Research Article |
Corresponding author: Piotr Gąsiorek ( piotr.lukas.gasiorek@gmail.com ) Academic editor: Martin Husemann
© 2020 Piotr Gąsiorek, Katarzyna Vončina, Peter Degma, Łukasz Michalczyk.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Gąsiorek P, Vončina K, Degma P, Michalczyk Ł (2020) Small is beautiful: the first phylogenetic analysis of Bryodelphax Thulin, 1928 (Heterotardigrada, Echiniscidae). Zoosystematics and Evolution 96(1): 217-236. https://doi.org/10.3897/zse.96.50821
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The phyletic relationships both between and within many of tardigrade genera have been barely studied and they remain obscure. Amongst them is the cosmopolitan Bryodelphax, one of the smallest in terms of body size echiniscid genera. The analysis of newly-found populations and species from the Mediterranean region and from South-East Asia gave us an opportunity to present the first phylogeny of this genus, which showed that phenotypic traits used in classical Bryodelphax taxonomy do not correlate with their phyletic relationships. In contrast, geographic distribution of the analysed species suggests their limited dispersal abilities and seems to be a reliable predictor of phylogenetic affinities within the genus. Moreover, we describe three new species of the genus. Bryodelphax australasiaticus sp. nov., by having the ventral plate configuration VII:4-4-2-4-2-2-1, is a new member of the weglarskae group with a wide geographic range extending from the Malay Peninsula through the Malay Archipelago to Australia. Bryodelphax decoratus sp. nov. from Central Sulawesi (Celebes) also belongs to the weglarskae group (poorly visible ventral plates VII:4-2-2-4-2-2-1) and is closely related to the recently described Bryodelphax arenosus Gąsiorek, 2018, but is differentiated from the latter by well-developed epicuticular granules on the dorsum. Finally, a new dioecious species, Bryodelphax nigripunctatus sp. nov., is described from Mallorca and, by the reduced ventral armature (II/III:2-2-(1)), it resembles Bryodelphax maculatus Gąsiorek et al., 2017. The latter species, known so far only from northern Africa, is recorded from Europe for the first time. A taxonomic key to the genus members is also presented.
cradle hypothesis, Everything is Everywhere hypothesis, geographic distribution, miniaturisation, phylogeny, ventral plates
Tardigrades are regarded as miniaturised panarthropods (
The aim of this study was to elucidate the phylogeny of Bryodelphax in relation to morphological traits used in its taxonomy, with application of the integrative approach, i.e. DNA barcoding and both qualitative and quantitative morphology, based on three new species that are described and illustrated herein. Our analyses reveal no congruence between the topology of the phylogenetic tree and the traditional taxonomic divisions of the genus (based on the presence of ventral armature), the reproductive mode or the development of dark, contrasting epicuticular granules on the dorsal plates. On the other hand, we show that phylogeny is tightly correlated with geography. In addition, an amended and updated key to the genus Bryodelphax is provided.
Specimens of the genus Bryodelphax were extracted from various moss and lichen samples collected in numerous European and Asian locales (details in Table
Collection data for the newly-sequenced species used in morphological and phylogenetic analyses.
Species | Sample code | Coordinates, altitude | Locality | Environment | Sample type, substrate | Collector |
---|---|---|---|---|---|---|
Bryodelphax australasiaticus sp. nov. | MY.240 | 5°27'05"N, 100°11'00"E, 4 m asl | Malaysia, Pulau Pinang, Pantai Keracut | beach dominated by Casuarina equisetifolia | moss, tree branch | Piotr Gąsiorek & Artur Oczkowski |
MY.241 | 5°27'05"N, 100°11'00"E, 4 m asl | Malaysia, Pulau Pinang, Pantai Keracut | beach dominated by Casuarina equisetifolia | moss, tree branch | Piotr Gąsiorek & Artur Oczkowski | |
MY.242 | 5°27'13"N, 100°11'08"E, 53 m asl | Malaysia, Pulau Pinang, Pantai Keracut | lowland rainforest | moss, rock | Piotr Gąsiorek & Artur Oczkowski | |
Bryodelphax decoratus sp. nov. | ID.546 | 1°50'33"S, 120°16'34"E, 800 m asl | Indonesia, Central Sulawesi, Lore Lindu, Bada Lembah | cacao tree plantation | moss, tree | Piotr Gąsiorek & Artur Oczkowski |
ID.548 | 1°50'33"S, 120°16'34"E, 801 m asl | Indonesia, Central Sulawesi, Lore Lindu, Bada Lembah | cacao tree plantation | moss+lichen, tree | Piotr Gąsiorek & Artur Oczkowski | |
Bryodelphax maculatus* | GR.050 (=780) | 35°23'23"N, 23°39'36"E, 374 m asl | Greece, Crete ,Vlatos | olive tree plantation | moss, olive tree | Peter Degma |
Bryodelphax nigripunctatus sp. nov.** | ES.264 (=716) | 39°57'00"N, 3°10'50"E, 160 m asl | Spain, The Balearic Islands, Mallorca, Cap de Formentor, Cala Figuera beach, near the road above | sea shore | moss, rock | Peter Degma |
Bryodelphax parvulus | IT.010 | 45°42'12"N, 13°42'53"E, 1 m asl | Italy, Trieste, Grignano Miramare | urban park | moss, wall | Alicja Witwicka |
Bryodelphax sp. nov. | ID.464 | 1°52'48"S 120°15'48"E, 778 m asl | Indonesia, Central Sulawesi, Lore Lindu, Bada Lembah | cacao tree plantation | moss, tree | Piotr Gąsiorek & Artur Oczkowski |
Bryodelphax sp. nov. | ID.846 | 3°10'52"S, 129°02'58"E, 295 m asl | Indonesia, Ambon, pass between Triana and Jerili/Sawai, Seram Tengah | mountain rainforest | lichen, palm tree | Piotr Gąsiorek & Łukasz Krzywański |
Processing data for populations of Bryodelphax investigated in this study. Types of analyses: LCM – imaging and morphometry in PCM/NCM, SEM – imaging in SEM, DNA – genotyping. Numbers indicate how many specimens were utilised in a given analysis.
Species | Sample code | Analyses | ||
---|---|---|---|---|
LCM | SEM | DNA | ||
Bryodelphax australasiaticus sp. nov. | MY.240 | 14 | 10 | 4 |
MY.241 | 1 | – | – | |
MY.242 | 2 | – | – | |
Bryodelphax decoratus sp. nov. | ID.546 | 9 | – | 5 |
ID.548 | 3 | – | – | |
Bryodelphax maculatus | GR.050 | 9 | – | 6 |
Bryodelphax nigripunctatus sp. nov. | ES.264 | 55 | 30 | 8 |
Bryodelphax parvulus | IT.010 | 8 | – | 4 |
Bryodelphax sp. nov. | ID.464 | 8 | – | 4 |
Bryodelphax sp. nov. | ID.846 | 13 | – | 4 |
Permanent microscope slides were made using Hoyer’s medium and examined under a Nikon Eclipse 50i PCM associated with a Nikon Digital Sight DS-L2 digital camera and Olympus BX51 PCM and DIC associated with a digital camera CCD ColorView III FW. Specimens for imaging in the SEM were prepared according to
DNA was extracted from individual animals (all examined under a 400× magnification PCM prior to DNA extraction) following a Chelex 100 resin (Bio-Rad) extraction method (
ModelFinder (
Raw morphometric data underlying the description of the new species are deposited in the Tardigrada Register under www.tardigrada.net/register/0064.htm (B. australasiaticus sp. nov.), www.tardigrada.net/register/0065.htm (B. decoratus sp. nov.), www.tardigrada.net/register/0066.htm (B. nigripunctatus sp. nov.). Type DNA sequences are deposited in GenBank.
Bayesian Inference and Maximum Likelihood trees shared identical topology (Fig.
BI and ML concatenated (18S rRNA + 28S rRNA) phylogenetic tree of Bryodelphax Thulin, 1928; Echiniscus spp. were used as outgroup taxa. Bayesian posterior probability values (≥ 0.90) are given above tree branches, whereas ML bootstrap support values (≥ 70) are below branches. The scale bar represents 0.01 substitutions/site in the Bayesian tree. Trait mapping (blue square – presence, empty square – absence): 1 – ventral plates; 2 – granules on dorsal plates; 3 – males in population.
Phylum: Tardigrada Doyère, 1840
Class: Heterotardigrada Marcus, 1927
Order: Echiniscoidea Richters, 1926
Family: Echiniscidae Thulin, 1928
Genus: Bryodelphax Thulin, 1928
B. australis
sp. n. in
5°27'05"N, 100°11'00"E, 4 m a.s.l.; Pantai Keracut, Pulau Penang, Malaysia. Holotype (adult female; slide MY.240.01) and seven paratypes (5 females, 2 juveniles; slides MY.240.01–04) deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University; two paratypes (2 females; slide MY.240.05) deposited in the Department of Zoology, Comenius University in Bratislava; one paratype (1 female; slide MY.240.06) deposited in the Natural History Museum of Denmark, University of Copenhagen; two paratypes (2 females; slide MY.240.07) deposited in the Department of Animal Biology, University of Catania; three paratypes (2 females, one larva; slides MY.241.02, MY.242.02) deposited in the Raffles Museum of Biodiversity Research, National University of Singapore.
Measurements [in µm] of selected morphological structures of mature females of Bryodelphax australasiaticus sp. nov. mounted in Hoyer’s medium (N – number of specimens/structures measured, Range refers to the smallest and the largest structure amongst all measured specimens; SD – standard deviation; sp – the ratio of the length of a given structure to the length of the scapular plate expressed as a percentage).
Character | N | Range | Mean | SD | Holotype | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
µm | sp | µm | sp | µm | sp | µm | sp | ||||||
Body length | 16 | 91 | – | 119 | 584 | – | 737 | 108 | 667 | 7 | 41 | 111 | 666 |
Scapular plate length | 16 | 15.2 | – | 17.9 | – | 16.2 | – | 0.8 | – | 16.6 | – | ||
Head appendages lengths | |||||||||||||
Cirrus internus | 15 | 4.7 | – | 6.6 | 30.2 | – | 42.4 | 5.7 | 35.4 | 0.6 | 4.0 | 5.6 | 33.9 |
Cephalic papilla | 12 | 2.3 | – | 3.3 | 13.9 | – | 21.1 | 2.9 | 18.0 | 0.3 | 2.3 | 2.9 | 17.6 |
Cirrus externus | 14 | 7.4 | – | 9.4 | 47.7 | – | 58.6 | 8.4 | 52.6 | 0.5 | 3.3 | 9.0 | 54.3 |
Clava | 11 | 1.8 | – | 3.1 | 10.7 | – | 20.4 | 2.3 | 14.0 | 0.4 | 2.8 | 1.9 | 11.2 |
Cirrus A | 17 | 23.2 | – | 28.7 | 144.0 | – | 183.6 | 25.8 | 160.0 | 1.6 | 11.6 | 24.6 | 147.7 |
Cirrus A/Body length ratio | 15 | 21% | – | 26% | – | 24% | – | 1% | – | 22% | – | ||
Claw heights | |||||||||||||
Claw I | 13 | 4.5 | – | 5.7 | 26.2 | – | 33.9 | 5.1 | 31.2 | 0.4 | 2.2 | 5.1 | 30.4 |
Claw II | 14 | 4.3 | – | 5.5 | 26.7 | – | 33.3 | 5.0 | 30.4 | 0.3 | 2.3 | 5.5 | 33.3 |
Claw III | 15 | 4.2 | – | 5.5 | 26.5 | – | 34.2 | 4.8 | 29.6 | 0.3 | 2.1 | 5.0 | 30.2 |
Claw IV | 13 | 4.9 | – | 6.2 | 30.7 | – | 38.4 | 5.4 | 33.3 | 0.4 | 2.7 | 5.4 | 32.2 |
The name refers to the currently identified geographic range of the new species that encompasses Asia and Australia. Adjective in the nominative singular.
Body pink, pearly opalescent; eyes absent or not visible after mounting in Hoyer’s medium. Primary and secondary clavae small and conical. Cirri interni and externi with poorly-developed cirrophores. Cirri A of typical length for Bryodelphax, i.e. reaching around 25% of the total body length. All dorsal plates with barely-discernible intra-cuticular pillars (better visible under a 1000× magnification), the centro-posterior portion of the caudal (terminal) plate has evident, largest pillars (Fig.
Venter with seven rows of faint, greyish plates (VII:4-4-2-4-2-2-1), of which two plates of the first, subcephalic row are located in a more ventrolateral position (Figs
Body 73–101 μm long in the two found juveniles. Dorsal and ventral plates developed similarly to adults. Scapular plate 12–16 μm long. Claws 3.7–4.8 μm long.
Body 80 μm long in a single found two-clawed specimen. Dorsal and ventral plates developed similarly to adults. Scapular plate 12.7 μm long. Claws 4.0–4.4 μm long.
Up to one egg in exuvia was found.
Single 18S rRNA haplotype (MT333468), two 28S rRNA haplotypes (MT333460–1) and single ITS-1 haplotype (MT333477).
Within the weglarskae group, only B. decoratus sp. nov., B. sinensis and B. instabilis have seven plate rows, but B. olszanowskii
Genotypic differential diagnosis: p-distances between the new species and the remaining Bryodelphax spp., for which DNA sequences are available, were as follows:
Two ventrolateral plates were not drawn in
1°50'33"S, 120°16'34"E, 800 m a.s.l.; Bada Lembah, Lore Lindu, Celebes (Sulawesi), Indonesia. Holotype (adult female, slide ID.546.15) and three paratypes (females; slide ID.546.12) deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University; three paratypes (females; slide ID.546.13) deposited in the Department of Zoology, Comenius University in Bratislava; three paratypes (females; slide ID.548.11) deposited in the Natural History Museum of Denmark, University of Copenhagen; one paratype (female; slide ID.546.14) deposited in the Department of Animal Biology, University of Catania; one paratype (female; slide ID.546.16) deposited in the Raffles Museum of Biodiversity Research, National University of Singapore.
Measurements [in µm] of selected morphological structures of mature females of Bryodelphax decoratus sp. nov. mounted in Hoyer’s medium (N – number of specimens/structures measured, Range refers to the smallest and the largest structure amongst all measured specimens; SD – standard deviation; sp – the ratio of the length of a given structure to the length of the scapular plate expressed as a percentage).
Character | N | Range | Mean | SD | Holotype | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
µm | sp | µm | sp | µm | sp | µm | sp | ||||||
Body length | 13 | 99 | – | 120 | 595 | – | 694 | 107 | 633 | 6 | 32 | 104 | 640 |
Scapular plate length | 13 | 16.1 | – | 18.2 | – | 16.9 | – | 0.7 | – | 16.2 | – | ||
Head appendages lengths | |||||||||||||
Cirrus internus | 13 | 4.6 | – | 7.0 | 28.5 | – | 42.3 | 6.0 | 35.7 | 0.8 | 4.2 | 5.4 | 33.0 |
Cephalic papilla | 11 | 2.5 | – | 3.5 | 15.4 | – | 20.5 | 3.1 | 18.4 | 0.4 | 1.7 | 3.3 | 20.5 |
Cirrus externus | 11 | 8.1 | – | 12.2 | 50.2 | – | 70.6 | 9.6 | 57.2 | 1.3 | 7.3 | 9.0 | 55.4 |
Clava | 9 | 2.2 | – | 3.0 | 13.1 | – | 18.4 | 2.6 | 15.3 | 0.2 | 1.8 | ? | ? |
Cirrus A | 12 | 24.1 | – | 27.7 | 137.6 | – | 169.5 | 25.9 | 153.4 | 1.2 | 9.5 | 27.4 | 169.3 |
Cirrus A/Body length ratio | 12 | 22% | – | 28% | – | 24% | – | 2% | – | 26% | – | ||
Claw heights | |||||||||||||
Claw I | 11 | 5.0 | – | 6.2 | 29.8 | – | 35.1 | 5.5 | 32.5 | 0.4 | 1.9 | ? | ? |
Claw II | 11 | 4.4 | – | 5.5 | 26.5 | – | 33.3 | 5.1 | 30.2 | 0.4 | 2.0 | 4.8 | 29.8 |
Claw III | 13 | 4.6 | – | 5.7 | 28.1 | – | 34.1 | 5.2 | 30.8 | 0.4 | 1.7 | 4.9 | 30.1 |
Claw IV | 13 | 5.2 | – | 6.4 | 32.2 | – | 39.2 | 5.8 | 34.6 | 0.4 | 2.4 | 5.2 | 32.2 |
From Latin decoratus = beautified, embellished. The name highlights the intricate and beautiful pattern of the dark epicuticular granules. Adjective in the nominative singular.
Body translucent; eyes absent or not visible after mounting in Hoyer’s medium. Primary and secondary clavae minute and conical. Cirri interni and externi with poorly developed cirrophores. Cirri A of typical length for Bryodelphax, i.e. reaching around 25% of the total body length. All dorsal plates with well-visible intra-cuticular pillars, the largest pillars present on the scapular, posterior portions of paired segmental and the caudal (terminal) plates (Fig.
Venter with extremely weakly delineated plates (VII:4-2-2-4-2-2-1), only slightly darker than the surrounding ventral cuticle and without clear, sclerotised margins. Dark epicuticular granules and intra-cuticular pillars absent. Leg papillae undetectable under LCM. Both pulvini and pedal plates absent (Fig.
Habitus of adult females of Bryodelphax decoratus sp. nov. (PCM): A – holotype, dorsal view (insert with the claws I, arrowhead indicates spur on internal claw); B – paratype, lateral view; C – frontal part of the body; D – central part of the body, sculpture of median and paired plates. Scale bars in µm.
Not found.
Not found.
Not found.
Two 18S rRNA haplotypes (MT333469–70) and two 28S rRNA haplotypes (MT333462–3) and single ITS-1 haplotype (MT333478).
The new species belongs to the weglarskae group and it must be compared with the three species (B. instabilis, B. olszanowskii and B. sinensis) with seven ventral plate rows or with ventrolateral plates in the first row present. Additionally, B. decoratus sp. nov. is compared with B. arenosus, as the new species can have very dim and barely discernible ventral plates and, in such cases, it resembles B. arenosus. Nevertheless, adult females of B. decoratus sp. nov. differ specifically from:
Genotypic differential diagnosis: p-distances between the new species and the remaining Bryodelphax spp., for which DNA sequences are available, were as follows:
39°57'00"N, 3°10'50"E, 160 m a.s.l.; near the road above Cala Figuera beach, Cap de Formentor, NE Mallorca, the Balearic Islands, Spain. Holotype (adult female; together with one male paratype in slide 716/45), allotype (adult male; slide 716/9) and 30 paratypes (9 females, 14 males, 3 specimens of unknown sex, 2 juveniles and 2 larvae; slides 716/1–5, 10, 13, 17 –20, 25, 27–29, 32–34, 41, 45, 47–48, 50–51) deposited in the Department of Zoology, Comenius University in Bratislava; 13 paratypes (6 females, 6 males and one specimen of unknown sex; slides 716/26, 38, 40, 42–44, 46, 49) deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University; 9 paratypes (4 females and 5 males; slides 716/6–8, 11–12, 22–24, 35) deposited in the Natural History Museum of Denmark, University of Copenhagen; 9 paratypes (4 females and 5 males; slides 716/14–16, 21, 31, 36–37) deposited in the Department of Animal Biology, University of Catania. Single paratype (male) mounted on a SEM stub (14.19) deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University. Eight specimens used for DNA extraction. Bryodelphax nigripunctatus sp. nov. was not accompanied by other species in the sample.
Measurements [in µm] of selected morphological structures of mature females of Bryodelphax nigripunctatus sp. nov. mounted in Hoyer’s medium (N – number of specimens/structures measured, Range refers to the smallest and the largest structure amongst all measured specimens; SD – standard deviation; sp – the ratio of the length of a given structure to the length of the scapular plate expressed as a percentage).
Character | N | Range | Mean | SD | Holotype | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
µm | sp | µm | sp | µm | sp | µm | sp | ||||||
Body length | 15 | 114 | – | 144 | 562 | – | 689 | 126 | 645 | 9 | 38 | 131 | 657 |
Scapular plate length | 15 | 18.0 | – | 21.7 | – | 19.6 | – | 1.1 | – | 19.9 | – | ||
Head appendages lengths | |||||||||||||
Cirrus internus | 11 | 6.1 | – | 8.9 | 32.9 | – | 42.8 | 7.3 | 37.4 | 0.8 | 3.3 | 7.5 | 37.4 |
Cephalic papilla | 14 | 2.6 | – | 3.7 | 12.6 | – | 19.7 | 3.1 | 15.9 | 0.4 | 1.9 | 3.3 | 16.5 |
Cirrus externus | 12 | 10.2 | – | 12.8 | 54.1 | – | 66.9 | 11.8 | 60.1 | 0.7 | 4.4 | 12.2 | 61.4 |
Clava | 10 | 2.7 | – | 3.1 | 12.3 | – | 16.9 | 2.9 | 14.8 | 0.1 | 1.3 | 3.0 | 15.0 |
Cirrus A | 15 | 24.8 | – | 31.0 | 120.7 | – | 163.7 | 28.0 | 143.6 | 1.6 | 11.0 | 26.3 | 132.4 |
Cirrus A/Body length ratio | 15 | 20% | – | 25% | – | 22% | – | 2% | – | 20% | – | ||
Body appendages lengths | |||||||||||||
Papilla on leg IV length | 8 | 1.4 | – | 2.3 | 7.2 | – | 12.5 | 1.8 | 9.5 | 0.3 | 2.0 | 1.5 | 7.6 |
Number of teeth on the collar | 10 | 2 | – | 5 | – | 3.3 | – | 0.9 | – | 2 | – | ||
Claw heights | |||||||||||||
Claw I | 12 | 7.0 | – | 8.3 | 35.1 | – | 44.4 | 7.8 | 39.8 | 0.5 | 3.1 | 7.2 | 36.0 |
Claw II | 9 | 7.0 | – | 8.8 | 36.1 | – | 44.3 | 7.6 | 39.6 | 0.5 | 2.8 | 7.7 | 38.8 |
Claw III | 13 | 6.7 | – | 8.3 | 36.1 | – | 46.2 | 7.6 | 39.3 | 0.5 | 3.1 | 7.6 | 38.1 |
Claw IV | 9 | 7.4 | – | 8.9 | 38.1 | – | 48.0 | 8.4 | 43.0 | 0.5 | 3.5 | ? | ? |
Measurements [in µm] of selected morphological structures of mature males of Bryodelphax nigripunctatus sp. nov. mounted in Hoyer’s medium (N – number of specimens/structures measured, Range refers to the smallest and the largest structure amongst all measured specimens; SD – standard deviation; sp – the ratio of the length of a given structure to the length of the scapular plate expressed as a percentage).
Character | N | Range | Mean | SD | Allotype | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
µm | sp | µm | sp | µm | sp | µm | sp | ||||||
Body length | 15 | 106 | – | 134 | 618 | – | 725 | 123 | 685 | 8 | 30 | 130 | 704 |
Scapular plate length | 15 | 16.1 | – | 19.5 | – | 17.9 | – | 1.1 | – | 18.5 | – | ||
Head appendages lengths | |||||||||||||
Cirrus internus | 13 | 6.3 | – | 9.9 | 35.8 | – | 51.7 | 7.7 | 42.8 | 1.0 | 4.6 | 8.5 | 46.0 |
Cephalic papilla | 14 | 3.1 | – | 5.6 | 19.0 | – | 32.0 | 4.6 | 25.5 | 0.8 | 3.9 | 5.2 | 28.1 |
Cirrus externus | 13 | 12.3 | – | 15.9 | 70.6 | – | 85.8 | 14.2 | 78.6 | 1.0 | 4.3 | 13.9 | 75.4 |
Clava | 11 | 2.8 | – | 4.7 | 17.6 | – | 24.2 | 3.8 | 21.2 | 0.5 | 1.9 | 4.1 | 21.9 |
Cirrus A | 15 | 26.8 | – | 32.6 | 141.3 | – | 187.3 | 29.3 | 163.8 | 1.9 | 11.4 | 30.2 | 163.4 |
Cirrus A/Body length ratio | 15 | 21% | – | 26% | – | 24% | – | 2% | – | 23% | – | ||
Body appendages lengths | |||||||||||||
Papilla on leg IV length | 8 | 1.7 | – | 2.4 | 9.7 | – | 12.8 | 2.0 | 11.4 | 0.3 | 1.0 | 2.0 | 10.9 |
Number of teeth on the collar | 12 | 3 | – | 5 | – | 3.9 | – | 1.0 | – | 5 | – | ||
Claw heights | |||||||||||||
Claw I | 11 | 7.3 | – | 8.7 | 37.6 | – | 50.3 | 8.1 | 45.1 | 0.5 | 3.4 | 8.3 | 44.8 |
Claw II | 10 | 7.1 | – | 8.8 | 41.2 | – | 48.5 | 8.0 | 44.7 | 0.5 | 2.5 | 8.8 | 47.9 |
Claw III | 14 | 7.0 | – | 9.2 | 38.5 | – | 49.5 | 8.0 | 44.7 | 0.6 | 3.3 | 9.0 | 48.6 |
Claw IV | 9 | 7.8 | – | 9.4 | 43.6 | – | 52.6 | 8.7 | 48.3 | 0.6 | 2.8 | ? | ? |
From Latin niger = black + punctum = dot, spot. The name underlines evident epicuticular granules appearing dark in PCM and contrasting with other elements of dorsal sculpture. Adjective in the nominative singular.
Body translucent without distinct colour and usually stout in females and more slender in males (Figs
Habitus of adults of Bryodelphax nigripunctatus sp. nov. (PCM): A – female (holotype, dorsolateral view); B – male (allotype, dorsal view); C – female (paratype, lateral view; Roman numerals signify epicuticular belts of granules on legs); D – male (allotype, ventral view, Roman numerals point out reduced ventral armature; insert with the claws II, arrowhead indicates spur on internal claw). Scale bars: 50 µm.
Details of cuticular sculpturing of Bryodelphax nigripunctatus sp. nov.: A – microscope focused on the epicuticular granules (allotype, NCM); B – microscope focused on the intracuticular pillars (allotype, NCM); C – frontal part of the body (allotype, PCM); D – frontal part of the body (holotype, PCM). Scale bars in µm.
Cephalic plate with an anterior chalice-like incision. Each segmental and median plate consists of the anterior and the posterior portion separated each from other with a transverse bright poreless stripe in PCM. Therefore, paired segmental plates are subdivided into the narrower anterior (ca. 1/3–2/5 of the plate length) and the wider posterior portions, trapezoidal anterior median plate 1 is subdivided just behind its anterior margin, pentagonal anterior m2 (the largest amongst the median plates) is divided at approximately equally-long portions, triangular anterior portion of median plate 3 is ca. two times as long (along median body axis) as the posterior one with rounded posterior margin (dividing transverse line of anterior median plates 2–3 correspond with posterior corners of paired segmental plates). Pentagonal posterior median plates 1–2 subdivided at portions of about same lengths. On each body side, the first two pairs of supplementary lateral platelets are connected with anterior and posterior median plates 1–2 and the third pair is connected with the posterior portion of m3 and with the anterior edge of caudal plate. Anterior platelets of each pair have very distinctly-thickened lateral (lower) margins (Figs
Venter with transverse rows of weakly-developed plates unevenly sculptured with epicuticular granules similar to those on the dorsal plates, but a bit smaller. There are three rows of ventral plates in females (the plate formula III:2-2-1) and two rows in males (II:2-2) (Fig.
In appearance as adults, but smaller (111–112 μm) and with ventral plates just marked with rows of granules. Selected measurements of a shorter specimen: cephalic papilla 3.1 μm, scapular plate 14.9 μm long, claws I–III 5.1–5.6 and claws IV 6.5 μm long.
83–85 μm long. Dorsal plates (especially median ones) mostly with poorly-delineated margins, supplementary lateral platelets absent. Epicuticular granules less numerous than in adults, concentrated mainly on posterior margins of the cephalic, scapular, both paired and caudal plates. Cuticular pores less numerous than in adults, but intracuticular pillars, stripes of granules on the outer surface of legs, papilla on legs IV and dentate collar IV well developed. Ventral plates not visible in laterally orientated larvae. Claws with spurs formed as in adults. Some measurements of shorter specimen: cephalic papilla 2.5 μm, claws II–III 4.6– 5.3 and claws IV 6.4 μm long.
Not found.
Two 18S rRNA haplotypes (MT333472–3), single 28S rRNA haplotype (MT333465).
Having ventral plates, Bryodelphax nigripunctatus sp. nov. belongs to the weglarskae group. Within the group, only B. amphoterus and B. maculatus have a reduced number of ventral plate rows to two or three, as in the new species. Consecutively, B. nigripunctatus sp. nov. differs from:
Genotypic differential diagnosis: p-distances between the new species and the remaining Bryodelphax spp., for which DNA sequences are available, were as follows:
Inter-generic tardigrade relationships are constantly being unravelled (
Regarding the phyletic relationships within the genus Bryodelphax, some intriguing conclusions can be drawn from the mapping of various phenotypic traits onto the phylogenetic tree (Fig.
Secondly, since the description of B. maculatus, dark epicuticular granules have received attention of taxonomists (
Thirdly, species exhibiting different modes of reproduction are scattered on the tree. Two of the three known dioecious Bryodelphax spp., B. instabilis and B. nigripunctatus sp. nov., are not directly related (Fig.
Last but not least, in contrast to phenotypic traits, geographic distribution of the analysed species suggests their limited dispersal abilities and seems to be a reliable predictor of phylogenetic affinities within the genus. This intriguing pattern has been recently shown in the genus Milnesium Doyère, 1840 by
It ought to be noted that the lengths of the tree branches in the case of the Oriental clade are considerably shorter than those for the Western Palaearctic clade (Fig.
Since the last key by
Schematic arrangement of the ventral plates in all members of the weglarskae group (species are arranged in order of the increasing reduction of the ventral armature). Known cases of ontogenetic variability and sexual dimorphism are depicted. Following species taken from
1 | Ventral plates present (the weglarskae group) | 2 |
– | Ventral plates absent (the parvulus group) | 13 |
2(1) | Two (subcephalic and genital) or three rows of ventral plates | 3 |
– | At least four rows of ventral plates | 5 |
3(2) | Ventral plate formula II:2-2, dark epicuticular granules absent, external claws with minute spurs | B. amphoterus (Durante Pasa & Maucci, 1975) |
– | Ventral plate formula different, dark epicuticular granules present, external claws spurless | 4 |
4(3) | Ventral plate formula III:2-2-1, entire venter and ventral plates covered with stripes of dark epicuticular granules, typical, short and stout Bryodelphax claws | B. maculatus Gąsiorek et al., 2017 |
– | Ventral plate formula II/III:2-2-(1), only ventral plates covered with dark epicuticular granules, long and slender, Pseudechiniscus-like claws | B. nigripunctatus sp. nov. |
5(2) | Ventral plate rows composed of 1–2 plates each | 6 |
– | Ventral plate rows composed of at least three plates each (excluding the subcephalic row) | 7 |
6(5) | Ventral plate formula VIII:1-1-2-2-2-2-2-1, dentate collar IV present |
B. parvuspolaris |
– | Ventral plate formula VII:2-2-2-2-2-2-1, dentate collar IV absent | B. sinensis (Pilato, 1974) |
7(5) | Four plates in the subcephalic row | 8 |
– | Two or no plates in the subcephalic row | 10 |
8(7) | Eight rows of ventral plates, plates typically developed and with dark epicuticular granules |
B. olszanowskii |
– | Seven rows of ventral plates, all plates faint and devoid of dark epicuticular granules | 9 |
9(8) | Ventral plate formula VII:4-4-2-4-2-2-1, dorsal plate margins uniformly thick and dark in PCM | B. australasiaticus sp. nov. |
– | Ventral plate formula VII:4-2-2-4-2-2-1, dorsal plate margins with separated epicuticular granules observable as dark points in PCM | B. decoratus sp. nov. |
10(7) | Ventral plate formula IX:2-2-5-2-4-2-2-2-1, cephalic cirri bifurcated at their tips | B. weglarskae (Pilato, 1972) |
– | Ventral plate formula different, cephalic cirri with a single tip | 11 |
11(10) | Ventral plate formula VII/IX:(2)-(1)-2/4-2-2/4-2-2-2-1, dioecious | B. instabilis Gąsiorek & Degma, 2018 |
– | Ventral plate formula different, parthenogenetic | 12 |
12(11) | Ventral rows immediately before legs II and III, composed of 2 plates each |
B. iohannis |
– | Ventral rows immediately before legs II and III composed of 4 plates each | 12 |
12(11) | Ventral plate formula X:2-1-4-4-2-4-2-1-2-1, cirrus A/body length ratio at least 24% |
B. aaseae |
– | Ventral plate formula IX/X:2-(1)-4-4-2-4-2-1-2-1, cirrus A/body length ratio below 24% |
B. kristenseni |
13(1) | Dentate collar IV present | 14 |
– | Dentate collar IV absent | 19 |
14(13) | Supplementary lateral plates absent |
B. brevidentatus |
– | Supplementary lateral plates present | 15 |
15(14) | Six supplementary lateral plates, more than ten teeth in the dentate collar | B. alzirae (du Bois-Reymond Marcus, 1944) |
– | Twelve supplementary lateral plates, fewer than ten teeth in the dentate collar | 16 |
16(15) | Papilla IV visible under LCM | 17 |
– | Papilla IV not visible under LCM | 18 |
17(16) | Endocuticular pillars in the scapular and the caudal (terminal) plate almost of the same size, pores evident and densely distributed on the anterior and lateral portions of the plates |
B. atlantis |
– | Endocuticular pillars in the scapular plate clearly smaller than pillars in the caudal (terminal) plate, pores evident only in the central portion of the paired plates |
B. meronensis |
18(16) | Teeth of the dentate collar long and acute | B. tatrensis (Węglarska, 1959) |
– | Teeth of the dentate collar short and blunt | B. mateusi (Fontoura, 1982) |
19(13) | Pores/pseudopores absent, endocuticular pillars scarcely visible only in the caudal (terminal) plate, large depressions (fossae) in poorly defined rows | B. dominicanus (Schuster & Toftner, 1982) |
– | Pores/pseudopores present, endocuticular pillars visible on all dorsal plates, depressions (fossae) absent | 20 |
20(19) | Lateral portions of dorsal plates ornamented either with dark epicuticular granules or elevations | B. arenosus Gąsiorek, 2018 |
– | Lateral portions of dorsal plates not ornamented | 21 |
21(20) | Supplementary lateral plates absent, internal claws spurless | B. ortholineatus (Bartoš, 1963) |
– | Supplementary lateral plates present, internal claws with spurs | 22 |
22(21) | Papilla IV visible under LCM |
B. crossotus |
– | Papilla IV not visible under LCM | 23 |
23(22) | The largest endocuticular pillars only in the central portion of the scapular plate | B. parvulus Thulin, 1928 |
– | The largest endocuticular pillars in the central portions of the scapular and the caudal (terminal) plate and posterior portions of paired segmental plates | B. asiaticus Kaczmarek & Michalczyk, 2004 |
Reinhardt M. Kristensen (University of Copenhagen), Roberto Guidetti (University of Modena and Reggio Emilia), Roberta Salmaso (Museum of Natural History of Verona) and Giovanni Pilato (University of Catania) are acknowledged for the loan of type material of some species. Alicja Witwicka, Artur Oczkowski and Łukasz Krzywański provided the moss samples or assisted in their collection. We are grateful to Sandra Claxton who consulted the morphology of individuals of B. australasiaticus sp. nov. from Australia and provided valuable microphotographs. Two reviewers, Matteo Vecchi and Łukasz Kaczmarek, kindly commented on the manuscript. The study and sampling were supported by the grant from the European Commission’s (FP6) Integrated Infrastructure Initiative programme SYNTHESYS (grant no. DK-TAF-6332 to PG), National Science Centre (2019/33/N/NZ8/02777 to PG, supervised by ŁM), and by the Polish Ministry of Science and Higher Education via the Diamond Grant (DI2015 014945 to PG, supervised by ŁM). Some of the analyses were carried out with the equipment purchased from the Sonata Bis programme of the Polish National Science Centre (grant no. 2016/22/E/NZ8/00417 to ŁM). This work was also supported by the Slovak Research and Development Agency under the contract No. APVV-15-0147 (to PD). We owe our sincere thanks to the Museum für Naturkunde, Berlin, for covering the publication charge. The Authors declare no conflict of interest.