Structure and signaling at hydroid polyp-stolon junctions, revisited

Area of Science:

• Cell Biology
• Physiology
• Colonial Organisms

Background:

• The gastrovascular system in colonial hydroids is crucial for homeostasis.
• Its precise functional biology, particularly at polyp-stolon junctions, is not well understood.

Purpose of the Study:

• To investigate the functional biology of the gastrovascular system in colonial hydroids.
• To identify the cellular mechanisms regulating fluid exchange at polyp-stolon junctions.

Main Methods:

• Utilized fluorescent probes (2',7'-dichlorodihydrofluorescein diacetate and rhodamine 123) to detect reactive oxygen species (ROS) and mitochondria.
• Employed confocal and transmission electron microscopy to visualize cellular structures.
• Applied pharmacological uncouplers (2,4-dinitrophenol) and physical manipulation (stolon removal) to assess cellular function.

Main Results:

• Identified mitochondrion-rich cells at polyp-stolon junctions exhibiting high ROS levels.
• ROS production was linked to mitochondrial activity and diminished by uncouplers or stolon removal.
• These cells, identified as myoepithelial cells, possess contractile myonemes that open/close polyp-stolon junction lumens.

Conclusions:

• Mitochondrion-rich cells at polyp-stolon junctions regulate gastrovascular fluid flow by acting as valves.
• ROS production by these cells is associated with their valve function.
• Cellular structure and function support a mechanism for active control of nutrient and fluid distribution in colonial hydroids.