Macrobiotus kathyae, Massa & Vecchi, 2024

Massa, Edoardo & Vecchi, Matteo, 2024, Description of Macrobiotus kathyae sp. nov. (Parachela: Macrobiotidae) and first records of tardigrades from Indiana (USA), Zootaxa 5471 (3), pp. 301-317 : 308-311

Macrobiotus kathyae sp. nov. Massa & Vecchi, 2024

urn:lsid:zoobank.org:act:BF1C7C35-18FE-4DD0-90E1-F5D7E5CFD091

Unidentified egg from sample 24a in Meyer et al., 2011.

( Tables 4–5 , Figures 2–3 , SM.01)

Etymology: The author M. Vecchi wishes to dedicate this species to Kathy Sheehan, to thank her for her help and support during his visit to IU Bloomington (Indiana, USA).

Material examined: 8 animals and 11 eggs. Specimens mounted on microscope slides in Hoyer’s medium (6 animals + 9 eggs) and processed for DNA sequencing (2 adult animals + 2 hatchlings from eggs).

Type locality: 39°09’32.5”N 86°31’37.3”W; 230 m asl: Bloomington , Indiana, USA; moss on tree bark; coll. 9 th June 2016 by Matteo Vecchi .

Type repositories: the holotype (C4015s6i), 5 paratypes (C4015s9e; C4015s14a, c, h), 1 egg (C4015s10a), and 2 eggs chorions (hologenophores molecular voucher; C4015sv1–2) are deposited in the Bertolani’s collection of the University of Modena and Reggio Emilia (Via Campi 213/5, 41125, Modena, Italy). One paratype and 8 eggs (C4015s13) are deposited in the invertebrate collection of the Smithsonian Institution National Museum of Natural History (10th St. & Constitution Ave. NW, Washington, DC 20560, United States).

Description of the new species

Animals (measurements and statistics in Table 4 )

In live animals, body translucent in smaller specimens and opaque whitish in larger animals; transparent after fixation ( Figure 2A ). Eyes present in live animals but visible in 60% of individuals after fixation. Cuticle is smooth, with oval and roundish cuticular pores easily visible under PCM and DIC (0.7–2.5 μm in diameter; Figure 2B ).

Mouth antero-ventral. Bucco-pharyngeal apparatus of the Macrobiotus type ( Figure 2C ), with ventral lamina and ten small peribuccal lamellae. Under PCM, the oral cavity armature is of the maculatus type, i.e., with only the third band of teeth (i.e., transverse ridges) visible ( Figure 2C,D ). The third band is seen as three dorsal and three ventral transverse ridges.

Pharyngeal bulb spherical, with triangular apophyses, two rod-shaped macroplacoids and a drop-shaped microplacoid ( Figure 2C ). The macroplacoid length sequence is 2<1. The first and the second macroplacoid have a central and a subterminal constriction, respectively. Microplacoid is one third of the first macroplacoid in length.

Claws Y-shaped, of the hufelandi type. Primary branches with distinct accessory points, a common tract, and an evident stalk connecting the claw to the lunula ( Figure 2E ). The lunulae are smooth in smaller specimens and smooth in claws I–III, but slightly crenate in claws IV of the larger specimens ( Figure 2E,F ). A divided cuticular bar with double muscle attachments is poorly visible ( Figure 2E ). One or two larger pores (2.6–3.5 μm in diameter) on the external cuticle of all legs are present ( Figure 2E ). Faint scattered dots (granulation), visible only in larger specimens, are present on dorsal side of the legs IV ( Figure 2G ).

Eggs (measurements and statistics in Table 5 )

Round eggs laid free ( Figure 3A,B ). One hatching individual confirms the link between egg and animal morphology ( Figure 3C ). The surface between processes is of the persimilis type, i.e., with a continuous smooth chorion (pores or reticulum not visible; Figure 3A ). The surface between the processes is wrinkled ( Figure 3A,D,F ). The processes walls are sigmoid ( Figure 3E,G ). Processes are of a modified hufelandi type ( Figure 3E,G ). The proper terminal disc is absent and instead 2–4 (rarely 5) sharp and straight spines, about half of the process height (spines 1.4–3.7 µm of length; processes 4.9–7.7 µm of length) are visible ( Figure 3E,G ). Sometimes, the proximal part of two spines is fused, giving the impression of one bifurcated spine ( Figure 3G ).

DNA sequences

GenBank accession numbers:

SSU: PP391285-6 (816–819 bp)

LSU: PP391287-8 (700–720 bp)

COI: PP386932-5 (531–634 bp)

ITS2: PP391289-90 (360–362 bp)

Phenotypic differential diagnosis

Due to the low number of specimens and the presence of discrete morphological character differentiating the new species, we did not consider morphometric characters in the differential diagnosis. By having an egg chorion of the persimilis type (smooth or wrinkled chorion; Kaczmarek et al. 2023), and an OCA of the maculatus type ( Kaczmarek & Michalczyk 2017), M. kathyae sp. nov. resembles Macrobiotus anemone Meyer, Domingue & Hinton 2014 and Macrobiotus naskreckii Bąkowski, Roszkowska, Gawlak & Kaczmarek, 2016 . However, the new species differs specifically from:

— M. anemone : by having eyes (absent in M. anemone ), and in the eggs by having spines in the distal part of the processes (thick tentacular arms in M. anemone ).

— M. naskreckii : by having smooth or weakly crenated lunules IV (lunules IV dentate in M. naskreckii ), and in the eggs by having spines in the distal part of the processes (very small terminal dish M. naskreckii ).

Additionally, by having appendages instead of a proper terminal disc on the distal part of egg processes, M. kathyae sp. nov. also resembles also Macrobiotus annewintersae Vecchi & Stec 2021 and M. anemone (considered above). However, the new species differs specifically from:

— M. annewintersae : by having smooth or weakly crenated lunules IV (lunules IV dentate in M. annewintersae ), by having a maculatus type OCA (patagonicus type OCA in M. annewintersae ), and in the eggs by having spines in the distal part of the processes (thick tentacular arms in M. annewintersae ).

Figures

FIGURE 2. Macrobiotus kathyae sp. nov. animals. A) In toto habitus. B) Dorso-caudal cuticular pores. C) Bucco-pharyngeal apparatus. D) Ventral Oral Cavity Armature (OCA). E) Claws III. F) Claws IV. G) Granulation on legs IV. Indented filled arrowheads indicate constrictions in the macroplacoids. Filled arrowhead indicates the third band of the OCA. Empty indented arrowhead indicates the cuticular bar with double muscle attachments under claws III. Empty arrowhead indicates a large pore on external cuticle of legs. C–G) Holotype. C, D, F) DIC. A, B, E, G) PhC. A, C, D, F) EDF. Scale bars: A 50 µm; B–G 10 µm.

FIGURE 3. Macrobiotus kathyae sp. nov. eggs. A, B) In toto eggs. C) Newborn hatching from egg. D) Chorion surface between processes. E) Egg processes section. F) Chorion surface between processes. G) Egg processes. Empty arrowhead indicates wrinkles on egg surface. Filled arrowhead indicates the fused proximal part of two spines, giving the impression of one bifurcated spine. B) DIC. A, C–F) PhC. B, C, E) EDF Scale bars: A–C 20 µm; D–G 5 µm.