Diaforobiotus islandicus ( Richters, 1904 )

Stec, Daniel, 2023, Integrative taxonomy helps to revise systematics and questions the purported cosmopolitan nature of the type species within the genus Diaforobiotus (Eutardigrada: Richtersiusidae), Organisms Diversity & Evolution (New York, N. Y.) 23 (2), pp. 309-328 : 311-314

publication ID	https://doi.org/ 10.1007/s13127-022-00592-6
persistent identifier	https://treatment.plazi.org/id/FE448785-FF88-8560-FCDF-FD4AFABAF927
treatment provided by	Felipe
scientific name	Diaforobiotus islandicus ( Richters, 1904 )
status

Treatment

Diaforobiotus islandicus ( Richters, 1904)

ZooBank: urn:lsid:zoobank.org:act:8D6288A7-024D-44F8-821D-A841E8AE7157

Macrobiotus islandicus Richters, 1904 View in CoL

Macrobiotus ruffoi Maucci, 1973 View in CoL

Diaforobiotus islandicus IS. 042 in Stec et al. (2020c) and in Stec and Morek (2022)

Figs. 1 View Fig , 2 View Fig , 3 View Fig , 4 View Fig and 5 View Fig , Tables 2 and 3

Etymology: The name “islandicus ” refers to the country where it was originally discovered by Richters in 1904, which is Iceland.

Material examined: 20 animals and 13 eggs: specimens mounted on microscope slides in Hoyer’s medium (18 animals + 10 eggs), fixed on SEM stub (0 + 3), and used for DNA extraction and sequencing (2 + 0; in Stec et al. (2020c)) .

Animals (measurements and statistics in Table 2).

When alive, body pale yellow to light orange; after fixation in Hoyer’s medium body transparent ( Fig. 1A View Fig ). Large, black granular eyes present, visible also in specimens mounted in Hoyer’s medium. Body cuticle smooth, without granulation but with circular or elliptical pores sometimes with uneven edges (0.7–2.4 µm in diameter) distributed randomly on the entire body cuticle with the largest pores present in the dorso-caudal cuticle ( Fig. 1 View Fig B-D). Pores on the ventral side of the body more scattered than on the dorsal side ( Fig. 1 View Fig B-C). Granulation absent on all legs. Pulvini present on each leg I–III on the internal leg surface ( Fig. 1D View Fig ).

Claws slender, of the richtersiusid type, with common tract with a system of internal septa, and with an evident stalk connecting the claw to the lunula ( Fig. 2A, B View Fig ) as described by Lisi et al. (2020). The common tract longer than the half of the entire claw height ( Fig. 2A, B View Fig ). Primary and secondary branches form an acute angle at the bifurcation ( Fig. 2A, B View Fig ). Primary branches with prominent accessory points clearly protruding from the branch ( Fig. 2A, B View Fig ). Lunulae, slightly trapezoidal in shape, present on all legs, with lunulae in hind leg being distinctly larger ( Fig. 2A, B View Fig ). Lunulae on all the legs equipped with clearly visible teeth (several in lunulae I–III and up to 20 in lunulae IV; Fig. 2A, B View Fig ). A single continuous cuticular bar and paired muscle attachments present present proximally to claws on legs I–III ( Figs. 1A View Fig and 2A View Fig ). In PCM, in the leg midsection (lateral perspective on the leg), the cuticular bar is visible as a strong and distinct thickening ( Fig. 1A View Fig ).

Mouth antero-ventral. Relatively short bucco-pharyngeal apparatus ( Fig. 3A View Fig ) with ten peribuccal lamellae, rigid buccal tube, bent anteriorly, with ventral lamina. Based on PCM observations, the oral cavity armature is well developed and composed of three bands of teeth ( Fig. 3B, C View Fig ). The first band is composed of very small granular teeth positioned posteriorly to peribuccal lamellae, visible as faint granulation in PCM ( Fig. 3B, C View Fig ). The second band of teeth is composed of several rows of granular teeth (larger than teeth of the first band), of which the most posterior row comprises the larger teeth ( Fig. 3B, C View Fig ). The teeth of the third band are located within the posterior portion of the oral cavity, anteriorly to the buccal tube opening ( Fig. 3B, C View Fig ). The third band of teeth is divided into the dorsal and the ventral portion ( Fig. 3B, C View Fig ). The dorsal portion is composed of three large teeth ( Fig. 3B View Fig ). The two lateral teeth are visible as lateral ridges positioned just before buccal tube opening, whereas the medial circular tooth is positioned further towards the pharynx in the buccal tube ( Fig. 3B View Fig ). The ventral portion of the third band of teeth is fainter in PCM compared to the dorsal portion ( Fig. 3C View Fig ). The ventral portion is composed of two small indistinct lateral teeth (in PCM faintly visible as granular) and a medial circular tooth ( Fig. 3C View Fig ). Pharynx spherical, with triangular apophyses, three anterior cuticular spikes (typically only two are visible in any given plane) and two rod-shaped macroplacoids (2<1) ( Fig. 3A, D, E View Fig ). The first macroplacoid is anteriorly narrowed and constricted in the middle, whereas the second has a subterminal constriction ( Fig. 3D, E View Fig ). Microplacoid absent. Remarks: Residual of the additional thickening of ventral lamina reported for Diaforobiotus by Lisi et al. (2020) not visible in the examined specimens. Most probably the difference in visibility of this structure is caused by the usage of different mounting media (Hoyer’s medium in this study and polyvinyl-lacto-phenol in Lisi et al. (2020)).

Eggs (measurements and statistics in Table 3).

Laid freely, yellowish to light orange, spherical with slender conical processes (base diameter nearly three times smaller than process height) and smooth egg surface without areolation or reticulation ( Figs. 4 View Fig A-F and 5A-F). In PCM only, egg surface between processes has densely and evenly distributed, dark dots that probably constitute pillars or supporting structures within the labyrinthine layer of the chorion ( Fig. 4A, B, D, F View Fig ). Dark thickenings/projections around egg processes bases absent. The egg processes are surrounded by a ring of several small pores (0.1–0.5 µm in diameter) that are usually clearly visible in PCM and in SEM ( Figs. 4 View Fig A-F and 5B-F). The process apices sometimes exhibit a faint projection at the top ( Figs. 4E View Fig and 5D View Fig ). Nearly entire process surface (excluding the most basal portion) is covered by granulation: dark dots of rough/jagged wall in the process midsection ( PCM)/clear nodular granules ( SEM) ( Figs. 4A, C, E View Fig and 5 View Fig B-E).

Reproduction: The new species is dioecious: both males with testes and females with ovaries were recorded within the neotype population. Other secondary sexual phenotypic characters, e.g. gibbosities on the hind legs in males, absent.

DNA sequences: The DNA sequences of four molecular markers (18S rRNA, 28S rRNA, ITS-2 and COI) associated with the neotype population have been previously published by Stec et al. (2020c). All markers were represented by the same haplotype, hence only one sequence per marker was uploaded in GenBank. The respective GenBank accession numbers are given in Table 1.

Locality: 63° 52′ 53" N, 22° 27′ 21" W; Grindavík , Iceland; moss on lava rock; coll. 27.07.2018 by Wojciech Witaliński GoogleMaps .

Type depositories: The neotype (slide IS.042.07 with 4 neoparatypes), as well as 11 neoparatypes (slides: IS.042.*, where the asterisk can be substituted by any of the following numbers, 04–06, 08) and 9 eggs (slides: IS.042.* 01–03, 10–11) are deposited at the Institute of Systematics and Evolution of Animals , Polish Academy of Sciences , Sławkowska 17, 31–016, Kraków, Poland . A further 2 neoparatypes (slide: IS.042.* 09) and 1 egg (slide: IS.042.* 12) are deposited at the Department of Animal Taxonomy and Ecology , Institute of Environmental Biology , Adam Mickiewicz University in Poznań , Uniwersytetu Poznańskiego 6, 61–614 Poznań, Poland .