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abril 30, 2024
01:11 AM MSK
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março 2, 2024
11:03 PM MSK
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novembro 20, 2022
05:38 PM UTC
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novembro 27, 2023
06:05 PM MSK
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novembro 8, 2023
05:28 PM MSK
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janeiro 15, 2021
03:44 PM UTC
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fevereiro 18, 2024
04:47 PM WIB
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fevereiro 5, 2024
07:30 PM UTC
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junho 13, 2022
08:20 AM MSK
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setembro 1, 2019
11:24 PM MSK
Descrição
Удивительное место - Зеленая гора рядом с Воскресенском, целиком состоящая из фосфогипсовых отвалов Воскресенского химкомбината. Почти вся гора покрыта мхом, растущим на чистом удобрении! Похоже, он хорошо себя тут чувствует, чего не скажешь о многих других растениях.
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dezembro 2, 2022
09:29 PM MSK
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dezembro 2, 2022
09:29 PM MSK
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dezembro 31, 2023
10:58 AM CET
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dezembro 3, 2023
05:10 AM UTC
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fevereiro 3, 2023
11:35 AM CST
Adicionado na data
maio 25, 2023
05:19 PM EDT
Descrição
Paramecium caudatum from the decomposing leaf debris in my long-neglected freshwater garden pond. Imaged in Nomarski DIC on Olympus BH2 using SPlan 20x and 40x objectives plus variable phone camera cropping on Samsung Galaxy S9+. The population ranges from 187-225 um in length. The cells are cigar-shaped with the posterior end bluntly pointed and with a group of slightly longer cilia compared to the otherwise uniform ciliation. Early microscopists likened its shape to that of a slipper, and commonly referred to it as the "slipper animalcule." The oral groove/ vestibulum is long and slightly oblique; buccal cavity with one endoral membrane and 2 peniculi. There is a single large ellipsoid macronucleus and 1 round compact micronucleus. " Using light microscopy, however, it is possible to discriminate only the Mi type of P. caudatum from the nucleus of other two species. P. caudatum always has the Mi with the so-called “cap”, a space without chromatin at the nuclear pole" (1). Two contractile vacuoles, each with radial canals, are present at the aboral surface which serve to excrete excess water taken up from the outside, regulating the water contents of the body. Radially distributed "collecting canals" give the contractile vacuoles a distinctive star-like shape. The cell is enclosed by a cellular envelope (cortex) densely studded with spindle-shaped extrusomes called trichocysts.
Discussion adapted from: https://en.wikipedia.org/wiki/Paramecium_caudatum
P. caudatum feed on bacteria and small eukaryotic cells, such as yeast and flagellate algae. the accumulated food particles, at the posterior end of the cytopharynx, are directed by the long cilia into the rounded, ball-like mass in the endoplasm called food vacuole. The food vacuoles are circulated by the streaming movement of the endoplasm which is called cyclosis. In hypotonic conditions (freshwater), the cell absorbs water by osmosis. It regulates osmotic pressure with the help of bladder-like contractile vacuoles, gathering internal water through its star-shaped radial canals and expelling the excess through the plasma membrane. When moving through the water, they follow a spiral path while rotating on the long axis.
Paramecium have two types of nuclei, a large macronucleus and a varying numbers of smaller micronuclei depending on the species. P. caudatum has 1 compact round macronucleus. The macronucleus controls somatic gene expression and the micronucleus controls reproduction. Like all ciliates, Paramecia reproduce asexually, by binary fission. During reproduction, the macronucleus splits by a type of amitosis, and the micronuclei undergo mitosis. The cell then divides transversally, and each new cell obtains a copy of the micronucleus and the macronucleus. Fission may occur as part of the normal vegetative cell cycle. Under certain conditions, it may be preceded by self-fertilization (autogamy), or it may follow conugation, a sexual phenomenon in which Paramecia of compatible mating types fuse temporarily and exchange genetic material. During conjugation, the micronuclei of each conjugant divide by meiosis and the haploid gametes pass from one cell to the other. The gametes of each organism then fuse to form diploid micronuclei. The old macronuclei are destroyed, and new ones are developed from the new micronuclei. Without the rejuvenating effects of autogamy or conjugation a Paramecium ages and dies. Only opposite mating types, or genetically compatible organisms, can unite in conjugation.
I observed a Paramecium in the early mid stages of transverse fission with formation of two oral anlagen and a beginning constriction of the cortex dividing into two cells.
Paramecium genus: biodiversity, some morphological features and the key to the main morphospecies
discrimination. Sergei I. Fokin. Protistology 6 (4), 227–235 (2010/11)
https://www.researchgate.net/publication/285129115
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julho 13, 2023
01:13 AM MSK
Descrição
Fossil ammonite Pavlovia pavlovi
Jurassic period, tithonian age
Russia, Moscow Oblast, Elkino
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dezembro 13, 2021
09:18 PM CET
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junho 12, 2022
03:50 PM UTC
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março 13, 2023
10:00 AM UTC
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abril 9, 2023
06:27 PM UTC
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maio 14, 2022
12:07 AM EEST
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março 22, 2023
09:27 PM MSK
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julho 14, 2022
12:17 AM MSK
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maio 6, 2022
11:04 PM MSK
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outubro 1, 2022
09:10 PM MSK
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dezembro 17, 2022
08:25 PM UTC
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janeiro 29, 2023
12:10 AM JST
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janeiro 29, 2023
12:10 AM JST
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junho 29, 2022
04:46 PM MSK
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setembro 11, 2022
04:50 AM UTC
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janeiro 29, 2023
02:28 PM MSK
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janeiro 31, 2023
05:50 PM MSK
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janeiro 24, 2023
08:19 PM MSK
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março 20, 2022
11:05 AM HKT
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maio 20, 2022
07:00 PM SAST
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abril 21, 2022
07:49 AM UTC
Adicionado na data
janeiro 20, 2022
08:18 PM CET
Descrição
Lots of fruiting bodies at various stages on one log
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janeiro 13, 2023
02:40 AM MSK
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janeiro 13, 2023
02:41 AM MSK
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janeiro 21, 2023
02:03 PM UTC
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julho 16, 2022
12:38 PM UTC
Descrição
Close up cardinal butterfly or Argynnis Pandora on dry sticks
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janeiro 8, 2023
09:01 PM MSK
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novembro 14, 2022
01:24 AM +05
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dezembro 26, 2022
08:36 AM UTC
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janeiro 6, 2023
12:48 PM UTC
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setembro 4, 2022
02:11 PM UTC
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novembro 13, 2020
06:29 PM MSK
What
Mégera
(Lasiommata megera)
Adicionado na data
agosto 6, 2022
12:10 AM +07
What
Mégera
(Lasiommata megera)
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agosto 25, 2022
12:28 PM UTC
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setembro 6, 2022
08:33 AM +07
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dezembro 30, 2022
04:50 PM UTC
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janeiro 2, 2023
03:07 PM UTC
What
Circe
(Brintesia circe)
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setembro 4, 2022
01:50 PM MSK
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dezembro 31, 2021
09:24 AM UTC
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setembro 4, 2022
12:09 PM MSK
Descrição
on common oak (Quercus robur) bark, days/на стволе дуба, днём
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agosto 13, 2011
12:05 AM EDT
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julho 2, 2022
04:47 PM EDT
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julho 1, 2022
08:55 PM UTC
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junho 12, 2022
11:53 AM UTC
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junho 13, 2022
06:03 AM MSK
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junho 10, 2022
10:30 AM MSK
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junho 8, 2022
06:22 PM MSK
What
Abibe
(Vanellus vanellus)
Adicionado na data
junho 6, 2022
08:29 AM MSK
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junho 6, 2022
06:56 PM MSK
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junho 4, 2022
01:17 AM MSK
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maio 27, 2022
06:36 PM MSK
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maio 27, 2022
06:40 PM MSK
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maio 26, 2022
12:39 PM MSK
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maio 20, 2022
10:06 AM SST
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maio 17, 2022
08:01 PM UTC
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maio 15, 2022
09:26 PM MSK
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maio 15, 2022
03:06 PM MSK
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maio 15, 2022
12:40 PM UTC
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maio 15, 2022
12:42 PM UTC
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maio 14, 2022
03:42 PM MSK
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maio 2, 2022
10:29 AM MSK
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maio 2, 2022
07:59 AM UTC
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maio 2, 2022
08:15 AM UTC
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maio 2, 2022
11:22 AM UTC
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abril 29, 2022
09:56 PM MSK
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abril 29, 2022
09:48 AM MSK
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setembro 26, 2021
08:48 AM MSK
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setembro 26, 2021
02:30 PM MSK
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setembro 26, 2021
02:34 PM MSK
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julho 11, 2021
10:47 PM MSK
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julho 11, 2021
05:41 PM MSK
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julho 11, 2021
05:52 PM MSK
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junho 30, 2021
10:16 AM MSK
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junho 30, 2021
02:57 PM MSK
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junho 3, 2021
04:24 AM SST
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julho 5, 2021
01:08 AM MSK
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julho 4, 2021
11:45 PM MSK
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julho 4, 2021
11:45 PM MSK
Adicionado na data
julho 4, 2021
05:44 PM EDT