Summer distribution patterns of the backswimmer,Anisops wakefieldi(Hemiptera: Notonectidae), in a New Zealand pond

Abstract

The relative abundance of different-sized Anisops wakefieldi in a small, fishless pond was determined from sweep-net samples taken along one open-water and two shoreline transects at noon on two dates, and at noon and midnight on a third date. During the day, large individuals occurred only along the shore, whereas smaller ones occurred both along the shore and in open water. At night, large individuals also occurred in the open water. The diurnal size-class segregation suggests that young individuals migrate into less preferred, open water to avoid interference and cannibalism from larger individuals. The shoreline may be preferred during the day because it provides greater food resources or a refuge from visually feeding avian predators. Laboratory experiments in containers with floating aquatic plants at one end complemented the field data. When alone, both small and large A. wakefieldi sought cover during the day and moved into open water at night. During the day, the presence of large † Corresponding author. Received 22 January 1999; accepted 4 June 1999 individuals induced small ones to move into open water. The results of this study on a notonectid population are consistent with some earlier ones in demonstrating that interactions between large and small size classes may lead to pronounced spatial segregation of size classes, and show for the first time that spatial distributional patterns during the day and night may be very different. M99003

Habitat overlap of enemies: temporal patterns and the role of spatial complexity

“…1, 2). Similar nocturnal horizontal migrations are known to occur regularly in Johnson Pond (S. Hampton and I. Duggan, unpublished) and have been reported for the southern hemisphere notonectid Anisops (Gilbert et al 1999). Although habitat expansion by Notonecta enhanced total predation pressure on Buenoa slightly (Fig.…”

“…Accordingly, Strohmeier et al (1989) reported that effects of red-striped newts on macroinvertebrate populations in enclosures were weak and inconsistent. Gilbert et al (1999) have proposed that predation by birds might drive nocturnal horizontal migration of the notonectid Anisops. Although mallard ducks reside in Johnson Pond and are known to include littoral macroinvertebrates in their diets (McNeil et al 1995;Cox et al 1998), little is known of avian impacts on aquatic invertebrate communities.…”

Aquatic Hemiptera community structure in stormwater retention ponds: a watershed land cover approach

“…We chose to focus on fully aquatic hemipterans because they are widespread insects capable of colonizing nearly all types of aquatic habitats, and are often one of the first successional stages in newly created water bodies, such as artificial ponds (Papacek, 2001). Both herbivorous (most Corixidae) and carnivorous (Notonectidae, Belostomatidae, Nepidae, Pleidae), these bugs have considerable influence on aquatic food webs, feeding on zooplankton, insects, and small vertebrates, and serving as prey for large insects and fish (e.g., Murdoch et al, 1984;Hickley et al, 1994;Blaustein, 1998;Gilbert & Burns, 1999;Hampton et al, 2000). Additionally, the economic importance of at least three of these families as biological control agents of disease-carrying mosquitos is well established (Nam et al, 2000;Saha et al, 2007, reviewed in Papacek, 2001.…”

Gas exchange and dive characteristics of the free-swimming backswimmer Anisops deanei

“…Two setups were run simultaneously alongside one another, because backswimmers aggregate naturally in groups and a pilot study found that pairs undertake longer dives than solitary individuals (Miller, 1966b;Bailey, 1987;Gilbert et al, 1999). Each dive chamber contained 850 ml of reverse osmosis water and 75 ml of gas space.…”