and diazinon, as the cause of C. dubia toxicity. The extent of the C. dubia mortality was highly correlated with quantities of these OPs applied in the river watersheds. C. dubia mortality occurred during more months of our 2001/2002 study than in the 1990s investigations. During 2001/2002, the extensive C. dubia mortality observed in New River samples was caused by OP insecticide pollution that originated from Mexico. Mortality to N. mercedis in New River samples was likely caused by contaminants other than OP insecticides. Our studies document OP insecticide-caused pollution of the Alamo River over a 10-year period and provide the necessary information for remediation efforts.

Causes of ambient toxicity in the Calleguas Creek watershed of southern California.

A combination of toxicity tests, chemical analyses, and Toxicity Identification Evaluations (TIEs) were used to investigate receiving water toxicity in the Calleguas Creek watershed of southern California. Studies were conducted from 1995 through 1999 at various sites to investigate causes of temporal variability of toxicity throughout this system. Causes of receiving water toxicity varied by site and species tested. Investigations in the lower watershed (Revolon Slough, Santa Clara Drain, Beardsley Wash) indicated that toxicity of samples to the cladoceran Ceriodaphnia dubia was due to elevated concentrations of the organophosphate pesticide chlorpyrifos, while causes of intermittent toxicity to fathead minnows (Pimephales promelas) and the alga Selanastrum capricornutum were less clear. Investigations at sites in the middle and upper reaches of the watershed (Arroyo Simi and Conejo Creek) indicated that the pesticide diazinon was the probable cause of receiving water toxicity to Ceriodaphnia. Elevated ammonia was the cause of toxicity to fathead minnows in the upper watershed sites. Results of these and previous studies suggest that biota are impacted by degraded stream quality from a variety of point and non-point pollution sources in the Calleguas Creek watershed. Water quality resource manager's efforts to identify contaminant inputs and implement source control will be improved with the findings of this study.

Structural evidence for two different testicular types in teleost fishes.

Testicular structure in Salmoniformes, Perciformes, Cypriniformes, and Atheriniformes has been examined and reinterpreted on the basis of two different tubular types, distinguished from each other by the intratubular distribution of spermatogonia. In the salmoniform, perciform, and cypriniform teleosts studied, spermatogonia are distributed along the entire length of the testicular tubules. However, in the atheriniform teleosts spermatogonia are restricted to the distal end of the tubule. Sperm development in teleosts is cystic, cysts being comprised of Sertoli-cell processes. In both testicular types described, Sertoli cells phagocytize spermatid residual bodies. Together with the germ cells, they comprise the only intratubular cell types within the teleostean testis. Boundary cells are located immediately outside of the tubule basement membrane. They do not form a complete layer over the tubule surface; therefore, interstitial Leydig cells and blood vessels may border directly upon the tubular basement membrane.

Photoperiod effects on carbohydrate metabolites in the goldfish, Carassius auratus: role of the pineal and retinal pathways.

The effects of exposure to various photoregimes or to constant darkness on liver glycogen and plasma glucose levels in the goldfish were examined during different seasons. In addition, pinealectomized fish and optic nerve sectioned fish were exposed to the photoregimes to assess the potential role of the pineal organ and retinal pathways in mediating photoperiod effects. Neither photoperiod manipulation nor exposure to constant darkness affected liver glycogen levels in experiments conducted during October and January. Photoperiod alteration and exposure to constant darkness resulted in changes of liver glycogen and plasma glucose levels during May, suggesting that response to photoperiod varies with season. Likewise, optic nerve sectioning altered liver glycogen levels during May, but not during October or January, indicating that retinal pathways may be involved in mediating photoperiod effects. During both October and May pinealectomy resulted in a lowering of liver glycogen levels independent of photoregime ; the extent to which hepatic glycogen levels were decreased by pinealectomy was affected by lighting conditions. Plasma glucose levels were elevated in pinealectomized fish regardless of photoregime during May ; the degree of this increase varied with lighting conditions. Our data suggest that the pineal organ does not mediate photoperiod effects on plasma glucose and hepatic glycogen levels, but that there is a functional relationship between this organ and carbohydrate metabolism.

The effects of pinealectomy on pituitary prolactin levels in Carassius auratus exposed to various photoperiod-temperature regimes.

Pinealectomy has an influence on pituitary prolactin levels in goldfish maintained under certain photoperiod-temperature regimes. The effects of pinealectomy on pituitary prolactin content depend on photoperiod and time of sampling. Thus, differences between pinealectomized and sham operated animals may be due to a shift of a daily variation in pituitary prolactin levels. The pineal in fishes may thus be involved in photoperiod influences on daily prolactin rhythms.