Small Puddles Research Articles

ESTIMATES OF POPULATION SIZE AND SURVIVAL OF IMMATURE STAGES OF FOUR SPECIES OF AEDES (DIPTERA: CULICIDAE) IN A TEMPORARY POND

AbstractA temporary pond close to Calgary, Alberta, was studied for 2 years. In the spring of the first year (1974) the pond filled with water to a much higher level than normal and it did not dry and reflood until August. The first flooding hatched eggs of Aedes euedes, A. cataphylla, A. excrucians, A. fitchii, A. flavescens, and A. mercurator; the second flooding hatched eggs of A. vexans and A. cinereus. Estimates of larval population size were made for the latter two species and little larval mortality occurred until the pond was reduced to a few small puddles, when larvae became stranded. The pond dried completely before the pupal stage was attained. Fifty per cent of surviving A. vexans larvae attained instar II in 3.7 days, instar III in 6.6 days, and instar IV in 10.3 days. A. cinereus developed more slowly.In the second year (1975) the pond contained water from the middle of April to the beginning of June, and did not refill in the summer. Estimates of larval population sizes were made for A. euedes and A. mercurator. These larvae shared a preference for the deeper water in the centre of the pond. Their numbers declined at rates of 9% per day for A. euedes and 7% per day for A. mercurator. Larvae in the second instar survived a period of 3 days when the water surface was covered with ice and snow, but A. euedes experienced a sharp drop in numbers at this time.Fifty-three per cent of the eggs of A. vexans survived a period of 1 year in areas not flooded with water at appropriate temperatures for hatching.

Tadpoles, Predation and Pond Habitats in the Tropics

Tadpoles involved in predator-prey interactions were studied in tropical wet forest in Costa Rica under laboratory and field conditions. Larvae of the frog Leptodactylus pentadactylas and naiads of the odonate Pantala flavescens are important predators on larvae of several species of frogs. The predators discriminate the prey on the basis of size and species, but not type of habitat in which predation occurs. A graphical model is proposed to illustrate the relationships between species diversity and habitat complexity as they affect the composition of tadpole communities. The model is used to evaluate the relative importance of abiotic and biotic factors in determining the use of specific kinds of aquatic habitats by frogs with larval stages. Predation by permanent aquatic predators (primarily fish) is considered to be the most important biotic factor influencing the temporal and spatial composition of tadpole communities. The development and maintenance of predatory feeding modes, including cannibalism, in certain tadpoles is examined in light of the model. MOST TADPOLES are generalized herbivores (Jenssen 1967) that either scrape plant material from a substrate or filter planktonic food directly from the water. Only a few species are known to be carnivorous although some instances of cannibalism among tadpoles have been reported (Bragg 1964). We were surprised, therefore, to find a well-developed predator-prey system in which tadpoles of one species were carnivores on other tadpoles. This finding was unusual not only because documented instances of tadpoles feeding on other tadpoles are relatively rare, but also because the carnivorous tadpoles were found in relatively small puddles. The predator-prey interactions studied occur in small rain-filled tropical puddles characteristically utilized by opportunistic breeders. Experiments were run to study the relative ability of predators to capture prey and their preference for certain prey species, to ascertain the influence of microhabitat on predator-prey interactions, and to evaluate the influence of prey size on their ability to escape predation. Results of these experiments led to a consideration of tadpole habitats and to those factors controlling the diversity of tadpole communities. A model is used to illustrate the relationship between pond complexity and predation as they affect the species composition of a tadpole community. The predatory feeding mode of tadpoles is considered in light of this model.

Surfactants in Water Drown Honey Bees 123

Apis mellifera L. drowned in water containing as little as 25 ppmv of Multi-Film X-77®, and higher concentrations (100 ppmv and above) caused very heavy losses. Yet X-77 and 6 other surfactants (Brij® 30, Brij® 92, dimethyl sulfoxide, Span® 20, Tween® 20, and XF-1-3655 (nonionic water soluble silicone-glycol copolymer)) were relatively nontoxic to the bees as stomach poisons. Drowning occurred when the X-77 water was supplied in plastic buckets, dirt ponds, and cement ditches. The bees preferred water without X-77 to water containing X-77 by more than a 10 to 1 margin when given a free choice on drip boards or in cement ponds. X-77 retained sufficient activity to drown bees in cement ponds for more than 60 days after it was added at 500 ppmv to the water. During hot weather in June, July, and August, 1971, caged colonies with X-77 added to their water supply quickly ceased rearing brood, and all unsealed larvae died and some of the colonies died. Yet colonies receiving the same treatment during cooler weather did not suffer any observable damage although there was a continuous and heavy loss of water carriers. Surfactants in small ponds, puddles, or irrigation ditches could cause bee losses. Given free choice, bees preferred water without X-77, but collected large quantities of water containing surfactant when confined to cages or when in apiaries with no other water source available.

Water-retention characteristics of coarse rock particles

Water is retained on large particles of non-porous rock as a film of water about 0.1 mm thick on rock surfaces, as 0.006 to 0.180 ml droplets held at contact points between adjacent particles, and as small puddles of water on the upper surfaces of the rock. Water retained at contact points accounts for most of the water stored within aggregates of particles with diameters smaller than 30 mm. Whereas with diameters larger than 100 mm, water retained on the rock surfaces, particularly water puddled on top of the rock, accounts for most of the water. Infiltrating water will not wet all the rock surfaces. More than 50% of the surfaces may be dry at depth. The total amount of rainfall needed to initiate ground-water recharge in many areas having coarse rock particles at the surface is probably less than 1.0 cm.

Aspects of Osmotic Regulation in Crabs Showing the Terrestrial Habit

1. Terrestrial and semi-terrestrial crabs generally demonstrate the ability to regulate osmotically in dilute and concentrated sea water. 2. Osmotic regulation in terrestrial and semi-terrestrial crabs is not adaptive for aquatic life since osmotic stresses such as dilute and concentrated sea water are rarely experienced by these animals. Besides many such animals drown when completely immersed. 3. The branchial chamber of Pachygrapsus contains a volume of fluid equal to a maximum of about 3 per cent of the body volume. Thus, regulation against branchial fluid made concentrated by evaporation would not be adaptive as proposed by Jones because the total salt therein could not elevate the blood concentration above concentrations normally experienced in nature. 4. The respiratory rate of Pachygrapsus decreases when the crab is desiccated. This explains why the terrestrial behavior of Pachygrapsus is limited to brief periods. 5. Pachygrapsus can absorb water against a gradient when it has been desiccated. 6. The ability to regulate in concentrated sea water (hypo-osmotic regulation) is believed to be a manifestation of a mechanism for the conservation of water, namely, elimination of salts. 7. The mechanism involved in hyper-osmotic regulation seems to be necessary to the mechanism of hypo-osmotic regulation but apparently has no adaptive consequence such as salt elimination. 8. The coconut crab, Birgus latro, shows special adaptations to terrestrial life. a. It can drink water from small puddles. b. It can keep its respiratory membranes moist by placing water into the gill chamber without becoming immersed. c. It can control the concentration of its body fluids by selecting water of the appropriate salinity.

Small Puddles

Small Puddles