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. 2023 Mar 10;12:e81405. doi: 10.7554/eLife.81405

Figure 6. Formation and structure of epidermal slime produced by wounded skin.

(A) Schematic of epidermal slime formation when epidermis is wounded, with threads and granules from ruptured epidermal thread cells (ETCs) mixing with mucus from ruptured large mucous cells (LMCs). (B) Epidermal slime on pin tip, stained with eosin to show threads. (Right) Scanning electron microscopy (SEM) image of epidermal slime on pin tip, with enlarged areas showing stretched and unstretched threads. (C) A schematic of the slime formation by mixing of cellular contents from an open wound on epidermis. SMC, small mucous cell. (D) SEM images of a shallow abrasion wound, with insets showing damaged ETCs with partially released threads and granules. (E) Epidermal slime collected on sandpaper. Note the slime accumulated at the leading edge of the sand grain (asterisk) and the elongated slime at the trailing edge. (F) Thin film of epidermal slime collected by scraping with sandpaper, showing the scaffolding of mucus by threads, and the alignment of threads with the scraping direction. See more details in Figure 6—figure supplements 1–3.

Figure 6.

Figure 6—figure supplement 1. Formation of epidermal slime.

Figure 6—figure supplement 1.

Newly wounded hagfish skin was fixed, dehydrated, and observed using scanning electron microscopy (SEM). (A–B) Formation of epidermal slime on abraded skin, with details showing the slime as a mixture of mucus, epidermal thread cell (ETC) threads and small mucous cells. (C) The release of ETC granules and threads from laceration wounds made with a scalpel.
Figure 6—figure supplement 2. Structure of epidermal slime.

Figure 6—figure supplement 2.

(A) Epidermal slime observed using differential interference contrast (DIC) microscopy, showing epidermal thread cell (ETC) threads, granules, and detached small mucous cells (SMC). (B) Epidermal slime collected after scraping hagfish skin with a pin and observed using bright-field microscopy, showing individual ETC threads. (C) Small mucous cells (SMC) appeared mostly intact in epidermal slime, although may have been ruptured. Here, we show small mucous cells with nuclei highlighted using DAPI.
Figure 6—figure supplement 3. Structure of epidermal slime.

Figure 6—figure supplement 3.

(A–C) After scraping hagfish skin with rough surfaces (sand paper and wood), we observed epidermal slime adhered to these surfaces using scanning electron microscopy (SEM). The epidermal slime appeared as thin strings or sheets adhered to the protruding surfaces, with the rest trailing or crossing over gaps. From top to bottom, images show details of the epidermal slime with progressively increasing magnification. Dashed boxes denote enlarged areas.