Review of a New Pest of Rice, Tadpole Shrimp (Notostraca

Review of a New Pest of Rice, Tadpole Shrimp (Notostraca: Triopsidae), in the Midsouthern
United States and a Winter Scouting Method of Rice Fields for Preplanting Detection
Kelly V. Tindall1,2 and Kent Fothergill2
1
2
University of Missouri, Division of Plant Sciences, P.O. Box 160, Portageville, MO 63873.
Corresponding author: Kelly V. Tindall, Conservation Seeding and Restoration, Inc., 506 Center St. West, Kimberly, ID 83341 (e-mail: [email protected]).
J. Integ. Pest Mngmt. 3(3): 2012; DOI: http://dx.doi.org/10.1603/IPM12001
ABSTRACT. Tadpole shrimp, Triops longicaudatus (LeConte), are a species of temporary, freshwater habitats. Tadpole shrimp are pests
of rice production systems in California and have recently been found impacting Missouri rice fields and present in northeastern Arkansas
rice fields. These impacts take the form of stand reduction by direct feeding on seedlings and uprooting seedlings during foraging. In
addition, their foraging behavior causes water to become muddy, which reduces light penetration to submerged seedlings and consequently delays the development of the rice plant. Once rice is past the seedling stage, tadpole shrimp may be beneficial. This article
provides information on the life cycle of tadpole shrimp, describes a new method for scouting for tadpole shrimp in rice fields, and
provides scouting results and management implications.
Tadpole shrimp, Triops longicaudatus (LeConte) (Branchiopoda: Notostraca: Triopsidae) (Fig. 1), are a species of temporary, freshwater
habitats (Longhurst 1955). Puddles and temporary pools are ideal
environments for tadpole shrimp. When considering production of
rice, a rice field is flooded and drained, sometimes several times in a
season, which mimics the environment of a temporary pond. Therefore, a rice field is an ideal environment for tadpole shrimp because
they are pests of water-seeded rice production systems in California
(Godfrey and Espino 2009) and recently were found in rice fields in
the midsouthern United States (Tindall et al. 2009). This article
provides information on the life cycle of the tadpole shrimp, describes
a new method of scouting for tadpole shrimp in rice fields, and
provides scouting results and management implications.
Life History
Distribution. Tadpole shrimp live in freshwater, temporary ponds
from Central and South America north to 50° latitude in western North
America (Longhurst 1955). In North America, tadpole shrimp were
considered a western species until their eastward range expansion into
Oklahoma, Missouri, and Illinois (Taylor et al. 1987, Tindall et al.
2009, Ridings et al. 2011). It is unknown how tadpole shrimp dispersed east, but dispersal can occur via floodwaters (Taylor et al.
1987); wind (Cáceres and Soluk 2002, Nathan et al. 2005, Graham and
Wirth 2008); birds (Green and Figuerola 2005); and pet trade (Halliday 2008) (Fig. 2).
Biology of Tadpole Shrimp. Tadpole shrimp display large amounts
of morphological variation and exist in populations that may or may
not contain males (Sassaman et al. 1997). Although eggs may not have
to have a period desiccation (Scott and Grigarick 1979), other research
shows that eggs need a period or multiple periods of drying before
hatching (Fry and Mulla 1992). The length of time that eggs are viable
is not known but eggs are viable for at least 34 mo (Scott and
Grigarick 1979). If their behavior is similar to a related species, the
brine shrimp, Artemia franciscana Kellogg, tadpole shrimp eggs may
survive substantially longer because brine shrimp eggs were found to
be viable after 10,000 yr, but this is an exceptional length of time for
a resting state (Browne 1993). Immature tadpole shrimp do not all
hatch from desiccated eggs at the same time when exposed to water;
rather, the eggs laid by a single female hatch over several floodings
(Hildrew 1985, Brendonck and Persoone 1993, Simovich and Hathaway 1997).
Females have two brood pouches on the 11th segment and can
carry as many as 68 eggs per pouch. She will carry the eggs anywhere
from 19 h to several days (Scott and Grigarick 1978) before she lays
them on decaying or living plant material, algae, or in the soil
(Takahashi 1977a). Tadpole shrimp females lay an average of 81 eggs
in 24 h (Scott and Grigarick 1978) but as many as 246 eggs can be laid
in 1 d by an individual (Takahashi 1977a). A female is able to lay eggs
throughout her life after she reaches sexually maturity, although as she
ages, eggs become misshapen (Scott and Grigarick 1978).
Several factors affect the hatching of eggs, which hatch at water
temperatures ⬎61°F, but optimal hatch occurs when water temperature is 63–75°F (Scott and Grigarick 1979). Eggs do not hatch in
water that is 84°F or warmer. When exposed to saline water at a
concentration of 999 ppm, eggs are able to hatch, but not at concentrations of 2,996 ppm; however, when eggs were removed from the
high saline concentration and exposed to freshwater, eggs hatched
(Horne 1967). Although eggs hatch when the pH of water is 3.1–10.1,
the optimal pH for egg hatch is 5.6 (Scott and Grigarick 1979). The
depth of flood does not appear to affect the propensity of an egg to
hatch. However, the depth at which eggs are buried in the soil affects
their propensity to hatch; as little as 1.27 cm (0.5 in.) of soil over them
can prevent eggs from hatching (Scott and Grigarick 1979). Eggs also
require dissolved oxygen present in the water to hatch (Scott and
Grigarick 1979).
Given the appropriate conditions, eggs will hatch within 24 h after
being exposed to water (Takahashi 1977a; Scott and Grigarick 1978,
1979). After hatching, the tadpole shrimp will grow and, like other
arthropods, will molt. After their first molt, they resemble the adult.
Eventually, they will molt 10 –15 times before becoming adults and
are sexually reproductive (Scott and Grigarick 1978). A tadpole
shrimp bears a resemblance to tadpoles and possesses a mud-colored,
shovel-shaped shield over the front portion of its body and two long
tails originating from the last segment. They are ⬇1.52 cm (0.6 in.)
when they reach sexual maturity and will continue to molt after
reaching adulthood until they reach their full size of 3.8 cm (1.5 in.)
(Godfrey and Espino 2009).
Some of the factors that affect egg hatch also influence immature
and adult tadpole shrimp development. The optimal development of
tadpole shrimp occurs at 77– 86°F (Scott and Grigarick 1979). Although individuals reared at 86°F were smaller than those reared at
lower temperature, they reached sexual maturity at an earlier age
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Key Words: Triops longicaudatus, tadpole shrimp, rice scouting, integrated pest management
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JOURNAL OF INTEGRATED PEST MANAGEMENT
(Fry-O’Brien andMulla 1996). The optimal pH for immature tadpole
shrimp survival is 5.7–5.9 (Hamasaki and Ohbayashi 2000). Sexually
mature tadpole shrimp occur as early as 8 –10 d after eggs are exposed
to water (Takahashi 1977a, Scott and Grigarick 1978) and are ⬇1.52
cm (0.6 in.) or larger (Godfrey and Espino 2009). Because tadpole
shrimp have hemoglobin in their blood, they are able to survive in
water with a low concentration of dissolved oxygen (Horne 1971).
The average lifespan of tadpole shrimp after hatching from the egg is
32 d, but they can live as long as 49 d in the laboratory (Scott and
Grigarick 1978).
Young tadpole shrimp feed on diatoms and protozoa in the mud
(Longhurst 1955). Older instars have feeding behaviors similar to that
of the adults, which consume vegetative material and aquatic invertebrates (Walton et al. 1990). They are also cannibalistic (Scott and
Grigarick 1978).
Damage to Rice. To understand how and when tadpole shrimp are
a pest of rice, one must understand the different planting methodologies used in rice production in the United States. Farmers either
dry-seed or water-seed their fields when planting rice. Dry-seeding
involves drill-seeding or dry-broadcasting seed in dry soil. The field
may be flushed (an intermittent shallow flood followed by drainage)
several times to allow rice to germinate and grow in absence of rainfall
but before applying a flood. A flood is established typically around the
4 –5 leaf stage so that plants are not completely submerged at the time
of flooding (Blanche et al. 2009). Water-seeding involves planting
Fig. 2. Advertisement for the sale of tadpole shrimp.
pregerminated or dry seeds by air into a flooded field. There are three
strategies for establishing floods in water-seeded rice: delayed flood,
pinpoint flood, and continuous flood. In a delayed flood system, water
is drained from the field shortly after planting and the field is flushed
periodically (if needed) until the establishment of the flood, which
occurs several weeks after rice emerges through the soil. When the
field is flooded, plants are not typically completely submerged. In a
pinpoint flood system, the field is briefly drained so that roots can
anchor into the soil. The field is usually without water for 3–5 d before
the flood is applied and seedlings are submerged. In a continuous
flood system, the flood is not drained until rice is mature before
harvest (Blanche et al. 2009).
Water-seeded rice planted with pinpoint or continuous floods is
vulnerable to damage by tadpole shrimp because the submerged, small
seedlings do not have root systems strong enough to tolerate their
foraging behavior. Once rice plants break the surface of the flood,
plants are considered to be safe from injury by tadpole shrimp (Godfrey and Espino 2009). Tadpole shrimp hatch within 24 h after eggs
come in contact with water (Takahashi 1977a; Scott and Grigarick
1978, 1979); therefore, tadpole shrimp hatch soon after the field is
flooded. They begin to grow, feeding on microorganisms in the soil.
These young tadpole shrimp do not damage rice, but after the first
several molts, they adopt the feeding habits of the adults, and will feed
directly on the seeds and young seedlings (Scott and Grigarick 1978).
In addition, they will forage on the soil surface where their shovelshaped heads stir the soil and uproot the small seedlings (Fig. 3) This
activity muddies the water, which reduces penetration of light to
submerged seedlings (Fig. 4) (Godfrey and Espino 2009). Uprooting
seedlings reduce stand, which can reduce yield, and muddy water
reduces photosynthesis and delays maturity. Because tadpole shrimp
can reach full size within 8 –10 d (zharvTakahashi 1977a, Scott and
Grigarick 1978), rice plants have ⬍8 d to break the surface of the
flood.
The issue of stand loss can be greater depending on the variety
of rice planted and the seeding rate. Hybrid rice varieties are
planted at a lower seeding rate (20 –30 lbs/A for delayed floods)
than conventional varieties (70 –110 lbs/A for delayed floods). For
continuous and pinpoint flood systems, seeding rates are typically
higher. Low seeding rates makes stand loss more critical than at
high seeding rates. Therefore, varieties, like hybrids, are more
susceptible to stand loss because of tadpole shrimp than varieties
planting at higher seeding rates. For example, losing 10% of a stand
planted at 30 lbs/A is more detrimental than losing 10% of a stand
planted at 90 lbs/A.
Because tadpole shrimp do not hatch from eggs until exposed to
water, rice that is grown in dry-seeded systems and not flooded until
rice is at the 4 –5 leaf stage should be safe from tadpole shrimp injury.
This practice promotes large plants with adequate root systems when
the field is flooded. However, heavy rainfall or flooding shortly after
seeding can cause drill seeded rice to mimic a water-seeded rice
production system if the field is not able to be drained; this situation
can lead to tadpole shrimp damaging rice in a dry-seeded system.
Control Options. The number one control option for tadpole shrimp
is to avoid water-seeding rice and to flood a field after the rice has an
established root system. However, in fields that are water-seeded, the
field should be seeded as soon as possible after the flood is established
because tadpole shrimp hatch once a field is flooded. This will
minimize the amount of time that tadpole shrimp grow and maximize
the growth of rice plants while tadpole shrimp are still small. The idea
is that the rice will grow out of the vulnerable stage before tadpole
shrimp can damage the rice.
Draining a field can be useful in killing tadpole shrimp, but rainfall
can prevent this from being effective (Godfrey and Espino 2009).
However, greater input costs (i.e., additional applications of herbicide,
fertilizer, or both; pumping costs; and other expenses) are associated
with draining (Hesler et al. 1992, Quisenberry et al. 1992, Thompson
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Fig. 1. Tadpole shrimp adults.
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TINDALL AND FOTHERGILL: A REVIEW OF TADPOLE SHRIMP AND SCOUTING
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Fig. 5. Tadpole shrimp congregated in a low area after drainage of
the field.
et al. 1994). From a pesticide standpoint, pyrethroids are effective at
killing tadpole shrimp (Walton et al. 1990, Mulla et al. 1992); however, tadpole shrimp are not on the label but may be controlled when
targeting other early season insect pests of rice. Godfrey and Espino
(2009) provide treatment information for California rice production,
but products labeled vary by state. Therefore, it is important in to
consult your local University extension office for products available in
your area.
Because animals can spread eggs (Green and Figuerola 2005), it is
likely that eggs can be transported from an infested field to a noninfested field on the soles of boots of workers or on agricultural
equipment when moving between fields.
Beneficial Characteristics of Tadpole Shrimp. Tadpole shrimp do
not damage only rice when foraging in rice fields. They are just as
likely to uproot small weed seedlings as well (Takahashi 1977b,
Yonekura 1979, Croel and Kneitel 2011). Therefore, if rice is past
Fig. 4. Muddy water caused by shrimp foraging activities which
reduces light penetration causing reduced growth rate of
submerged plants.
Fig. 6. The presence of muddy water in flooded subsample
containers indicates presence of tadpole shrimp.
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Fig. 3. The uprooting of rice seedlings is characteristic of tadpole
shrimp damage resulting from foraging activities. Photographic
Credit: Jack Kelly Clark, courtesy University of California Statewide
IPM Program.
the vulnerable stage, tadpole shrimp can serve as a biological
control of weeds. Tadpole shrimp have been employed in transplanted rice production systems to control weeds. Yonekura (1979)
recommends infesting paddies with tadpole shrimp at a rate of 5/ft2
to be effectively control weeds. Also, they are predaceous on small
insects, including aquatic stages of mosquitoes (Fry-O’Brien and
Mulla 1996).
Scouting Methodology and the Missouri Distribution Survey. In the
spring of 2010, a distribution survey was undertaken to determine
where this pest occurs in rice-producing areas of Missouri. After failed
attempts to locate tadpole shrimp in fields during the spring with
aquatic sweep nets, we modified the methods of Weeks and Marcus
(1997) and sampled for desiccated resting eggs. After harvest, the top
inch of soil in a (162.56-cm2) (64-in.2) area was removed with a
shovel from five different locations (subsamples) within each sampled
field. Low areas of the field were targeted because tadpole shrimp
congregate in areas where water remains in the field after it is drained
(Fig. 5). There was a distance of at least 15.24 m (50 ft) between
subsamples. Subsamples were placed into individual plastic bags and
transported to the laboratory where the soil was dried completely to
enhance egg hatch (Fry and Mulla 1992). Drying was accomplished
by opening the plastic bags and exposing the collected soil to air for
up to 2 wk under greenhouse bench conditions.
After drying, the soil from each subsample was placed in its
own plastic container, sized such that soil depth would be no ⬎1.27
cm (0.5 in). Tap water was poured into a large container and
allowed to come to room temperature because the temperature of
water can impact egg hatch. Once at room temperature, water was
added as needed to the containers of soil to maintain a 5.8-cm
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JOURNAL OF INTEGRATED PEST MANAGEMENT
Fig. 7. Distribution of rice fields scouted for tadpole shrimp in
southeastern Missouri post-2010 rice harvest.
Acknowledgments
We thank the entomology crew at the University of Missouri for
field assistance. This work was supported by a grant from the Missouri
Rice Research and Merchandising Council.
References Cited
Blanche, B., D. Harrell, and J. Saichuk. 2009. General agronomic guidelines,
pp. 3–15. In J. Saichuck (ed.), Louisiana rice production handbook. Louisiana State University Agricultural Center, Baton Rouge, LA.
Brendonck, L., and G. Persoone. 1993. Biological/ecological characteristics of
large freshwater branchiopods from endorheic regions and consequences for
their use in cyst-based toxicity tests, pp. 7–35. In T. LaPoint and P. W.
Greig-Smith (eds.), Standardization of aquatic toxicity tests. Lewis Publishers, Boca Raton, FL.
Browne, R. A. 1993. Sex and the single brine shrimp. Natural History 102:
34 –39.
Cáceres, C. E., and D. A. Soluk. 2002. Blowing in the wind: a field test of
overland dispersal and colonization by aquatic invertebrates. Oecologia 131:
402– 408.
Croel, R. C., and J. M. Kneitel. 2011. Ecosystem-level effects of bioturbation
by the tadpole shrimp Lepiduruspackardi in temporary pond mesocosms.
Hydrobiologia 665: 169 –181.
Fry, L. L., and M. S. Mulla. 1992. Effect of drying period and soil moisture on
egg hatch of the tadpole shrimp (Notostraca: Triopsidae). Journal of Economic Entomology 85: 65– 69.
Fry-O’Brien, L. L., and M. S. Mulla. 1996. Optimal conditions for rearing the
tadpole shrimp, Triops longicaudatus (Notostraca: Triopsidae), a biological
control agent against mosquitoes. Journal of the American Mosquito Control
Association 12: 446 – 453.
Godfrey, L. D., and L. A. Espino. 2009. Rice tadpole shrimp. In University of
California IPM pest management guidelines: rice. UC ANR Publication
3465 Invertebrates. (http://www.ipm.ucdavis.edu/PMG/r682500111.html).
Graham, T. B., and D. Wirth. 2008. Dispersal of large branchiopod cysts:
potential movement by wind from potholes on the Colorado Plateau. Hydrobiologia 600: 17–27.
Green, A. J., and J. Figuerola. 2005. Recent advances in the study of longdistance dispersal of aquatic invertebrates via birds. Diversity and Distributions 11. 2: 149 –156.
Halliday, S. 2008. MyTriops. (http://mytriops.com).
Hamasaki, K., and N. Ohbayashi. 2000. Effect of water pH on the survival rate
of larvae of the the American tadpole shrimp Triops longicaudatus (LeConte) (Notostraca: Triopsidae). Applied Entomology and Zoology 35:
225–230.
Hesler, S. L., A. A. Graigarick, M. J. Oraze, and A. T. Palrang. 1992. Effects
of temporary drainage on selected life history stages of the rice water weevil
(Coleoptera: Curculionidae). Journal of Economic Entomology 85: 950 –
956.
Hildrew, A. G. 1985. A quantitative study of the life history of a fairy shrimp
(Branchiopoda: Anostraca) in relation to the temporary nature of its habitat,
a Kenyan rainpool. Journal of Animal Ecology 54: 99 –110.
Horne, F. R. 1967. Effects of physical-chemical factors on the distribution and
occurrence of some southeastern Wyoming phyllopods. Ecology 48: 472–
477.
Horne, F. R. 1971. Some effects of temperature and oxygen concentration on
phyllopod ecology. Ecology 52: 343–347.
Longhurst, A. R. 1955. A review of the Notostraca. Bulletin of the British
Museum of Natural History 3: 1–55.
Mulla, M. S., M. Zgomba, H. A. Darwazeh, and J. D. Chaney. 1992. Efficacy
and selectivity of two pyrethroid insecticides against the predator Triops
longicaudatus (Notostraca: Triopsidae) and Culex tarsalis larvae. Bulletin
of the Society of Vector Ecology 17: 51–56.
Nathan, R., N. Sapir, A. Trakhtenbrot, G. G. Katul, G. Bohrer, M. Otte, R.
Avissar, M. B. Soons, H. S. Horn, M. Wikelski, et al. 2005. Long-distance
biological transport processes through the air: can nature’s complexity be
unfolded in silico? Diversity and Distributions 11: 131–137.
Quisenberry, S. S., G. B. Trahan, A. M. Heagler, B. McManus, and J. F.
Robinson. 1992. Effect of water management as a control strategy for rice
water weevil (Coleoptera: Curculionidae) Journal of Economic Entomology
85: 1007–1041.
Ridings, J. W., S. R. Schell, and T. W. Stearnes. 2011. The first record of
American tadpole shrimp (Triops longicaudatus) in Illinois. Transactions of
the Illinois State Academy of Science 130: 49 –50.
Sassaman, C., M. A. Simovitch, and M. Fugate. 1997. Reproductive isolation
and genetic differentiation in North American species of Triops (Crustacea:
Branchiopoda: Notostraca). Hydrobiologia 359: 125–147.
Scott, S. R., and A. A. Grigarick. 1978. Observations on the biology and
rearing of the tadpole shrimp Triops longicaudatus (LeConte) (Notostraca:
Triopsidae). Wasmann Journal of Biology 36: 116 –126.
Scott, S. R., and A. A. Grigarick. 1979. Laboratory studies of factors affecting
egg hatch of Triops longicaudatus (LeConte) (Notostraca: Triopsidae).
Hydrobiologia 63: 145–152.
Simovich, M. A., and S. A. Hathaway. 1997. Diversified bet-hedging as a
reproductive strategy of some ephemeral pool anostracans (Branchiopoda).
Journal of Crustacean Biology 17: 38 – 44.
Takahashi, F. 1977a. Pioneer life of the tadpole shrimps, Triops spp. (Notostraca: Triopsidae). Applied Entomological Zoology 12: 104 –117.
Takahashi, F. 1977b. Triops spp. (Notostraca: Triopsidae) for the biological
control agents of weeds in rice paddies in Japan. Entomophaga 22: 351–357.
Downloaded from http://jipm.oxfordjournals.org/ by guest on October 27, 2016
(2-in) flood for 15–21 d. The containers were kept in a greenhouse
in Portageville, MO by using natural light (winter to spring day
lengths) at 75°F. However, tadpole shrimp are hatched easily under
household conditions (Halliday 2008). Given that tadpole shrimp
can complete their life cycle on average in 32 d (Scott and Grigarick 1979), the containers should be examined for tadpole shrimp
2 and 3 wk after adding water. A bright light or small fish net will
aid in the detection of the tadpole shrimp. In addition, the water
typically appears muddy, indicating tadpole shrimp presence as
well (Croel and Kneitel 2011) (Fig. 6). When examining samples,
many arthropods other than tadpole shrimp are recovered, so it is
important to wait at least 2 wk before examining samples to ensure
proper identification. The longer tadpole shrimp develop, the more
likely that they will be identified correctly. Longhurst (1955) is a
useful reference for identifying the Notostraca.
Using the methodology described above, tadpole shrimp were
detected in nine of 42 fields (Fig. 7) and all tadpole shrimp positive
fields were associated with the Little River drainage system. Seven of
the nine positive fields had more than one subsample with tadpole
shrimp present. If a field was found positive for tadpole shrimp, the
total number collected was usually ⬍15 per field and tadpole shrimp
were not recovered from every subsample. From one field, tadpole
shrimp were recovered from every subsample, for 71 in total collected
from this field.
Although this methodology was found to be effective for determining the distribution of tadpole shrimp, current data are not sufficient to determine economic thresholds, detection thresholds, or both.
However, the authors feel that a heavily infested field, like the one
field sampled that had tadpole shrimp present in all five subsamples,
likely would be detected. Regardless of the numbers of tadpole shrimp
found in a field, if samples test positive for tadpole shrimp, the farmer
should be aware of the risk associated with water-seeding the field and
should consider drill-seeding that field. If the farmer must water-seed,
efforts should be made to seed the field as quickly as possible after the
flood is established (Godfrey and Espino 2009) and planting low
seeding rates should be avoided. In addition, the field should be
watched closely to ensure stand loss does not become problematic in
the field.
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Taylor, C. M., R. M. Bryant, Jr., and R. E. Hartman. 1987. Eastward range
extension of the tadpole shrimp, Triops longicaudatus (LeConte), in Oklahoma. Proceedings of the Oklahoma Academy of Science 67: 75–76.
Thompson, R. A., S. S. Quisenberry, G. B. Trahan, A. M. Heagler, and G.
Giesler. 1994. Water management as a cultural control tactic for the rice
water weevil (Coleoptera: Curculionidae) in southwest Louisiana. Journal of
Economic Entomology 87: 223–230.
Tindall, K. V., K. Fothergill, W. Minson, and B. Ottis. 2009. A new pest of rice
in Missouri: range expansion of Triops longicaudatus (Crustacea: Notostraca: Triopsidae) into the Northern Mississippi River Alluvial Plains. Florida Entomologist 92: 503–505.
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Walton, W. E., H. A. Darwazeh, M. S. Mulla, and E. T. Schreiber. 1990. Impact
of selected synthetic pyrethroids and organophosphorous pesticides on the
tadpole shrimp, Triops longicaudatus (LeConte) (Notostraca: Triopsidae). Bulletin of Environmental Contamination and Toxicology 45: 62– 68.
Weeks, S. C., and V. Marcus. 1997. A survey of the branchiopod crustaceans
of Ohio. Ohio Journal of Science 97: 86 – 89.
Yonekura, M. 1979. Biological control of weeds by tadpole shrimps in paddy
field - weed efficacy of tadpole shrimps in transplanted rice fields. Journal
of Weed Science and Technology 24: 64 – 68.
Received 1 January 2012; accepted 20 June 2012.
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