Lactarius akahatsu Tanaka, Bot. Mag.
Index Fungorum number: 216349
Pileus 60–120 mm diam., plano-convex to widely infundibuliform, irregular; margin straight to very irregular-wavy, (translucently) striate (up to 12 mm); surface smooth, sticky, greasy to slightly viscid, weakly zonate in some specimens, with distinct zones near the margin in other specimens, zones consisting of watery spots; colour partly pale orange (4A4/5 near the centre), deeper orange in other places (5A/B6 to 6A7/8), more whitish orange when dry, with emerald green shades when older. Lamellae decurrent with a small tooth, distant, abundant; colour orange (5A5) but staining greenish when bruised, dirty brownish orange when older; edge entire, paler. Stipe 30–46 × 11–20 mm, irregularly cylindrical, tapering downwards, central to slightly eccentric; surface smooth, slightly viscid; colour orange-buff (5A4–6). Context rather firm, ± 6 mm thick in the pileus, hollow in the stipe, pale cream to whitish but soon pinkish buff to pale orange when cut, especially underneath the pileipellis; colour unchanging; smell agreeable, sweetish or flowery; taste agreeable, mild, like nuts. Latex scarce, bright orange (6A8) to deep orange. Spores 7.5–7.9–8.4 × 5.5–6–6.5 (6.8) µm, broadly ellipsoid to ellipsoid (n = 120, Q = 1.22–1.33–1.44); ornamentation up to 0.5 µm high, of rather broad ridges and isolated warts, forming a rather complete reticulum; plage distally slightly amyloid, ± centrally additional amyloid spots often present. Basidia 35–50 × 9–10 µm, subclavate, 4-spored, often containing oil-droplets; sterigmata 3.5 –5 µm long. Pleuromacrocystidia very scarce, 50–55 × 6–8 µm, emergent, fusiform with a moniliform apex, contents needle-shaped, thinwalled. Pseudocystidia abundant, 4–5.5 µm broad, not or slightly emergent, often tortuous; contents oleiferic. Lamellar edge sterile without cheilomacrocystidia; cheiloleptocystidia 9.5–22 × 4–8 µm, subclavate to irregular, hyaline or with ochre granular contents (in 10% KOH), thin-walled. Pileipellis an ixocutis, 50–250 μm thick; composed of mostly strongly shrivelled and gelatinised hyphae in the upper layer, hyphae 1–3 μm diam. Stipitipellis a cutis, 70–100 μm thick, composed of thin-walled, strongly interwoven hyphae 2–4 μm diam.; no shrivelled hyphae present. Clamp connections absent.
Habitat: On the ground in lowland Pinus kesiya forests. Distribution: Described from Japan where the species occurs with Pinus densiflora, P. thunbergii, P. liuchuensis etc. and introduced on the Bonin Islands (Hongo, 1960, 1977). Recorded here for the first time from Thailand.
Material examined: JAPAN, Tottori, Tottori-shi, Uemachi (Bairian), under planted Pinus thunbergii in garden, 27 September 1997, leg. E. Nagasawa, TMI 22601 (TMI) –THAILAND, Chiang Mai Prov., Mae Teng Distr., Tung Joaw village, forest trail, 1300 m alt., N19°08.07' E98°38.90', secondary forest with Pinus kesiya, Castanopsis etc., 20 June 2004, leg. R. Walleyn & A. Verbeken 2004-015 (GENT), leg. Huyen T. Le 115 (CMU, SFSU) –ibid., road side, 1350 m alt., under Pinus kesiya, 21 June 2004, leg R. Walleyn & A. Verbeken 2004-036 (GENT), leg. Huyen T. Le 121 (CMU, SFSU) – Chiang Mai Prov., Mae Teng Distr., Highway 1095 at 22 km marker, 750 m alt., N19°07.57' E98°45.65', xeric broad-leaf forest (Dipterocarpus spp. + teak) with Pinus kesiya, under Pinus, 23 June 2004, leg. R. Walleyn & A. Verbeken 2004-076 (GENT), leg. Huyen T. Le 127 (CMU, SFSU) – ibid., solitary to gregarious on the soil, rainforest dominated by Dipterocarpus sp. and Pinus kesiya trees, 21 June 2005, Huyen T. Le 287 (CMU, GENT, SFSU) – ibid., solitary to gregarious on the soil under Pinus kesiya trees, rain forest dominated by Dipterocarpus sp. and Pinus kesiya trees, 04 June 2006, Huyen T. Le 392 (CMU, GENT, SFSU) – ibid., solitary on the soil under Pinus kesiya trees, rain forest dominated by Dipterocarpus sp. and Pinus kesiya trees, 11 June 2006, Huyen T. Le 424 (CMU, GENT, SFSU) – Chiang Mai Prov., Mae Teng Distr., Huai Nam Dang National Park, nature trail, 1530 m alt., N19°18.29' E98°35.88', forest with Pinus kesiya, Dipterocarpus sp., Bamboo & scattered Castanopsis, 28 June 2004, leg. R. Walleyn & A. Verbeken 2004-141 (GENT), leg. Huyen T. Le 162 (CMU, SFSU) – ibid., solitary on the soil and pine leaves, forest with Pinus kesiya, Dipterocarpus sp., Bamboo & scattered Castanopsis, 29 June 2005, Huyen T. Le 330 (CMU, GENT, SFSU).
Notes: Molecular analysis revealed such a close relationship between these Thai collections and the Japanese L. akahatsu that they can be considered conspecific. The description above is entirely based on Thai material. Lactarius akahatsu seems to be a common species in Japan, characterised by its generally orange appearance and orange latex that slowly becomes red on the context. It is unmistakably different from L. hatsudake, a species with red latex from the beginning. The Japanese specimens differ from the ones collected in Thailand by the behaviour of the latex, which slowly becomes vinaceous red or stays orange respectively. Microscopically pleuroand cheilomacrocystidia are more abundant in the Japanese collections. L. akahatsu is appreciated as an edible mushroom in Thailand.
Fig. 1 a. Lactarius akahatsu. a. Basidiocarp. b. Spores. c. Basidia. d. Marginal cells. Scale bars
= 10 mm (basidiocarp) and 10 μm.