Behavioral and physiological adaptations to high-flow velocities in chubs (Gila spp.) native to Southwestern USA.

Morphological streamlining is often associated with physiological advantages for steady swimming in fishes. Though most commonly studied in pelagic fishes, streamlining also occurs in fishes that occupy high-flow environments. Before the installation of dams and water diversions, bonytail (Cyprinidae, Gila elegans), a fish endemic to the Colorado River (USA), regularly experienced massive, seasonal flooding events. Individuals of G. elegans display morphological characteristics that may facilitate swimming in high-flow conditions, including a narrow caudal peduncle and a high aspect ratio caudal fin. We tested the hypothesis that these features improve sustained swimming performance in bonytail by comparing locomotor performance in G. elegans with that of the closely related roundtail chub (Gila robusta) and two non-native species, rainbow trout (Oncorhynchus mykiss) and smallmouth bass (Micropterus dolomieu), using a Brett-style respirometer and locomotor step-tests. Gila elegans had the lowest estimated drag coefficient and the highest sustained swimming speeds relative to the other three species. There were no detectible differences in locomotor energetics during steady swimming among the four species. When challenged by high-velocity water flows, the second native species examined in this study, G. robusta, exploited the boundary effects in the flow tank by pitching forward and bracing the pelvic and pectoral fins against the acrylic tank bottom to 'hold station'. Because G. robusta can station hold to prevent being swept downstream during high flows and G. elegans can maintain swimming speeds greater than those of smallmouth bass and rainbow trout with comparable metabolic costs, we suggest that management agencies could use artificial flooding events to wash non-native competitors downstream and out of the Colorado River habitat.

When outgroups fail; phylogenomics of rooting the emerging pathogen, Coxiella burnetii.

Rooting phylogenies is critical for understanding evolution, yet the importance, intricacies and difficulties of rooting are often overlooked. For rooting, polymorphic characters among the group of interest (ingroup) must be compared to those of a relative (outgroup) that diverged before the last common ancestor (LCA) of the ingroup. Problems arise if an outgroup does not exist, is unknown, or is so distant that few characters are shared, in which case duplicated genes originating before the LCA can be used as proxy outgroups to root diverse phylogenies. Here, we describe a genome-wide expansion of this technique that can be used to solve problems at the other end of the evolutionary scale: where ingroup individuals are all very closely related to each other, but the next closest relative is very distant. We used shared orthologous single nucleotide polymorphisms (SNPs) from 10 whole genome sequences of Coxiella burnetii, the causative agent of Q fever in humans, to create a robust, but unrooted phylogeny. To maximize the number of characters informative about the rooting, we searched entire genomes for polymorphic duplicated regions where orthologs of each paralog could be identified so that the paralogs could be used to root the tree. Recent radiations, such as those of emerging pathogens, often pose rooting challenges due to a lack of ingroup variation and large genomic differences with known outgroups. Using a phylogenomic approach, we created a robust, rooted phylogeny for C. burnetii. [Coxiella burnetii; paralog SNPs; pathogen evolution; phylogeny; recent radiation; root; rooting using duplicated genes.].

Botulinum toxin injections as a method for chemically denervating skeletal muscle to test functional hypotheses: a pilot study in Lepomis cyanellus.

In this study, we demonstrate that botulinum toxin can be used to chemically denervate muscles to test functional hypotheses. We injected research-grade type A botulinum toxin complex into pectoral fin abductors (abductor superficialis) of green sunfish (Lepomis cyanellus) to determine whether chemical denervation would eliminate the ability of a particular muscle to contribute to overall pectoral fin movements. Reduction of target muscle activity occurred within 8 d of the injection, and paralysis was confirmed using electromyography. No paralysis was seen in the adjacent muscles (abductor profundus) or in positive controls (saline injections). Paralysis occurred more slowly and at lower doses than previously documented for mammals. However, botulinum toxin complex (500 kDa) was used here, whereas previous studies have used purified toxin (150 kDa). Therefore, differences in physiological responses between fish and mammals cannot yet be distinguished from differences caused by the toxin type. However, we note that the toxin complex is less likely to diffuse across muscle fascia (because it is large), which should minimize paralytic effects on adjacent muscles. We suggest that botulinum toxin holds great promise as a chemical denervation agent in functional studies of animal locomotion and feeding behaviors.

Does feeding behavior facilitate trophic niche partitioning in two sympatric sucker species from the American Southwest?

We examined two sympatric desert fishes, Sonora suckers (Catostomus insignis) and desert suckers (Pantosteus clarkii), and asked, does feeding behavior facilitate trophic niche partitioning? To answer this question, we conducted laboratory-based feeding trials to determine whether morphology alone facilitates the diet separation between the relatively unspecialized, omnivorous Sonora sucker and the more morphologically specialized, algivorous desert sucker or whether behavioral differences accompany morphological specialization. We predicted that (1) algivorous desert suckers would maximize contact between jaws and substrate and produce a large mouth-gape to facilitate scraping attached food-material; (2) omnivorous Sonora suckers would be more effective suction feeders when consuming unattached food items from the benthos; and (3) because they are anatomically specialized for scraping, desert suckers could not alter their feeding behavior when presented with different prey types, whereas relatively unspecialized Sonora suckers could vary behavior with prey type. We found that both species maximized jaw contact when feeding on benthic-attached food, although desert suckers produced a greater gape area. We also found that Sonora suckers were more effective suction feeders when feeding on benthic-unattached prey. Counter to our initial predictions, both species altered key aspects of feeding behavior in response to different prey types/locations. It appears that both sucker species can function as generalist feeders to exploit a variety of prey types within their natural habitat; indeed, this behavioral versatility may allow desert and Sonora suckers to respond to the cyclic environmental changes that are characteristic of the aquatic habitats of the American Southwest.