Romano III, F. A. 2009. Tardigrada of the Gulf of Mexico, Pp. 809–813 in Felder, D.L. and D.K. Camp (eds.), Gulf
of Mexico–Origins, Waters, and Biota. Biodiversity. Texas A&M University Press, College Station, Texas.
• 42
Tardigrada of the Gulf of Mexico
Frank A. Romano, III
Tardigrades are microscopic invertebrates that belong to
the phylum Tardigrada (proposed by Ramazzotti in 1962).
First described by Goeze in 1773 and commonly recognized as “Water Bears” (Wassar Bär) by observers, tardigrades are best classified as one of the “lesser-­known protostomes” (Nelson 1991). Tardigrades, the current name
in use since the 18th century (adopted by Spallanzini in
1776 [Kinchin 1994]), is also a descriptive name based on
the animal’s lumbering gait (tardi-­slow, ­grade-­walker).
Tardigrades are generally considered cosmopolitan in
their distribution and are commonly found in a variety of
marine, freshwater, and terrestrial habitats (Ramazzotti
and Maucci 1983, Nelson 1991, Kinchin 1994): sand, algae,
rooted aquatic vegetation, soil, leaf litter, mosses, lichens,
and liverworts (McInnes 1994). These bilaterally symmetrical micrometazoans are generally flattened on their
ventral side and convex on their dorsal side and average
250–500 µm in length as adults (see Dewel, Nelson, and
Dewel 1993 for detailed morphology). Adult body lengths
range from 50 µm in juveniles to over 1200 µm in adults,
although marine tardigrades rarely exceed 500 µm and
adults of some may be less than 100 µm (Pollock 1976, Nelson 2002). The body is composed of 5 somewhat indistinct
segments, including a cephalic segment (without legs) that
usually bears appendages called cirri, and 4 trunk segments
each supporting a pair of lobopodous legs that terminate in
either claws and / or sucking discs. The first 3 pairs of legs
are directed ventrolaterally and are the primary means of
locomotion, while the fourth pair is directed posteriorly
and is used primarily for grasping the substrate. Tardi-
Tardigrada. After Pollock 1976.
grades have a complete digestive system and a body cavity
that forms a ­fluid-­filled hemocoel, which functions in circulation and respiration. Respiration is entirely cutaneous.
Reproductive modes include sexual (hermaphroditic and
gonochoristic) and parthenogenic (Bertolani and Rebecci
1999). The nervous system consists of a dorsal lobed brain,
a ventral nerve cord, and paired ventral segmental ganglia
(Dewel and Dewel 1996, Nelson 2002). Tardigrades feed by
piercing with hardened stylets the cells of bacteria, algae,
plants (mosses, liverworts, and lichens), or animals (protozoans, rotifers, nematodes, larvae, and other small invertebrates) and sucking out the contents using a muscular
pharynx. In some cases, the whole organism is ingested.
Detritus may also be a major nutrient source of some species. Regardless of their specific habitat (marine, freshwater, or terrestrial), all tardigrades are aquatic because
they require a film of water surrounding the body to be
active. Some, those that are ­limno-­terrestrial, can undergo
809
810 ~ Tardigrada
cryptobiosis when environmental conditions become
unfavorable (e.g., loss of the film of water), creating an
environmentally resistant state. This latent state has a significant impact on the ecological role of ­limno-­terrestrial
tardigrades (Kinchin 1994 and references within).
Tardigrade Taxonomy
Marcus (1929) established the major taxa within the phylum Tardigrada, splitting the group in two and forming the
classes Eutardigrada and Heterotardigrada. The genus Macrobiotus was defined in 1834 (a eutardigrade), and the genus
Echiniscus was defined in 1840 (a heterotardigrade). Within
the heterotardigrades the most useful morphological characters are cephalic appendages, cuticular extensions, claws
and / or sucking discs, and the pattern of dorsal cuticular
plates. Within the eutardigrades the more important morphological characters are the claws, buccopharyngeal apparatus, and cuticle structure (smooth, granulated, or bearing tubercles). A third class, Mesotardigrada was proposed
by Rahm (1937) based on a single species, Thermozodium
esakii Rahm, 1937, discovered in a hot spring near Nagasaki, Japan. Neither type material nor type locality have survived, and no other mesotardigrade has been discovered.
Thus, this class is of dubious status (Nelson 2002).
Tardigrade Phylogeny
In the past, tardigrades have been associated with arthropods or with various aschelminths (Ramazzoti and Maucci
1983). The 18S rRNA studies by Garey, Krotec et al. (1996)
and Garey, Nelson et al. (1999) suggest that tardigrades are
a monophyletic sister group of the arthropods. Ecdysozoa,
defined as a clade of molting animals, provides support
for the close relationship between tardigrades and arthropods (Aguinaldo et al. 1997), as well as between tardigrades and some of the “aschelminths.” Comparisons to
fossil lobopods and arthropods suggest that tardigrades
branch between the Onychophora and Euarthropoda
and are most likely derived from an anomalocariid-­like
member of the euarthropod stem group (Nelson 2002).
The marine heterotardigrades have the greatest number
of plesiomorphic characters and are considered the sister
group for all other tardigrades (Nelson 2002).
Marine Tardigrades
The first marine tardigrade was discovered by Dujardin in 1851. Marcus (1929), in his monograph, recorded
only 6 species of marine tardigrades. These were considered to be rare components of the marine ecosystem.
Schulz described several new species (1935 and 1955), and
­Renaud-­Mornant produced 32 publications describing 9
genera and 27 new species. In her review, ­Renaud-­Mornant
(1982) reported 22 genera of heterotardigrades, with a total
of 56 species found in various marine habitats from subtidal beaches to the deep-­sea. Today, marine tardigrades
are known to inhabit all seas from the intertidal and subtidal zones down to the abyssal zones. They exhibit high
species richness in all habitats, although populations tend
to be small and patchy in distribution. The low number of
species in most marine genera is indicative of their ancient
origin and their morphological diversity (Nelson 2002). In
the intertidal zone on sandy beaches, they are found typically in the interstitial community. In the subtidal zone,
they are present in all types of substrates, with morphological adaptations in response to different subtidal environmental requirements (Nelson 2002).
Gulf of Mexico Tardigrades
The literature concerning tardigrades from the Gulf of
Mexico (GMx) is minimal at best. The first reports were by
Chitwood (1951, 1954) on the occurrence of Bathechiniscus tetronyx Steiner, 1926, in Aransas Bay, Texas. Ramazzotti (1962) considered this identification to be inaccurate
and redescribed these specimens as Styraconyx sargassi
Thulin, 1942. King (1962) reported on the occurrence
of Batillipes mirus Richters, 1909, from Alligator Harbor,
Florida, and Riggin (1962) described a new species, Batillipes friaufi, also from Alligator Harbor, Florida. McKirdy
(1974) reported that only 38 marine tardigrades had been
described worldwide. He recorded 6 species of Batillipes
from Florida, of which B. dicrocercus Pollock, 1970 (Fort
Walton Beach) and B. tubernatis Pollock, 1971 (several
sites in Florida) were added to the Gulf of Mexico fauna.
In 1984 Kristensen and Higgins reviewed the status of
marine tardigrades, suggesting that 22 genera and 56 species were recorded from a wide variety of marine habitats from the deep-­sea to beaches. At this time the known
marine tardigrade fauna of the Gulf of Mexico consisted
of only 2 genera and 5 species. Since then, to my knowledge, the only literature reporting marine tardigrades in
the Gulf of Mexico is that of Nichols, Nelson, and Garey
(2006), which reports B. mirus from Dauphin Island, Alabama, and 2 records that were based upon a Gulf of Mexico deep-­sea research cruise during 2000 (see Baguley
et al. 2006). Materials from the latter effort were examined
Romano ~ 811
by Romano, Gallo, D’Addabbo, and Sanduli (Romano,
Gallo, D’Addabbo and Montagna 2006, Romano, Gallo,
D’Addabbo, Sanduli et al. 2006). Those samples taken
from the Texas / Mexico border to the Florida peninsula
over depths of 625–3150 m produced 6 species of marine
tardigrades and 5 genera, with at least one of these representing a new species that remains undescribed: Coronarctus laubieri ­Renaud-­Mornant, 1974; C. stylisetus
­Renaud-­Mornant, 1987; C. n. sp.; Angursa abyssalis Pollock, 1979; Euclavarctus convergens ­Renaud-­Mornant,
1983; E. thieli ­Renaud-­Mornant, 1975; Styraconyx sp.; and
Proclavarctus sp. None of these species have ever been published as being present in the Gulf of Mexico. In addition,
a single specimen of Paradoxipus orzeliscoides Kristensen
and Higgins, 1989, is known from a sample of dredge tailings from the Mobile Bay, Alabama ship channel, and many
specimens of Batillipes mirus, B. friaufi, and B. dicrocercus
are known from intertidal and subtidal sands on Dauphin
Island and Sand Island, Alabama (F. Romano, unpublished
data, specimens archived in Jacksonville State University’s
invertebrate collection).
The classification and nomenclature adopted here
generally follow that compiled by Miller and Beasley and
maintained at the academy of natural sciences in Philadelphia, Pennsylvania (http: // tardigrade.acnatsci.org / science / ). Families, genera, and species are arranged
alphabetically. Depth data are based on records of collections from the Gulf of Mexico.
Abbreviations
The following abbreviations are used in the accompanying
checklist under “Habitat-­Biology”: ben = benthic; bns = bay
and nearshore; bsl = beach and shoreline; dps = deep sea;
ins = interstitial; sft = soft substrates (mud, sands, clays);
sgm = Sargassum. Abbreviations used under the heading
“Overall geographic range” are as follows: SE = southeastern United States and the Bahamas; NE = northeastern
United States and Atlantic Canada; SA = Atlantic coast of
South America; EA = eastern Atlantic; SS = Sargasso Sea;
MD = Mediterranean Sea; IO = Indian Ocean; WP = western Pacific; EP = eastern Pacific; SP = South Pacific; AN =
Antarctica; GO =only known from the Gulf of Mexico.
References
1. Aguinaldo, A., J. Turbeville, L. Linford, M. Rivera, J. Garey,
R. Raff, and J. Lake. 1997. Evidence for a clade of nema-
todes, arthropods, and other moulting animals. Nature
387: 489–493.
2. Baguley, J. G., P. A. Montagna, W. Lee, L. J. Hyde, and
G. T. Rowe. 2006. Spatial and bathymetric trends in
Harpacticoida (Copepoda) community structure in the
northern Gulf of Mexico deep-­sea. Journal of Experimental
Marine Biology and Ecology 330: 327–341.
3. Bertolani, R., and L. Rebecchi. 1999. Tardigrada. Pp.
703–718 in E. Knobil and J. D. Neill, eds. Encyclopedia of
Reproduction, Vol. 4. Academic Press, San Diego.
4. Chitwood, B. G. 1951. A marine tardigrade from the Gulf
of Mexico. The Texas Journal of Science 3(1): 111–112.
5. Chitwood, B. G. 1954. Tardigrades of the Gulf of Mexico.
Pp. 325 in Gulf of Mexico, Its Origin, Waters, and Marine
Life. Fishery Bulletin 89. Fishery Bulletin of the Fish and
Wildlife Service, Vol. 55, Washington, D.C.
6. Dewel, R., and W. Dewel. 1996. The brain of Echiniscus
viridissimus Peterfi, 1956 (Heterotardigrada): a key to
understanding the phylogenetic position of tardigrades
and the evolution of the arthropod head. Pp. 35–49 in
S. McInnes and D. Norman, eds. Tardigrade Biology.
Proceedings of the Sixth International Symposium on
Tardigrada, August 1994, Cambridge, England. Zoological
Journal of the Linnaean Society of London, Vol. 116.
7. Dewel, R. A., D. R. Nelson, and W. C. Dewel. 1993.
Tardigrada. Pp. 143–183 in F. W. Harrison and M. E. Rice,
eds. Microscopic Anatomy of Invertebrates. Vol. 12:
Onychophora, Chilopoda, and Lesser Protostomata.
Wiley-­Liss, New York.
8. Dujardin, F. 1851. Sur les Tardigrade et sur une espèce a
longs pieds vivant dans l’eau de mer. Oberservations
Zoologiques 15: 161–167.
9. Garey, J. R., M. Krotec, D. R. Nelson, and J. Brooks. 1996.
Molecular analysis supports a ­tardigrade-­arthropod
association. Invertebrate Biology 115(1): 79–88.
10. Garey, J. R., D. R. Nelson, L. Y. Mackey, and J. Li. 1999.
Tardigrade phylogeny: congruency of morphological and
molecular evidence. Zoologischer Anzeiger 238:
205–210.
11. Goeze, J. A. E. 1773. Uber den Kleinen Wasserbär. Pp. 67 in
H. K. Beobachtg Bonnet, ed. Abhandlungen aus der
Insectologie, Ubers. Usw. 2.
12. Kinchin, I. M. 1994. The Biology of Tardigrades. Blackwell
Publishing Company, London.
13. King, C. E. 1962. The occurrence of Batillipes mirus
Richters (Tardigrada) in the Gulf of Mexico. Bulletin of
Marine Science of the Gulf and Caribbean 12(2): 201–203.
14. Kristensen, R. M., and R. P. Higgins. 1984. A new family of
Arthrotardigrada (Tardigrada: Heterotardigrada) from the
812 ~ Tardigrada
Atlantic coast of Florida, U.S.A. Transactions of the
American Microscopical Society 103: 295–311.
15. Marcus, E. 1929. Tardigrada. Klassen und Ordnungen des
tierreichs 5: 1–608.
16. McInnes, S. J. 1994. Zoogeographic distribution of
terrestrial / freshwater tardigrades from current literature.
Journal of Natural History 28: 257–352.
17. McKirdy, D. J. 1974. Batillipes (Heterotardigrada):
comparison of six species from Florida (U.S.A.) and a
discussion of taxonomic characters within the genus. Pp.
177–223 in R. P. Higgins, ed. International Symposium on
Tardigrades, Pallanza, Italy, June 17–19, 1974. Memorie
dell’Istituto Italiano di Idrobiologia, Supplement 32.
18. Nelson, D. 1991. Tardigrada. Pp. 501–521 in J. H. Thorp
and A. P. Covich, eds. Ecology and Classification of North
American Freshwater Invertebrates. Academic Press,
London.
19. Nelson, D. R. 2002. Current status of the Tardigrada:
evolution and ecology. Integrative and Comparative
Biology 42: 652–659.
20. Nichols, P. B., D. R. Nelson, and J. R. Garey. 2006. A family
level analysis of tardigrade phylogeny. Hydrobiologia 558:
53–60.
21. Pollock, L. W. 1970. Batillipes dicrocercus n. sp., Stygarctus
granulatus n. sp. and other Tardigrada from Woods Hole,
Massachusetts, USA. Transactions of the American
Microscopical Society 89(1): 38–52.
22. Pollock, L. W. 1971. On some British marine Tardigrada,
including two new species of Batillipes. Journal of the
Marine Biological Association of the United Kingdom 51:
93–103.
23. Pollock, L. W. 1976. Marine flora and fauna of the
northeastern United States. Tardigrada. NOAA Technical
Report NMFS CIRC 394: 1–24.
24. Pollock, L. W. 1979. Angursa bicuspis n. g., n. sp., a marine
arthrotardigrade from the western North Atlantic.
Transactions of the American Microscopical Society 98(4):
558–562.
25. Rahm, G. 1937. A new order of tardigrades from the hot
springs of Japan (Furu-­Section, Unzen). Annotationes
Zoologica Japonenses 16: 345–352.
26. Ramazzotti, G. 1962. Il Phylum Tardigrada. Memorie
Istituto di Idrobiologia 16: 1–595.
27. Ramazzotti, G. 1972. Il Phylum Tardigrada (Seconda
edizione aggiornata). Memorie Istituto di Idrobiologia 28:
1–732.
S ubmitted: August 2007
Accepted: August 2007
28. Ramazzotti, G., and W. Maucci. 1983. Il Phylum Tardigrada. III edizione riveduta ed aggiornata (English
translation by C. W. Beasley 1993). Memorie dell’Istituto
Italiano di Idrobiologia Dottor Marco de Marchi 41:
1–1012.
29. Renaud-­Mornant, J. 1974. Une nouvelle famille de
tardigrades marins abyssaux: les Coronarctidae fam. nov.
(Heterotardigrada). Comptes rendus des seances de
l’Academie des Sciences 278: 3078–3090.
30. Renaud-­Mornant, J. 1975. Deep-­sea Tardigrada from
“Meteor” Indian Ocean Expedition. “Meteor” Forsch.­Ergebnisse 21: 54–61.
31. Renaud-­Mornant, J. 1982. Species diversity in marine
Tardigrada. Pp. 148–178 in D. Nelson, ed. Proceedings of
the Third International Symposium on Tardigrada.
Johnson City, Tennessee, U.S.A. 1980. East Tennessee State
University Press, Johnson City.
32. Renaud-­Mornant, J. 1983. Tardigrades abyssaux nouveaux
de la sous-­famille des Euclavarctinae, n. subfam. (Arthrotardigrada, Halechiniscidae). Bulletin Museum National
d’Histoire Natural, Paris, 4e Ser., 5, Sect. A(1): 201–219.
33. Renaud-­Mornant, J. 1987. Bathyal and abyssal Coronarctidae (Tardigrada), descriptions of new species and
phylogenetical significance. Pp. 229–252 in R. Bertolani,
ed. Biology of Tardigrades. Selected Symposia and
Monographs, Unione Zoologica Italiana, Modena.
34. Richters, F. 1909. Marine Tardigraden. Verhandl. d.
Deutsch. Zool. Gesellschaft 19: 84–94.
35. Riggin, G. T. 1962. Tardigrada of southwest Virginia: with
the addition of a description of a new marine species from
Florida. Virginia Agricultural Experiment Station,
Technical Bulletin 152: 1–145.
36. Romano, F. A., III, M. Gallo, R. D’Addabbo, and P. Montagna. 2006. A first look at deep-­sea tardigrades in the
northern Gulf of Mexico. Southeastern Biologist 54: 253.
37. Romano, F. A., III, M. Gallo, R. D’Addabbo, R. Sanduli,
J. Baguley, and P. Montagna. 2006. Bathyl tadigrades of the
northern Gulf of Mexico (U.S.A.). Abstracts of the 38th
Congresso dell Società Italiana di Biologia Marina Santa
Margherita Ligure (GE): 104–105.
38. Schulz, E. 1935. Actinarctus doryphorus nov. gen., nov. sp.,
ein mekwürdiger Tardigrad aus der nordsee. Zoologischer
Anzeiger 111: 285–288.
39. Schulz, E. 1955. Studien an marinen Tardigradem. Keiler
Meeres 11: 74–79.
40. Thulin, G. 1942. Ein neuer mariner Tardigrad. Meddel.
Göteborg Museum of Zoology 99: 1–10.
Romano ~ 813
Taxonomic summary for Tardigrada of the Gulf of Mexico.
Family
Batillipedidae
Halechiniscidae
Coronarctidae
Total
Total species
Number endemic species
4
5
3
0
0
1
12
1
Checklist of Tardigrada from the Gulf of Mexico.
Taxon
Class: Heterotardigrada
Order: Arthrotardigrada
Family: Batilipedidae
Batillipes dicrocercus Pollock, 1970
Batillipes friaufi Riggin, 1962
Batillipes mirus Richters, 1909
Batilipes tubernatis Pollock, 1971
Family: Halechiniscidae
Subfamily: Coronarctinae
Coronarctus laubieri ­Renaud-­Mornant, 1987
Coronarctus sp.
Coronarctus stylisetus Renaud-­Mornant, 1987
Subfamily: Euclavarctinae
Euclavarctus convergens Renaud-­Mornant, 1983
Euclavarctus thieli Renaud-­Mornant, 1975
Proclavarctus sp.
Subfamily: Halechiniscinae
Paradoxipus orzeliscoides Kristensen & Higgins,
1989
Subfamily: Styraconyxinae
Angursa abyssalis Pollock, 1979
Styraconyx sargassi Thulin, 1942
Styroconyx sp.
1
Habitat-­
Biology
ins, bsl, sft
ins, bns, bsl, sft
ins, bsl, sft
ins, bns, bsl, sft
Depth
(m)
0–2
0–2
0–10
0–2
Overall
geographic range
GMx
range
References / Endnotes
NE, SE, MD
GO
NE, SE, EA, IO, EP
SE, EA, SA
ne
nne
ne
ne
23
17
35
13
17
ins, dps, sft
ins, dps, sft
ins, dps, sft
1975–6150
763–3000
3000
EA, MD, IO
GO
EA, MD, IO
nw
nw–nne
nnw
26
36, 37
36, 37
36, 37
ins, dps, sft
ins, dps, sft
ins, dps, sft
2743
2635
2600
EA, IO
EA, IO, SP
ne
nnw
nnw
36, 37
36, 37
36, 37 1
SE
nne
2
EA, AN
SS, EA, MD, SP, EP
nnw–nne
nnw
nnw
ins, bns, sft
na
ben, dps, sft
sgm, bns
ben, sft
763–2020
1
1565–2600
35
36, 37
4, 5
36, 37 1
Single specimen that was too damaged to identify to species.
Based on a single specimen found in fresh dredging from the ship channel in or just outside of Mobile Bay that was deposited on the beach on Dauphin Island,
Alabama.
2