During
the formation of the Hawaiian islands, lava flows created caves, cracks,
gas pockets and smaller, interconnected subterranean spaces. Subterranean
faunas have been known to be a part of temperate continental cave systems,
but obligate cave inhabiting animals were long thought to be absent from
tropical and island systems. However, in 1971, two remarkable, eyeless
cave arthropods, a spider and amphipod,
were discovered in caves on Kauai. The Kauai cave wolf spider (Adelocosa
anops), and the Kauai cave amphipod (Spelaeorchestia koloana)
are known only from a single exposed lava flow that covers approximately
4 square miles on the southern coast of Kauai. In 1995, a third
endemic species, an as yet unclassified species of isopod,
was documented in the Kauai caves. These endemic species are critical
components of the cave ecosystems and are possibly the last representatives
of what was once a more diverse and populous cave community. The
cave spider and the amphipod were listed as endangered
species on January 14, 2000. The amphipod and isopod are
detritivores who feed primarily on rotting
tree roots that penetrate the cave roofs whereas the spider is a carnivore
and preys upon the amphipod and alien arthropods that venture underground.
The
only source of water is rain or irrigation water that percolates in from
above. The Kauai caves have low populations and a limited species
diversity. The extinction of any one of the remaining endemics could
have disastrous effects on the cave ecosystem. One of the most biologically
diverse of the five known Kauai caves is located directly under the fairway
of the Kiahuna Golf Course. Over 30 different pesticides are commonly
used on golf courses in Hawaii, including insecticides to control turf
grass pests. The Kiahuna Golf Course declined to specify the pesticides
they use. Methods: This study chose to focus on organophosphates and carbamates because these classes of chemicals account for a large percentage of the pesticides used on golf courses and their immediate physiological effects on arthropods can be quantified. Organophosphates and carbamates exert their toxicity by suppressing the production of the cholinesterase enzymes necessary for the breakdown of the neurotransmitter acetylcholine and the normal functioning of the peripheral and central nervous systems. The cave arthropods were feared to be at risk for several reasons: 1) The populations of endemic arthropods are very low; 2) These animals exist in a highly restricted habitat from a single lava flow. 3) The porous soil and caves may cause direct run-off into them from the golf course; 4) The absence of light in the caves prolongs the time required for the breakdown of pesticides; 5) Insecticides are designed to be highly toxic to arthropods; 6) The tendency of these cave animals to seek water can make them particularly susceptible to pesticides.
The objectives of this study were to 1) Determine the presence or absence of a contaminant pathway into the caves by comparing organophosphate and carbamate concentrations in cave soils and in the water entering the golf course and control caves; 2) Extrapolate the presence or absence of exposure and physiological effects on endemic cave arthropods, caused by carbamate and organophosphate pesticides, by comparing cholinesterase inhibition levels in alien arthropods living in the golf course and control caves; and 3)Use study data to determine the need for altering pest management practices at the golf course and specify pesticides of concern. Water, soil and cockroach samples were collected from the caves three times during 1998. Water and soil analysis was contracted to the University of Hawaii's Department of Environmental Biochemistry, and the cockroach samples were analyzed by the Hawaii Institute of Marine Biology.
Results: The chemical analysis of soil and water samples taken in the cave did not indicate that carbamate or organophosphate pesticides were penetrating the cave. Likewise, the lack of cholinesterase inhibition in the cave cockroaches indicated that there was not a complete pathway for these pesticides from the golf course to the endemic cave arthropods.
Discussion
and Recommendations: Several
observations over time indicate that the highest population of spiders
and amphipods occurred when water and organic matter (food) was recently
introduced into the caves. Possibly, the lack of sufficient food,
water, and the presence of alien predators in the caves, spiders and
roaches, may be a limiting factor.
Since this study was completed, Kiahuna Golf Course has agreed to plant
deep-rooting vegetation over the entire length of the cave (replacing
the golf course fairway) and will also maintain the currently posted
signs prohibiting entrance to the cave. This will greatly decrease
the risk of pesticides and fertilizers dripping into the cave, in addition
to providing a much needed food source in the form of roots growing
through the cave roof. The USFWS hopes to obtain similar conservation
agreements for the area around the control caves, which the golf course
intends to develop in the near future.
Lava tube ecosystems are present in several other coastal areas
of the State, particularly on the islands of Hawaii and Maui.
These ecosystems contain many rare, cave-adapted arthropods and are
subject to nonpoint source pollution of the water that percolates down
to the caves from residential areas, golf courses, and other sources.
It is therefore quite likely that this type of study will need to be
repeated in these areas.
Definitions:
amphipod: Amphipod crustaceans are
peracarid crustaceans, typically ranging in size from 2 to 50 mm, although
a few may be larger. Amphipods are common in aquatic ecosystems
throughout many parts of the world, inhabiting marine, brackish, and
freshwater environments. Most amphipods are detritus feeders or
scavengers and feed by filtering water or sediment through their appendages.
A few species also live in terrestrial ecosystems. Back
to Top
arthropods: A large group of animals distinguished by having a chitinous, segmented exoskeleton (outer skeleton) and jointed appendages. Back to Top
detritivores: Plants and animals supply organic matter to the soil system through shed tissues and death. Consumer organisms that feed on this organic matter, or detritus, are known as detritivores or decomposers. The organic matter that is consumed by the detritivores is eventually converted back into inorganic nutrients in the soil. Back to Top
isopod: The isopod is a very small crustacean, measuring only 5 to 15 millimeters in length. The order of isopoda has about 4,000 different species. Also in the order of isopoda there are pill bugs and wood lice. The isopod has 19 appendages, each used for different things. Some are used for walking, some for swimming, some for antennae, and some for eye stalks. Isopods are mostly flat from the top to the bottom with a shield-like head. Isopods also have a major resemblance to a shrimp and have mostly the same anatomy. You would most likely find an isopod in or near a pond or ocean. There are two different kinds of isopods, salt water and fresh water Back to Top
Learn more by reading the following full report: Li, Q. Sakuda, K. Harada, R. and Guo, F. Analysis of WaterSamples for Low Levels of Pesticides and Analysis of Inhibition of Neurotransmitter Breakdown in Insects. Dept. of Env. Biochem. University of Hawaii 1998.
For More Information on this topic visit:
Two
Hawaiian Cave Animals Added to Endangered Species List
Kaua`i
Cave Wolf Spider and Kaua`i Cave Amphipod
The
Biology of Amphipods- Amphipod Gallery
The
Biology of Isopods - Isopod Gallery
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