2012 SOUTHEASTERN NATURALIST 11(3):469–476
Tardigrades of the University of Central Arkansas
Campus, Conway, AR
Marshalluna Land1, Adam Musto1, William R. Miller2, David E. Starkey1,
and Jeffrey D. Miller1,3,*
Abstract - Tardigrades were recovered from samples of moss and lichen growing on
the bark of seven species of trees on the University of Central Arkansas (UCA) campus
in Conway, AR. Of the 11 genera of tardigrades previously reported from the state, five
were found in the UCA campus samples; of the 25 species previously reported, five were
found in the UCA campus samples. Two species (Milnesium eurystomum, Macrobiotus
polyopus) are new records for the state; one species of Echiniscus (arctomys group) could
not be identified and may be new. Tardigrades were not uniformly distributed among
available habitats (moss, lichen) or substrates (trees).
Terrestrial tardigrades are small (0.5 mm) metazoans that typically inhabit
mosses and lichens growing on trees, rocks, and the ground (McInnes 1994,
Miller 1997). Little is known about their ecology, although other aspects of their
biology are better documented (Kinchen 1994). Tardigrades are best known for
their ability to survive conditions such as extreme cold and heat in a desiccated
state called cryptobiosis (Miller 1997). Recently, tardigrades have become the
first multi-celled animal to survive the vacuum, radiation, and temperature of
outer space (Jonsson et al. 2008).
The distributions of North American taxa are poorly known (McInnes 1994,
Miller 1997). Multiple genera of tardigrades have been reported from the states
contiguous to Arkansas (Louisiana: Hinton et al. 2010, Meyer and Domingue
2011; Mississippi: Hinton and Meyer 2009, Mitchell and Romano 2007;
Missouri: Hidalgo and Combs 1985, Hohl et al. 2001, Lehmann et al. 2007; Oklahoma:
Beasley 1978, Beasley and Pilato 1987, Lee and Woolever 1983; Texas:
Hinton and Meyer 2007, Mehlen 1969, Miller and Mehlen 2007).
To date, only three papers deal with tardigrades of Arkansas. Beasley and
Pilato (1987) described a new species Doryphoribius gibber Beasley and Pilato
based on specimens found in Benton County. Meyer (2001) reported 21 species
from sites in Benton, Crawford, Franklin, Polk, and Washington counties.
Meyer (2006) reported on the distribution and abundance of tardigrades in small
samples in the Ouachita Mountains; he added two species to the state biodiversity
list and extended the distribution of four others.
1Department of Biology, University of Central Arkansas, Conway, AR 72035. 2Department
of Biology, Baker University, Baldwin City, KS 66006. 3Biological Research and
Education Consultants, 446 Dearborn Avenue, Missoula, MT 59801. *Corresponding
author - BioResEdCon@gmail.com.
470 Southeastern Naturalist Vol. 11, No.3
This report extends tardigrade distribution and diversity to Faulkner County in
the central part of the state, and offers analyses for patterns of habitat associations.
Materials and Methods
The study area was the developed part of the University of Central Arkansas
(UCA) campus, Conway, AR. Mosses and lichens were sampled to represent their
occurrence on mature trees during December 2009 and March 2010. Each tree
(substrate) was identified and located with a handheld GPS unit. Each habitat
sample (approximately 5 x 5 cm) was scraped into a small paper bag and dried at
room temperature. The dry samples were divided; half was stored as a herbarium
sample and the other half was soaked in 25 ml of bottled water for 24 hours.
Three 2-ml aliquots of the debris were extracted with a disposable pipette and
examined at 20x magnification under a dissecting microscope. Specimens were
mounted on a glass slide in PVA (polyvinyl alcohol) media with an Irwin loop.
The cover slip was sealed with clear fingernail polish and the location of the
specimen marked on the slide. Specimens were examined with an Olympus DX-
60 differential interference contrast (DIC or Nomarski) microscope. The keys
found in Ramazzotti and Maucci (1983), Nelson and McInnes (2002), and Pilato
and Binda (2010) were used for identification.
Chi-square tests were used to compare expected occurrence to the observed
data (Zar 1999). The expected or null hypothesis is for uniformity of dispersion
based on the assumptions that within a small area (the campus): (a) all species are
distributed equally, (b) all substrates (trees) support all habitats (moss and lichen)
equally, and (c) the occurrence of a tardigrade indicates that the conditions were
within the survivable range of the species. Therefore, a statistical difference from
the expected uniformity of occurrence of habitats and tardigrades provided evidence
of habitat preference by the species.
Sixty-nine samples (40 moss, 29 lichen) were collected from 14 trees of
seven species (Table 1) on the UCA campus (35°04'52.5"N, 92°27'46.5"W) in
Conway, AR. Two classes, three orders, three families, five genera, and eight
species of tardigrades were recovered. The species identified were Echiniscus
maucii Ramazzotti, Milnesium tardigradum Doyère, Milnesium eurystomum
Maucci, Macrobiotus cf. hufelandi C.A.S. Schultze, Macrobiotus polyopus Marcus,
Paramacrobiotus tonollii (Ramazzotti), Minibiotus intermedius (Plate), and
an unidentifiable species of Echiniscus in the arctomys group that may be new.
Seven specimens were classified as Macrobiotus cf. hufelandi, but without eggs
the identification was considered tentative.
One hundred and two tardigrades were recovered; 36 (35.3%) were found
in lichen samples, and 66 (64.7%) were recovered from moss (Table 1). Moss
and lichen habitats on two of six genera of trees (Quercus [oak], Liquidambar
[sweet gum]) were home to all eight species and more than 81.4% of the
specimens (Table 1). Two species, Minibiotus intermedius (n = 42) and
2012 M. Land, A. Musto, W.R. Miller , D.E. Starkey, and J.D. Miller 471
Table 1. Numbers of tardigrades recovered from habitats on substrates on the UCA campus. M. i. = Minibiotus intermedius, M. t. = Milnesium tardigradum,
M. h. = Macrobiotus hufelandi, E. m. = Echiniscus mauccii, M. e. = Milnesium eurystomumm, P. t. = Paramacrobiotus tonollii, M. p. = Macrobiotus polyopus,
and E.sp. 3. = Echiniscus sp. 3.
Substrate Habitat recovered M. i. M. t. M. h. E. m. M. e. P. t. M. p. E. sp. 3
Quercus accutissima Carruthers Moss 15 12 1 2
(Sawtooth Oak) Lichen 7 5 2
Quercus phellos L. Moss 27 5 16 1 1 2 2
(Willow Oak) Lichen 11 2 5 2 1 1
Liquidambar styraciflua L. Moss 14 6 5 1 1 1
(Sweet Gum) Lichen 9 6 1 1 1
Magnolia grandiflora L. Moss 1 1
(Southern Magnolia) Lichen 3 1 2
Prunus serotina Ehrhart Moss 3 1 1 1
(Black Cherry) Lichen 2 2
Liriodendron tulipifera L. Moss 3 2 1
(Tulip Tree) Lichen 3 3
Catalpa speciosa (Warder ex Barney) Moss 3 3
Engelmann (Northern Catalpa) Lichen 1 1
Totals 102 42 37 7 6 4 3 1 2
% specimens by species 41.2 36.3 6.9 5.9 3.9 2.9 1.0 2.0
Substrates selected (n = 7) 6 3 3 6 3 2 1 1
Specimens per habitats (moss/lichen) 26/13 24/13 6/1 2/4 3/1 3/0 0/1 2/0
472 Southeastern Naturalist Vol. 11, No.3
Milnesium tardigradum (n = 37), comprised 77.5% of the specimens; the other
six species contributed only 22.5% to the total (Table 1). Five tardigrade species
occurred in both moss and lichen habitats, while two species (Paramacrobiotus
tonollii, Echiniscus sp. 3), were found only in moss habitats, and one species
(Macrobiotus polyopus) was only recovered from a lichen sample. The average
number of tardigrades recovered per sample ranged from 7.5 to 0.25, with
a mean of 1.48. Moss samples yielded a mean of 1.65 tardigrades per sample,
while the lichen samples yielded a mean of 1.24.
Moss and lichen habitats did not occur uniformly (χ2 = 8.64, df = 1, P < 0.05).
Likewise, tardigrades were not distributed evenly on the substrates (χ2 = 199.14,
df = 6, P < 0.05). Accepting the differential occurrence of the habitats, we altered
the assumption of tardigrade occurrence to be proportional to the availability of
moss (64.7%) and lichen (35.3%) habitats. Still, tardigrades were not distributed
in proportion to the habitat (χ2 = 87.05, df = 13, P < 0.05; Table 2).
Because chi-square of the total is a summation of the individual chi-squares
for the parts, it is possible to evaluate the contribution of the parts to the total.
Our individual calculated chi-square values ranged from 0.19 to 44.67, and three
calculated values were significantly greater than the critical value (Table 2). The
tardigrades from the moss and lichen habitats found on Magnolia grandiflora
(Southern Magnolia) substrate exhibited a reversal of the expected ratios,
resulting in significant values for chi-square (moss: χ2 = 24.36, lichen: χ2 = 44.67,
df = 1, P < 0.05). The lichen samples from Liriodendron tulipifera (Tulip Tree)
Table 2. Chi-squared analysis of the occurrence of tardigrades recovered from moss and lichen
samples on trees of the University of Central Arkansas campus. Trees = # of trees sampled, tard./
substrate = # of tardigrades recovered per substrate, % tard. = % tardigrades, χ2 = calculated χ2
with df = 1, tard./habitat = # of tardigrades recovered per habitat, % spec. = % specimens.
Tard./ % # Tard./ %
Substrate trees substrate tard. χ2 Habitat samples habitat spec. χ2
Quercus accutissima 1 22 21.6 30.32A Moss 2 15 68.2 0.19
(Sawtooth Oak) Lichen 2 7 31.8 0.34
Quercus phellos 5 38 37.3 130.77A Moss 16 27 71.1 0.62
(Willow Oak) Lichen 10 11 28.9 1.14
Liquidambar styraciflua 4 23 22.5 34.54A Moss 10 14 60.9 0.23
(Sweet Gum) Lichen 8 9 39.1 0.42
Magnolia grandiflora 1 4 3.9 1.35 Moss 4 1 25.0 24.36A
(Southern Magnolia) Lichen 2 3 75.0 44.67A
Prunus serotina 1 5 4.9 0.63 Moss 2 3 60.0 0.34
(Black Cherry) Lichen 3 2 40.0 0.63
Liriodendron tulipifera 1 6 5.9 0.18 Moss 3 3 50.0 3.34
(Tulip Tree) Lichen 2 3 50.0 6.13A
Catalpa speciosa 1 4 3.9 1.35 Moss 3 3 75.0 1.64
(Northern Catalpa) Lichen 2 1 25.0 3.00
df = 6 df = 13
Totals 14 102 199.14B 69 102 87.05C
Asignificant (χ2 [0.05] = 3.84, df = 1)
Bsignificant (χ2 [0.05] = 12.59, df = 6)
Csignificant (χ2 [0.05] = 22.36, df = 13)
2012 M. Land, A. Musto, W.R. Miller , D.E. Starkey, and J.D. Miller 473
contained significantly more tardigrades than expected (lichen: χ2 = 6.12, df = 1,
P < 0.05; Table 2.)
The taxonomy and distribution of tardigrades in Arkansas are poorly described.
Only three papers have dealt with tardigrades in the western and northwestern
portions of the state (Table 3). We have reduced the list of species found by
Meyer (2001) by one. Echiniscus banus Caskey, 1971 is not a described species
(Degma et al. 2011a). It should be, but its description has never been published.
It was reported in a 1971 unpublished Master’s thesis titled “The Tardigrades of
Texas” by D.S. Caskey at Lamar University. We have imbedded the reference
here and listed the animals as Echiniscus sp. 2 in Table 3.
Table 3. Tardigrades of Arkansas. Key: 1= Beasley and Pilato 1987; 2 = Meyer 2001; 3 = Meyer
2006; 4 = this report. Counties: B = Benton, C = Crawford, Fa = Faulkner, Fr = Franklin, P = Polk,
and W = Washington.
Genus species B C Fa Fr P W
Echiniscus mauccii Ramazzotti, 1956 4 2
E. virginicus Riggin, 1962 3 2
Echiniscus sp. 1 2 2 2 2
Echiniscus sp. 2 (E. banus Caskey, 1971) 2
Echiniscus sp. 3 4
Pseudechiniscus brevimontanus Kendall-Fite 2
and Nelson, 1996
P. novaezelandiae (Richters, 1908) 2 2
P. suillus (Ehrenberg, 1853) 2 2 2
Milnesium tardigradum Doyère, 1840 2 2 4 2 2, 3 2
M. eurystomum Maucci, 1991 4
Astatumen trinacriae (Arcidiacono, 1962) 2
Diphascon (Diphascon) alpinum Murray, 1906 2
Hypsibius calcaratus Bartoš, 1935 2 2
H. convergens (Urbanowicz, 1925) 2
Ramazzottius baumanni (Ramazzotti, 1962) 3
R. oberhaeuseri (Doyère, 1840) 2 3 2
Doryphoribius gibber Beasley and Pilato, 1987 1
Macrobiotus echinogenitus Richters, 1904 2 2 2 2 2
M. cf. harmsworthi (Murry, 1907) 2 3
M. cf. hufelandi C.A.S. Schultze, 1833 4 2
M. islandicus Richters, 1904 2
M. occidentalis Murray, 1910 2 2
M. polyopus Marcus, 1928 4
Macrobiotus sp. 1 2 2 2 2, 3 2
Macrobiotus sp. 2 2 2 2 2
Paramacrobiotus tonollii (Ramazzotti, 1956) 4 3
P. areolatus (Murray, 1907) 2
Minibiotus furcatus (Ehrenberg, 1859) 2
M. intermedius (Plate, 1888) 2 2 4 2 2, 3 2, 3
474 Southeastern Naturalist Vol. 11, No.3
The samples collected on the UCA campus contained 5 of the 11 genera previously
found in Arkansas and 5 of the 25 known species. Two species (Milnesium
eurystomum, Macrobiotus polyopus) are new records for the state; Echiniscus sp.
3 could not be identified to species and may be a new record for the state because
Meyer (2001) reported two unidentified species for the genus but did not describe
them sufficiently to allow comparison.
On a larger scale, three tardigrade species (Milnesium tardigradum, Minibiotus
intermedius, Macrobiotus cf. hufelandi) are cosmopolitan in distribution
(McInnes 1994) and are likely to be widespread in Arkansas. Two other species
(Macrobiotus tonolli, Echiniscus maucci) are restricted to North America and
have known distributions in contiguous states, Missouri and Tennessee (McInnes
1994). As such, their occurrence in Arkansas was not unexpected. Two species
(Milnesium eurystomum, Macrobiotus polyopus) are new records for the state.
One species (Macrobiotus polyopus) has previously been reported only from
South America and Southeast Asia; the extension of its range to North America is
unusual but not unexpected because tardigrades are believed to be wind dispersed
(Miller 1997). Isolated records of species known previously only from other
continents may also be the product of passive transport by the global movement
of ornamental plant products or other human actions (Kinchin 1994). This global
transport might make a tardigrade species invasive, and with their documented
ability to be a vector for plant pathogenic bacteria (Krantz et al. 1999), might
elevate them to an economically important level.
The differences in the number of tardigrades recovered from the habitat
samples collected from a single substrate species when compared to the number
collected from any of the other single substrate species indicates that the habitat/
substrate combination likely impacts the suitability of the habitat for tardigrades.
Therefore, a species that exhibits an unequal distribution may be expressing habitat
The total number of tardigrades recovered from moss and lichen provides
an indication of the suitability of the habitats to support tardigrades. In general,
moss supported more tardigrades numerically and taxonomically than lichen
Two species (Minibiotus intermedius, Milnesium tardigradum) were recovered
in higher numbers from almost every habitat from each substrate where they
occurred with other species (Table 1). The exceptions to their ubiquitous distribution
include the lack of these species from moss growing on Southern Magnolia,
and lichen on Prunus serotina (Black Cherry) and Tulip Trees, and both habitats
on Catalpa speciosa (Northern Catalpa) (Table 1).
On average, 64.7% of the specimens were recovered from moss samples
regardless of the substrate on which the moss grew (Table 1). The exception
to the general pattern occurred on Southern Magnolia. On this tree, the ratio of
tardigrades recovered from moss and lichen samples was reversed (Table 2). In
addition, the number of tardigrades was higher than expected on the Tulip Tree.
Although the numbers of specimens are low, the reversal in the expected pattern
in these two substrates indicates further collection and analysis are warranted.
2012 M. Land, A. Musto, W.R. Miller , D.E. Starkey, and J.D. Miller 475
The difference in the distribution of moss and lichen, perhaps as a consequence
of the characteristics of the substrate (tree), may be a major contributing
factor to distribution of tardigrades. The more frequent occurrence of tardigrades
in moss on oak trees than on the Southern Magnolia tree may reflect the difference
in the bark structure and water dynamics. Oak trees have a much rougher
bark than Southern Magnolia trees, which may affect the ability of the moss to
adhere and grow on the substrate.
Although raising the issue of subtle aspects of tardigrade ecology, the results
of the present study are descriptive rather than predictive. The number of tardigrades
and the species composition found in a sample vary considerably over
a short distance (Degma et al. 2011b, Meyer 2006, Miller et al. 1994). At the
present time, cataloging species and reporting relative abundance in samples is
important to assembling a clearer picture of the diversity and distribution of tardigrades
on local, regional, and continental scales.
We wish to acknowledge the support of the study by the Department of Biology of the
University of Central Arkansas. W.R. Miller was supported by the Department of Biology
of Baker University and NSF Grant DEB 0640847.
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