Prehrana žaba porodice Dendrobatidae kao izvor otrovnih alkaloida

undergraduate thesis

• Title (english): Dietary source for skin alkaloids of Dendrobatid poison frogs
• Author: Senka Baškiera
• Mentor: Milorad Mrakovčić (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2010, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Žabe porodice Dendrobatidae sadrže otrovne alkaloide u kožnim žlijezdama. Dugo se smatralo da ih same sintetiziraju, no istraživanjem je dokazano kako su alkaloidi ipak porijeklom od malih člankonožaca kojima se hrane. Vršena su istraživanja koja bi dokazala teoriju o postanku alkaloida iz prehrane. To je uključivalo uzgoj žaba u kavezu u kojemu su vinske mušice bile jedini izvor prehrane. U tim uvjetima pronađeno je vrlo malo alkaloida. Uzgoj u kavezu sa svježim lišćem sakupljenim iz njihovog izvornog staništa, dalo je drugačiji profil alkaloida. Žabe sakupljene iz prirodne okoline, naravno, sadržavale su sve alkaloide koje ta vrsta inače sadrži. No one koje su uzgajane u staklenom terariju, potpuno izolirane od okoline, nisu sadržavale otrovne alkaloide. Ovakav je ishod pokusa bio i za očekivati uz postavljenu hipotezu i prijašnja istraživanja. Žabe ove porodice većim dijelom koriste mrave u prehrani. Istraživanja su uključivala različite vrste ove porodice, a njima se htjela naći poveznica između njih i mrava porodice Formicidae preko raznih spojeva pumiliotoksina koristeći plinsku kromatografiju i masenu sprektrometriju. Istraživanja su pokazala kako mravi rodova Brachymyrmex i Paratrechina sadrže navedene spojeve. Prisutnost pumiliotoksina u ovim mravima, kao i u ekstraktima kože Dendrobates pumilio, zajedno s pronalaskom B. depilis u želucima ovih žaba, definitivno može stajati kao dokaz da ove žabe koriste navedene mrave kao izvor prehrane i pumiliotoksina. Prema dobivenim rezultatima može se zaključiti sljedeće: prisutnost člankonožaca uvjetuje pojavu alkaloida. A njihova koncentracija i raznolikost ovisi o raspoloživosti plijena. Aposemija je pojava za koju se smatra da se razvija zajedno s pojavom otrovnosti, a komparativnim je analizama utvrđena veza između obojenosti i otrovnosti jedinki. Upravo im je ta otrovnost omogućila dnevni način života i bezbrižno kretanje bez brige od napada predatora, a sposobnost sakupljanja otrovnih alkaloida iz organizama kojima se hrane, učinila ih je veoma uspješnom skupinom životinja.

Abstract (english)

Dendrobatid frogs contain a variety of poisonous alkaloids in the skin glands. These alkaloids were initially considered to be synthesized by these frogs, but later studies showed they were actually of dietary origin. There were many research efforts to test the dietary hypothesis. Such work included placing frogs into outdoor cage with a diet of only fruit flies. The occurrence of alkaloids in skin extracts from these captive-raised frogs was very low. Another group of captive-raised frogs placed in outdoor screened cage, but provided with fresh leaf litter gathered from the area where these frogs were common, showed different alkaloid profile. And as expected, wild-caught frogs contained all alkaloids known to that species. Frogs raised in large glass terrarium, isolated entirely from natural surroundings, had no detectable alkaloids in the skin extracts. All of the results were as expected from previous studies and consistent with a given hypothesis. Dendrobatid frogs consume a high proportion of ants as part of their diet in the wild. Using gas chromatographic-mass spectral analysis, many tests were made on a variety of dendrobatid frog species to find a connection between formicine ants and these frogs. That connection was found in the presence of pumiliotoxins in both groups. Pumiliotoxins were detected in ants of the genera Brachymyrmex and Paratrechina. The presence of pumiliotoxins in these ants as well as in skin extracts of the dendrobatid frog Dendrobates pumilio, coupled with the presence of these ants in stomach contents of Dendrobates pumilio, strongly suggests that these ants represent a dietary source for pumiliotoxins in these populations of frogs. Based on results of all research it can be said that arthropods are the source of poison alkaloids in dendrobatid frogs and that their amount and variety is determined only by the availability of those arthropods in their environment. A comparative approach was used to test a prediction of the hypothesis of aposematism: coloration will evolve in tandem with toxicity. And it's the combination of two that allows them to have a diurnal lifestyle and to live carelessly, freed from any fear of predation. This made them to be very successful and well adapted species.

• Keywords: žabe; Dendrobatidae; otrovni alkaloidi
• Keywords (english): frogs; Dendrobatidae; poisonous alkaloids
• Language: croatian
• URN:NBN: urn:nbn:hr:217:978917
• Study programme: Title: Ecology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-03-22 09:07:40