Evidence for infection influencing survival of the freshwater copepod Salmincola californiensis, a parasite of Pacific salmon and trout.

OBJECTIVE: We explore apparent infection of Salmincola californiensis arising during investigations involving this lernaeopodid copepod parasitic on Pacific salmon and trout Oncorhynchus spp. METHODS: We noted occasional unusual coloration of adult female copepods collected from the wild. These females were bright blue and pink in contrast to the cream white coloration characteristic of the copepod. We also observed that similar color patterns developed under laboratory settings when copepod eggs were held for hatching. In paired egg cases, we found consistent hatching failure of blue and pink eggs and patterns in apparent disease development that would be consistent with both vertical and horizontal transmission. RESULT: Attempts to identify the cause of the apparent infection using genetic methods and transmission electron microscopy were inconclusive. CONCLUSION: Iridovirus infection was initially suspected, but bacterial infection is also plausible. This apparent reduced hatching success of S. californiensis warrants further exploration as it could reduce local abundances. Given the potential importance of a disease impacting this copepod, a parasite that itself affects endangered and commercially important Pacific salmon and trout, future research would benefit from clarification of the apparent infection through additional sequencing, primer development, visualization, and exploration into specificity and transmission.

Laboratory infection rates and associated mortality of juvenile Chinook Salmon (Oncorhynchus tshawytscha) from parasitic copepod (Salmincola californiensis).

Pacific salmon (Oncorhynchus spp.) rearing in lakes and reservoirs above dams have been known to become heavily infected with an ectoparasitic copepod (Salmincola californiensis). Little is known about the factors that affect the parasite infection prevalence and intensity. However, previous research suggests that the parasite may negatively affect the fitness and survival of the host fish. The effect of water temperature, confinement and the density of the free-swimming infectious stage of S. californiensis, the copepodid, on infection prevalence and intensity was evaluated by experimentally exposing juvenile Chinook Salmon (O. tshawytscha). Infection rates observed in wild populations were achieved under warm water (15-16°C) and high copepodid density (150-300/L) treatment conditions. Infection prevalence and intensity were also significantly higher in larger fish. During the infection experiment, 4.5% of infected fish died within 54 days with mortality significantly related to copepod infection intensity. The potential for autoinfection was compared to cross-infection by cohabitation of infected fish with naïve fish. Previously infected fish had significantly greater infection intensity compared with naïve fish, indicating that infected fish can be reinfected and that they may be more susceptible than naïve fish.

Template-directed self-assembly by way of molecular recognition at the micellar-solvent interface: modulation of the critical micelle concentration.

By incorporating the concepts of structural preorganisation and complementarity in concert with non-covalent donor-acceptor [ππ] and hydrophobic interactions, a duo of π-electron deficient bipyridinium-based linear and gemini amphiphiles capable of responding to molecular templation have been designed and synthesised. When combined with π-electron rich di(ethylene glycol)-disubstituted 1,5-dihydroxynaphthalene, a dramatic decrease in the critical aggregation concentration by ≈66% was observed with concomitant increases in the hydrodynamic diameter, ζ-potential, and Langmuir surface pressures of the micellar solutions-thus enhancing the detergents' efficiency and effectiveness at lowering the surface tension of water. By employing a phase separation model that takes into account the degree of counterion binding to the micellar aggregate superstructure, the effects of donor-acceptor templation on the Gibb's free energy of micellisation (ΔG) for the amphiphiles was quantified. It was found that donor-acceptor templation was capable of lowering ΔG by up to 1.75 kcal mol(-1) at which point it was observed, while under the influence of molecular templation, that linear single hydrophobic tailed detergent molecules exhibit properties characteristic of double-tailed phospholipid-like gemini surfactants.