Sponge development and antiquity of animal pattern formation

Area of Science:

• Developmental biology
• Evolutionary developmental biology
• Marine biology

Background:

• The last common ancestor of animals shared traits with sponges (Porifera) and other animals.
• Investigating demosponge Reniera offers insights into ancient developmental processes.

Purpose of the Study:

• To identify ancient and conserved developmental processes in animal evolution.
• To understand embryogenesis and metamorphosis in the demosponge Reniera.

Main Methods:

• Observation of Reniera embryogenesis and metamorphosis.
• Analysis of cell division, differentiation, and patterning.
• Identification of expressed transcription factor genes.

Main Results:

• Reniera embryogenesis displays features of eumetazoan development, including cell size dimorphism and differentiation into ciliated cells.
• Embryos develop into layered structures with patterned cell populations, forming a larva capable of environmental sensing without neurons.
• Pigment cell patterning involves cell migration and rearrangement, potentially guided by morphogen gradients.
• Diverse metazoan-specific transcription factor genes are expressed during Reniera embryogenesis.

Conclusions:

• The last common metazoan ancestor possessed the genetic architecture for cell specification, patterning, and differentiation.
• Early animals likely had the capacity for forming localized functional units, or simple tissues.