A Dissenters' View on AppleSnail Immunobiology

Area of Science:

• Invertebrate immunology
• Gastropod biology
• Evolutionary developmental biology (evo-devo)

Background:

• Gastropod immune systems are poorly understood, particularly in apple snails (Ampullariidae).
• Existing knowledge relies on limited empirical data, necessitating a critical synthesis.

Purpose of the Study:

• To review and synthesize current knowledge on gastropod and apple snail immunobiology.
• To test the evo-devo hypothesis of immune system origin in the reno-pericardial complex.
• To identify immune effectors and processes in Ampullariidae, focusing on *Pomacea canaliculata*.

Main Methods:

• Comprehensive literature review spanning morphological, molecular, and "omics" studies.
• Critical revision of existing findings on *Pomacea canaliculata* and *Marisa cornuarietis*.
• Analysis guided by an evo-devo hypothesis.

Main Results:

• The gastropod immune system may have originated in the reno-pericardial complex, with specialized hemocytes.
• Hemocyte aggregations in the kidney are crucial for immune responses in apple snails.
• Hemocyte nodule formation is a significant defense mechanism for isolating and eliminating intruders.

Conclusions:

• The reno-pericardial complex is a likely origin for the gastropod immune system.
• Apple snail hematopoiesis is centered in kidney-based hemocyte islets.
• Further research is needed to fully elucidate the internal defense system of apple snails.