Ponce, Suzán and Francke
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POPULATION STRUCTURE OF CENTRUROIDES BALSASENSIS (SCORPIONES:
BUTHIDAE) IN THE BALSAS DEPRESSION, MÉXICO.
JAVIER PONCE SAAVEDRA1, HUMBERTO SUZÁN-AZPIRI2* AND OSCAR F. FRANCKE 3
1= Laboratorio de Entomología “Sócrates Cisneros Paz”, Facultad de Biología,
Universidad Michoacana de San Nicolás de Hidalgo, Edificio B4 2º. Piso, Ciudad
Universitaria, Morelia, Mich. C.P. 58040, México.
2= Escuela de Biología, Universidad Autónoma de Querétaro, C.U. Cerro de las
Campanas, s/n, Querétaro, Qro. C.P 76010, México.
3= Colección Nacional de Arácnidos, Instituto de Biología, Departamento de Zoología,
Universidad Nacional Autónoma de México. Tercer Circuito Exterior sin número,
Cuidad Universitaria Apartado Postal 70-153 Mexico D. F., 04510
*Correspondent: hsuzan@sunserver.uaq,mx
ABSTRACT--The Balsas Depression in the state of Michoacán, México is a region
with average diversity of scorpions. A bimonthly population survey of a recently
described species of the genus Centruroides was conducted at two permanent sites. The
sampling quadrats measured 400 m2. The relative abundance, sex ratio and population
density of the dominant scorpion species in the zone, Centruroides balsasensis Ponce
and Francke, were estimated using the simple capture-recapture method of LincolnPetersen. Some aspects of the surface activity of the individuals at the moment of
capture were recorded. Densities varied through the year depending on season and food
availability, between 0.023 individuals/m2 and 0.18 individuals/m2. The sex ratio fit the
Ponce, Suzán and Francke
2
1:1 expected, and the principal activity detected in the sampling nights was ambushing,
mainly over stones or over bare soil. The average litter had 26.2 young, and the duration
of the first three instars of development (216 days) suggest that this species requires at
least two years to reach maturity.
Key words: Scorpions, Centruroides balsasensis, population structure, sex ratio, instars
and scorpions.
RESUMEN -- La Depresión del Balsas en el Estado de Michoacán, México es una
región con una amplia distribución de alacranes. Se llevó a cabo un monitoreo
bimensual en poblaciones de una especie recientemente encontrada del género
Centruroides en dos sitios permanentes de muestreo. Los cuadrantes muestreados tenían
400 m2. Se determinó la abundancia relativa, proporción de sexos y densidad
poblacional de la especie de alacranes dominante en la zona, Centruroides balsasensis
Ponce y Francke, por medio de el método simple de marca recaptura de LincolnPetersen. Se estudiaron algunos aspectos de la actividad aparente de los individuos al
momento de ser capturados. Las densidades encontradas variaron entre 0.023 individuos
/m2 y 0.18 individuos /m2 dependiendo de la disponibilidad de alimento y época del
año. La proporción de sexos fue de 1:1 como se esperaba, y la principal actividad
detectada en las noches de muestreo fue el asecho, sobre rocas y suelo desnudo. El
promedio de escorpiones por camada fue de 26.2 y el tiempo de duración promedio de
los tres primeros instares de desarrollo fue de 216 días, lo cual sugiere que esta especie
requiere al menos de dos años para alcanzar la madurez.
Palabras clave: Alacranes, Centruroides balsasensis, estructura de poblaciones,
proporción sexual, instares.
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The genus Centruroides comprises scorpions of the family Buthidae which has
several species with great biological and medical importance. In México, although this
genus has the greatest medical importance of all scorpions, information regarding its
biology is scarce and mainly related to taxonomic aspects (Moreno et al., 1998; Ponce
and Beutelspacher, 2001). The incomplete knowledge of scorpion diversity and
distributions often leads to the discovery of new species when faunistic surveys of
scorpions are conducted in relatively well-known regions (Ponce, 2003). Specifically
for the Balsas Depression (Balsas Basin) in the State of Michoacán, México, two new
species where reported for the first time in 2003 (Ponce, 2003) One of them, a recently
described species of the genus Centruroides, C. balsasensis Ponce and Francke, is the
subject of this study.
Information about population structure and dynamics of scorpions in México is
almost null. Density estimations detected in medical reports or taxonomic descriptions
only mention them as “abundant” or “scarce”. Therefore, quantitative knowledge of
densities and other demographic parameters become fundamental for the management
of scorpions (Polis, 1990a). It is important to note that worldwide we have knowledge
of basic population biology for only three scorpion species (Polis, 1990b).
Habitat micro-characterization is another important factor in the scorpion’s life
history (Polis, 1990b; Benton, 2001; Lourenço, 1988; Lourenço and Cloudsley
Thompson, 1999). Some species inhabit a wide array of habitats and geographical
regions, while others have restricted distributions in specialized habitats (Francke, 1981;
Polis, 1990a).
Species of the genus Centruroides are considered as opportunistic (Polis, 1990b)
and tend to be active foragers with high motility (Stahnke, 1971). Therefore, the
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4
estimations of basic demographic parameters such as density must be accompanied by
a characterization of the habitat used by the particular species.
Biomass is another factor to be considered in population analyses. The easiest
way to estimate biomass is the multiplication of density times the average weight of
individuals. However, differences in size and age must be considered (Polis, 1990b).
Shorthouse (1971) and Marples and Shorthouse (1982 ) used the average weight as
function of age groups to estimate biomass production of Urodacus yaschenkoi (Birula)
(Scorpionidae: Urodacinae) in Australia; Bacon (1972) with Uroctonus mordax Thorell
(Vaejovidae) in the United States, and Polis (1990b) for three species of the family
Buthidae. Those estimations show that scorpions are among those terrestrial arthropods
with highest biomass per hectare, ranking only below ants and termites.
The majority of tropical scorpions do not have well defined reproductive seasons
(Benton, 2001), and the highest percentage of matings occur after the females have
given birth (Benton, 2001). Scorpions are viviparous, and the size of the litter is
apparently negatively correlated with the size of the young individuals (Francke, 1981;
Brown, 2001).
The objectives of the present study are: a) to determine the relative importance
of Centruroides balsasensis in two scorpion communities; b) to describe basic
population parameters such as density, age structure, sex ratio and biomass for this
species; c) and to describe the apparent activities and habitat use of the species.
METHODS
AND
MATERIALS--Study area – The Balsas Depression is a wide
structural depression formed by the lowest parts of the Balsas River Watershed, located
mainly in the state of Michoacán, México (Toledo and Ordóñez, 1993). Two contrasting
sites with Centruroides balsasensis populations were selected in the lowest altitudinal
region of the Balsas Depression. The first site, located on Turitzio mountain, in the
Ponce, Suzán and Francke
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municipality of Huetamo (18°31.69´N, 100°55.45´W, altitude: 450-550 m), is
characterized by a hot and humid isothermal climate (with a mean monthly temperature
of 28°C with a thermal variation of 5°C year-round), and a tropical deciduous forest
dominated by arboreal trees of the genus Bursera (Rzedowski, 1978). The second
population was located near the town of Churumuco (18°39.28´N, 101°39.28´ W,
altitude: 370-500 m) in the municipality with the same name. This region is hotter and
drier than Turitzio, with a mean monthly temperature of 30°C and variation of 5°C
year-round, and a tropical deciduous forest dominated by columnar cacti such as
Backembergia militaris and Stenocereus quevedonis (Guevara-Féfer, 1981).
Population structure-- Fieldwork was conducted in the years 2000-2001 with the
populations of Centruroides balsasensis at the two selected sites. Population size and
structure were determined for each site by bimonthly samplings and simple markrecapture methods or Lincoln-Petersen methodology (Krebs, 2000). The sampling was
conducted during clear nights with black light lamps (wavelength = 300 nm) that allow
a 6-8 m vision (Sissom et al., 1990).
Sampling events for each site consisted of two consecutive fieldwork nights. On
the first night we walked randomly in an area approximately 3 km2 to determine the
scorpion community of each site. Two points were located at random and from those we
installed two 400m2 quadrats where we marked (with acrylic fluorescent non-toxic
paint) all C. balsasensis individuals with a sampling effort of 2 hrs/man. All individuals
were marked on the mesosoma, and the following data were collected: maximum
length, sex, time of capture, life stage (adult, juvenile) and apparent activity. On the
second night all recaptured individuals were subjected to a second measurement.
Collected data were used to determine population size, density estimates, sex ratios, life
stage, and juvenile-adult proportions.
Ponce, Suzán and Francke
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Population size was determined with the program Mark-Recapture of the
Ecological Methodology (second edition) Book (Krebs, 2000).
Sex ratio was determined separately for adult and juvenile scorpions,
considering if the animals were captured or recaptured. Sex ratio was tested with a nonparametrical concordance test using as a null hypothesis the 1:1 sex ratio reported for
non-parthenogenic scorpions (Polis and Sissom, 1990).
The total length registered for each captured individual determined its life stage
according to a growth factor calculated in laboratory specimens according to Francke
and Sissom (1984), and by the determination of the instars necessary for scorpions to
reach adult age (Francke, 1976). The estimated number of instars for C. balsasensis are
seven immature plus one adult stage (Ponce, 2003), and the field estimations agree with
laboratory observations on partial life histories (Ponce, 2003).
The assignation of field-captured and field-measured individuals to a given
instar was made after measuring the total length of body for each individual and an
estimation procedure based on the growth factor of 1.3 obtained for this species (Ponce,
2003) (Table 1). The knowledge of the actual measurement of newborn ( = first instar)
and adult females (those carrying young on their backs) was fundamental in establishing
the estimated instar sizes (Francke and Sissom, 1976). After each mark-recapture date, a
group of scorpions were collected and preserved to be measured in the laboratory. This
sample (n =192) was divided into groups according to the measure of the total body
length: Adults, instar VII, instar VI and those from the instars V to I which were
considered as "juveniles".
Fresh weight biomass estimations for the two populations were obtained by an
average of individual weights obtained from a sample of 10 scorpions per site. The
mark-recapture studies indicated a 62:38 ratio of adults: juveniles in Turitzio and 74:26
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in Churumuco. The proportions obtained for both localities were averaged and then the
fresh-weight biomass estimation was determined with 7 adults and 3 juveniles (instars
IV and V) selected in the laboratory, and with the average individual weight we
estimated the fresh weight of the scorpions in a particular date and place.
In order to estimate the average size of a litter we counted the number of
newborn (first or second instar) carried by females detected in the field, and 13 female
scorpions which gave birth under laboratory conditions (27°C  2 and relative humidity
55% 10%). Raising the newborn in the laboratory enabled us to measure growth
(confirming the 1.3 growth rate at each molt used in the instar-size estimates above) and
to estimate the average duration for the first four instars.
In each of the permanent sites an environmental data logger HOBO H8 (H08004-02) collected temperature, relative humidity and light intensity data every six hours
for one year.
Apparent activity and use of habitat-- For all the mark-recapture dates we
registered the apparent activity of the scorpions captured in order to analyze behavioral
population patterns. The basic activities (considered after Polis, 1990b) were: a)
ambushing (stationary position with the metasoma and pedipalps upright, and the
pedipalp chelae open); b) resting; c) walking; d) eating; e) in courtship (couples
grasping by the pedipalps). For each scorpion we also recorded sex, habitat utilization
and estimated age (juvenile or adult), according to the results of the assignation of
instars to the scorpions previously measured in the laboratory.
RESULTS-- Species and sexual proportions of the scorpion communities after all
samplings in Churumuco and Turitzio indicated that Centruroides balsasensis was the
dominant species for both sites (Figure 1). In Churumuco the relative abundance for all
Ponce, Suzán and Francke
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individuals, regardless of sex, was 64% for C. balsasensis, followed by Vaejovis aff.
variegatus (31%), Vaejovis sp. (4.94%) and Diplocentrus sp. (0.62%). In Turitzio the
numbers were 57% for C. balsasensis , followed by Vaejovis sp. (22%) and Vaejovis
aff. variegatus (21%).
We marked a total of 259 C. balsasensis on the first night of sampling for both
sites; and on the second night recorded 78 scorpions recaptured and 155 new captures in
the 400m² quadrats. In Churumuco 177 scorpions were marked (49 recaptured), and in
Turitzio 82 scorpions marked (29 scorpions recaptured). The number and proportion of
adults to juveniles for each sampling date and locality are described in Table 2.The
density of animals per quadrat for each sampling date are described in Table 3. In
Churumuco the minimum density estimated was 17 scorpions per quadrat (0.04/m²) in
July- August, and the maximum was of 73 per quadrat (0.18/m²) (Figure 2) in JanuaryFebruary. In Turitzio we obtained a minimum estimation of 7 scorpions per quadrat
(0.02 /m²) in May-June, and a maximum estimation of 27 scorpions per quadrat
(0.07/m²) in July-August (Figure 3). Densities obtained were lower than other species of
the family Buthidae in the world (Table 4). Locally the densities in Turitzio were lower
than Churumuco ( P <0.05) probably due to the climatic and vegetation differences
between the localities, although both have deciduous dry forest, there are difference in
the species composition and vegetal community structure as well as the annual
precipitation and temperature (Ponce et al., 2004). The pattern of the population
densities in Churumuco shows the maximum was observed in January-February,
decreasing toward the rainy season and recovering during the last two months of this
season (Figure 2); whereas in Turitzio we observe the pattern of the population densities
decreasing in the dry season followed by a rapid upward response at the beginning of
Ponce, Suzán and Francke
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the rainy season (Figure 3). Therefore, densities seem to depend both on food
availability and weather fluctuations.
The sex ratio for 535 individuals captured (or recaptured) in the quadrats
indicated that the populations fit the expected sex ratio of 1:1 for both juveniles and
adult scorpions (Table 5). In all the capture-recapture dates the same proportion was
observed.
The recapture percentages for males, females and juveniles on 11 recapture dates
were not significantly different (Wilcoxon/Kruskal-Wallis one-way test, χ2 = 0.172,
d.f.= 2, P=0.92). However, at least some males were always recaptured the night
following marking [ X = 31.8%, s.d. = 0.14, range 13% (1 of 8) to 57% (4 of 7)], which
was not the case for females [ X = 34.8%, s.d. = 0.31, range 0% (0 of 7) to 100% (3 of
3)] or juveniles [ X = 36.5%, s.d. = 28.8, range 0% (0 of 1) to 100% (1 of 1)],
suggesting some difference in displacement activity patterns. However, the analyzed
sample sizes are very low and this aspect deserves further study.
Life stages were determined for 492 individuals captured or recaptured in the
field. The adult/juvenile proportions in Churumuco fluctuate between 66% and 80%
always with more adults than juveniles. These proportions were lower in Turitzio where
they fluctuate between 54% and 75% (Table 2). After the instars were assigned to the
192 scorpions captured and measured in the laboratory, adults represented 60.4 % of the
population, 22 % corresponded to instar VII, 10% to instar VI, and 7% to instar V or
younger.
Adult and juveniles densities were variable in time. Adults increased between
March and June, simultaneously with an instar VII decrease (Figure 4). In August and
September the densities of instars VII densities increased considerably as a result of
recruitment from instar VI, while adult densities decreased (Figure 4).
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Cannibalism of juveniles by adults was observed only once, in January (the
driest month of the year). Also, predation by C. balsasensis on Vaejovis sp. was
observed in the field once, in Turitzio in August.
In the field, we observed mating events at different months of the year (March,
June, August and December) and birth events (females with newborn scorpions of instar
I on their back’s) were recorded in March, August and September; although the
frequency of those events in each month were not recorded. However, the increase in
adults noted in Churumuco in March and in Turitzio in June, suggest a higher
reproductive activity between March and June, providing abundant prey for the
pregnant females during the rainy months and better survival possibilities for the new
litters (Figures 2, 3).
The low percentage of scorpions smaller than instar IV (7%), suggests a
population structure dominated by adults and with a low reproductive (recruitment) rate;
or younger scorpions are harder to detect because of their size and/or their activity is
limited to avoid cannibalism. However, the variation between dates of capture was high,
and could reflect a sampling bias to the easiest detectable sizes (larger).
Fresh-weight laboratory measurements (7 adults and 3 individuals of instars VII
and VI; i. e., the proportion of adult to juveniles recorded in the field) indicated that
average individual weight was 1.16 g (min = 0.267g; max = 2.107g). With the densities
detected in each site and date, the biomass field estimations fluctuate between 0.174
kg/ha and 3.447 kg/ha (Table 6).
The average number of offspring was 26.18 (standard error of 1.336), with a
minimum of 19 and maximum of 36 young scorpions per litter, from 13 births recorded
in the laboratory. The births occurred between March and October, which closely
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matches the months where females with young were detected in the field (March
through September).
We never detected iteroparity, and some of the females survived in the
laboratory up to 14 months after the birth of newborns. With the individual observations
of the young scorpions we determined the average duration of the first four instars:
instar I or newborn the average time was 13 days (n = 7); instar II lasted 113.4 days (n =
5); instar III 90.7 days (n = 3) and instar IV 46 days (n = 1).
Apparent activity-- In both permanent observation sites we recorded the activity
of 492 scorpions (including 78 recaptures and 155 new captures), and in adjacent sites
we recorded the activity of other scorpions detected in the sampling nights; thus, a total
of 512 scorpions provided us with a total of 1024 observations. According to the total
body length measurements made in the field, we assigned age to “adults” and
“juveniles” for data analysis. It was observed that juveniles represented 28% of the
sightings; 40% were male adults and 32% female adults (Table 7).
The principal activity detected in the sampling nights was ambushing (50.39%),
mainly on stones (20.89%) or on bare ground (31.05%); but shrubs (14.45%) and
branches of trees (8.98%) were also common sites for ambushing and hunting (Table 7).
When the scorpions were resting (44.1% of all activities recorded) we detected them
under leaf litter (54.54%), beneath stones (34.54%), in dry wood stems (4.54%), and
beneath the bark of trees (4.54%) and only 1.84% in other sites.
Activities of juvenile scorpions were dominated by ambushing (49.15%)
walking over bare ground or leaf litter (34.74 %), and when resting (8.36%) the young
scorpions were commonly detected on branches of herbaceous plants, but we never
found them beneath the bark of trees (Table 7).
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To analyze the surface activity we did specific mark-recapture studies with exact
location records on a 20 x 20 m quadrat on consecutive nights in June, August and
September 2001 at the Churumuco site. Out of 63 total marked individuals only 29 were
recaptured the following night, even though the searches extended for up to 30 m away
from the quadrats to look for “strays.” The shortest displacements recorded were by
two juveniles which moved 0.39 and 0.41 m, respectively; and the furthest were by two
males that moved 18.16 and 24.97 m, respectively. The average displacement for all
recaptured individuals was 6.41 m (n=29), and Kruskal-Wallis analyses indicate no
significant differences with respect to sex or age categories (χ2 = 2.052, d.f. = 2, P =
0.358), nor among the three sample periods (χ 2 = 2.156, d.f. = 2, P = 0.340).
DISCUSSION-- The species composition and relative abundance of the dominant
species for both localities studied (four species in Churumuco and three species in
Turitzio) represented the most common pattern reported for scorpion communities in
the world (Polis, 1990b). Species richness between three and seven species where
reported for 68% of the communities, and situations where a dominant species
comprised more than 40% of the individuals are also extremely common (more than
80%) (Polis, 1990b). However, communities with four species and a relative abundance
for the dominant species between 60 and 80% (like Churumuco) were reported only
once (Polis, 1990b).
The low density numbers for the region, compared with those of other parts of
the world (Polis, 1990b), suggest that in extremely warm places without a marked
winter season (like the Balsas Depression) food availability might be the key factor
controlling densities and not weather fluctuations (McReynolds, 2004). However, our
density estimates were obtained by single mark-recapture methods that could be
Ponce, Suzán and Francke
13
influenced by the season of the year, foraging behavior, motility and the supposition
that the population is closed (no demographic changes during the sampling period).
Therefore, the sampling method could produce differences in density estimations.
However, Yamashita (2004) used single mark-recapture for closed populations and the
Jolly-Seber method for open populations and his results were similar (140 and 110
scorpions, respectively, for the study site).
Population structure reflected a 1:1 sex ratio for all the life stages, and data
suggested a continuous and synchronic replacement of the instars through the year with
generations overlapping.
The surface activity in Turitzio was greater in July-October and in Churumuco it
was in August-October, closely matching the activity periods reported for C. vittatus in
Arkansas and Texas (McReynolds, 2004; Yamashita, 2004); however, in Churumuco
we observed another peak of activity in January.
In both localities reproductive activities throughout the year indicated
similarities with other tropical species (Polis, 1990b), in contrast with temperate species
that do have a marked temperature-related seasonality.
The duration of the first life stages (Instar I-IV) of 216 days suggest that C.
balsasensis requires more than a year to reach sexual maturity. Similar results for other
species were described by Francke and Sissom (1984).
Density estimations obtained for C. balsasensis were lower compared to other
Buthidae species reported (Table 4). The highest value obtained for the region is lower
than the lowest value reported for Centruroides exilicauda in Baja California or to the
Centruroides margaritatus densities reported in Costa Rica (Polis, 1990b) and clearly
lower than Leiurus quinquestriatus in Israel. However, densities seem high if we
compare them with the values reported for Compsobuthus werneri judaicus (Birula) in
Ponce, Suzán and Francke
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Israel (Zinner y Amitai, 1969 in Polis, 1990b), Tityus fasciolatus in Brazil (Lourenςo
1978 in Polis, 1990b) and for Centruroides vittatus in Arkansas (Table 4).
The average body weight of Centruroides balsasensis calculated in our study
(1.16 g/individual) and a biomass range between 0.174-3.447 kg/ha are consistent with
those reported by Polis (1990b) for Centruroides margaritatus (Gervais) and
Centruroides exilicauda (Wood)(1 g/individual and 2.0-5.0 kg/ha for the populations),
but significantly lower than those of Leiurus quinquestriatus (Ehrenberg)(with a weight
of 1.5 g/individual and a biomass of 16.5 kg/ha) (Polis 1990b). However, in order to
validly compare biomass estimations we must know the biomass changes through the
year, because of the changes in size and weight observed between the rainy and dry
seasons of the year as a result of fluctuations in food availability (it is not known during
which season the estimates were made for L. quinquestriatus and the other species
previously reported).
Yamashita (2004) obtained individual weights for adults of Centruroides vittatus
of 0.41g (males) and 0.49 g (females) using data of surveys made in March to
November in Arkansas. This individual weight is clearly lower that any of the data
published for other Buthidae species, and considerably lower than our data. This lower
weight is also reflected in the low biomass registered per hectare that was of only 0.11
to 0.133 kg/ha, although the obtained density for this species was of 0.024 to 0.029
scorpions for square meter. In southern Texas the estimation for this species was of
0.074 individuals/m² (Brown et al., 2002).
Our surface-activity studies corroborate that Centruroides species are active
foragers with high motility. Six recaptured juveniles, about 4 cm long, moved an
average of 4.51 m overnight; 12 adult females, about 7-8 cm long, moved an average of
5.22 m overnight; and 11 adult males, also 7-8 cm long, moved an average of 8.75 m.
Ponce, Suzán and Francke
15
There are no statistically significant differences in the distances moved by each group,
but the sample sizes are small and the observed variation is wide. Further observations
are necessary to test the hypotheses (a) that juveniles wander less to reduce the risk of
predation, and (b) that males venture further in search of potential mates.
Acknowledgements
The authors are grateful to Rocío J. Moreno B, Erwin P. Miranda L., Leticia
Escalante J., Marco A. Villaseñor R., Ramón Cancino M., Elvia Lemus O. and Erasto
Hernández C. of the Universidad Michoacana for their support in the field work. We
also thank to the Research Coordination of the Universidad Michoacana for their
financial support for this work. Finally we are grateful for the diligent review of the
manuscript provided by W. David Sissom.
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population of the arid zone scorpion Urodacus yaschenkoi (Birula 1903).
Australian Journal of Ecology 7: 119-127.
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Publications in Scorpiology. 17: 35-45.
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Scorpiones) de cuatro localidades de la zona de transición a la tierra caliente
del Estado de Michoacán. Memorias del XXXIII Congreso Nacional de
Entomología, Acapulco, Gro. México. Pp 440-442.
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Stanford University Press, Stanford, Ca. Pp 1-8.
POLIS, G. A. 1990B. Ecology. In Polis, G.A. Editor. The Biology of Scorpions. Stanford
University Press, Stanford, Ca. Pp 247-293.
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of Scorpions. Stanford University Press, Stanford, Ca. Pp 161-223.
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(Scorpiones: Buthidae), en la depresión del Balsa en el estado de Michoacán.
Ph. D. diss. Universidad Autónoma de Querétaro, Querétaro, México. 276pp.
PONCE, S.J. AND C.R. BEUTELSPACHER. 2001. Alacranes de Michoacán UMSNH.
Ediciones Michoacanas, Morelia, Michoacán, México 103pp.
PONCE, S. J. AND O. F. FRANCKE. 2004 .Una nueva especie de alacrán del género
Centruroides Marx (1890) (Scorpiones, Buthidae) de la Depresión del Balsas,
México. Acta Zoológica Mexicana (n.s.) 20(2):221-232.
PONCE, S. J., E. CARRANZA G., R. J. MORENO B., E. P. MIRANDA L., A. L. ESCALANTE J.,
M. A. VILLASEÑOR R. AND R. CANCINO M. 2004. Caracterización de dos
variantes de Selva Baja Caducifolia en la Depresión del Balsas, Michoacán,
México. Biológicas No. 6: 56-67. http://bios.biologia.umich.mx.
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Urodacus yaschenkoi (Birula, 1904). Ph. D. diss., Australian National
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Polis, G.A. Editor. The Biology of Scorpions. Stanford University Press,
Stanford, Ca. Pp 445-461.
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Scorpionida). Entomological News 88: 111-120
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review of terrestrial habitats. In. Ramamoorthy T., R. Bye, A. Lot and J. Fa.
Editors. Biological diversity of Mexico. Oxford Univ. Press. N.Y., pp 757777.
YAMASHITA, T. 2004. Surface activity, biomass, and phenology of striped scorpion,
Centruroides vittatus (Buthidae) in Arkansas. Euscorpius-Ocassional
Publications in Scorpiology 17:25-33.
18
Ponce, Suzán and Francke
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TABLE 1 -- Estimated values of total body length for the instars of Centruroides
balsasensis according to the growth factor of 1.3. The max and min values were
estimated using the confidence limits for each age group ( P <0.05).
(Newborns individuals or
Instar I) Observed
Mean: 9.5
Max: 12.2
Min: 07.8
Instar
II
III
IV
V
VI
VII
Adult
Estimations of body length (mm)
Mean
Max.
12.3
15.9
16.0
20.6
20.8
26.8
27.0
34.8
35.2
45.3
45.7
58.9
59.4
76.6
Min.
10.1
13.2
17.1
22.3
29.0
37.6
48.9
Ponce, Suzán and Francke
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TABLE 2—Proportion of adults and juveniles of Centruroides balsasensis per sampling
date, quadrat and locality
Date
Adults
19
22
20
13
18
92
(60.1%)
Juveniles
7
19
17
3
15
61
(39.9%)
% Ad
73.1
53.7
54.1
75.0
54.6
% Juv
26.9
46.3
45.9
25.0
45.4
Date
Adults
September (2000) 16
November (2000) 47
January (2001)
92
March (2001)
39
June (2001)
27
September (2001) 29
250
Subtotal
(73.9%)
Juveniles
6
18
33
10
7
15
89
(26.1%)
% Ad
72.7
72.3
73.6
79.5
79.4
65.9
% Juv
27.2
27.6
26.4
20.4
20.5
34.0
Sampling date
Locality:
Turitzio
(n = 153)
October (2000)
January (2001)
March (2001)
June (2001)
August (2001)
Subtotal
Sampling date
Locality:
Churumuco
(n = 339 )
Ponce, Suzán and Francke
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TABLE 3-- Densities of Centruroides balsasensis per quadrat
Density estimated for quadrats of 400 m²
Confidence Limits
Locality and Date
Estimation
Lower
Upper
17.0
10
62.7
18.2
11.6
51.5
37.4
26.5
81.7
16.8
11.9
30.1
72.7
53.9
112.3
12.3
9.3
19.8
35.5
24.1
66.6
9.5
6.0
29.6
26.4
16.6
65.1
25.0
15.7
60.7
43.6
25.9
115.4
Churumuco.
September (2000)
Turitzio.
October (2000)
Churumuco.
November (2000)
Turitzio.
January (2001)
Churumuco.
January (2001)
Turitzio.
March (2001)
Churumuco.
March (2001)
Turitzio.
June (2001)
Churumuco.
June (2001)
Turitzio.
August (2001)
Churumuco.
September (2001)
Ponce, Suzán and Francke
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TABLE 4-- Comparison of Centruroides balsasensis densities in the Balsas Depression with other Buthidae densities reported in
literature.
SPECIES
Centruroides
balsasensis
Ponce
DENSITY
GEOGRAPHIC
(ind/m2)
REGION
and 0.02-0.18
HABITAT
Balsas Depression, México
Francke
Tropical
REFERENCE
deciduous This study
forest
Centruroides margaritus (Gervais)
0.4
Costa Rica
Tropical low lands
Polis 1990b
Centruroides exilicauda (Wood)
0.2-0.5
Baja California (South)
Xerophytic shrubland
Polis 1990b
Centruroides vittatus (Say)
0.024-
Pope
0.029
USA
forested area
Centruroides vittatus (Say)
0.0736
West Texas
Desert
Brown et al. 2002
Compsobuthus werneri judaicus (Birula)
0.0017
Israel
Mediterranean
Zinner
y Amitai
1969
In:
Polis
y
Levy
In:
Polis
County,
Arkansas. Rocky upland semi- Yamashita 2004
1990b
Leiurus quinquestriatus (Hemprich and 1.12
Ehrenberg)
Israel
Desert
Shulov
1978
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1990b
Tityus fasciolatus Pessoa
0.0002
Brazil
Termite mounds
Lourenςo 1978 In:
Polis 1990b
Ponce, Suzán and Francke
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Table 5-- Sex ratios of Centruroides balsasensis in the Balsas Depression, Michoacán.
(n = 380 adults and 155 juveniles). Null hypotheses are for a 1:1 male (M) to
female (F) sex ratio.
Adults
Captured and marked
Recaptures
New captures
Values
F=92: M=114
F=26: M=32
F=56: M=60
Juveniles
Captured and marked
Recaptures
New captures
F=31: M=43
F=26: M=32
F=10: M=13
χ² calc.
2.35
0.64
0.14
Probability
0.1253 n.s.
0.4308 n.s.
0.7103 n.s.
2.28
0.4
0.14
0.1630 n.s.
0.4308 n.s.
0.5316 n.s.
Ponce, Suzán and Francke
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Table 6 -- Estimated biomass per hectare of Centruroides balsasensis in the Balsas
Depression, Michoacán. (Estimation based on 1.16 g per individual).
ESTIMATED
MINIMUM
MAXIMUM
(kg)
(kg)
(kg)
0.493
0.290
1.8183
0.5278
0.3364
1.4935
1.0846
0.7685
2.3693
0.4872
0.3451
0.8729
2.1083
1.5631
3.2567
0.3567
0.2697
0.5742
1.0295
0.6989
1.9314
0.2755
0.174
0.8584
0.7656
0.4814
1.8879
0.725
0.4553
1.7603
1.2644
0.7511
3.3466
DATE / SITE
Churumuco. September (2000)
Turitzio. October (2000)
Churumuco. November (2000)
Turitzio. January (2001)
Churumuco. January (2001)
Turitzio. March (2001)
Churumuco. March (2001)
Turitzio. June (2001)
Churumuco. June (2001)
Turitzio. August (2001)
Churumuco. September (2001)
Ponce, Suzán and Francke
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Table 7 -- Apparent activity and use of habitat by Centruroides balsasensis at the
Balsas Depression in Michoacán (total of observations n = 1024).
Activity
Adult fem. Juvenile fem. Adult males Juvenile males Total
Ambush
84
32
102
40
258
Walking
26
18
50
36
130
Eating
3
1
4
4
12
Courtship
1
0
1
0
2
Resting
37
14
49
10
110
Subtotal:
512
Use of habitat
Beneath stones
12
4
22
0
38
Base of trees
10
1
10
2
23
On litter foliage
14
11
21
14
60
Stone cavity
3
0
0
0
3
Stem cavity
2
1
2
0
5
Beneath cortex
3
0
2
0
5
Between stones
1
1
6
1
9
Over brush
14
5
7
6
32
Over ground
36
22
65
23
146
Over stone
47
5
46
9
107
Over plant
3
4
2
1
10
Over branch
16
9
12
9
46
Over stump
2
0
2
0
4
Over stem
11
2
9
2
24
Subtotal:
512
157
1024
Total
325
130
412
Ponce, Suzán and Francke
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A
60
PERCENT
50
40
males
females
30
20
10
0
cesp
vava
vaci
disp
SPECIES
SPECIES
B
70
60
50
40
30
20
10
0
males
females
cesp
vava
vaci
PERCENT
disp
Ponce, Suzán and Francke
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Ponce, Suzán and Francke
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Ponce, Suzán and Francke
30
Ponce, Suzán and Francke
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Figure 1. Species and sexual proportions after all samplings for the scorpion
communities of Churumuco (A) and Turitzio (B). (cesp= Centruroides balsasensis,
vava=Vaejovis variegatus, vaci=Vaejovis cisnerosi, and disp=Diplocentrus sp.).
Figure 2. Temperature and precipitation fluctuations in a yearly basis and its correlation
to densities detected in 2001 at Churumuco (hashed vertical lines indicate onset and
termination of the rainy season).
Figure 3. Temperature and precipitation fluctuations in a yearly basis and its correlation
to densities detected in 2001 at Turitzio (hashed vertical lines indicate the onset and
termination of the rainy season).
Figure 4. Stage or instars proportion fluctuation in 2001 for Churumuco and Turitzio
populations.