Effects of flash flooding on mosquito and community dynamics in experimental pools.

Pulsed disturbances of larval mosquito sites are likely to have a direct negative effect on mosquitoes but may also have indirect effects due to the alteration of community structure. These altered communities may become attractive to gravid mosquitoes searching for oviposition sites when the disturbances decrease the abundance of mosquito antagonists such as competitors, which often results in an increase in mosquito food resources. However, flash flood disturbances in intermittent riverbeds can also remove mosquito food resources such as algae, so that the net effect of flash floods could be either to increase or decrease mosquito abundance. We conducted an outdoor mesocosm experiment to assess the effects of flash floods on mosquito oviposition habitat selection and larval abundance during the post-disturbance period of community recovery. Mesocosms were artificially flooded. Mosquito oviposition, immature abundance, invertebrate species diversity, chlorophyll a, and abiotic parameters were monitored. Our results showed that the flash flood negatively affected phytoplankton and zooplankton, leading to a decrease of mosquito oviposition in flooded mesocosms compared to non-flooded mesocosms. More broadly, this study indicates how disturbances influence mosquito oviposition habitat selection due to the loss of food resources in ephemeral pools, and it highlights the importance of considering the effects of disturbances in management, habitat restoration, and biodiversity conservation in temporary aquatic habitats.

Parallel habitat acclimatization is realized by the expression of different genes in two closely related salamander species (genus Salamandra).

The utilization of similar habitats by different species provides an ideal opportunity to identify genes underlying adaptation and acclimatization. Here, we analysed the gene expression of two closely related salamander species: Salamandra salamandra in Central Europe and Salamandra infraimmaculata in the Near East. These species inhabit similar habitat types: 'temporary ponds' and 'permanent streams' during larval development. We developed two species-specific gene expression microarrays, each targeting over 12 000 transcripts, including an overlapping subset of 8331 orthologues. Gene expression was examined for systematic differences between temporary ponds and permanent streams in larvae from both salamander species to establish gene sets and functions associated with these two habitat types. Only 20 orthologues were associated with a habitat in both species, but these orthologues did not show parallel expression patterns across species more than expected by chance. Functional annotation of a set of 106 genes with the highest effect size for a habitat suggested four putative gene function categories associated with a habitat in both species: cell proliferation, neural development, oxygen responses and muscle capacity. Among these high effect size genes was a single orthologue (14-3-3 protein zeta/YWHAZ) that was downregulated in temporary ponds in both species. The emergence of four gene function categories combined with a lack of parallel expression of orthologues (except 14-3-3 protein zeta) suggests that parallel habitat adaptation or acclimatization by larvae from S. salamandra and S. infraimmaculata to temporary ponds and permanent streams is mainly realized by different genes with a converging functionality.

Influence of nymphal Anax imperator (Odonata: Aeshnidae) on oviposition by the mosquito Culiseta longiareolata (Diptera: Culicidae) and community structure in temporary pools.

We assessed the overall (consumptive plus non-consumptive) and non-consumptive effects of nymphal Anax imperator (Aeshnidae: Odonata) on experimental pool communities by comparing three treatments: (1) control (no Anax); (2) free Anax (Anax was not constrained); and (3) caged Anax (Anax, enclosed within a cage, could not consume prey outside the cages, but could possibly influence them via perceived risk of predation). Fewer egg rafts of the mosquito Culiseta longiareolata were found in the free Anax treatment compared to the other two treatments. There was no statistically significant difference in the number of egg rafts between control and caged Anax pools. Thus, while Culiseta females apparently oviposit fewer egg rafts in the presence of unconstrained Anax, they did not respond to predation risk from the caged Anax. Larval Culiseta densities were drastically reduced by free Anax; there was nearly a 100% reduction in the number reaching metamorphosis (pupae) and a 100% reduction in emergence (pupal exuviae). There were no significant treatment effects on densities of crustaceans, Daphnia magna and Heterocypris sp., or on chironomid pupal exuviae. Ceratopogonid pupal abundance was higher in free Anax pools than in the other two treatments toward the end of the experiment. Free Anax caused a trophic cascade, presumably by strongly reducing the dominant periphyton grazer, Culiseta larvae; periphyton mass was greater in the free Anax treatment than in the control. However, there was no behavioral trophic cascade, i.e., no difference in periphyton abundance between the control and caged Anax treatment.

A new coccidian from Acomys cahirinus Desmarest, 1819, from Evolution Canyon, Lower Nahal Oren, Mount Carmel, Israel.

In 1994, fresh fecal samples were collected and examined for coccidian parasites from 43 spiny mice (Acomys cahirinus) and from 60 wood mice (Apodemus mystacinus). The 2 genera of rodents inhabit an area in Lower Nahal Oren. Mount Carmel, Israel, known as Evolution Canyon, which consists of opposite-facing slopes that are geologically identical, but micro-climatically very different. Acomys cahirinus is found primarily on the warmer and drier south-facing slope (SFS), whereas A. mystacinus primarily inhabits the cooler and wetter north-facing slope (NFS). None of the samples from the A. mystacinus contained coccidia, but 6 of 43 (14%) A. cahirinus individuals were discharging eimerian oocysts that we describe herein as a new species. Five of the 6 positive samples were from the SFS. Sporulated oocysts are ovoidal to subspheroidal, 26.5 x 22.9 (21-29 x 19-26) microns, without a micropyle, but with an oocyst residuum of 1 to several large clear globules and a medium-sized refractile polar body; they contain lemon-shaped sporocysts, 10.4 x 8.1 (10 11 x 7-10) microns, with a sporocyst residuum and Stieda body, but no sub-/or parastieda body. Sporozoites lie side by side, completely filling oocysts; each contains a large posterior refractile body.

Predation by a cyprinodontid fish, Aphanius mento, on Culex pipiens: effects of alternative prey and vegetation.

We assessed the effects of an alternative prey species (Daphnia magna) and a submergent plant (Ceratophyllum demersum) on the efficiency of the fish, Aphanius mento, to prey on mosquito (Culex pipiens) larvae in the laboratory. Aphanius mento is an untested biological control candidate of mosquitoes. When D. magna was introduced with equal numbers of Cx. pipiens larvae, there was a 50.7% reduction in predation by A. mento on the mosquito larvae. However, the more D. magna a fish ate, the more Cx. pipiens it consumed. Ceratophyllum demersum did not affect predation rates on Cx. pipiens larvae.

Effects of various factors on the efficiency of minnow traps to sample mosquitofish (Gambusia affinis) and green sunfish (Lepomis cyanellus) populations.

The effects of various factors on the efficiency of the Gee minnow trap to sample populations of mosquitofish, Gambusia affinis, in both rice field enclosures and a laboratory tank were assessed. Immature green sunfish, Lepomis cyanellus, were assessed in the laboratory tank only. Trap efficiency (percent catch) was greater for larger mosquitofish [greater than or equal to 35 mm total length (TL)] than for smaller mosquitofish. Immature green sunfish (25-40 mm TL) were caught at higher rates than either size class of mosquitofish. In the laboratory, trap efficiency increased with increasing mosquitofish density, but density had no effect in field enclosures. Vegetation did not affect trap efficiency. Minnow traps, lying on the substrate, caught a similar percent of available mosquitofish when water depths were 8 and 16 cm but a significantly smaller percent when 24 cm. In contrast, green sunfish, assessed at 8 and 24 cm, were trapped at a higher rate at 24 cm. These results demonstrate the importance of determining the effects of environmental factors on trap efficiency before using direct trap counts to assess effects of these factors on fish abundance.