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I polpi, pugili a otto braccia - Il giornale del mare
Skip to content Anche un astuto cacciatore come un polpo a volte ha bisogno di aiuto. Animale enigmatico ed intelligente, il polpo passa molto tempo a cercare piccoli molluschi e crostacei ben nascosti sotto la sabbia o tra le rocce. Spesso però il polpo crea alleanza con pesci. Predare, nascondersi o per ricevere segnali d’allarme. In Mediterraneo è facile notare ad esempio le interazioni tra un polpo ed una perchia .
In acque tropicali, queste interazioni avvengono più frequentemente. Il polpo caccia in solitaria sia durante le ore di luce ma in particolar modo durante la notte. Ogni tanto però qualche preda sfugge alla presa mortale del polpo. Sfortunatamente per la preda in fuga, diverse specie di pesci cooperano con il polpo per andare a recuperare la preda fuggita e riportarla al legittimo proprietario . Ma sembra che ci sia qualcosa di più di una cooperazione. Sembra che il polpo sia il vero “boss” del gruppo e se uno dei pesci non collabora a dovere viene “steso” dal cefalopode con un bel gancio.
A dirlo una ricerca effettuata da Eduardo Sampaio, dottorando presso l’Università di Lisbona in Portogallo e autore principale di un nuovo studio che documenta il comportamento dei polpi.
Le triglie ad esempio sembrano essere considerate dal polpo come collaboratori, altri pesci come le piccole cernie nere come un possibile concorrente. Motivo per il quale quest’ultima specie viene spesso allontanata dal pasto a suon di “sganassoni”.
“Questi gruppi di predatori sono complessi. Ogni membro ha una diversa strategia di caccia e un diverso livello di predazione “, afferma Sampaio. “In una situazione come questa, ci dovremmo aspettare che i meccanismi di controllo dei partner si evolvano per contribuire a garantire una distribuzione più equa del profitto”.
Grazie a delle camere posizionate sui fondali Sampaio e la sua equipe hanno mostrato le dinamiche di gruppo che portano il polpo ad allontanare dal gruppo altri pesci.
“C’è solo una straordinaria storia evolutiva in questo comportamento “, afferma Redouan Bshary , biologo marino dell’Università di Neuchâtel in Svizzera. Redouan Bshary che studia i polpi da diverso tempo (ma anche dei rapporti tra cernie e murene).
https://youtu.be/Uf8QfPF6Q_E
Mentre c’è ancora molto da imparare sul comportamento del polpo, documentarlo è un grande passo avanti, afferma Sampaio. “Prima dovevamo trovare i polpi, il che è difficile … Poi abbiamo dovuto trovare i polpi che cacciavano insieme ai pesci, che è ancora più raro.” I polpi sono noti per stringere alleanze con altre specie per trovare cibo, ma è tutt’altro che comune. Chelsea Bennice, biologa marina presso la Florida Atlantic University non ha mai visto prove dirette di comportamenti di caccia collaborativi nei polpi, ma afferma di aver visto che tendono a scacciare i pesci che si avvicinano troppo. Ciò sembra suggerire che questo comportamento esista anche al di fuori dei contesti collaborativi come meccanismo di pura competizione.
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Sapevo che era intelligente, ma organizzare il procacciamento del cibo è eccezionale !
Andiamo su Marte, ma quante cose della natura ci sono sconosciute.
Complimenti !
Agostino