Milnesium matheusi, Kaczmarek, Lukasz, Grobys, Daria, Kulpa, Adam, Bartylak, Tomasz, Kmita, Hanna, Kepel, Marta, Kepel, Andrzej & Roszkowska, Milena, 2019

Kaczmarek, Lukasz, Grobys, Daria, Kulpa, Adam, Bartylak, Tomasz, Kmita, Hanna, Kepel, Marta, Kepel, Andrzej & Roszkowska, Milena, 2019, Two new species of the genus Milnesium Doyere, 1840 (Tardigrada, Apochela, Milnesiidae) from Madagascar, ZooKeys 884, pp. 1-22 : 1

Milnesium matheusi sp. nov. Figures 1-3 , 4-5 , Tables 4 , 5

Material examined.

Holotype and 18 paratypes, all from sample No 139: Ivohibory forest, Madagascar, lichen sample from quartz rocks, coll. Marta Kepel and Andrzej Kepel.

Description.

Adult females ( Fig. 1 , Table 4 ) with no modified claws I. Body light yellow before fixation and transparent afterwards, eyes present (in 89% of measured specimens). Dorsal cuticle sculptured with pseudopores, not arranged in bands, sparsely distributed and not forming a reticular design ( Fig. 2 ). Six peribuccal papillae and six peribuccal lamellae present around the mouth opening. Two cephalic papillae positioned laterally. Peribuccal papillae slightly longer than lateral papillae.

The buccal apparatus of the Milnesium type ( Figs 1 , 3 ). The buccal tube wide and short (standard width, on average 46% of its length), and slightly funnel-shaped, wider anteriorly (posterior diameter on average 89% of the anterior diameter) (Table 4 ). The pharyngeal bulb elongated, pear-shaped and without placoids or septulum.

Claws of the Milnesium type, slender ( Figs 4 , 5 ). Primary branches on all legs with small, but distinct accessory points detaching from the branch at its greatest curvature ( Fig. 5 , arrowhead). Secondary branches with rounded basal thickenings ( Figs 4 , 5 ). All secondary branches on all legs with three points (claw configuration: [3-3]-[3-3]). Single, long transverse, cuticular bars present under claws I–III ( Fig. 4 , arrow).

Adult males (Table 5 ) with modified claws I. Similar to females but clearly smaller, with secondary branches of claws I modified into strong hooks and with a different proportion of peribuccal and lateral papillae length (peribuccal papillae clearly shorter than lateral), eyes present only in 33% of measured specimens.

Eggs oval, smooth and deposited in the exuvium as in all other known Milnesium species.

DNA sequences.

We obtained good quality sequences for the applied molecular markers: 28S rRNA sequence (GenBank: MN191503), 756 bp long; COI sequence (GenBank: MN187056), 628 bp long; ITS-2 sequence (GenBank: MN239906), 218 bp long.

Type locality.

Madagascar, 22°37'07.7"S, 46°43'14.5"E, ca. 1187 m asl, Fianarantsoa Province, Ivohibory forest.

Etymology.

The second author with great pleasure dedicates this species to her fiance - Mateusz Wojciechowski.

Type depositories.

The holotype and 13 paratypes (slides: MAD139/14, MAD139/16, MAD139/18, MAD139/19, MAD139/34, MAD139/35, MAD139/42, MAD139/56, MAD139/72) are deposited at the Department of Animal Taxonomy and Ecology, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 6, Poznań, Poland; five paratypes (slides: MAD139/12, MAD139/13, MAD139/15) are deposited at the Natural History Museum, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark.

Morphological differential diagnosis.

The new species with three points on the secondary branches of all claws (claw configuration [3-3]-[3-3]) and a rather wide buccal tube, in relation to its length, is most similar to: Mil. beatae Roszkowska, Ostrowska & Kaczmarek, 2015, Mil. bohleberi Bartels, Nelson, Kaczmarek & Michalczyk, 2014, Mil. eurystomum Maucci, 1991, Mil. shilohae Meyer, 2015 and Mil. tumanovi Pilato, Sabella & Lisi, 2016, but it differs from:

1. Milnesium beatae , only reported from Argentina and USA ( Roszkowska et al. 2015; Tibbs et al. 2016) by: narrower buccal tube (25.2-35.9 [47.6-57.9] and 23.1-31.1 [42.4-50.8] anterior and standard width, respectively, in the new species vs. 37.0-53.5 [70.3-78.9] and 32.0-42.5 [58.1-65.6] anterior and standard width respectively in Mil. beatae ), smaller standard width/length ratio of the buccal tube (42%-51% in new species vs. 58%-66% in Mil. beatae ) and larger posterior/anterior width ratio (84%-94% in new species vs. 69%-76% in Mil. beatae ).

2. Milnesium bohleberi , only recorded from North Carolina and Tennessee (USA) ( Bartels et al. 2014) by: presence of pseudopores on dorsal cuticle, shorter peribuccal papillae (10.0-12.0 [18.6-22.1] in new species vs. 15.5-20.3 [27.2-32.3] in Mil. bohleberi ), smaller pt values of anterior, standard and posterior widths of the buccal tube (47.6-57.9, 42.4-50.8, 41.1-50.3, respectively, in new species vs. 63.4-74.7, 54.5-64.0, 52.4-62.0, respectively, in Mil. bohleberi ), smaller standard width/length ratio of the buccal tube (42%-51% in new species vs. 54%-64% in Mil. bohleberi ) and slightly shorter claws (see Table 4 below and Bartels et al. (2014: Table 1 ) for the exact differences in claw dimensions).

3. Milnesium eurystomum reported from a few localities in Argentina, Chile, Greenland, Mongolia and USA (see review by Kaczmarek et al. 2016) by: shorter buccal tube (51.3-62.5 in new species vs. 70.8-77.5 in Mil. eurystomum ), stylet supports inserted in a more posterior position (pt = 66.1-69.4 in new species vs. ca. pt = 60.0-60.3 in Mil. eurystomum ), narrower buccal tube (25.2-35.9 [47.6-57.9], 23.1-31.1 [42.4-50.8] and 23.0-30.2 [41.1-50.3] anterior, standard and posterior width, respectively, in new species vs. 53.7-55.9 [72.1-75.8], 45.9-47.9 [61.8-64.8] and 33.9-41.0 [43.7-57.9] anterior, standard and posterior width, respectively, in Mil. eurystomum ), smaller standard width/length ratio of the buccal tube (42%-51% in new species vs. 62%-65% in Mil. eurystomum ) and larger posterior/anterior width ratio (84%-94% in new species vs. 61%-76% in Mil. eurystomum ).

4. Milnesium shilohae , only reported from the type locality in Hawaii (USA) ( Meyer 2015) by: presence of pseudopores on dorsal cuticle, presence of similar in length spurs on internal and external claws (internal and posterior spurs larger than external and anterior spurs in Mil. shilohae ), slightly longer lateral papillae (9.4-10.7 in new species vs. 5.0-9.0 in Mil. shilohae ), slightly longer buccal tube (51.3-62.5 in new species vs. 38.4-50.3 in Mil. shilohae ), stylet supports inserted in a more anterior position (pt = 66.1-69.4 in new species vs. pt = 75.5-77.5 in Mil. shilohae ) and larger spurs on some external and anterior claws (see Table 4 below and Table 3 in Meyer (2015) for the exact differences in claw dimensions).

5. Milnesium tumanovi , only recorded from the type locality in the Crimea (Ukraine) ( Pilato et al. 2016) by: presence of pseudopores on dorsal cuticle, funnel-shaped buccal tube (cylindrical in Mil. tumanovi ) and stylet supports inserted in a more posterior position (pt = 66.1-69.4 in new species vs. ca. pt = 52-54 in Mil. tumanovi ).

Genotypic differential diagnosis.

The ranges of uncorrected genetic p-distances between Mil. matheusi sp. nov. and species of the genus Milnesium , for which molecular marker sequences are available from GenBank (see Table 6 for details), are as follows:

1. 28S rRNA: 4.5-6.7% (5.4% on average), with the most similar being Milnesium sp. from North America (JX888585.1, JX888586.1, JX888587.1) (unpublished) and the least similar being Mil. wrightae sp. nov. (MN191504.1) (present studies);

2. COI: 20.1-38.8% (23.3% on average), with the most similar being Mil. variefidum Morek, Gąsiorek, Stec, Blagden & Michalczyk, 2016 from UK (KT951663.1) ( Morek et al. 2016) and the least similar being Mil. t. tardigradum from Spain (FJ435810.1) ( Guil and Giribet 2012);

3. ITS-2: 17.8-31.1% (23.7% on average), with the most similar being Mil. t. tardigradum from Germany (JF951049.1) ( Michalczyk et al. 2012) and the least similar being Mil. cf. granulatum from USA (MK681879.1) ( Jackson and Meyer 2019).

Figures

Figures 1 - 3. Milnesium matheusi sp. nov. 1 Habitus (ventral view) (holotype) 2 dorsal cuticle with pseudopores (holotype) 3 buccal tube (holotype). All in PCM.

Figures 4, 5. Milnesium matheusi sp. nov. 4 Claws II (paratype), arrow indicates bar under claw 5 claws IV (holotype), arrowhead indicates small accessory point. All in PCM.