Figure 2: The tumour in two species of Hydra is formed by accumulation of ISCs.
From: Naturally occurring tumours in the basal metazoan Hydra
(a) Morphology of tumorous (tumour), normal (control) and oogenesis-induced (female) polyps of H. oligactis and P. robusta. Abnormal tumorous tissue (T), developing female gonad at oogenesis stage 3–4 (♀) and mature egg (E) are indicated. (b) Cross-sections through polyp body column demonstrate swelling of the ectodermal tissue in tumorous polyps (T), resembling female gonad (♀) at early oogenesis stages (1–3). In H. oligactis, tumour tends to be localized to one side of the body column, whereas in P. robusta multiple local accumulations of interstitial-like cells can be seen on histological sections. Scale bar, 50 μm. (c) ISC are accumulated in the ectodermal tissue layer (EC) in tumorous polyps and in females undergoing oogenesis. Scale bar, 15 μm. (d) Immunostaining reveals abundant cells positive for germline marker periculin inside the tumour tissue and female gonads. In control polyps only rare periculin-positive germline cells are observed (outlined). Scale bar, 50 μm.
