First record of Dactylobiotus parthenogeneticus Bertolani , 1982 ( Eutardigrada : Murrayidae ) in Mexico

In this paper we provide the first record of the eutardigrade Dactylobiotus parthenogeneticus Bertolani, 1982 from Mexico (North America). Our report increases the range of this species and the number of tardigrade species known from Mexico to 43 taxa.

To date, only few studies on Mexican water bears have been conducted and the tardigrade fauna of this region is very poorly known.Up to now, only 42 tardigrade taxa have been reported from Mexico (Heinis 1911;May 1948;Schuster 1971;Beasley 1972;Claps and Rossi 2002;Pilato and Lisi 2006;Beasley et al. 2008;Kaczmarek et al. 2011), including only one freshwater species, Doryphoribius evelinae (Marcus, 1928) reported by Schuster (1971) from Chihuahua State.Moreover, 16 of the reported taxa represent rather doubtful records and need of confirmation (Kaczmarek et al. 2014b).
The genus Dactylobiotus Schuster, 1980 is widespread throughout the world and contains 17 exclusively freshwater species (Degma and Guidetti 2007;Degma et al. 2015).However, the taxonomic position of its type species D. macronyx (Dujardin, 1851) is still unclear and two other species, D. aquatilis Yang, 1999 andD. henanensis Yang, 2002, need to be re-evaluated; as taxonomically important characters were omitted in the original descriptions (see: Kaczmarek et al. 2008).In this short note, we provide the first report of this genus from Mexico.
All specimens were extracted according to Dastych (1980Dastych ( , 1985) ) and Ramazzotti and Maucci (1983) from an algal sample (Stigeoclonium sp.) collected from the Santa Catarina River in Huasteca Canyon (Garza García Municipality, Figure 1) in June 2014.No eggs of D. parthenogeneticus were found in the field samples.However, some of the extracted specimens were put into Petri dish together with algae filaments and cultured until they deposited eggs.All individuals and eggs were fixed and mounted on microscope slides in polyvinyl alcohol with Evanol and lacto-phenol (PVA mounting medium from BioQuip Products Inc., catalogue number 6371A).Observations, measurements and photomicrographs were taken using Phase Contrast Microscopy (PCM) (AmScope T690C-PCT200-PL with digital camera AmScope MU1000).All measurements are given in micrometers (μm).Structures were measured only if their orientations were suitable.The body length was measured from the mouth opening to de end of the body excluding the hind legs.The macroplacoid length sequence is given according to Kaczmarek et al. (2014a).Claw lengths were measured according to Binda and Pilato (1999).Only external claws (anterior in claws IV) were measured.The pt ratio is the ratio of the length of a given structure to the length of the buccal tube, expressed as a percentage (Pilato 1981).Morphometric data were handled using the "Macrobiotoidea" ver.1.1 template available from the Tardigrada Register (Michalczyk and Kaczmarek 2013).
The specimens of D. parthenogeneticus were identified using the keys in Ramazzotti and Maucci (1983), Kaczmarek et al. (2012) and based on the original species description (Bertolani 1982).The specimens are deposited in the Coleccion Carcinológica-FCB-UANL at Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, México (FCB-UANL-TARDI-22 -LAM-0006, FCB-UANL-TARDI-22-LAM-0008, eggs: FCB-UANL-TARDI-22 -LAM-0007).Teeth are rounded or slightly oval granules and spaces between teeth usually as wide as teeth themselves; these teeth decrease in size towards the front.The third band of teeth is composed of two ventro-lateral and two dorsolateral teeth, which are in the shape of transverse ridges.It has oval ventro-median and dorso-median tooth which are distinctly separated from the ventrolateral and dorso-lateral teeth.
Diagnosis (measurements and pt values are given in Tables 1-2): Freshwater eutardigrade (Figure 2).Body white (in live specimens) or transparent (after fixation in PVA).Eyes present (in 100% of live specimens and in 80% of fixed individuals).Cuticle without gibbosities, spines or pores, but with two dorso-lateral conical papillae.
Bucco-pharyngeal apparatus of the Macrobiotus type with ventral lamina and ten peribuccal lamellae (Figure 3).Peribuccal papulae absent.Mouth antero-ventral.Oral cavity armature well developed, consisting of two bands of teeth.The first band of teeth in the anterior present on all legs.Accessory points well developed on the primary branches of claws (Figure 4), but better visible on hind legs (Figure 5).
Eggs are large spherical or slightly oval (Figure 6) and laid free.Eggs processes in shape of small, sharp and wide (at the base) cones.The majority of processes have a single sharp tip, but some may have two or even three tips (Figure 7).Processes and surface between processes smooth under PCM.
Dactylobiotus parthenogeneticus is known from Italy (Modena, Emilia, Sicily, Sardinia, Marche and Lazio), Greece and Spain (Despeñaperro, Jaen and Sumidero del Calderon, Cantabria) (Bertolani 1981(Bertolani , 1982;;Binda and Pilato 1999;Guil 2002).In South America, the species was reported from Buenos Aires and Las Pampas in Argentina and from La Paz in Bolivia (Meyer 2013;Kaczmarek et al. 2015).In this paper, we present a first record of this species from Mexico.
As it was mentioned in the introduction, the tardigrades of Mexico are very poorly known (for example, in Costa Rica, a country almost 40 times smaller, 61 taxa have been reported, while in Mexico there are only 42 (Kaczmarek et al. 2014b)).Out of 32 Mexican states, 23 have never had tardigrade reports.The state with the highest number of reported tardigrade taxa is Chihuahua, with 13 species, followed by Chiapas with 12 reported species.With this new record, the number of tardigrades from Mexico increases to 43    species, from which 41 are terrestrial and only two are freshwater (Kaczmarek et al. 2011;Kaczmarek et al. 2014b).Moreover, it is the first record of tardigrade species for the state of Nuevo León.

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List 11(4): 1723, 25 August 2015 doi: http://dx.doi.org/10.15560/11.4.1723ISSN 1809-127X © 2015 Check List and Authors Notes oN GeoGraphic DistributioN Moreno et al. | New record of Dactylobiotus parthenogeneticus in Mexico portion of the oral cavity is absent or not visible under PCM.The second band of teeth placed in the posterior portion of the oral cavity, just before the third band of teeth.The band is continuous and composed of 4-5 irregular rows of small, densely arranged teeth.

Figure 1 .
Figure 1.Map showing the first records of Dactylobiotus parthenogeneticus in México, state of Nuevo León.

Table 1 .
Measurements (in µm)and pt values of selected morphological structures of specimens of Dactylobiotus parthenogeneticus mounted in PVA medium (N, number of specimens/ structures measured; Range refers to the smallest and the largest structure found among all measured specimens; SD, standard deviation).

Table 2 .
Measurements (in µm) of selected morphological structures of eggs of Dactylobiotus parthenogeneticus mounted in PVA medium (N, number of eggs/structures measured; Min, the smallest; Max, the largest structure found among all measured eggs; SD, standard deviation, three processes per egg were measured).