Anthoceros telaganus Stephani., 1005

Ibarra-Morales, Ariadna, 2021, Anthoceros subtilis and A. telaganus (Anthocerotaceae): two new records for America from the hornwort flora of Mexico, Phytotaxa 529 (1), pp. 93-104 : 97-100

Anthoceros telaganus Stephani. Fig. 4 , 5.

Type:— Indonesia, Java, I’rov. Preanger, Telaga bodas, Schiffner #19 (holotype G-G00061328, isotype NY-NY00231473) .

Monoicous. Plants growing on soil in rosettes. Thallus dark green, growing up to 15 mm in length and 15 mm in width. Dorsal lamellae are scarce to abundant. Margins of thallus lobulate or irregularly crenulate. Thallus up to 15 cells (368–845 μm) thick in solid regions, cavernous, schizogenous cavities 113–286 × 159–481 μm, 1–2 layers of schizogenous cavities in transverse section. One chloroplast per cell with a central pyrenoid. Rhizoids hyaline and unbranched. Ventral spheric Nostoc colonies are abundant. Antheridia scattered. Antheridial chamber with up to 10 antheridia per cavity, yellowish to brown, 59–106 μm in length, and with four-tiered jacket cell arrangement. Archegonia not observed. Involucres erect and cylindrical, up to 5 mm long, surface smooth to abundantly lamellate, 7–9 cells (154–262 μm) thick in solid regions, cavernous, schizogenous cavities 32–86 × 45–154 μm, 1 (–2) layer of schizogenous cavities in transverse section.

Up to seven sporophytes per gametophyte. Sporophyte foot with a layer of palisade-like cells. Capsules erect, up to 30 mm long, opening by two longitudinal valves. Epidermal layer of capsule one cell thick in transverse section. Epidermal cells of capsule rectangular, elongated, 7–14 × 57–121 μm and thick-walled, stomata abundant (10 per mm 2), 34–46 × 44–64 μm.Assimilative layer 3–5 cells (32.89–114.4 μm) thick in transverse section. Columella present within sporophyte, extending to the tip, rigid and brownish to blackish, 16 cells in cross section. Sporogenous layer one spore tetrad thick. Pseudoelaters elongate, thin-walled, dark brown at maturity, 39.8–104.9 μm (73.2±16.8, n=19) long, 3.8– 26.7 μm in width, 1–2 cells at maturity. Spores black at maturity, 32.7–53.21 μm (40.48±3.8, n=44) in diameter. Distal spore surface has numerous spinose-lamellate projections, up to 3.7 μm in height, frequently irregularly confluent at their bases, often tipped by a papilla of 0.53–2.98 μm in diameter. Proximal spore surface has a distinct trilete mark, 0.9–3.66 μm in width, irregularly covered with verrucae, a smooth strip along either side of trilete mark, up to 3.98 μm in width (2.89 μm in average), triangular areas covered with numerous spinose-lamellate projections, up to 3.8 μm in height, frequently irregularly confluent at their bases, tipped by a papilla of 0.64–3.25 μm in diameter.

Habitat:—Growing on the sides of roads and around coffee plantations in tropical montane cloud forest, with other hornworts such as A. subtilis and Phaeoceros sp., 1200 –1300 m.

Distribution:— Indonesia (Java and Sumatra) ( Meijer 1957, Hasegawa 1998, Söderström et al. 2010) and Mexico.

Affinities and differentiation:—Only one species known from Mexico, Anthoceros orizabensis ( Stephani 1916: 965) Hässel de Menéndez (1990: 211) (SEM spore micrographs of this species can be found in Hässel de Menéndez (1990), plate 4, fig. 9 on page 212), resembles the spore ornamentation of A. telaganus , sharing the smooth strip along the trilete mark. Nevertheless, the smooth strip in A. orizabensis is incomplete, not reaching the equatorial girdle of the spores; moreover, the distal face of the spore has spines in A. orizabensis , while A. telaganus has a spinose-lamellate reticulated distal face.

FIGURE 5. Scanning electron microscopy (SEM) micrographs of spores from Mexican populations of Anthoceros telaganus . A-B. From A. Ibarra-Morales 2019-11; C-D. From A. Ibarra-Morales 2019-20. A & C distal surface, B & D proximal surface.

Other American species that share the smooth strip along the spore trilete mark of the proximal face are Anthoceros cavernosus Stephani (1916: 998) , A. caucasicus Stephani (1923: 427) and A. fusiformis Austin (1875: 28) ( Hässel de Menéndez 1990, Sérgio et al. 2020). Anthoceros fusiformis frequently presents a strap shaped thallus and lacks a pyrenoid in the chloroplasts ( Hasegawa 1993), both characters differentiate it from A. telaganus . Regarding A. cavernosus and A. caucasicus , both species have spores with spinose outgrows reticulated at the base with ridges enclosing both lumina and pits on the distal face, and the proximal face with scattered spinose outgrowths, sometimes confluent at their bases (SEM spore micrographs of these species can be found in Hässel de Menéndez 1990 and Sérgio et al. 2020). In A. telaganus the spores present blunter papillate projections and an incomplete reticulum on the distal face, while the proximal face presents spinose-lamellate projections that are tipped by a papilla.

In the location here reported, A. subtilis can be differentiated from A. telaganus by spore ornamentation, mature spore color and size, light brown to brown in the first species and black in the second, and smaller spores in A. subtilis . Plants not bearing sporophytes are difficult to differentiate. Thalli of Anthoceros subtilis are smaller and paler in color than those of A. telaganus . Anthoceros telaganus also presents an abundantly lamellate thallus morphotype that could be easily identified in this location.

Specimens examined:— MEXICO. Chiapas: Unión Juarez, roadside, 1260 m, 15°03’35”N 92°04’44”W, 24 July 2019, Ariadna Ibarra-Morales 2019 -11 (FCME); 1438 m, 15°04’03”N 92°04’53”W, 26 July 2019, Ariadna Ibarra-Morales 2019-20 (FCME).

Remarks: —Within the mature region of the sporophyte, colorless and shrunken (probably aborted) spores were observed amongst black mature regular-size spores in all plants examined of this species. The percentage of these inviable spores could not be estimated, but it was observed frequently that at least one spore of almost every tetrad displayed this condition and remain attached to a fully mature spore. This phenomenon was not observed in any other hornwort species growing in the same locations.

Morphological variation within Mexican plants of this species was observed mainly in two characters: dorsal lamellae on the thallus and spore ornamentation. Dorsal lamellae on the thallus presented a variation range from nearly absent to abundant and plants expressing different ranges of this character could be found in the same population, but generally not close together in the same rosette. Regarding spore ornamentation, spores of northern populations (A. Ibarra -Morales #2019-20) were, in most of the individuals examined, more spinose and forming a more reticulated pattern (Fig. 5C–D) when compared to the ornamentation of southern populations (A. Ibarra -Morales #2019-11) (Fig. 5A–B); nevertheless, both spore morphologies were present in all collections.

It is noteworthy that the type ( Stephani 1916) and the collections here described, present similar ecological preferences, both being collected at or near coffee plantations. Meijer (1957) also states that this species grows on cultivated areas at 700–2000 m, and on earth walls and roadsides.

Figures

FIGURE 4. Anthoceros telaganus. A. Whole plant. B. Thallus transverse section with schizogenous cavities. C. Antheridia with tiered jacket cell arrangement. D. Involucre transverse section with schizogenous cavities. E. Sporophyte transverse section with epidermal layer (ep), assimilative layer (as), spore (sp) and columella (co). F. Epidermal layer of capsule with stomata. G. Spore ornamentation on distal surface (i), proximal surface (ii) and pseudoelaters.