Dose-Response Relationships for Experimental Heterochrony in a Colonial Hydroid

Area of Science:

• Developmental Biology
• Colonial Animal Morphology
• Physiological Ecology

Background:

• Hydractiniid hydroids exhibit diverse colony forms, from sheet-like to runner-like.
• These patterns reflect heterochronic variation, altering polyp and stolon development timing.
• Within-colony gastrovascular flow is a potential regulator of this variation.

Purpose of the Study:

• To investigate the causal relationship between gastrovascular flow rate and heterochronic variation in Podocoryne carnea.
• To determine if feeding manipulation and 2,4-dinitrophenol (uncoupler) affect morphology through similar or different mechanisms.
• To explore the interplay between flow rate, metabolism, and colony development.

Main Methods:

• Experimental manipulation of feeding in clonal replicates of Podocoryne carnea.
• Treatment of colonies with 2,4-dinitrophenol to uncouple oxidative phosphorylation.
• Measurement of within-colony gastrovascular flow and resulting morphological changes.

Main Results:

• A dose-response relationship exists between gastrovascular flow and heterochronic traits.
• Both feeding manipulation and dinitrophenol treatment altered flow, leading to similar morphological responses.
• Feeding altered flow by changing stolon thickness; dinitrophenol reduced absolute flow.
• Both treatments induced metabolic activation, suggesting a potential direct effect on development.

Conclusions:

• Gastrovascular flow rate is a causal factor in hydroid heterochronic variation.
• Both flow rate and metabolic state likely influence colony development.
• Further research is needed to disentangle the specific roles of flow and metabolism.