Octopus and Squid in Rapa Nui and other Pacific Islands

By Sergio Carrasco, Universidad Católica del Norte, ESMOI, Coquimbo

Octopus and squid have appeared in the tales of migration throughout Polynesia since early times and are part of the relationships of commerce, family connections and mythology. It is said that the eight arms of the octopus extend to the farthest reaches of the Polynesian triangle, connecting Aotearoa (New Zealand), Hawai’i and Rapa Nui in one unified body instead of being just an abstract geometric symbol. (Figure 1).

The octopus, squid and cuttlefish, called cephalopods, are species with sensory capacities that amply surpass those of other mollusks (example, sea snails, called “pipi” in Rapa Nui) and of many marine species, such as fish and crustaceans. However, the cephalopods have a very short life cycle that rarely extends beyond two years. In spite of their short individual existence, their importance as a group of species has maintained over a long time and made them sacred creatures with an important role in rituals and mythology of Polynesia. Stories refer to them as guardians, as a god of the sea and fishing or as a symbol of navigation (Figures 2, 3). In general, and in the traditional Polynesian language, they are referred to as feke, although there are phonetical and structural differences according to the different but related languages – he’e in Hawai’i, wheke in Aotearoa (New Zealand) and heke in Rapa Nui.

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Figura 1. Mapa de la Polinesia del autor Te Rangi Hiroa/Sir Peter Buck, en: E.M. DeLoughrey (2007). Routes and Roots. Navigating Caribbean and Pacific Island Literatures.

Within the Polynesian triangle, diverse species of octopus and squid reside in both coastal waters and in deep ocean, having evolved into different forms and sizes. Even today we have little solid information on the life cycle of most of the species of the Pacific Islands. Nonetheless, all these share similar characteristics in the manner in which they are born, grow and develop. During their first months of life, these diminutive individuals, called “paralarvae” (given their great resemblance to the adults and their little resemblance to the larvae of other invertebrates), disperse in the ocean carried by the marine currents and assisted by their speedy form of swimming similar to rocket propulsion, which makes them very difficult to catch in their native habitat.

Figura 2. En Rapa Nui, cerca de trece petroglifos de pulpos han sido documentados, la mayoría grabados en rocas de la costa norte de la isla. Imágenes
de: G. Lee (1992). Rock art of Easter Island, symbols of
power, prayers to the gods (Vol. 17). Institute of Archaeology University of California.

Figura 3. En la mitología Maori, Te Whekea- Muturangi era un pulpo monstruoso al que se enfrentó el navegante Kupe en la Bahía de Whekenui, Aotearoa. El wheke era una criatura salvaje y un guardián.

Recently (2015-2016), researchers from the Millennial Nucleus of Ecology and Sustainable Management of Oceanic Islands (ESMOI) of the Catholic University of the North in Coquimbo (Chile) held studies in both deep waters (100 m/330 ft) and shallow waters (20 cm/8 in) in different coastal sectors of the Island and on the Apolo seamount. Results confirmed the presence of paralarvae (between 1 and 5 mm in length of sheath) of several species of cephalopods, which would indicate that reproduction of individual adults would probably be occurring nearby. The species registered were identified based on their morphological characteristics (shape of body) and their genetics (traces of DNA), showing the presence of species that (1) have been previously registered on Rapa Nui and (2) others which are known to science but have never before been registered on Rapa Nui or in continental Chile. The following photographs show identified paralarvae, belonging to 4 species of squid and 1 species of octopus.

Through genetic studies, it was possible to corroborate that the latter photo corresponds to paralarvae of the endemic octopus, Octopus rapanui, a species native to the Island that has not been registered in any other part of the world. Its short life cycle and the relatively warm temperatures of the waters around Rapa Nui allow these small paralarvae (~1 mm) to reach adult size (~70 cm/28 in) in approximately one year.

Figura 4. En orden descendente: (A) Ommastrephes bartamii; escala 1.5 mm (B) Chtenopteryx sp.;escala 1.5 mm (C, D) Enoploteutidos indeterminados,escala 2.5 mm(E) Octopus rapanui (escala 0.5 mm).
In descending order: (A) Ommastrephes bartamii; scale 1.5 mm (B) Chtenopteryx sp.; scale 1.5 mm (C, D) undetermined Enoploteutidos, scale 2.5 mm (E) Octopus rapanui; scale 0.5 mm.

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Figura 5. Pulpos rapanui en Playa Anakena durante Rapanui octopus at Anakena Beach during Agosto 2018 / August 2018

In their juvenile and adult stages, this species presents a characteristic purple color with protuberances of a brownish-yellow color. On their skin, you can also observe some shades of blue, which become more evident when exposed to stronger light, such as on night dives. The arms are slim and rather long in comparison to the size of their bodies (2/3s of the total length of the animal) and are joined by wide membranes which make them efficient hunters, even in the intricate base of corals around the Island. This species is not habitually observed during daylight hours, even by experienced divers, but there are sometimes opportunities to observe their wonderful forms and colors (Figure 5).

In general terms, the cephalopods not only constitute an important historic source within the cultures which have inhabited the varied islands of the Pacific, but have also played (and continue to play) a crucial role in the various trophic levels of the sea, becoming important nutritional vectors (as both predators and prey) for many different species of invertebrates and vertebrates of the higher trophic levels, including tuna, sharks, sea birds and up to humans (Figure 6). For this reason, it is important to know their biology and life story in order to achieve an efficient conservation of their populations.

Figura 6. Ilustración de un cardumen atunes aleta amarilla en busca de su presa, calamares, del autor Cristián Silva Araki, en: P. Núñez (2014). He ´a´amu o te kahi rāua ko te korohu’a hi hika e tahi: Una historia entre montes submarinos.

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