Distinct cell proliferation patterns underlying the development of defensive crests in Daphnia longicephala

The freshwater crustacean Daphnia is well known for its expression of morphological defenses in the presence of predators. Research into this phenomenon has mostly centered on the ecology and evolution of Daphnia defenses; information is limited on the cellular mechanisms that underlie site-specific tissue growth. We aimed to determine these cellular mechanisms, specifically those associated with the development of defensive crests in D. longicephala. With the help of a cell-proliferation assay we monitored changes in the epidermal tissue of naive and predator-exposed D. longicephala. Based on our results, we propose that cell division is delayed in favor of cell growth, which results in crest formation. Further, we identify specific regions of proliferative activity in a timedependent manner. Defense development starts in the ventral region, before extending in the cranial and then dorsal directions. We demonstrate that these cellular changes begin as early as 2 h after predator exposure. Our results provide new insights into the cellular processes underlying morphological defense expression in Daphnia.

Automated summary

The cellular mechanisms underlying morphological defense expression in Daphnia, particularly the development of defensive crests, have been investigated. The study found that cell division is delayed in favor of cell growth, leading to crest formation. The defense development starts in the ventral region and extends towards the cranial and dorsal directions. These cellular changes begin as early as 2 hours after predator exposure.