Urban Roadway Runoff Is Lethal to Juvenile Coho, Steelhead, and Chinook Salmonids, But Not Congeneric Sockeye.

We compared the sensitivity of closely related Pacific salmon and steelhead (Oncorhynchus spp.) to untreated urban stormwater runoff across three storm events. Juvenile coho, sockeye, steelhead, and Chinook were exposed for 24 h to untreated urban runoff and then transferred to clean water for 48 h. As anticipated from previous studies, coho were highly susceptible to runoff toxicity, with cumulative mortality rates ranging from 92%-100% across the three storms. By contrast, juvenile sockeye were unaffected (100% survival), and cumulative mortality rates were intermediate for steelhead (4%-42%) and Chinook (0%-13%). Furthermore, coho died rapidly following the onset of stormwater exposure (generally <4 h), whereas mortality in Chinook and steelhead was delayed by 1-2 days. Similar to previous findings for coho, steelhead and Chinook did not recover when transferred to clean water. Lastly, significant mortality occurred in coho even when roadway runoff was diluted by 95% in clean water. Our findings extend the urban runoff mortality syndrome in salmonids and point to a near-term need for sublethal studies in steelhead and Chinook to more precisely understand stormwater risks to threatened species recovery efforts in the western United States.

Distribution of fine neurites of stomatogastric neurons of the crab Cancer borealis: evidence for a structured neuropil.

The neuropil of the stomatogastric ganglion of the crab Cancer borealis contains many neuronal processes that may be arranged either at random or in some form of orderly structure. In this study, we provide evidence for two types of order in the neuropil, a segregation of the processes based on their size and a cell-specific distribution to the fine neurites. Identified neurons were injected with Lucifer yellow, fixed, and imaged as whole mounts with a confocal microscope. Four cell types were analyzed using the serial images, two pyloric neurons, one mixed pyloric/gastric neuron, and one gastric neuron. All of the neurons consisted of a approximately 60-microns-diameter soma, a approximately 20-microns-diameter primary neurite projecting into the center of the neuropil, a number of < 10-microns-diameter medium-sized neurites radiating away from the center, and many < 3-microns-diameter fine neurites around the periphery of the neuropil. The neuropil can, therefore, be divided into three layers, a central core containing the largest neurites, an intermediate region containing both medium-sized and fine neurites, and a peripheral neuropil containing mostly fine neurites. The distribution of the fine neurites was mapped using a three-dimensional grid. We found that the fine neurites were distributed not at random within the neuropil but in consistent, cell-specific patterns.

Organization of the stomatogastric neuropil of the crab, Cancer borealis, as revealed by modulator immunocytochemistry.

We used antibodies to a number of neuromodulatory substances, including serotonin, FLRF amide, red pigment-concentrating hormone, substance P, proctolin and cholecystokinin, to investigate the distribution of molecules similar to these substances in the stomatogastric ganglion of the crab, Cancer borealis. No immunoreactivity was seen in the region of the cell bodies that surrounds the neuropil and little was found in the core of the neuropil (where the primary neurites of the intrinsic neurons occupy most of the space). Instead, modulator immunolabel was densely packed in the more peripheral portion of the neuropil that surrounded the core. Within this peripheral neuropil, profiles appeared quite uniformly distributed. Double-labeling showed that there were limited differences in distribution between the labels examined in our study. The only immunolabeled structures that showed a distinct differential distribution within the stomatogastric neuropil were a population of >/=10 microm varicosities that arose from a pair of input fibers that we termed the large varicosity fibers. These varicosities were immunolabelled by antisera for three different peptides. Taken collectively, these data shows that there is a stereotyped distribution of modulator immunoreactivity within the crab stomatogastric neuropil. However, this segregation is more rudimentary than that reported for the intrinsic stomatogastric neurons.