FIRST CARNIVOROUS FUNGUS FROM SANTONIAN TAIMYR AMBER

1. FIRST CARNIVOROUS FUNGUS
FROM SANTONIAN TAIMYR AMBER
M. M. Sukhomlyn *(1), E. E. Perkovsky (2), M. S. Ignatov (3,4) and D. V. Vasilenko (5,6)
(1) Institute of Evolutionary Ecology, National Academy of Sciences of Ukraine, Kiev, Ukraine
(2) Schmalhausen Institute of Zoology, National Academy of Sciences of Ukraine, Kiev, Ukraine
(3) Moscow State University, Moscow, Russia
(4) Tsitsin Main Botanical Garden, Russian Academy of Sciences, Moscow, Russia
(5) Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow, Russia
(6) Cherepovets State University, Cherepovets, Vologda Region, Russia
*e-mail: suhmary@ukr.net
The fungus reported in this study was found in Yantardakh, Taimyr, situated in the north of Eastern Siberia.
Locality and horizon: Yantardakh, Kheta Formation, Upper Cretaceous, Santonian.

2. Yantardakh Lagerstätte (below) is situated on the right bank of the
Maimecha River 3 km upstream of its confluence with the Kheta
River, a left source of the Khatanga River.
The amber in Yantardakh was collected by the expeditions of the PIN in 1970, 1971
(http://palaeoentomolog.ru/Publ/amberproject.html) and 2012 (Rasnitsyn et al., 2016); more
than 6,000 inclusions were found in total. Only an undescribed fungus was found on a small
beetle collected in 2012 (Makarov & Perkovsky, 2020) in addition to this mycelium.
A sample PIN 3130/222 is kept in the collection of the Borissiak
Paleontological Institute, Russian Academy of Sciences, Moscow,
Russia (PIN) since 1970. The mycelium is preserved in the sample.
Fruit bodies are absent.
The sample was examined and photographed using an Olympus
CX41 stereomicroscope, an Infinity 2-2 camera (2080 x 1536 px) and
LAS V3.8 software.

3. Fungal mycelium is slightly branched, the
hyphae (2-4 µm wide) are located mainly
parallel to each other (A, B), branch at an
acute angle, and the branches retain the
orientation of the frontal expansion of the
mycelium, sometimes forming bundles (C,
D, E).

4. In some areas, septa are visible (H-M). On the
mycelium, two types of outgrowths are
formed, located perpendicular to the parent
hypha. The former of its (F) are rather long
(some up to 45 µm, the majority - 35 µm),
and common, latter are short (12-16 µm)
peg-shaped, formed with a lower frequency
(G). The formation of arthroconidia (oidia)
on the mycelium is observed (H, I, J).

5. On the hyphae, there are large numbers of globular formations
resembling drops of liquid or oil secreted by fungi (A, B). The
average size of drop-shaped structures is about 12.5 µm,
although some of them are up to 15 µm.

6. Clamp connections are observed in large numbers on the mycelium (D, E). They have a
characteristic medallion shape, in which there is a clear gap between the anastomosis and
the hyphae. The average width of the clamp connections equals 6 -7 µm, and the length is up
to 12 µm. Long processes often extend precisely from the clamp connections.
.
It should be noted the presence of a ring-shaped hyphal
formation, reminiscent of the trapping rings of modern
Basidiomycetes (C). The inner diameter of the ring is 24 µm and
the outer diameter is 33 µm.

7. However, by the presence of septa (arrow)
and individual microstructures, it is possible
to establish a more accurate systematic
attachment of the fungus. The presence of
clamp connections on mycelium in Taimyr
amber may indicate the presence of a
Basidial fungus, since clamp connections are
structures that occur in modern species of
the Basidiomycetes and are present as an
integral part of the secondary mycelium in a
number of species.
Considering that a number of formations (rings in the form of trapping loops, heads with
liquid drops, peg-like outgrowths) characteristic for nematophagous fungi were found in
our sample, it is logical to assume that we are dealing with an ancient representative of
this particular ecological group.
We analyzed the similarity of our specimen with extant species of this ecological group.
Рис.4. Кольцо и пряжки на мицелии.
C
B
Fragments of mycelium, in principle, are very difficult to attribute to
any taxonomic group of fungi, due to their poorly informative
morphology.

8. They are classified according to the presence, morphology and action of trapping structures.
There are several groups of nematophagous fungi:
Among the basidial fungi, there are representatives of all groups.
These fungi are known mainly as wood-root fungi, since their habitat is decaying wood. In
this environment, the available nitrogen concentration is low. Thus, the capacity of fungi
to feed on nematodes is a significant advantage.
There are about 200 species of extant nematophagous fungi, belonging to
different taxonomic groups: Chytridiomycota, Ascomycota,
Basidiomycota, and also Zoopagomycotina and Mucorоmycotina
(1) fungi that capture nematodes using adhesive or mechanical hyphal traps;
(2) endoparasitic fungi using their spores;
(3) fungi parasitizing on eggs and females;
(4) toxin-producing fungi that immobilize nematodes before invasion;
(5) fungi that produce special attacking devices (structures that mechanically damage the nematode
cuticle).
We excluded the possibility of our sample belonging to groups 2 and 5, since the species of
these groups have very characteristic structures for trapping nematodes, which are absent
in our sample.

9. Group Species Structures
5th group. Fungi
that produce
special attacking
devices
(structures that
mechanically
damage the
nematode
cuticle)
2nd group.
Endoparasitic
fungi using their
spores
Coprinus comatus
Stropharia
rugosoannulata
Hyphoderma spp.
Part of the species
Hohenbuehelia
(anamorh
Nematoctonus) :
N. concurrens
spiny balls
acanthocytes
hourglass-
shaped adhesive
knobs
stephanocysts
Few of them form special attacking devices:
Luo et al, 2004; Darron, 2013,; Zouhar et al., 2013; Soares et al. 2018; Yang etal., 2020; http://www.mycolog.com/chapter15.html

10. Pleurotus tuberregium
Hibbett, Thorn, 1994
Nematoctonus robustus
Sample PIN 3130/222
Sample PIN 3130/222
Most nematophagous Basidial
fungi have devices for catching
nematodes or releasing toxins
(groups 1 and 4).
Among these, the majority belongs to the monophyletic family Pleurotaceae (genera
Nematoctonus and Pleurotus). Most species of the genera are white-rot fungi.
hourglass-shaped
adhesive knobs
secreted droplets of toxin
Thorn R.G. et al., 2015

11. Ishizaki et al., 2015
Pleurotus
salmoneostramineus
Among extant species, our specimen is closest to the toxin-producing
species of nematophagous fungi, which have teardrop-shaped
formations on the mycelium and do not form hourglass-shaped adhesive
knobs, characteristic for Hohenbuehelia

12. Peniophorella praetermissum,
Conocybe lactea,
Conocybe albipes,
Flammulina velutipes,
and their attack pattern on nematodes
is similar to that of Pleurotus.
Flammulina velutipes
Ferreira et al., 2019
Conocybe lactea
Walton, 2018)
Conocybe albipes - secretory appendages
Barron,2013
Secretory appendages similar to those in Pleurotus have been found
on the hyphae of a number of fungi belonging to order Agaricales:
However, Conocybe lactea’s stem of the droplet-
forming head is rather high and characteristically
widened at the base.

13. Tanney, Hutchison , 2012
Among nonagaricoid fungi, the only description of the secretory cells
presence that immobilize nematodes is known in Climacodon
septentrionalis, a polypore fungus that causes white-rot. However,
these formations in C. septentrionalis differ significantly from the
secretory structures of the genera Pleurotus and Conocybe.

14. S. M. Badalyan, 2011
Coprinellus radians
Coprinopsis strossmayeri
Sample PIN 3130/222
Oudemansiella mucida,
Pleurotus citrinopileatus,
P. pulmonarius,
Macrolepiota affinis,
Tricholoma mongolicum,
Coprinus comatus.
Coprinellus radians
In our sample, in addition to drop-
shaped formations on the mycelium,
trapping rings were also observed.
The formation of twisted hyphae similar to trapping rings
was previously noted in culture of a number of
Basidiomycetes, e. g.:
Their formation may depend on the
concentration of nitrogen in the environment.
We observed the formation of loops and rings in culture of
P. ostreatus and Heterobasidion annosum (unpublished
data).

15. Among this group one should pay attention to the genus
Amylostereum, which has clamp connections ,
hyphae of appropriate sizes, mycelium hyphae coloration
(yellow-brown tones) and characteristic outgrowths on the
clamp connections .
Dapeng Li et al., 2015
Sample PIN 3130/222
Sample PIN 3130/222
Amylostereum areolatum
Third group.
Fungi parasitizing eggs and females
A.P. Baxter et al., 1995

16. However, members of Amylostereum are characterized by
the presence of cystidia , which are absent in our
sample. This can be explained either by young mycelium,
since cystidia are formed on the mycelium after several
weeks of growth, or by the presence in the sample of the
ancient ancestor Amylostereum, which did not have such
structures. It has been established that in modern species,
these structures play an important role in the infection of
nematodes, however, the mechanism used by the fungus to
attach to the nematode is unknown.
Amylostereum areolatum, Russulales
A.P. Baxter et al., 1995
Sample PIN 3130/222
Amylostereum is able to form
arthroconidia
In addition,
Amylostereum areolatum and
Amylostereum chailletii
parasitize on females of mycophagous
nematodes Deladenus siricidicola
and D. proximus.

17. Thus, we reported the first basidial fungus
from Taimyr amber. This is evidenced by the
presence of septate mycelium and the
presence of clamp connections. The
presence of loops resembling trapping rings,
peg-like processes and tear-shaped
formations on the mycelium may indicate
that this fungus was a wood-destroying
nematophagous species.
However, it is still difficult to give an
unambiguous answer regarding the
belonging of the sample to a specific
family or even order. In our opinion, it
is closest to the species of the genus
Amylostereum associated with
nematodes.
This finding can help in assessing
the time of carnivorous
Basidiomycota divergence,
whose representatives don’t
have such a rich diversity of
species and traps as carnivorous
Ascomycota does.

18. The presented results will be useful for tracing the
evolution of nematophagous fungi and their trapping
devices for inhibiting nematodes and are a contribution to
documenting the stages of the Earth's mycobiota
formation as a special evolutionary group of organisms,
providing important evidence in favor of not only
individual groups of fungi that appeared at the early stages
of historical development, but also the co-evolutionary
relationships of fungi and representatives of other
kingdoms of living beings.
ACKNOWLEDGMENTS : This work was supported by the Center for Collective Use "Herbarium
MBG RAS” Grant 075-15-2021-678 and RFBR 19-04-00046 .