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Found latched onto the lower neck of the family (standard-sized) dog.

It appears to have been extracted intact (using the ol' forceps-grab&tug method), and was quite active during the short photo-op, then it nestled into it's new home in the coals of the wood stove...then, moments later, we all heard a noticeable "¡¡POP!!", and we all laughed.

such a cool organism to look at under the microscope! some of the tips had very mobile balls inside them, and it was hard to distinguish if they were flagellated spores or if it was Brownian motion. the spheres that had exited the tip segments were not seen traveling on their own

Thalassiosira curviseriata Takano 1983

SEM images of the marine diatom Thalassiosira curviseriata Takano 1983. Phylum: Bacillariophycophyta, Subphylum: Bacillariophytina, Class: Mediophyceae, Order: Thalassiosirales, Family: Thalassiosiraceae. Valve view images.

Girdle view:
Cells discoid. Valve face is flat, 5–18 μ m in diameter.
Valve face with central concavity, mantle high and slanting. Connecting is thread long. Cells also found embedded in mucilage to form large colonies. Several large disc-shaped chloroplasts. Forms chains.
Valve view: Valve with radial rows of areolae (26 to 30 areolae in 10 mm). Siliceous granules all over the surface and in this specimen there are occassonal slicicious spinules on the valve face. One or probably more often, two central or sub-central strutted processes The central processes adjacent to a more or less off centered annulus. One marginal ring of 4 to 7 conspicuous winged strutted processes (MSPs), two wings per process opposing into two or three branches. Marginal processes 2.3–5.4 µm apart, this specimen is 5.1-5.9 µm apart.
The labiate process is close to a marginal strutted process just inside the marginal ring of strutted processes. Thalassiosira tealata Takano has one central process and marginal processes with longer wings than those of T. curviseriata. Additionally, the distance between MSPs are closer in T. tealata. (Hasle and Syvertsen. 1996, Hoppenrath et al. 2007, Li et al. 2014, Park et al. 2016).

A new record for Western Canada marine waters.

Methods:
Sections of the eelgrass Zostera marina were boiled in concentrated sulfuric acid until full digestion, rinsed with distilled and deionized water, further briefly cleaned with 30% hydrogen peroxide, rinsed, dried and filtered onto 12 mm round 0.8 µm Teflon filters. Filters were placed on 13 mm aluminum SEM stubs with double sided tape. Imaged with a Hitachi s4800 SEM.
Thank you Ron Read for the imaging and Elaine Humphrey for SEM and imaging support at the Advanced Microscope Facility, University of Victoria, British Columbia, Canada. Thank you to Arjan van Asselt for collecting and preparation of samples.

References:

Hasle, G.R. & Syvertsen, E.E. (1996). Marine Diatoms. In: Identifying Marine Phytoplankton. (Tomas, C.R. Eds). San Diego: Academic Press.

Guiry, M.D. & Guiry, G.M. 2007, AlgaeBase version 4.2. World-wide electronic publication, National University of Ireland, http://algaebase.org, searched April 10, 2022.

Hoppenrath, M., Beszteri, B., Drebes, G., Halliger, H., Van Beusekom, J.E.E. , Janisch, S. and Wiltshire, K. H. (2007) Thalassiosira species (Bacillariophyceae, Thalassiosirales) in the North Sea at Helgoland (German Bight) and Sylt (North Frisian Wadden Sea) – a first approach to assessing diversity, European Journal of Phycology, 42:3, 271-288, DOI: 10.1080/09670260701352288

Li, Y. and Lu, S. (2013). The genus Thalassiosira off the Guangdong coast, South China Sea. Botanica Marina; 56(1): 83–110. DOI: 10.1515/bot-2011-0045

Park et al. (2016). Species diversity of the genus Thalassiosira (Thalassiosirales, Bacillariophyta) in South Korea and its biogeographical distribution in the world. in Phycologia Volume 55 (4), 403–423.. DOI: 10.2216/15-66.1

Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms, Biology & Morphology of the Genera. Cambridge University Press, Cambridge, UK. pp. 132-133.