Mechanisms of cnidocyte development in the moon jellyfish Aurelia

Abstract

Stinging cells called cnidocytes are a defining trait of the cnidarians (sea anemones, corals, jellyfish, and their relatives). In hydrozoan cnidarians such as Hydra, cnidocytes develop from interstitial stem cells set aside in the ectoderm. It is less clear how cnidocytes develop outside the Hydrozoa, as other cnidarians appear to lack interstitial stem cells. We addressed this question by studying cnidogenesis in the moon jellyfish (Aurelia) through the visualization of minicollagen-a protein associated with cnidocyte development-as well as transmission electron microscopy. We discovered that developing cnidoblasts are rare or absent in feeding structures rich in mature cnidocytes, such as tentacles and lappets. Using transmission electron microscopy, we determined that the progenitors of cnidocytes have traits consistent with epitheliomuscular cells. Our data suggests a dynamic where cnidocytes develop at high concentrations in the epithelium of more proximal regions, and subsequently migrate to more distal regions where they exhibit high usage and turnover. Similar to some anthozoans, cnidocytes in Aurelia do not appear to be generated by interstitial stem cells; instead, epitheliomuscular cells appear to be the progenitor cell type. This observation polarizes the evolution of cnidogenesis, and raises the question of how interstitial stem cells came to regulate cnidogenesis in hydrozoans.

Minicollagens play the governing role in polar capsule formation in parasitic cnidarians, the Myxozoa

“…1A). This suggested the presence of PMTs in studied proteins consistent with previous reports from cnidarians (Engel et al, 2001; Adamczyk et al, 2008; Gold et al, 2019). Our computational analyses of minicollagens performed to predict PMTs revealed that both proteins showed O-linked glycosylations and numerous hydroxylations (Fig.…”

Microbiota regulates life-cycle transition and nematocyte dynamics in jellyfish

“…The expression of other genes linked to nematogenesis, PaxA , Mef2 , and SoxB2 , 33 was also upregulated from AES to AE ( Figure 4 J). The expression of Ggt1 , Nematogalectin, and AurNcol-1 , which maintain nematocyst structure and discharge, 33 , 34 , 35 was considerably downregulated in AP but upregulated to different degrees from AES to AE, compared with that in the same stages of the control group ( Figure 4 J). Similarly, the expression of DKK3 , Nas4 , Nas8 , MACPF domain protein , and Toxin TX1 , encoding nematocyst venom proteins, 34 , 36 was downregulated in AP and elevated thereafter, compared with that in the same stage of the control treatment ( Figure 4 J).…”

Single-cell transcriptomic analyses reveal the cellular and genetic basis of aquatic locomotion in scyphozoan jellyfish

“…First, nematocytes, which are capable of predation and defence, could be recognised by their co-expression of genes encoding multiple venoms and capsule proteins, such as minicollagen 19 , DKK3 18 and Collagen-like 18 (Figure 2b, d; Figure S2; Table S1). The proportion of nematocytes showed a steady increase from planula to medusa, indicating predation strategies of Aurelia changed during development (Figure 2c).…”

“…In addition, the composition of cell types captured by single-cell sequencing was comparable across 6 different life stages, and marked changes were observed in the proportions of cell types during development (Figure 2c). First, nematocytes, which are capable of predation and defence, could be recognised by their co-expression of genes encoding multiple venoms and capsule proteins, such as minicollagen 19 , DKK3 18 and Collagen-like 18 (Figure 2b, d; Figure S2; Table S1). The proportion of nematocytes showed a steady increase from planula to medusa, indicating predation strategies of Aurelia changed during development (Figure 2c).…”