Functional traits driving species role in the structure of terrestrial vertebrate scavenger networks

Species assemblages often have a non-random nested organization, which in vertebrate scavenger (carrion-consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the "role" of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species "normalized degree"), and the role of that species in the nested structure of the assemblage (i.e., the species "paired nested degree"), therefore identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages.

Effect of Lidocaine on Olfactory Perception in Humans

Objective:

The effect of local anesthesia to the nasal mucosa on olfactory acuity is the subject of some debate. This study was aimed to investigate the effect of local anesthesia on olfactory perception.

Materials and Methods:

Six healthy participants, five males and one female, were chosen from the academic population of Cardiff University. Olfactory perception was monitored at intervals following administration of 4% lidocaine to the nasal mucosa in the volunteers. Lidocaine was administered using a nasal spray as used in routine otolaryngological investigations. The olfactory stimulus (amyl acetate) was delivered directly to the nostril using an olfactometer. Olfactory perception was determined by the use of a 13 trial, forced choice scoring task.

Results:

Lidocaine caused a small, transient reduction in olfactory perception. The maximum reduction in olfactory perception (35%) was achieved by 60 mg lidocaine 15 min following administration, but perception could be increased to almost normal levels by increasing the odor stimulus dose. Detection of the lowest stimulus strength returned to normal levels after 30 min.

Conclusions:

Intranasal application of lidocaine, caused a reduction in olfactory perception, however, did not abolish the olfactory function 15 min following administration. Physiological/psychometric olfactory testing would not be precluded under these circumstances, and the effects of anesthesia could be overcome by increasing the stimulus strength.

Gyrodactylus salmonis infection impairs the olfactory system of rainbow trout

Monogenean worms are ectoparasites that are known to be infectious to a wide variety of fish. Few species of monogenean parasites have been reported in the olfactory chamber of fish in current peer-reviewed literature. However, the impacts of these parasites on the olfactory system are not well understood. In this study, the effects of Gyrodactylus salmonis on the olfactory system structure and performance were investigated in rainbow trout (Oncorhynchus mykiss). The olfactory performance of the infected fish was examined using an electro-olfactography (EOG) technique, while the ultrastructure of the olfactory rosette was studied using scanning electron microscopy (SEM) and light microscopy (LM). The infected rainbow trout displayed reduced responses to two standard olfactory cues (L-alanine and TCA). The SEM micrographs revealed that many regions of the olfactory epithelium in the infected fish were heavily pitted and the LM examination of the olfactory epithelium showed local proliferation of mucous cells in the sensory regions as compared to the control group. The results of this study demonstrated that G. salmonis causes physical damage to the olfactory system of fish that lead to olfactory impairment.