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Paramecium nephridiatum V. Gelei, 1925 from the brackish estuarine pond Pussy's Pond, an offshoot of Acabonac Harbor. The population arose after feeding the culture with boiled wheat seeds. Imaged in Nomarski DIC on Olympus BH2S using SPlanapo 40 0.95 and SPlan 100 1.25 oil objectives plus variable phone camera cropping on Samsung Galaxy S9+.

The cells measure from 100-165 um in length. There is a large oval macronucleus usually situated slightly anterior to the cell equator and 3-4 small endosomal-type micronuclei can be observed with exact focus in the anterior end of the cell remote from the macronucleus- an important specific character of P. nephridiatum according to Fokin et al 1999 (1) The oral apparatus is situated posterior to the macronucleus with the cytostome roughly equatorial. There is an inconspicuous tuft of long caudal cilia. The two contractile vacuoles, one anterior and one posterior, have up to 15 short radiating canals and 2-3 excretory pores- another important specific characteristic of P. nephridiatum (1). There is a dense investment of subpellicuar extrusomes. The pellicle is divided into rectangular spaces on optical sectioning of the surface, a feature not mentioned by Fokin et al 1999. These features point strongly to P. nephridiatum. However, the more posterior location of the oral opening (as opposed to slightly anterior to the middle of the cell) and the peculiar pellicular division into rectangular spaces suggest that this might be a cryptic species of P. nephridiatum. Indeed, Przyboś et al 2019 describe 6 cryptic species within P. nephridiatum (2)

The cell shape with its rounded posterior end, and broad anterior part is of the "bursaria" type (Wichterman 1986) or "woodruffi" type according to Jankowski (1969). The oral opening is situated a little anterior to the middle of the cell. The cell surface is uniformly ciliated except for several long caudal cilia located close to the posterior end of the dorsal side, but not on the top. The abundant subpellicular trichocysts are distributed uniformly. Specimens were about 145 x 47 um long in vivo but shrank 10% after the silver nitrate impregnation. In silver-impregnated specimens, there were ~38 rows of ventral kineties and ~35 dorsal kineties. The preoral suture is distinct, but the postoral suture is very obscure. The cytoproct is situated in the posterior third. The vestibular zone is conspicuous and is terminated by the distinctive shape of the buccal opening. Two peniculi and open quadrulus are located on the dorsal and left wall of the buccal cavity. The endoral membrane is situated along the entire right edge of the buccal opening but its dikinetids are not recognizable in all specimens. It has 15 dikinetids on the average. The buccal cavity size various around 30 um. On the dorsal side of the body the contractile vacuole pores are very distinctive both on impregnated specimens as well as in living cells. Usually, both contractile vacuoles have more than one pore each, typically two or three. However, we have found two stocks (WCh-1 and WS-12) where one of the contractile vacuoles quite often (up to 50%) had only one pore. Both contractile vacuoles usually have 8-14 collecting canals, ten on average. Numerous crystals were very often found in the cytoplasm, but their quantity and location varied, probably depending on the culture conditions. The nuclear apparatus is located in the anterior part of the cell. One slightly ellipsoid or ovoid macronucleus, ~30x36 um in living cell and ~17x23 um in stained cells, on average, resides just anterior to the equator of the cell. In Feulgen-stained cells the macronucleus has a very intense colour. The three to four spherical micronuclei of the "endosomal" type (Fokin 1997), ~3 um in diam. (on average) are distributed irregularly along the anterior part of cell. Endocytobiotic bacteria are often found in the cytoplasm (Fokin 1989) and can also be found in the perinuclear space and in the macronucleus (Fokin 1989; Fokin and Sabaneyeva 1997)" (1).

"Swimming behavior - During swimming this species spirals on its long axis in both directions (Fokin 1987). We could not find any simple triggers (food, time) for changing this swimming direction. Typically, "left spiral swimmers" and "right spiral swimmers" were present at the same time in the culture. During the several years of investigation of this trait there was some preference of the cells from the same stocks to spiral in the left direction. Remarks- Gelei (1925) described a new species of Paramecium, Paramecium nephridiatum, based on the material which he had found in his laboratory aquarium. This population was in fact a mixture of the new species and Paramecium caudatum (Gelei 1938). This was the reason why some features of the new ciliate were similar to P. caudatum so that no one recognized this new species in nature, though reference to P. nephridiatum was made by Kahl (1931) and Kalmus (1931). Gelei (1938) redescribed the species from a native population (Tisza River, Szeged, Hungary) using a "clean culture". For unknown reasons, this new description did not attract the attention of protozoologists and in all subsequent reviews, P. nephridiatum was considered a nonvalid species (Vivier 1974; Wichterman 1953, 1986) even when the article of Gelei (1938) was listed in the references. Only once was P. nephridiatum mentioned in a short abstract as a species living in Florida, USA (Bovee 1983), although characters of the species were not listed in this publication. Since 1983, one of us (S. F) has repeatedly collected a species of Paramecium with multiple contactile vacuole pores, which is a distinctive trait of P. nephridiatum, although it was considered for a time as a feature of Paramecium woodruffi (Agamaliev 1983; Fokin 1986), Jankowski (pers. commun.)" (1).

"Occurrence and ecology- A number of stocks of P. nephridiatum were isolated from the sea shores of northern Europe: the North, Baltic, White, and Barents Sea coasts. It was detected during sampling in Woods Hole, MA, USA, Atlantic Ocean and on Sakhalin Island, Sea of Okhotsk. The salinity of these samples varied from 1.5-32 % The species was also found in a fresh-water body in Jerusalem Zoo, Israel. Samples were taken mainly during the summer, from mid-April (Wood Hole) to November (North Sea coast).

Sampling of the same wild population of P. nephridiatum (Sredny Island, White Sea, Russia) has been repeated every year since 1990 to observe long-time changes in the population, as well as the euryhaline ability of the species. This population was present at salinities from 4-35% and in the temperature range from 10-25” C. Very often the populations of P. nephridiatum occurred at the lower limit of oxygen concentrations. They were mainly feeding on bacteria. In the same samples these other ciliates were usually found: Prorodon sp., Frontonia marina, Metopus sp., P. calkinsi, P. woodruffi, and sometimes P. duboscqui" (1).

1. Sergei I. Fokin, Thorsten Stoeck, and Helmut J. Schmidt; Rediscovery of Paramecium nephridiatum Gelei, 1925 and its Characteristics. J.Eukaryot.Microbiol. 46(4):416-426, 1999
2. Evaluation of the molecular variability and characteristics of Paramecium polycaryum and Paramecium nephridiatum, within subgenus Cypriostomum (Ciliophora, Protista). Ewa Przyboś, Maria Rautian, Alexandra Beliavskaia, Sebastian Tarcz . Mol Phylogenet Evol . 2019 Mar:132:296-306

Video: https://youtu.be/Pmvk5Baer_U
Sampling location: A water sample was collected from Istok Lake near the shore, where snags and aquatic vegetation were present.
Date and time of collection: 16 Jul 2023 at 3 PM
Date and time of observation: 20 Jul 2023 at 6 PM
The sample was stored at room temperature in a plastic container.

Habitat hypersaline lake.
Image 1 - Male, dorsal view.
Image 2 - Female, dorsal view.
Image 3 - Male head, frontal view, showing the distal segments of the second antennae to be i) flat, ii) broadly triangular, iii) with pointed apices directed medially.
Image 4 - Habitat.
The major solution salt in this lake is sodium carbonate (Cummings, J.M. 1940. Saline and Hydromagnesite Deposits of British Columbia, Bulletin No. 4. BC Dept of Mines: 160pp)

Observation of a single specimen.
After rehydrating, the rotifer crawled for only a short time before returning to its contracted state, having found nothing of interest.

The sample was obtained from moss collected in the forest and stored at room temperature for three days prior to observation.

Video: https://youtu.be/38P-ilxFzfo

Habitat small, shallow lake.
Image 1 - Male, ventral view.
Image 2 - Female, ventral view.
Image 3 - Female, left lateral view, with eggs and two attached spermatophores.
Image 4 - Male 5th legs, posterior view, showing hyaline process on distal portion of inner margin of right exopod 1.
Image 5 - Male right 1st antenna, showing process on antepenultimate segment.
Image 6 - Female dorsal posterior view, showing 1) metasomal wings essentially symmetric, 2) the left lobe of the genital segment significantly smaller than the right, and 3) the lobes of the genital segment within the middle third of the segment - all points of difference between this species and the closely-related L. siciloides.

Bright-field microscopy. Between barbs, on internal surface of detached Threskiornis molucca molucca primary feather.

Image 1: body
Image 2: anterior; upper focal-plane
Image 3: anterior; central focal-plane
Image 4: anterior; lower focal-plane
Image 5: posterior; upper focal-plane
Image 6: posterior; lower focal-plane
Image 7: mites on feather
Image 8: feather

Habitat small, permanent pond.
Image 1 - male, ventral view.
Image 2 - female, ventral view.
Image 3 - male 5th pair of legs, posterior view.
Image 4 - male right first antenna, showing apex with a pointed outwardly-produced process (hence denticornis = toothed horn).

Habitat small, temporary, grassland pool.
Image 1 - female, ventral view with eggs and two attached spermatophores.
Image 2 - male, ventral view.
Image 3 - male 5th pair of legs, posterior view, showing i) inner and distal processes on left exopod 2 forming a pincer-like structure, ii) spiniform process on outer distal corner of right basis.
Image 4 - male right first antenna, showing short, curved, spinous process at distal end of antepenultimate segment.
Image 5 - female posterior dorsum showing elongate outer sensilla on metasomal wings.
Image 6 - female 5th pair of legs.

Fig. 1-3: Valve view
Fig. 4-6: Girdle view
GIF and Fig. 7-9: A few images as the diatom rotates

A water sample was taken from the bank of the Vuoksi River. The sample was stored at room temperature and observed one day after collection.

Video: https://youtu.be/n7HxWvJmyp4

Observation of Entomoneis ornata https://www.inaturalist.org/observations/192091414

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.

1. 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

A gastrotrich from genus Turbanella from the superficial intertdal benthos of marine estuary Acabonac Harbor at Louse Point. The length is 375 um.

Turbanellidae is a family of worms belonging to the order Macrodasyida. Macrodasyida is an order of gastrotrichs.[1] Members of this order are somewhat worm-like in form, and not more than 1 to 1.5 mm in length. Macrodasyids are almost in entirely marine and live in the sediment in marine or brackish water, but two species have been discovered in freshwater. They can be distinguished from other gastrotrichs by the presence of two pores on either side of the pharynx, that allow excess water to be expelled during feeding. The body is dorsally flattened and there are tubular adhesive glands at both ends and on the lateral surfaces. These animals are detritivores and are hermaphrodites.

The genus Turbanella Schultze, 1853, contains 29 similar species. Morphological variability within and among species of Turbanella is extensive and has led to considerable synonymy (Hummon 2001). Several species of Turbanella are considered cosmopolitan (Wieser 1957; Ruppert 1977; Clausen 2000). "There are several species of Turbanella which give appearances of distributions on both sides of the Atlantic Ocean. They include: T. ambronensis Remane, 1943, T. bocqueti Kaplan, 1957 sensu Boaden, 1974, T. cornuta Remane, 1924, T. hyalina Schulze, 1857 and now T. amphiatlantica n. sp., but not, as we argue, T. mustela Wieser, 1957. Their locations are summarized in Hummon (2009), but see also d’Hondt (1971), Hummon (1997) and Todaro et al. (2008). All of these species are intertidal, sometimes shallow subtidal, and hence are expected to be euryosmotic over a wide range of salinities" (1).

1. Turbanella amphiatlantica, a new species of Gastrotricha (Macrodasyida) from eastern North America and northwest Europe William D. Hummon and Jennifer L. Kelly. Meiofauna Marina, Vol. 18, pp. 61-70, Sept. 2011

Imaged in Nomarski DIC on Olympus BH2 using SPlan 20x objective plus camera phone cropping on Samsung Galaxy S9+.

Possibly the second record west of the Continental Divide, the first being http://n2t.net/ark:/65665/39d93e4e8-a728-44d6-b31e-86529dc0e56e

Habitat temporary pool with much vegetation.
Image 1 - male head showing fan-shaped antennae with three pointed tips.
Image 2 - male, ventral view.
Image 3 - male right second antenna, lateral view.
Image 4 - knob at base of distal segment of male left second antenna. Although Hartland-Rowe in his 1967 description of the species describes this knob as round, it's actually more-or-less pear shaped.
Image 5 - frontal view of male head.
Image 6 - habitat.

Female. Habitat small, shallow lake.
Image 2 - antennal setation 0-0-1-3 / 1-1-3, antennal spines 0-1-0-1 / 0-0-1, distal expansion of antennae with subapical ventral angulation.
Image 3 - dorsal serrations.
Image 4 - ventral-lateral view, showing the pronounced dorsal ridge.
Image 5 - postabdomen, showing that the dorsal rim is not bilobed (unlike some other members of this genus).
Image 6 - seta natatoria, showing the proximal segment to be longer than the distal, and to have no bristle-setae.
Image 7 - Habitat.

in the absence of a trunk or stone to lean on, a capybara may be an option;
I have observed these two individuals do this twice;

see also
https://www.inaturalist.org/journal/nelson_wisnik/21258-the-friendly-capybara

Female. Jelly coat not visible.
Habitat: open water of lake.
H. glacialis is morphologically indistinguishable from H. gibberum, but their distributions are largely separate. The location of this specimen was very far from the area where both co-exist. See section 'Differential Diagnosis' on page 29 of the paper below:
https://www.researchgate.net/profile/Sarah-Adamowicz/publication/287753132_Three_New_Cryptic_Species_Of_The_Freshwater_Zooplankton_Genus_Holopedium_Crustacea_Branchiopoda_Ctenopoda_Revealed_By_Genetic_Methods/links/5b22930b0f7e9b0e374325fd/Three-New-Cryptic-Species-Of-The-Freshwater-Zooplankton-Genus-Holopedium-Crustacea-Branchiopoda-Ctenopoda-Revealed-By-Genetic-Methods.pdf