Piepkleine octopuslarven, een groot dilemma: pijn of geen pijn?
Kunnen piepkleine octopuslarven pijn ervaren? Het antwoord onthult evenveel over deze dieren als over ons als mensen. Niet de wetenschappelijke feiten, maar overtuigingen en intuïties geven de doorslag.
Een verhaal over pijn
Bij dieren met een ruggengraat—gewervelden—zoals honden, katten, en vogels zijn we zeker dat ze pijn ervaren. Stap per ongeluk op de poot van je hond en zijn gejank laat geen ruimte voor twijfel. Omdat gewervelden ons vertrouwd zijn, herkennen we hun emoties en voelen we sneller empathie. Voor ongewervelden—dieren zonder ruggengraat, zoals insecten—ligt dat anders. Hun vreemde uiterlijk en gebrek aan herkenbare emoties maken dat we ons minder snel verbonden voelen met hen. Hierdoor denken we minder snel dat ze pijn voelen en krijgen ze in wetenschappelijk onderzoek niet dezelfde bescherming als gewervelden. Toch vormt één groep ongewervelden een uitzondering: de koppotigen (Cephalopoda), waaronder de gewone octopus (Octopus vulgaris; Fig. 1).
Figuur 1: Gewone octopus (Octopus vulgaris)
De gewone octopus in de spotlights
Bekend als één van de slimste ongewervelden, toont de gewone octopus zijn vindingrijkheid door uit aquaria te ontsnappen en voorwerpen als gereedschap te gebruiken. Bovendien groeit ook het wetenschappelijk bewijs dat ze pijn kunnen ervaren. Daarom besloot de Europese Unie in 2013 dat alle levende koppotigen, ook de gewone octopus, wettelijke bescherming verdienen tijdens wetenschappelijk onderzoek, net zoals gewervelden. Die bescherming geldt niet alleen voor volwassen octopussen, maar ook voor hun pas uitgekomen larven, de paralarven (Fig. 2).
Figuur 2: Paralarve van de gewone octopus (Octopus vulgaris)
En daar ontstaat een dilemma, want terwijl er bewijs is dat volwassen dieren pijn kunnen ervaren, ontbreekt dit volledig voor de paralarven. Moeten deze larven uit voorzorg dezelfde bescherming krijgen als volwassen octopussen? Of is bescherming pas op zijn plaats als de wetenschap onomstotelijk bewijs levert? En vooral: hoe verschillend kijken wetenschappers en het brede publiek naar die kwestie?
Die vragen vormden het vertrekpunt voor het masteronderzoek van biologe Jill Monnissen (KU Leuven). In haar studie bracht ze twee werelden samen: biologie en filosofie. Enerzijds onderzocht ze of genen die in verband staan met pijnbeleving al aanwezig zijn in de piepkleine paralarven. Anderzijds peilde ze met een enquête naar de meningen van biologen en het brede publiek. Haar conclusie? Hoewel biologische data veel kunnen onthullen, zijn het uiteindelijk overtuigingen en intuïties die de doorslag geven in ethische debatten.
De bouwstenen van pijn
Voor het biologisch luik van haar onderzoek keek biologe Jill Monnissen naar zes genen die mogelijk een rol spelen bij het waarnemen van schadelijke prikkels en dus pijn. Met een geavanceerde techniek bracht ze in beeld waar die genen actief zijn in paralarfjes van vijf en veertig dagen oud.
De resultaten waren opvallend: al bij jonge octopuslarven blijken bepaalde pijn-gerelateerde genen actief te zijn in specifieke delen van het lichaam. Bovendien werden sommige genen ook actiever naarmate de larven ouder werden. Samen wijst dit erop dat zelfs heel jonge octopuslarven al de moleculaire basis hebben om pijn en stress waar te nemen. Maar, zo benadrukt Monnissen, voorzichtigheid is geboden: het feit dat de bouwstenen aanwezig zijn, betekent nog niet dat de larven ook écht bewust pijn ervaren.
Van gen naar geweten
Maar wat doen mensen eigenlijk met zulke biologische informatie? Om dat te achterhalen, vertaalde biologe Jill Monnissen haar eigen genetisch experiment naar de filosofische praktijk. Via een online enquête legde ze deze biologische data voor aan drie groepen: biologen die met koppotigen werken, biologen die met andere dieren werken, en een brede groep niet-biologen zonder wetenschappelijke achtergrond.
Elke deelnemer kreeg een korte tekst te lezen over de expressie van pijn-gerelateerde genen in paralarven. Wat ze niet wisten, is dat er drie verschillende versies van deze tekst circuleerden. In de eerste versie kwamen de genen tot expressie, in de tweede niet, en in de derde was het experiment nog niet uitgevoerd, waardoor de uitkomst onzeker bleef. Vervolgens moesten de deelnemers hun oordeel vellen: hoe ethisch vinden ze onderzoek op octopuslarven en volwassen dieren? Hoe belangrijk vinden ze dit soort onderzoek voor de maatschappij? En geloven ze dat deze dieren pijn kunnen ervaren? De antwoorden leverden een verrassend beeld op.
Niet iedereen denkt hetzelfde
Wat bleek? De meegegeven wetenschappelijke informatie had weinig invloed. Of deelnemers lazen dat genexpressie aanwezig, afwezig of onzeker was, hun oordelen verschilden nauwelijks. Veel bepalender was hun eigen overtuiging: wie geloofde dat paralarven pijn kunnen ervaren, vond onderzoek met deze dieren sneller onethisch en minder belangrijk voor de maatschappij.
Ook de achtergrond van de deelnemers speelde een rol. Biologen die met koppotigen werken, waren het minst geneigd om het onderzoek onethisch te vinden, waarschijnlijk door hun ervaring met de dieren en vertrouwen in de regelgeving. Het brede publiek daarentegen was het meest geneigd het onderzoek onethisch te vinden. Zij waren voorzichtiger en gaven de octopuslarfjes sneller het voordeel van de twijfel: beter beschermen dan later spijt hebben. Daarnaast viel ook op dat leken vaak erg zelfverzekerd waren in hun oordeel, soms zelfs meer dan biologen met middelmatige ervaring. Mogelijk speelt hier een Dunning–Kruger-effect: wie minder vertrouwd is met de biologische complexiteit, kan zijn eigen begrip overschatten.
Nog opvallend was het verschil tussen mannen en vrouwen. Mannen benadrukten vaker de maatschappelijke relevantie van het onderzoek, ook als dat mogelijk pijn voor de paralarven betekende. Vrouwen kozen daarentegen vaker voor voorzichtigheid en extra bescherming van de paralarven. Dat sluit aan bij bredere studies die aantonen dat vrouwen doorgaans meer empathisch en risicomijdend oordelen in ethische dilemma’s.
Meer dan een octopusverhaal
Door genetische data te koppelen aan filosofische reflectie, maakt deze thesis een brug tussen laboratorium en maatschappij. De thesis van Monnissen levert niet alleen nieuwe biologische kennis op, maar ook een blik op onze eigen manier van redeneren. Haar onderzoek maakt duidelijk hoe lastig het is om wetenschappelijke informatie te vertalen naar beleid en ethiek. Complexe biologische data worden niet altijd correct geïnterpreteerd, en vaak wegen overtuigingen en intuïties zwaarder dan de feiten. Daarom is toegankelijke communicatie cruciaal. Want wanneer wetenschap en beleid samenkomen, zeker in grijze zones vol onzekerheid, moeten we begrijpen dat de keuzes die we maken net zoveel zeggen over onszelf als over de dieren die we willen beschermen.
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