Hepatic pigment cells of Proteidae (Amphibia, Urodela): A comparative histochemical and ultrastructural study

Abstract

Amphibian liver pigment cells, also known as Kupff er cells, contain various amounts of melanin, haemosiderin and lipofuscin. We used diff erent histochemical and ultrastructural methods to analyse and compare the level of hepatic pigmentation and the structure of hepatic pigment cells in the livers of three representatives of the family Proteidae; two subspecies of the hypogean Proteus anguinus (depigmented Proteus a. anguinus and pigmented Proteus a. parkelj ) and the epygean Necturus maculosus . Our analysis revealed differences at histological and ultrastructural level. While the percentage of the pigmented area and ultrastructural characteristics are similar in both subspecies of P. anguinus , great diff erences occur in the amount and structure of the pigment cells between P. anguinus and N. maculosus . Pigment cells are more numerous and compose larger pigmented clusters in P. anguinus . Th ey are structurally more heterogeneous and contain a larger amount of haemosiderin when compared to N. maculosus . Our results confi rm a high degree of variation in hepatic pigmentation among diff erent amphibian species. Because many factors infl uence the level of hepatic pigmentation in poikilotherms, diff erences among species from diff erent habitats and also among individuals of the same species are expected but are not easily explained. We propose two possible explanations for the large amount of iron present in Proteus anguinus : (1) accumulation of pigments due to the very low metabolic rate and extended lifetime; (2) large iron storage capacity as an adaptation to a low and discontinuous food supply in caves.

Long‐term starvation in cave salamander effects on liver ultrastructure and energy reserve mobilization

“…c). The ultrastructure and histochemistry of pigment cells in Proteus liver has already been described in detail separately (Prelovšek et al, ).…”

Monitoring health and reproductive status of olms (Proteus anguinus) by ultrasound

“…Large intracellular deposits of copper, lipofuscin, and haemosiderin were detected histologically. This has been described previously and linked to low metabolic rate, extended lifespan, and to the liver’s storage capacity, that buffers the scarce and infrequent food supply in their natural environment [ 10 , 39 ]. Inhomogeneities indicating pathology were not detected.…”

History and biology of the «black proteus« (Proteus anguinus parkelj Sket & Arntzen 1994; Amphibia: Proteidae): a review / Zgodovina in biologija črnega močerila (Proteus anguinus parkelj Sket & Arntzen 1994; Amphibia: Proteidae): pregledni članek

“…11C) Bizjak Mali et al 2001;Lužnik 2004) that are used to meet metabolic needs during food deprivation (Bizjak Mali et al 2013) and reflect adaptation to stress situations in its environment, such as sporadic and discontinuous food supplies and/or hypoxia. The second outstanding feature is the numerous pigment cells which are grouped in large clusters among the hepatocytes (Bizjak Mali et al 1999Prelovšek et al 2005Prelovšek et al , 2008, and contain haemosiderin (iron-storage complex), melanin, and lipofuscin (lipid-containing residues of lysosomal digestion) ( Fig. 11C-D).…”