► Proteus anguinus anguinus is neotene and troglobiont cave salamander. ► Concentration of PCB in its tissues from polluted area is extremely high. ► The PCB distribution in tissues is similar to ...distribution in other aquatic vertebrates exposed to PCB contamination. ► Proteus is capable of eliminating less chlorinated and mono-ortho PCB congeners.
For over two decades, a manufacturer of electrical capacitors disposed of its waste within the karstic hinterland of the Krupa River (Slovenia) resulting in the surroundings becomming heavily polluted with PCB. Albeit the extent of the contamination has been known since 1983 and the Krupa River has become one of the most PCB polluted river in Europe, the effects on the cave fauna of the region remain unknown. The most famous cave dweller of the Krupa hinterland is the endemic cave salamander Proteus anguinus anguinus. In this study we determine the levels of PCB in the tissues of the Proteus and in river sediments. The total concentration of PCB in individual tissue samples from specimens of the Krupa spring was between 165.59μgg−1 and 1560.20μgg−1dry wt, which is at least 28-times higher than those from an unpolluted site. The kidneys contained the lowest concentration, while the highest concentration was in subcutaneous fat and tissues with high lipid contents like visceral fat and liver. Total PCB concentrations in sediment samples from the Krupa River were between 5.47 and 59.20μgg−1dry wt showing that a high burden of PCB still remains in the region. The most abundant PCB congeners in all analyzed samples were di-ortho substituted (PCB #101, #118, #138 and #158), but higher proportion of mono-ortho PCB was present in sediments. The ability of Proteus to survive a high PCB loading in its environment and especially in its tissues is remarkable. Its partial elimination of low chlorinated and mono-ortho substituted congeners is also reported.
During the field work in Zagorska peć cave in Croatia, the olm, Proteus anguinus Laurenti, 1768 was observed in a siphon at depth of 113 m. This was not only the first time that this troglobiotic ...amphibian was recorded at such depths but also the first time that its research was done by cave-divers in its natural environment, at depths greater than 50 m. As such research is dangerous and difficult there was no previous data on the vertical distribution of the olm in the cave system. Further in situ research will provide valuable insight into species' environmental preferences and behaviour.
Cave shrimps of the subgenus Troglocaris (Atyidae), exhibit high variability in rostral length and dentition. In shrimp populations that co-occur with the amphibian predator Proteus anguinus, longer ...rostra armed with more numerous teeth are recorded. These shrimps are also larger than those living in a presumably Proteus-free environment. Discrepancies between molecularly established phylogenetic relationships and distributions of rostral length, as well as body size, directed our search towards possible environmental influences. These discrepancies suggest that rostral shape is not a reliable taxonomic character in some generic and many specific diagnoses in Atyidae. We discuss some taxonomic consequences of sexual and ontogenetic rostral differences with regard to the molecular phylogenetic tree. In preliminary laboratory observations, no frontal attack by Proteus was successful on shrimps with long rostra. Proteus also needed more time to swallow shrimps with long rostra.
The effects of long-term starvation and subsequent refeeding on haematological variables, behaviour, rates of oxygen consumption and intermediary and energy metabolism were studied in morphologically ...similar surface- and cave-dwelling salamanders. To provide a hypothetical general model representing the responses of amphibians to food stress, a sequential energy strategy has been proposed, suggesting that four successive phases (termed stress, transition, adaptation and recovery) can be distinguished. The metabolic response to prolonged food deprivation was monophasic in the epigean Euproctus asper (Salamandridae), showing an immediate, linear and large decrease in all the energy reserves. In contrast, the hypogean Proteus anguinus (Proteidae) displayed successive periods of glucidic, lipidic and finally lipido-proteic-dominant catabolism during the course of food deprivation. The remarkable resistance to long-term fasting and the very quick recovery from nutritional stress of this cave organism may be explained partly by its ability to remain in an extremely prolonged state of protein sparing and temporary torpor. Proteus anguinus had reduced metabolic and activity rates (considerably lower than those of most surface-dwelling amphibians). These results are interpreted as adaptations to a subterranean existence in which poor and discontinuous food supplies and/or intermittent hypoxia may occur for long periods. Therefore, P. anguinus appears to be a good example of a low-energy-system vertebrate.
Abstract
A review is given on several sensory systems that enable troglophile and troglobian urodele species to orient non-visually in their extreme hypogean habitat. A new sense was discovered ...allowing the animals to orient according to the Earth's magnetic field, which could serve as a basic and always available reference for general spatial orientation. Moreover, working with permanent magnetic field stimuli offers a very sensitive experimental method to discover the urodeles' thresholds for other sensory modalities such as light, sounds, and other stimuli, perhaps in competition or combination with the magnetic one. Proteus' audition as underwater hearing and light sensitivity due to its partly remaining sensory cells and/or skin sensitivity were studied. Excellent underwater hearing abilities had been demonstrated for Proteus with an acoustic behavioural method. The ability of sound pressure registration in Proteus is supposed to be attained by the tight anatomical junction between the ceiling of the oral cavity and the oval window. More generally, all non-visual sensory capabilities may facilitate certain behavioral strategies, compensating for missing visual orientation. Troglobians are more likely than others to own and regularly use the sensorial opportunities of a magnetic sense for spatial orientation. Compared to their epigean relatives, cave animals may have retained phylogenetically older sensorial properties, transformed or improved them, or finally acquired new ones which enabled them to successfully survive in dark habitats. Neighbor populations living on surface did not necessarily take advantage of these highly evolved sensory systems and orientation strategies of the troglobian species and may have lost them. E.g. Desmognathus ochrophaeus is partly adapted to cave life and exhibits good magnetic sensitivity, whereas, D. monticula and D. quadrimaculatus are epigean and, although living in rather dark places, did not demonstrate magnetic sensitivity when tested with our method.
Oogenesis in the neotenic, cave dwelling salamander
Proteus anguinus anguinus
has not been studied yet, and this study provides a detailed description of the early growth of the oocytes. Early ...previtellogene oocytes ranging from 100 to 600 µm in diameter were examined by light and transmission electron microscopy. The oocytes were divided into two stages based on size, color, and histology. Stage I oocytes can be identified by their transparent cytoplasm and a homogenous juxtanuclear mass, composed of numerous lipid droplets and mitochondria. Stage II oocytes are no longer transparent and have increased in diameter to 300– 600 µm, and many cortical alveoli differing in size have appeared. The common and most predominant ultrastructural characteristics of both stages of previtellogene oocytes are extensive quantities of smooth membrane, numerous mitochondria, and lipid droplets, as well as abundant free ribosomes. Myeline-like structures and remarkable annulate lamellae of closely packed membrane stacks are also frequently observed. Previtellogenic oocytes are the most predominant oocytes in the ovaries of
Proteus
, and while they possess certain structural characteristics typical for other amphibians, some features are unique and could result from adaptation to the subterranean environment.
AbstractAmphibian liver pigment cells, also known as Kupffer cells, contain various amounts of melanin, haemosiderin and lipofuscin. We used different 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 differences 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. They are structurally more heterogeneous and contain a larger amount of haemosiderin when compared to N. maculosus. Our results confirm a high degree of variation in hepatic pigmentation among different amphibian species. Because many factors influence the level of hepatic pigmentation in poikilotherms, differences among species from different 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.
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