Macrobiotus vladimiri, Bertolani, Biserov, Rebecchi and Cesari, 2011

Nowak, Bernadeta, Stec, Daniel, Online, Published & Version, Final, 2017, The first record of Macrobiotus vladimiri Bertolani, Biserov, Rebecchi & Cesari, 2011 (Tardigrada: Eutardigrada: Macrobiotidae: hufelandi group) from Poland, Turkish Journal of Zoology 41 (3), pp. 558-567 : 559-565

publication ID	https://doi.org/ 10.3906/zoo-1609-22
persistent identifier	https://treatment.plazi.org/id/594B832F-FFCA-FF96-7650-2C8EF7C7FBE2
treatment provided by	Felipe
scientific name	Macrobiotus vladimiri, Bertolani, Biserov, Rebecchi and Cesari, 2011
status

Treatment

Macrobiotus vladimiri, Bertolani, Biserov, Rebecchi and Cesari, 2011 View in CoL

( Tables 1–4, Figures 1–4 View Figure 1 View Figure 2 View Figure 3 View Figure 4 )

Material examined: Twenty-two animals (including 3 simplexes) and 2 eggs from Poland (mounted on microscope slides in Hoyer’s medium, slide codes: PL.103.19–25, 29, 30, 32, 35; preserved at the Department of Entomology , Institute of Zoology and Biomedical Research Jagiellonian University , Gronostajowa 9, 30-387 Krakow, Poland); 3 paratypes and 3 eggs from the type population (mounted on microscopic slides in polyvinyl-lactophenol, slide codes: C475-S2, C475- SU1 ; collected in Andalo ( Italy): 46°10′07″N, 11°00′01″E; 1050 m a.s.l.) GoogleMaps .

Description of Polish specimens:

Animals (measurements and statistics in Tables 1 and 2): Body white/transparent without any transversal bands of pigmentation, transparent after fixation in Hoyer’s medium ( Figure 1A View Figure 1 ). Eyes present (visible also after mounting). Body cuticle smooth with small round (diameter range: 0.5–1.1 µm) and oval (diameter range: 1.0–1.7 µm) pores, situated mostly on the posterior part of the dorsum and poorly visible under a light microscope (LM) ( Figure 1B View Figure 1 , empty arrowhead). Ventral cuticle smooth. Granulation on the external surface of legs I–IV present, but not very developed ( Figure 1C–D View Figure 1 ).

Mouth anteroventral. Buccopharyngeal apparatus of the Macrobiotus type ( Figure 2 View Figure 2 ), with 10 small peribuccal lamellae and ventral lamina. The oral cavity armature is composed of two bands of teeth (the first band is not visible under LM; Figure 2 View Figure 2 ). The second band of teeth is situated between the ring fold and the third band of teeth and comprises several rows of small, barely visible dots ( Figure 2 View Figure 2 , lower insert, empty indented arrowhead). The teeth of the third band are located within the posterior portion of the oral cavity, between the second band of teeth and the buccal tube opening ( Figure 2 View Figure 2 , empty arrowhead). The third band of teeth is discontinuous and divided into the dorsal and the ventral portion. It comprises three dorsal, distinctly separated, thin ridges ( Figure 2 View Figure 2 , empty arrowhead) and three ventral teeth: two lateral ridges ( Figure 2 View Figure 2 , lower insert) and one round or oval median tooth ( Figure 2 View Figure 2 , lower insert, empty arrowhead). Pharyngeal bulb spherical, with triangular apophyses, two rod-shaped macroplacoids (2 <1), and a triangular microplacoid ( Figure 2 View Figure 2 ). Both macroplacoids with slight central constrictions (in the second microplacoid being almost undetectable) ( Figure 2 View Figure 2 , upper insert).

Claws small and slender, of the hufelandi type ( Figures 3A and 3B View Figure 3 ). Primary branches with distinct accessory points. The common tract short and wide with an evident peduncle connecting the claw to the lunula ( Figures 3A and 3B View Figure 3 ). Lunulae on legs I–III smooth ( Figure 3A View Figure 3 ), but on legs IV slightly crenulated and occasionally with very faint indentations ( Figure 3B View Figure 3 ). Bars under claws absent.

Character N Range µm pt Mean µm pt SD µm pt Body length 10 403–540 39.6–43.9 30.6–34.7 5.2–6.6 3.3–4.5 26.1–29.8 9.9–14.0 6.0–9.2 2.3–3.9 16.8–24.3 19.3–26.8 10.8–12.7 8.2–10.9 10.2–12.1 7.0–11.2 10.6–12.9 9.3–10.8 10.6–12.3 7.1–10.5 11.1–13.3 9.4–12.7 10.5–12.8 6.9–10.9 13.1–15.1 10.5–11.8 12.6–16.2 10.3–13.5 997–1254 – 77.0–81.9 12.8–16.0 7.9–10.3 63.2–69.1 23.1–34.0 14.2–22.4 5.7–9.9 39.3–59.0 45.2–65.1 26.8–29.4 20.0–25.3 25.2–28.5 17.6–25.9 26.6–31.1 22.1–26.5 26.2–29.8 17.8–25.1 28.0–32.3 22.0–30.7 26.5–31.1 17.4–26.5 32.5–36.7 25.4–27.5 31.1–37.6 25.5–32.3 457 1104 50 94

Buccopharyngeal tube

Buccal tube length 10 Stylet support insertion point 10 Buccal tube external width 10 Buccal tube internal width 10 Ventral lamina length 8 Placoid lengths Macroplacoid 1 10 Macroplacoid 2 10 Microplacoid 10 Macroplacoid row 10 Placoid row 10 Claw 1 lengths External primary branch 8 External secondary branch 8 Internal primary branch 8 Internal secondary branch 8 Claw 2 lengths External primary branch 10 External secondary branch 10 Internal primary branch 10 Internal secondary branch 10 Claw 3 lengths External primary branch 10 External secondary branch 10 Internal primary branch 10 Internal secondary branch 10 Claw 4 lengths Anterior primary branch 10 Anterior secondary branch 10 Posterior primary branch 10 Posterior secondary branch 10 41.3 – 1.4 – 32.4 78.4 1.3 1.6 5.9 14.3 0.4 1.0 3.8 9.1 0.4 0.8 27.4 65.6 1.2 2.1 11.4 27.5 1.3 2.9 7.4 18.0 1.0 2.4 3.0 7.3 0.5 1.2 19.9 48.2 2.1 4.9 23.0 55.8 2.2 5.0 11.6 28.2 0.6 0.9 9.5 23.1 0.8 1.9 11.0 26.8 0.7 1.1 8.6 20.9 1.2 2.4 11.9 28.9 0.7 1.7 10.0 24.3 0.5 1.5 11.5 27.8 0.5 1.2 9.5 22.9 1.1 2.3 12.4 29.9 0.7 1.4 10.7 25.8 1.0 2.5 11.8 28.6 0.6 1.2 9.6 23.3 1.2 2.8 14.1 34.1 0.7 1.1 10.9 26.4 0.4 0.7 14.4 34.9 1.0 1.8 11.9 28.7 0.9 2.0

Eggs (measurements and statistics in Tables 3 and 4): Eggs laid freely, white, spherical ( Figures 4A and 4B View Figure 4 ). The surface between processes of the hufelandi type, i.e. chorion covered with a reticulum with oval or round meshes, slightly larger and wider in the peribasal ring around the processes ( Figures 4B and 4D View Figure 4 ). Processes of inverted goblet shape ( Figures 4A and 4C View Figure 4 ), and with concave distal disks that have jagged margins ( Figure 4D View Figure 4 ).

To date, M. vladimiri has been recorded from three European countries: Italy (Andalo, the type locality), Germany (St. Ulrich), and Spain ( Bertolani et al., 2011). The Spanish population was discovered only on the basis of DNA sequences ( Bertolani et al., 2011; Guil and Giribet, 2012). Therefore, the Polish locality is the fourth record for this species and, at the same time, it is also a first record for the Polish tardigrade fauna. Thanks to the detailed morphological and morphometric examination of the discovered tardigrades, we were able to identify them as M. vladimiri . Thus, now the number of known tardigrade species from Poland has risen to 103.

Character N Range µm pt Mean µm Pt SD µm pt Body length 3 322–419 33.5–40.2 26.5–31.1 5.7–6.9 4.7–5.8 22.9–25.8 9.1–11.0 5.4–7.4 1.9–2.6 15.7–20.3 18.7–24.5 8.9–9.6 6.9–7.2 8.4–8.9 6.7–7.0 9.1–9.2 7.1–7.9 8.5–9.1 6.7–7.3 9.2–10.5 7.3–8.2 8.8–9.9 7.1–8.1 10.7–11.4 10.4 11.4–13.1 8.3 805–1042 – 76.6–79.1 15.8–17.2 12.5–14.4 61.4–68.4 25.8–27.4 16.1–18.5 5.5–6.5 46.9–50.5 55.8–60.9 23.9–26.6 17.9–20.6 22.1–25.1 17.4–20.0 22.9–27.2 17.7–23.6 21.1–27.2 16.7–21.8 22.9–28.4 18.2–22.7 21.9–27.8 17.7–22.7 26.6–34.0 26.0 29.6–34.0 20.6 360 952 52 129

Buccopharyngeal tube

Buccal tube length 3 Stylet support insertion point 3 Buccal tube external width 3 Buccal tube internal width 3 Ventral lamina length 3 Placoid lengths Macroplacoid 1 3 Macroplacoid 2 3 Microplacoid 3 Macroplacoid row 3 Placoid row 3 Claw 1 lengths External primary branch 2 External secondary branch 2 Internal primary branch 2 Internal secondary branch 2 Claw 2 lengths External primary branch 2 External secondary branch 2 Internal primary branch 2 Internal secondary branch 2 Claw 3 lengths External primary branch 3 External secondary branch 3 Internal primary branch 3 Internal secondary branch 3 Claw 4 lengths Anterior primary branch 3 Anterior secondary branch 1 Posterior primary branch 3 Posterior secondary branch 1 37.9 – 3.8 – 29.5 77.8 2.6 1.2 6.3 16.6 0.6 0.8 5.2 13.7 0.6 1.0 24.5 64.8 1.5 3.5 10.1 26.8 1.0 0.9 6.5 17.2 1.0 1.2 2.2 5.9 0.4 0.5 18.4 48.5 2.4 1.9 22.2 58.3 3.1 2.6 9.3 25.2 0.5 1.9 7.1 19.3 0.2 1.9 8.7 23.6 0.4 2.1 6.9 18.7 0.2 1.8 9.2 25.0 0.1 3.0 7.5 20.6 0.6 4.2 8.8 24.2 0.4 4.3 7.0 19.2 0.4 3.6 9.7 25.8 0.7 2.8 7.7 20.4 0.5 2.3 9.3 24.8 0.6 2.9 7.6 20.2 0.5 2.5 11.2 29.7 0.4 3.9 10.4 26.0?? 12.1 32.1 0.9 2.3 8.3 20.6??

By comparing Polish individuals of M. vladimiri with paratypes from Italy, we have discovered several small morphometric differences in animals and eggs between the two populations. The type population is characterized

(N- number of eggs/structures measured; Range- the smallest and the largest structure among all measured eggs; SD- standard deviation).

medium (N- number of eggs/structures measured; Range- the smallest and the largest structure among all measured eggs; SD- standard deviation). by shorter primary branches of external and internal claws on the first pair of legs (external primary branch length: 8.9–9.6 µm [pt = 23.9%–26.6%] in the type population vs. 10.8–12.7 µm [pt = 26.8%–29.4%] in the Polish population; internal primary branch length: 8.4–8.9 µm [pt = 22.1%– 25.1%] in the type population vs. 10.2–12.1 µm [pt = 25.2%–28.5%] in the Polish population), a slightly wider buccal tube (buccal tube external width: 5.7–6.9 µm [pt = 15.8%–17.2%] in the type population vs. 5.2–6.6 µm [pt = 12.8%–16.0%] in the Polish population; buccal tube internal width: 4.7–5.8 µm [pt = 12.5%–14.4%] in the type population vs. 3.3–4.5 µm [pt = 7.9%–10.3%] in the Polish population), and larger eggs (egg bare diameter: 96.8–99.3 µm in the type population vs. 76.6–81.2 µm in the Polish population; egg full diameter: 104.5–109.2 µm in the type population vs. 90.0–96.9 µm in the Polish population) but with shorter processes (4.6–6.9 µm in the type population vs. 7.1–8.2 µm in the Polish population) compared to the Polish population. Moreover, the processes of the eggs from the type population measured in our work are slightly shorter than the dimensions presented by Bertolani et al. (2011) (4.6–6.9 µm in the type population measured by us vs. 6.5–8.0 µm in the original description), which extends the range of the variability within this trait in M. vladimiri . The differences in the external and internal primary branch lengths of claws on the first pair of legs might be caused by low sample size, especially for the type population. Moreover, paratypes were also generally smaller than animals from the newly found population (mean body length: 360 ± 52 µm in the type population vs. 457 ± 50 µm in the Polish population). The recent study by Morek et al. (2016) showed that cover slip pressure may influence the buccal tube morphometrics, but the pressure has to be considerable to cause detectable deformation. It is, however, possible that some medium types could also affect cuticular structures by softening them and making them more prone to deformation ( Morek et al., 2016). Given that the two populations were mounted in different media (polyvinyl-lactophenol and Hoyer’s), it could be hypothesized that the observed difference in buccal tube width is a preparation methodology artifact ( Nelson and Bartels, 2007). In fact, the buccal tube seems to have thicker walls with distinguishable external and internal walls when mounted in Hoyer’s medium, whereas in polyvinyl-lactophenol, the walls seem thinner and with no clear external and internal boundaries. This might be the reason why pt values of internal widths of the buccal tube do not overlap in these two populations while pt values of external widths do. Specimens mounted in Hoyer’s medium have shorter internal buccal tube width than specimens mounted in polyvinyl-lactophenol, which resulted in nonoverlapping pt ranges. Unfortunately, no studies investigating the effects of these media on tardigrade morphometric traits are available ( Morek et al., 2016); thus, currently it cannot be stated whether the difference in buccal tube diameter is a preparation artifact or a true difference between the two populations.

The shell morphology of freely laid eggs is used widely for delimiting tardigrade species because it provides a number of morphological and morphometric traits that vary considerably between species, even closely related