Meplitumen aluna sp. nov.

Claws of the Hypsibius-type. Bucco-pharyngeal apparatus of Itaquasconinae model but buccal tube with a spiral thickening also present anteriorly to the stylet support insertion point (Fig. 2 A, B arrow ‘a’). Only the very anterior portion of the buccal tube, where the apophyses for the insertion of the stylet muscles (AISM) are present, is the spiral thickening absent. The AISM are wide and flat ridges, symmetrical with respect to the frontal plane (Figs 2A; 3A, B, D) and their caudal processes point sideways. Peribuccal lamellae absent, papulae probably present (needs confirmation). No cuticular thickening is present between buccal and pharyngeal tube (Figs 2A, B; 3A, B). The stylet furcae have the caudal processes with non-swollen apices (Fig. 3D, arrow). The stylet supports are normally developed (Fig. 2A, arrow ‘b’). The pharyngeal bulb is long, without apophyses but with true, long placoids (Fig. 3A–C).

Figure 2. 

Bucco-pharyngeal tube of Meplitumen aluna gen. nov., sp. nov. A holotype (slide No. 00462), was invaded by fungal hyphae. The spiral thickening also anterior to the stylet supports insertion point is visible (arrow ‘a’). The arrow ‘b’ indicates the stylet supports. Arrow ‘c’ indicates the caudal processes pointing sideways of the wide and flat AISM B paratype (slide No. 00460). The spiral thickening also anterior to the stylet supports insertion point is visible (arrow ‘a’). Scale bar: 20 µm.

Figure 3. 

Bucco-pharyngeal apparatus of Meplitumen aluna gen. nov., sp. nov. A holotype B paratype (slide No. 00477); the arrow indicates a row of small teeth C detail of the pharyngeal bulb of the holotype with the long placoids well visible D bucco-pharyngeal apparatus of a paratype (slide No. 00461); the arrow indicates a stylet furca. Scale bar: 20 µm.

According to the definition in Pilato and Binda (2010), the bucco-pharyngeal tube of Itaquasconinae model, is subdivided into an anterior portion (buccal tube), rigid, without spiral thickening and without ventral lamina, and a posterior portion, generally flexible, provided with a spiral thickening (pharyngeal tube), as in Astatumen, Mesocrista, Platicrista and Itaquascon. In Meplitumen gen. nov. the bucco-pharyngeal apparatus differs from the above by having a spiral thickening also present anteriorly to the stylet support insertion point (Fig. 2A, B arrow ‘a’), which is similar to Astatumen but, unlike Astatumen, the stylet supports are present (Fig. 2A, arrow ‘b’), and mark the border between the posterior flexible portion of bucco-pharyngeal tube and the (almost) rigid anterior section. The sideways pointing caudal processes of the AISM, are similar to Platicrista, Itaquascon and Astatumen, but differ from Mesocrista (in which they point postero-laterally). The non-swollen apices (Fig. 3D, arrow) of the stylet furcae caudal processes are more similar to Platicrista (Fig. 4B, arrow ‘a’) than Mesocrista where the apices are clearly swollen (Fig. 4A, arrow ‘a’). The stylet furcae are clearly larger than those of Itaquascon (Fig. 4C, arrow ‘a’) and Astatumen (Fig. 4D, arrow ‘a’) whose caudal processes are very reduced.

Figure 4. 

Shape of the stylet furca (arrow ‘a’) in species of various genera of Itaquasconinae A Mesocrista spitzbergensis (Richters, 1903) B Platicrista angustata (Murray, 1905) C Itaquascon cambewarrense Pilato, Binda & Claxton, 2002 D Astatumen trinacriae (Arcidiacono, 1962). Arrow ‘b’ indicates the stylet supports. Scale bar: 10 µm.

Etymology. Considering that the bucco-pharyngeal apparatus of the new genus has characters present in Mesocrista, Platicrista, Itaquascon and Astatumen, we have chosen Meplitumen as generic name using the first letters of the name of the first three genera (Me-, Pl-, It-) and the final part of the name Astatumen (-umen).

San Lorenzo, Sierra Nevada de Santa Marta, Magdalena, Colombia.

Holotype (slide No. 00462), 5 paratypes (slides Nos. 00460, 00461, 00476, 00477), and two exuviae (slide No. 00492) from a sample dominated by lichens (Usnea, and Parmotrema) mixed with bryophytes (Sematophyllum, Frullania, Microlejeunea, and Leucolejeunea), collected in San Lorenzo (Colombia) at 11°06'16.9"N and 74°03'31.2"W, 2517 m a.s.l.. One paratype (slide No. 00545) collected in the type locality but in a different sample containing lichens (Parmotrema, Heterodermia, and Hypotrachyna) mixed with bryophytes (Meteoridium, Frullania, and Archilejeunea). One additional specimen (slide No. 00376) of a sample of liverworts (Frullania and Cheilolejeunea), collected in El Campano (Colombia) at 11°6'23.2"N and 74°5'19.2"W, 1368 m a.s.l. The type material was collected by Anisbeth Daza, Rosana Londoño and Sigmer Quiroga on 31 July 2015. The remainder of the material was collected by Anisbeth Daza, Rosana Londoño, Paula Sepúlveda and Sigmer Quiroga, on 21 March 2015.

The holotype and paratypes, and the additional specimen, are deposited in the Centro de Colecciones Biológicas de la Universidad del Magdalena (CBUMAG:TAR), Santa Marta, Colombia.

Body uncoloured. A faint, though difficult to see, cuticular roughness visible on the caudal portion of the body. Eyes probably absent (definitely absent after mounting and no information record when mounted). Bucco-pharyngeal apparatus of the Meplitumen-type of Itaquasconinae model (as described above). Mouth terminal. A row of small teeth is present in the caudal portion of the buccal cavity (Fig. 3B, arrow). Pharyngeal bulb long, without apophyses but with two long, narrow rod-shaped macroplacoids (the second more than double the length of the first); microplacoid and septulum absent. Stylet furcae well developed but the caudal processes have non-swollen apices (Fig. 3D, arrow). Claws of the Hypsibius-type, with main branches provided with accessory points; these points are well developed on the internal claws, short and thin externally. At the base of the claws, a structure interpretable as a very thin lunule is present; other cuticular thickenings on the legs absent.

We found eight specimens and two exuviae with eggs and it is interesting to note that three specimens were small and of similar body size, whereas the others are markedly longer and certainly adults as demonstrated by the size of the exuviae with eggs. Unfortunately, we have not been able to establish the sex of the specimens; in particular, whether the smallest were three young, or new-born specimens, or were males. It is interesting to note that some metric characters of the smaller specimens are very similar to those of the larger specimens, while others were markedly different (see Table 1). If they are young or new-born examples, we would expect structures to have allometric growth, but these have more marked differences than that we have observed in other species. This makes us suspect the smaller specimens may be males. In any case, we have chosen the holotype among the larger, definitely adult, specimens.

Body length 590 µm, uncoloured, cuticle with a faint, very difficult to see roughness in the caudal body portion (Fig. 5A, B, C arrows); as in other species, this cuticular roughness is not visible in some specimens. Eyes probably absent (definitely absent after mounting and no information record when mounted). Bucco-pharyngeal apparatus of the Meplitumen-type of Itaquasconinae model (Pilato and Binda 2010) (Figs 2 and 3), i.e., with the bucco-pharyngeal tube subdivided at the junction of the stylet supports into an anterior, almost rigid, buccal tube with spiral thickening (except the very anterior portion) (Fig. 2A, B, arrows ‘a’), and a posterior flexible portion with a more obvious spiral thickening. The mouth is terminal without peribuccal lamellae; peribuccal papulae probably present but requires confirmation. A row of small teeth present in the caudal portion of the buccal cavity (Fig. 3B, arrow). The AISM are flat, symmetrical with respect to the frontal plane, and with the caudal processes short and pointing sideways (Fig. 2A, arrow ‘c’). Bucco-pharyngeal tube 61.3 µm long, buccal tube 31.8 µm long (pbf index = 51.9) and 8.9 µm wide externally (pt index = 28.0), pharyngeal tube 29.5 µm long. No drop shaped thickening is present between buccal and pharyngeal tube (Figs 2A, B; 3A, B, D). The stylet furcae are well developed but have the caudal processes with non-swollen apices (Fig. 3D, arrow). Pharyngeal bulb (Fig. 3A, C) long, about 2.5 times its width (63.4 µm × 27.0 µm), without apophyses, but with two long, narrow, rod-shaped macroplacoids (Fig. 3A, B, C); first macroplacoid 10.9 µm long (pt = 34.3), the second 29.0 µm long (pt = 91.2); the entire placoid row is 40.7 µm long (pt = 128.0); microplacoid and septulum absent.

Figure 5. 

Meplitumen aluna gen. nov., sp. nov. Caudal extremity of the body where a faint roughness may be visible (arrows) A paratype (slide No. 00477) B and C paratype (slide No. 00460). Scale bar: 20 µm.

Claws of the Hypsibius-type well developed (Fig. 6A, B, C) with widened extreme basal portion. Reliable claw measurements, as in many species, are challenging due to the claw orientation affecting the apparent length. The main branch of both external and internal claws with accessory points; more evident in the hind legs. In all legs those points are more developed on the internal claws (Fig. 6A, B, C) and very short and thin on the external claws; particularly those of the first three pair of legs where they are often almost invisible. At the base of the claws a structure interpretable as a very thin lunule is present (Fig. 6A, B, C arrow). Other cuticular thickenings on the legs absent.

Figure 6. 

A–C claws of Meplitumen aluna sp. nov. (paratypes) A claws III B and C claws IV. The arrow indicates the structure interpretable as a very thin lunule D claws III of Platicrista angustata (Murray, 1905). It is evident that in Meplitumen aluna sp. nov. the claw secondary branches are longer and thinner than those of Platicrista angustata. Scale bar: 20 µm.

We found two exuviae, one with 5 and the other with 6 smooth eggs.

The specific epithet refers to the term “Aluna” which in Ika, the native language of the Kogui (an Amerindian ethnic group inhabiting the Sierra Nevada de Santa Marta), means the non-visible or spiritual world. Aluna is a name in apposition.

As mentioned above, the three smaller specimens (Fig. 7A, B) show some metric differences from the larger. The most obvious differences are the pt values relative to the buccal tube width, the placoid length, and claws II, III (less remarkably claw IV) length. In all legs of all specimens the percent ratio between the main branch length and the total claw length are compatible (Table 1). This later character and the high number of important non-variable characters indicate they belong to Meplitumen aluna sp. nov., but the differences made us consider they may be very young individuals or males.

Figure 7. 

Small specimens (juvenile or male) of Meplitumen aluna sp. nov. A bucco-pharyngeal apparatus of a paratype (slide No. 00476) B claws of the hind legs of another paratype (slide No. 00477). Scale bar: 20 µm.

The particular combination of the characters of the bucco-pharyngeal apparatus distinguishes the new species from all known species of Itaquasconinae. It is possible that the presence of spiral thickening in the “buccal tube”, and the lateral orientation of the caudal processes of the AISM was missed in some previously described species. In this case, any species found with these characters should be transferred into the new genus Meplitumen, though this may result in Meplitumen aluna sp. nov. becoming a junior synonym. Therefore, to avoid this remote risk, we found it opportune to compare the new species with all the similar, known species of Itaquasconinae independently from the extension of the spiral thickening.

It is unnecessary to compare all Itaquascon species, as the presence in Meplitumen aluna sp. nov. of true macroplacoids, a more developed and differently shaped stylet furca (with longer branches) (Figs 3D arrow, and 4C arrow ‘a’), and more robust stylet supports (Figs 2A arrow ‘b’, and 4C arrow ‘b’), clearly separate these species. Also, comparison with Astatumen species is unnecessary as the presence in Meplitumen aluna sp. nov. of stylet supports, true macroplacoids (lacking in Astatumen), and a more developed and differently shaped stylet furcae (with longer branches) (Figs 3D arrow, and 4D arrow ‘a’), separates these taxa.

The differences with Mesocrista species are also clear, as Gąsiorek et al. (2016) confirmed the lack of spiral thickening in the buccal tube. In addition, in Meplitumen aluna sp. nov. the stylet supports are inserted exactly between the buccal and the pharyngel tube (Fig. 2A), whereas in the two known species of Mesocrista a short portion of tube without spiral thickening is present after the stylet supports insertion point (see Gąsiorek et al. 2016: fig. 2a, b, figs 5 a, b; 7c). Furthermore, in the new species the caudal processes of the stylet furcae do not have swollen apices (compare Fig. 3D arrow, and Fig. 4A arrow ‘a’), the microplacoid is absent, and cuticular bars on the legs are absent.

We carefully examined Platicrista angustata (Murray, 1905) and ascertained the absence of spiral thickening in the buccal tube wall (Fig. 4B). In addition, Meplitumen aluna sp. nov. differs from Platicrista angustata in having thinner stylet supports (Figs 2A arrow ‘b’, and 4B, arrow ‘b’), and thinner and longer claw secondary branches (compare Fig. 6A–C with 6D). The new species differs from Platicrista cheleusis Kathman, 1990 by the lack of a polygonal pattern on the cuticle, and cuticular bars on the legs. It differs from Platicrista horribilis Kaczmarek & Michalczyk, 2003 in the claw shape, and by having the lunules (if they are such) on legs IV less developed and without teeth. Meplitumen aluna sp. nov. differs from Platicrista itaquasconoide (Durante Pasa & Maucci, 1975) by lacking the microplacoid, and a small basal spur on the claws of the hind legs. It is distinguished from Platicrista ramsayi Marley, 2006 by the lack of cuticular bars on the legs.

Platicrista affine (Mihelčič, 1951) is considered a nomen dubium (Ramazzotti and Maucci 1983, Dastych 1993, Marley 2006) and as the material studied by Mihelčič no longer exists, a comparison is impossible.