Mesobiotus ethiopicus, Stec & Kristensen, 2017

Stec, Daniel & Kristensen, Reinhardt Møbjerg, 2017, An integrative description of Mesobiotus ethiopicus sp. nov. (Tardigrada: Eutardigrada: Parachela: Macrobiotidae: harmsworthi group) from the northern Afrotropic region, Turkish Journal of Zoology 41 (5), pp. 800-811 : 802-809

Mesobiotus ethiopicus sp. nov.

( Tables 2–3 ; Figures 1–6 )

3.2. Material examined: 19 animals (including one simplex), 13 eggs mounted on microscope slides in Hoyer’s medium (some of the eggs were embrionated), three eggs fixed on SEM stubs, and three specimens processed for DNA sequencing.

3.3. Type locality: 13°16′N, 38°12′E; 3750 m a.s.l.: Ethiopia, Amhara Regional State, shaded rocks in the Semien Mountains, open Afro-alpine terrain, moss from a rock, coll. 15 February 2016 by Asger Ken Pedersen .

3.4. Etymology: The species is named after the country where it was discovered.

3.5. Type depositories: Holotype: slide ET.004.17, 13 paratypes (slides: ET.004/*, where the asterisk can be substituted by any of the following numbers: 17–19) and 8 eggs (slide: ET.004.20) are deposited at the Department of Entomology, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30- 387, Kraków, Poland. Five paratypes (slide: ET.004.21) and five eggs (slide: ET.004.22) are deposited in the Zoological Museum , Natural History Museum of Denmark , University of Copenhagen , Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark .

3.6. Description of the new species

Animals (measurements and statistics in Table 2 ): In live animals, body almost transparent in young specimens and white in adults; after fixation in Hoyer’s medium, body transparent ( Figure 1A ). Eyes absent (before and after fixation). Body cuticle smooth, i.e. without pores, spines, or sculpturing. Granulation on all legs absent.

Mouth anteroventral. Buccopharyngeal apparatus of the Macrobiotus type, with the ventral lamina and 10 small peribuccal lamellae ( Figure 2A ). The oral cavity armature well developed and composed of three bands of teeth ( Figures 2B–2G ). The first band of teeth is composed of numerous small granules arranged in several rows situated anteriorly in the oral cavity, just behind the bases of the peribuccal lamellae ( Figures 2B–2G ). The second band of teeth is situated between the ring fold and the third band of teeth and is composed of ridges parallel to the main axis of the buccal tube and granules, larger than those in the first band ( Figures 2B–2G ). Some teeth in the second band are clearly larger than other teeth in this band ( Figures 2B–2G , flat 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 ( Figures 2B–2G ). The third band of teeth is divided into the dorsal and the ventral portion. Under PCM, both dorsal and ventral teeth are visible as two lateral and one median transverse ridges ( Figures 2B–2G ). The ventromedian tooth is roundish and sometimes constricted or fully divided into two separate roundish teeth ( Figures 2C, 2E, 2G , arrow). Pharyngeal bulb ovoid ( Figures 2A ), with triangular apophyses, three rod-shaped macroplacoids and the drop-shaped (in lateral view) or triangular (in dorsoventral view) microplacoid placed closely to the third macroplacoid ( Figures 2A, 2H, and 2I ). The macroplacoid length sequence is 2<3<1. The first macroplacoid is anteriorly narrowed and the third has a subterminal constriction ( Figures 2H and 2I , empty arrowhead).

Claws of the Mesobiotus type, with a peduncle connecting the claw to the lunula, a basal septum, and welldeveloped accessory points situated parallel to the primary branch ( Figures 3A–3C ). Lunules under claws I–III smooth ( Figures 3A, 3B ), but under claws IV slightly serrated ( Figure 3C ). Single transverse bars present beneath claws I–III ( Figures 3A, 3B , arrow), whereas a horseshoe-shaped structure connects the anterior and posterior lunules on claws IV ( Figure 3C , filled flat arrowhead).

Eggs (measurements and statistics in Table 3 ): Laid freely, white, spherical with conical processes ( Figures 4A and 6A, 6B ). The processes are equidistant from each other ( Figures 4A–4D and 6A, 6B ) with bases of hexagonal shape ( Figures 4B–4D and 6A–6D ). The process surface seems to be reticulated under PCM but smooth under SEM ( Figures 4A–4D , 5A–5I , and 6A–6H ). The labyrinthine layer within the process walls appears as reticulation under PCM, with meshes varying in diameter on each process, with decreasing mesh size from bottom to top on each process ( Figures 4C, 4D and 5H ). Several pores in the top portion of the processes are present in the external process walls (clearly visible only in SEM) ( Figures 6E–6H ). Processes are terminated by several short, thin, and flexible filaments very susceptible to fracture, which are visible in both PCM ( Figures 5A–5I ) and SEM ( Figures 6E–6H ). Moreover, the processes are sometimes bifurcated ( Figures 5H–5I ). Six flat, narrow, often not fully developed ( Figures 4C, 4D and 6C , filled indented arrowhead), and only sometimes connected ( Figures 4C, 4D and 6D , filled flat arrowhead) areoles are present around each process. The inner areole surface is wrinkled but this trait is only clearly visible in SEM ( Figures 6C, 6D ), rarely and barely visible in PCM ( Figure 4C , asterisk).

3.7. DNA sequences and p-distances comparisons

We obtained sequences for all three of the above mentioned molecular markers from all three paragenophores. All markers were represented by single private haplotypes:

The 18S rRNA sequence (GenBank: MF678793), 800 bp long;

The 28S rRNA sequence (GenBank: MF678792), 772 bp long;

The COI sequence (GenBank: MF678794), 638 bp long.

The ranges of uncorrected genetic p-distances between the new species and species of the Mesobiotus harmsworthi group, for which sequences are available from GenBank, are as follows (from the most to the least conservative):

18S rRNA: 1.1%–5.7%, with the most similar being M. philippinicus from the Philippines (KX129793) and the least similar being M. cf. mottai from the Antarctic (KT226072);

28S rRNA: 7.2% between the new species and M. philippinicus from the Philippines (KX129794);

COI: 24.0%–24.3%, with the most similar being M. philippinicus from the Philippines (KX129796) and the least similar M. hilariae from Antarctica (KT226108).

Figures

Figure 1. Mesobiotus ethiopicus sp. nov. – PCM image of habitus: A – dorsoventral projection (holotype). Scale bar in µm.

Figure 2. Mesobiotus ethiopicus sp. nov.– PCM images of the buccal apparatus:A – an entire buccal apparatus (paratype); B–C – the oral cavity armature of the holotype, dorsal and ventral teeth respectively; D–E – the oral cavity armature of the paratype, dorsal and ventral teeth respectively; F–G – the oral cavity armature of the paratype, dorsal and ventral teeth respectively; H–I – placoid morphology of the paratype, ventral and dorsal placoids, respectively. Filled flat arrowheads indicate the larger teeth in the second band of teeth, arrows indicate the medioventral tooth in the third band of teeth, empty flat arrowheads indicate subterminal constrictions in the third macroplacoid. Scale bars in µm.

Figure 3.Mesobiotus ethiopicus sp. nov. – PCM images of claws: A – claws I with smooth lunules; B – claws II with smooth lunules; C – claws IV with moderately serrated lunules. All claw photos from the holotype. Arrows indicate the cuticular bars, the filled arrowhead indicates the horseshoe structure connecting the anterior and the posterior claw. Scale bars in µm.

Figure 4.Mesobiotus ethiopicussp.nov.– PCMimages ofthe eggs:A– midsection;B– surface;C–D –surfaces under1000× magnification. Asterisk indicates the wrinkled surface inside the areolae, filled indented arrowheads indicate poorly developed connection between the processes, filled flat arrowheads indicate rare fully developed connections between processes. Scale bars in µm.

Figure 5. Mesobiotus ethiopicus sp. nov. – PCM images of the midsection of various types of egg processes. Scale bars in µm.

Figure 6. Mesobiotus ethiopicus sp. nov.– SEM images of eggs:A–B – entire view of 2 different eggs; C–D – egg surface between processes; E–F – egg processes; G–H – a top part of the processes terminated by several short flexible filaments. Filled indented arrowheads indicate poorly developed connection between the processes, filled flat arrowheads indicate rare fully developed connections between processes. Scale bars in µm.

Tables

Table 3. Measurements (in µm) of selected morphological structures of eggs of Mesobiotus ethiopicus

Character	N	Range	Mean	SD
Egg bare diameter	12	62.2 – 74.6	68.8	3.7
Egg full diameter	12	89.5 – 117.5	104.1	7.2
Process height	33	15.3 – 23.6	19.7	2.4
Process base width	33	13.1 – 22.5	18.2	1.7
Process base/height ratio	33	77% – 117%	94%	9%
Distance between processes	33	2.4 – 5.1	4.1	0.7
Number of processes on the egg circumference	10	10 – 12	10.7	0.7