Table 1.

Criteria for the semi-quantification of the histopathological alterations observed in the midgut gland of Littorina littorea upon Cd exposure: Digestive cell integrity loss, Integrity loss of digestive tract epithelium, Lumen visibility of midgut gland tubules, Presence of Ca cells in midgut gland connective tissue. The appraisal of the apparent histopathological status is ranked in arbitrary units from 0 to 4, with 0 being the control value and 4 the worst possible status.

Endpoint	Score
	0	1	2	3	4
Digestive cell integrity loss	Control integrity	Slightly lower cells	Lower cells slightly vacuolated epithelium	Low cells Vacuolated epithelium	Disintegrated tissue
Integrity loss of digestive tract epithelium	Control integrity	Slightly lower cells	Slightly lower cells slightly vacuolated epithelium	Slightly lower cells vacuolated epithelium	Disintegrated tissue
Lumen visibility of midgut gland tubules	<10% of the area of the tubule	<30% of the area of the tubule	<40% of the area of the tubule	<50% of the area of the tubule	>50% of the area of the tubule
Presence of Ca cells in the midgut gland connective tissue	<30% of the connective tissue	<45% of the connective tissue	<60% of the connective tissue	<85% of the connective tissue	>85% of the connective tissue