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Pit connection

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Title: Pit connection  
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Subject: Drachiella (alga), Axostyle, Lorica (biology), Microbial cyst, Eyespot apparatus
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Pit connection

In algal anatomy, a pit connection is a hole in the septum between two algal cells, and is found only in the red algae[1] - specifically, all orders except the Porphyridiales and haploid Bangiales.[2] They are often stoppered with proteinaceous "pit plugs". By contrast, many fungi (only ascomycetes and basidomycetes, as other groups lack septa) contain septal pores - an unrelated phenomenon.[3]

Characteristics

A sieve-like membrane may cover the pit in living algae,[4] but in the majority of algae a plug forms, likely limiting the transfer of metabolites between neighbouring cells.[2][5]

Formation

Primary pit connections are formed between cells in the same filament, derived from the same parent cell by its division.[4] Such connections are always single, and usually circular;[4] this is a result of their method of formation. The septum is formed as the walls of a filament grow inwards, dividing the cell; this results in a hole in the middle of the tube where the walls don't quite merge.[2] Thus pit connections are visible in the youngest of septa, widening as the septum thickens, until in some cases they may ultimately occupy the entire septum.[4] Secondary connections, by contrast, occur between unrelated cells, and serve a role in transferring cell contents and nutrients.[2] They may even form between cells of different species, as in the parasite Holmsella.[6]

References

  1. ^
  2. ^ a b c d
  3. ^
  4. ^ a b c d
  5. ^
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External links

  • Transverse SEM images of pit connections in the coralline Synarthrophyton can be seen in Figs. 54 & 60 in
  • (Lower quality) transverse SEM images of pit connections in the coralline Phymatolithon are available on page 138 at .
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