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Size increase without genetic divergence in the Eurasian water shrew Neomys fodiens.

ABSTRACT: When a population shows a marked morphological change, it is important to know whether that population is genetically distinct; if it is not, the novel trait could correspond to an adaptation that might be of great ecological interest. Here, we studied a subspecies of water shrew, Neomys fodiens niethammeri, which is found in a narrow strip of the northern Iberian Peninsula. This subspecies presents an abrupt increase in skull size when compared to the rest of the Eurasian population, which has led to the suggestion that it is actually a different species. Skulls obtained from owl pellets collected over the last 50 years allowed us to perform a morphometric analysis in addition to an extensive multilocus analysis based on short intron fragments successfully amplified from these degraded samples. Interestingly, no genetic divergence was detected using either mitochondrial or nuclear data. Additionally, an allele frequency analysis revealed no significant genetic differentiation. The absence of genetic divergence and differentiation revealed here indicate that the large form of N. fodiens does not correspond to a different species and instead represents an extreme case of size increase, of possible adaptive value, which deserves further investigation.

SUBMITTER: Balmori-de la Puente A

PROVIDER: S-EPMC6874603 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Size increase without genetic divergence in the Eurasian water shrew Neomys fodiens.

Balmori-de la Puente Alfonso A Nores Carlos C Román Jacinto J Fernández-González Angel A Aymerich Pere P Gosálbez Joaquim J Escoda Lídia L Castresana Jose J

Scientific reports 20191122 1

When a population shows a marked morphological change, it is important to know whether that population is genetically distinct; if it is not, the novel trait could correspond to an adaptation that might be of great ecological interest. Here, we studied a subspecies of water shrew, Neomys fodiens niethammeri, which is found in a narrow strip of the northern Iberian Peninsula. This subspecies presents an abrupt increase in skull size when compared to the rest of the Eurasian population, which has ...[more]

PMID: 31758027

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Project description:BACKGROUND:Animal toxins can have medical and therapeutic applications. Principally, toxins produced by insects, arachnids, snakes and frogs have been characterized. Venomous mammals are rare, and their venoms have not been comprehensively investigated. Among shrews, only the venom of Blarina brevicauda has been analysed so far, and blarina toxin has been proven to be its main toxic component. It is assumed that Neomys fodiens employs its venom to hunt larger prey. However, the toxic profile, properties and mode of action of its venom are largely unknown. Therefore, we analysed the cardio-, myo- and neurotropic properties of N. fodiens venom and saliva of non-venomous Sorex araneus (control tests) in vitro in physiological bioassays carried out on two model organisms: beetles and frogs. For the first time, we fractionated N. fodiens venom and S. araneus saliva by performing chromatographic separation. Next, the properties of selected compounds were analysed in cardiotropic bioassays in the Tenebrio molitor heart. RESULTS:The venom of N. fodiens caused a high decrease in the conduction velocity of the frog sciatic nerve, as well as a significant decrease in the force of frog calf muscle contraction. We also recorded a significant decrease in the frog heart contractile activity. Most of the selected compounds from N. fodiens venom displayed a positive chronotropic effect on the beetle heart. However, one fraction caused a strong decrease in the T. molitor heart contractile activity coupled with a reversible cardiac arrest. We did not observe any responses of the insect heart and frog organs to the saliva of S. araneus. Preliminary mass spectrometry analysis revealed that calmodulin-like protein, thymosin ?-10, hyaluronidase, lysozyme C and phospholipase A2 are present in the venom of N. fodiens, whereas thymosin ?4, lysozyme C and ?-defensin are present in S. araneus saliva. CONCLUSION:Our results showed that N. fodiens venom has stronger paralytic properties and lower cardioinhibitory activity. Therefore, it is highly probable that N. fodiens might use its venom as a prey immobilizing agent. We also confirmed that S. araneus is not a venomous mammal because its saliva did not exhibit any toxic effects.

Project description:BackgroundVenom production has evolved independently many times in the animal kingdom, although it is rare among mammals. Venomous shrews produce toxins in their salivary glands and use their venoms to hunt and store prey. Thus far, the toxicity and composition of shrew venoms have been studied only in two shrew species: the northern short-tailed shrew, Blarina brevicauda, and the Eurasian water shrew, Neomys fodiens. Venom of N. fodiens has potent paralytic activity which enables hunting and storing prey in a comatose state. Here, we assayed the hemolytic effects of extracts from salivary glands of N. fodiens and the common shrew, Sorex araneus, in erythrocytes of Pelophylax sp. frogs. We identified toxins in shrew venom by high-performance liquid chromatography coupled to tandem mass spectrometry.ResultsOur results prove, confirming a suggestion made four centuries ago, that S. araneus is venomous. We also provide the first experimental evidence that shrew venoms produce potent hemolysis in frog erythrocytes. We found significant concentration-dependent effects of venoms of N. fodiens and S. araneus on hemolysis of red blood cells evaluated as hemoglobin release. Treatment of erythrocytes with N. fodiens venom at concentrations of 1.0 and 0.5 mg/ml and with S. araneus venom at concentration of 1.0 mg/ml caused an increased release of hemoglobin. Our findings confirm that hemolytic effects of N. fodiens venom are stronger than those produced by S. araneus venom. We identified four toxins in the venom of N. fodiens: proenkephalin, phospholipase A2 (PLA2), a disintegrin and metalloproteinase domain-containing protein (ADAM) and lysozyme C, as well as a non-toxic hyaluronidase. In the venom of S. araneus we found five toxins: proenkephalin, kallikrein 1-related peptidase, beta-defensin, ADAM and lysozyme C. PLA2 and ADAMs are likely to produce hemolysis in frog erythrocytes.ConclusionsOur results clearly show that shrew venoms possess hemolytic action that may allow them to hunt larger prey. Since a member of the numerous genus Sorex is venomous, it is likely that venom production among shrews and other eulipotyphlans may be more widespread than it has previously been assumed.

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Size increase without genetic divergence in the Eurasian water shrew Neomys fodiens.

Publications

Size increase without genetic divergence in the Eurasian water shrew Neomys fodiens.

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