Milnesium validum, Lisi, 2017

Lisi, Oscar, 2017, Two new species of Eutardigrada from Victoria Land, Antarctica, Zootaxa 4317 (3), pp. 541-558 : 548-554

Milnesium validum sp. nov.

Fig. 6 , Table 2

Type locality. Antarctica: Shore of Carezza Lake , 71° 43’ S 164° 03’E.

Material examined. (collected by Prof. Salvatore Motta between 1990.12.15 and 1991.1.12): shore of Carezza Lake: the holotype (slide No. 4035) and two paratypes (slides nos. 4036–4037) in a moss sample; Lamplugh Island (75° 34’S 162° 55’E): two paratypes (slides Nos. 4038 and 4047) in a moss sample, together with Acutuncus antarcticus ; Edmonson Point (74° 21'S, 165° 10'E): two exuviae (slide No. 4039 with 2 eggs, and 5777 with 9 eggs) in a moss sample, together with Acutuncus antarcticus .

Type repository. Holotype and paratypes are preserved in the collection of Binda & Pilato in the Department of Biological , Geological and Environmental Sciences ( Section of Animal Biology “ Marcello La Greca ” of the University of Catania, Italy).

Specific diagnosis. Body colourless; cuticle smooth; eye spots present; six peribuccal and two lateral papillae present; mouth terminal with six triangular peribuccal lamellae with basal stripes; cylindrical buccal tube not very wide; stylet supports inserted on the buccal tube at 61.1–64.8% of its length; claws of the Milnesium type with a [3- 3]-[3-3] configuration; primary branches with thin accessory points; secondary claws stout, with distal portion clearly wider than the basal portion; each with a rounded basal thickening (lunule); a long cuticular bar present under claws I–III.

Description of the holotype. Body 482 µm long; colourless; cuticle smooth without pseudopores, reticulum, tubercles or gibbosities; eyes present; six cephalic and two lateral papillae present; bucco-pharyngeal apparatus of Milnesium type ( Fig. 6 A) (buccal tube rigid without ventral lamina; apophyses for the insertion of the stylet muscles in the shape of very short and flat ridges symmetrical with respect to the frontal plane and without caudal processes; pharyngeal bulb without apophyses, placoids or septulum). Mouth terminal with six triangular peribuccal lamellae with basal stripes; buccal tube cylindrical 55.6 µm long, not very wide (16.6 µm externally at the level of the stylet supports insertion point, pt index value = 29.9); stylet supports inserted on the buccal tube at 62.0% of its length (pt = 62.0); stylet furca with well-developed branches ( Fig. 6 A); pharyngeal bulb pear-shaped.

Claws of the Milnesium type ( Figs. 6 B–D); secondary claws stout, with the distal portion clearly wider than the basal portion ( Figs. 6 B–D) and with three points, configuration [3-3]-[3-3]; the second point (point b, according to the terminology used by Binda & Pilato 1990) is clearly longer and wider than the other two, particularly at the distal point ( Figs. 6 B–D). Primary claws on legs I, 20.0 µm long (pt = 36.0) and secondary claw, 14.5 (pt = 26.1); the percent ratio secondary/primary claw is 72.5; primary claws on legs II, 20.7 µm long (pt = 37.2); secondary claw II, 15.0 µm long (pt = 27.0); the secondary/primary claw percent ratio is 72.5; primary claws on legs III, 22.0 µm long (pt = 39.6), secondary claw III could not be measured; primary claws on legs IV, 26.9 µm long (pt = 48.4), secondary claws on legs IV, 16.9 µm (pt = 30.4); the secondary/primary claw percent ratio is 62.8.

Primary claws with thin accessory points; each secondary claw base with rounded basal thickening (lunule) ( Fig. 6 D, arrow); a long cuticular bar is present under the claws I–III ( Fig. 6 B, arrow).

Eggs smooth laid in the exuvium (we found an exuvium with two eggs and another with nine eggs).

Remarks: The paratypes are similar to the holotype in both qualitative and quantitative characters ( Table 2). Together with Milnesium validum sp. nov. we found specimens of Acutuncus antarcticus .

Etymology: the specific name validum (validus = vigorous) refers to the robustness of the secondary claws.

Milnesium validum sp. nov Differential diagnosis: Within the genus Milnesium twelve species with smooth cuticle, six peribuccal lamellae and [3-3]-[3-3] claw configuration are known: Milnesium brachyungue Binda & Pilato, 1990 ; Milnesium eurystomum Maucci, 1991 ; Milnesium asiaticum Tumanov, 2006 ; Milnesium antarcticum Tumanov, 2006 ; Milnesium longiungue Tumanov, 2006 ; Milnesium zsalakoae Meyer & Hinton, 2010 ; Milnesium barbadosense Meyer & Hinton 2012 ; Milnesium bohleberi Bartels, Nelson, Kaczmarek & Michalczyk, 2014 , Milnesium shilohae Meyer, 2015 ; Milnesium minutum Pilato & Lisi 2016 ; Milnesium sandrae Pilato & Lisi, 2016 and Milnesium tumanovi Pilato, Sabella & Lisi, 2016 .

In the following comparisons, and to save repartition, the detailed quantitative data of the single species are reported in Table 3 where several, significant differences are recognizable; in cases where there are few metric differences (i.e. Milnesium shilohae and Milnesium minutum ) these are indicated in the text.

szalokoae, Milnesium barbadosense , Milnesium tumanovi , Milnesium sandrae anđ Milnesium antrcticum in µm, with the pt inđex values, anđ the percent ratio between the seconđary anđ the

primary claw lengths. The measurements relative to the holotype of Milnesium brachyungue are slightly đifferent from those inđicateđ in the đescription of the species because in this paper a unique

criterion (đifferent from that useđ by Binđa & Pilato 1990) of measurement for all the species has been ađopteđ. The đata for the holotype of Milnesium szalakoae Meyer & Hinton 2010 , Milnesium

barbadosense Meyer & Hinton 2012 , anđ the holotype of Milnesium antarcticum Tumanov, 2006 are from the original đescriptions of these species.

Milnesium Milnesium Milnesium Milnesium Milnesium Milnesium Milnesium Milnesium antarcticum brachyungue asiaticum longiungue szalakoae barbadosense tumanovi sandrae

. Sliđe 3940 5105 5103 3904 4290 5104 holotype paratype paratype holotype holotype Crimea : Yalta Hawaii Islanđ

holotype holotype paratype holotype

Bođy length 801 685 747 477 686.4 744 567??

Milnesium validum sp. nov. differs from Milnesium eurystomum and Milnesium bohleberi by having a narrower, cylindrical, instead of a wide, clearly funnel-shaped buccal tube.

Milnesium validum sp. nov. differs from Milnesium brachyungue by having higher pt values of both the primary and secondary claw lengths, and lower percent ratio values between the secondary claw and primary claw lengths ( Figs. 6 B–D and 7B, C; Tables 2 and 3); this ratio difference is particularly marked for legs IV where the ratio values are 60–63 in Milnesium validum sp. nov. and c. 81 in Milnesium brachyungue ( Tables 2 and 3).

The new species differs from Milnesium asiaticum in having longer buccal tube with respect to the body length (percent ratio c. 11 in the new species and 6.5–8 in Milnesium asiaticum ) ( Tables 2 and 3); secondary claws stouter with the distal portion clearly wider than the basal portion ( Figs. 6 B–D and 8B,C); slightly lower values of the pt index relative to the main branches of claws I–III and, as a consequence, higher percent ratio between the secondary claw lengths and the primary claw lengths ( Table 2 and 3).

Milnesium validum sp. nov. differs from Milnesium longiungue by having primary claws with accessory points; stouter secondary claws with the distal portion clearly wider than the basal portion ( Figs. 6 B–D and 9B, C); lower pt index values relative to primary claw lengths (the difference is particularly marked in claw IV where the pt value is 46.6–48.4 in the new species and 83–88 in Milnesium longiungue ); and higher values of the percent ratio between the secondary claw and the primary claw lengths ( Tables 2 and 3).

The new species differs from Milnesium zsalakoae by having primary claws with accessory points; lower pt index values relative to the primary claws (the difference is particularly marked in claw IV where the pt value is 46.6–48.4 in the new species and 95–103 in Milnesium zsalakoae according to Meyer & Hinton 2010) ( Tables 2 and 3); and higher percent ratio between the secondary claw lengths and the primary claw lengths ( Table 2 and 3).

Milnesium validum sp. nov. differs from Milnesium barbadosense by having eyes; buccal tube clearly longer with respect to the body length (percent ratio c. 11 in the new species, 7–9 on Milnesium barbadosense ) ( Figs. 6 A, and Fig. 1 A,B of Meyer & Hinton 2012); stylet supports inserted on the buccal tube in a more anterior position: pt = 61.1–64.8 in the new species, 66–84 in Milnesium barbadosense according to Meyer & Hinton, 2012 ( Tables 2 and 3.) (N.B we think this very wide range for Milnesium barbadosense should be confirmed that it is not more than one species).

The new species differs from Milnesium shilohae in having the stylet supports inserted on the buccal tube in a more cephalic position (pt = 61.1–64.8 in the new species, 75.5–77.5 in Milnesium shilohae according to Meyer 2015); by having the basal spurs almost as developed as, or more developed than the other points, while in Milnesium shilohae they are clearly less developed than the other points ( Fig. 6 B, D and figure 2 of Meyer 2015).

The new species differs from Milnesium minutum by having larger body size, narrower buccal tube (the pt index value is 29.9–34.4 in specimens of the new species more than 400 µm long, and about 38.6–42.4 in specimens of Milnesium minutum about 300 µm long); and it differs in having stouter secondary claws.

Milnesium validum sp. nov. differs from Milnesium tumanovi by having buccal tube longer with respect to the body length (the percent ratio is c. 11 in the new species and c. 7 in Milnesium tumanovi ); and narrow with respect to the buccal tube length (the pt index value is 29.9–34.4 in the new species and c. 55 in Milnesium tumanovi ); stylet supports inserted on the buccal tube in a more posterior position (pt = 61.1–64.8 in the new species, c. 52 in Milnesium tumanovi ); stouter secondary claws with basal spur as developed as, or more developed than the other points, while in Milnesium tumanovi they are clearly less developed than the other points ( Figs. 6 B, D and figures 4B, C in Pilato et al. 2016); lower pt index values relative to the secondary claws IV, and lower percent ratio between the secondary claw length and the primary claw length of that pair of legs where the ratio values are 60–63 in the new species, and c. 76 in Milnesium tumanovi ) ( Tables 2 and 3).

Milnesium validum sp. nov. differs from Milnesium sandrae by having buccal tube longer with respect to the body length (the percent ratio is c. 11 in the new species and c. 7 in Milnesium sandrae ), and narrower with respect to the buccal tube length (the pt index is 29.9–34.4 in the new species, and 45–48 in Milnesium sandrae ) ( Figs. 6 A and 10A); secondary claws slightly stouter ( Figs. 6 B–D and 10B,C); slightly lower values of the pt index relative to the secondary claws and lower values of the percent ratio between the secondary and the primary claws (that a ratio is 70.9–75.8 in the claws I–III and 60–63 in claw IV of the new species, while 78.6–85.5 and 70.4–71.4 respectively in Milnesium sandrae ( Tables 2 and 3).

Milnesium validum sp. nov. is similar to Milnesium antarcticum but the stylet supports are inserted on the buccal tube wall in a slightly more cephalic position (pt = 61.1–64.8 in the new species, 66.6–71.3 in Milnesium antarcticum ); overall, by having clearly stouter secondary claws with shorter basal portion ( Figs. 6 B–D and 11B– D), and with the distal point clearly more slender than the basal, while in Milnesium antarcticum this difference is less marked ( Figs. 6 B–D; 11B–D, and figures 17–18 in Tumanov 2006); the pt index values of the claws I–III seem to be slightly higher in the new species ( Tables 2 and 3).

We have to report here and correct a misidentification published by us in a very recent paper (Pilato et al. 2016), regarding our new Milnesium species ( Milnesium validum sp. nov.) and Milnesium antarcticum . In Pilato et al. (2016), we compared Milnesium tumanovi with a Milnesium antarcticum from our collection that we had erroneously attributed to Milnesium antarcticum , and which we are now describing as a new species ( Milnesium validum sp. nov.).

We had used our best specimen (slide No. 4035, which is now the holotype of Milnesium validum sp. nov.), as an example of Milnesium antarcticum , both for the images and measurements (see: figure 8 and table 2 in Pilato et al. 2016). This was done because our specimen was in much better state than the paratypes of Milnesium antarcticum that are deposited in our collection. As a consequence, photographs published in Pilato et al. (2016), as Milnesium antarcticum , are actually the holotype of the new species ( Fig 6 ). To eliminate any doubts, Fig. 11 presented here is of a paratype of Milnesium antarcticum (see also figures 17 and 18 in Tumanov 2006), and in Table 3 we indicated quantitative characters of a Milnesium antarcticum paratype, and the holotype of this species according to Tumanov (2006).

Figures

FIGURE 1. Mixibius felix. sp. nov. A, Bucco-pharyngeal apparatus of the holotype (slide No. 4535). B, Bucco-pharyngeal apparatus of a paratype (slide No. 4539) in lateral view: the hook-shaped apophyses for the insertion of the stylet muscles are visible (the ventral indicated by arrow “ a ”, the dorsal by arrow “ b ”), both followed by a thickening of the buccal tube wall. C, Claws of the second pair of legs of a paratype (slide No. 4540); an accessory point of the external claw (arrow) is visible. D, Claws of the hind legs of a paratype (slide No. 4531). Scale bars = 10 µm.

FIGURE 6. Milnesium validum sp. nov. A, Bucco-pharyngeal apparatus of the holotype (slide No. 4035). B, Claws of the second pair of legs of the holotype. The arrow indicates the cuticular bar near the claws. C, Claws of the hind legs of the holotype. D, Claws of the second pair of legs of a paratype (slide N. 4038). The arrow indicates a lunule. Scale bars = 10 µm.

FIGURE 11. Milnesium antarcticum (paratype, slide No. 5104). A, Bucco-pharyngeal apparatus. B, Claws of the second and third pairs of legs. C, Claws of the first and second pairs of legs. D, Claws of the hind legs. Scale bars = 10 µm.