Paralarvae of cephalopods in channels and fjords of the southern tip of Chile (46-53 degrees S)

Abstract

Cephalopods are common in Chilean waters; however, there is little information on the distribution and abundance of their early life stages. In the austral spring seasons of 2008 and 2009 zooplankton samples were collected during two oceanographic cruises (CIMAR 14, CIMAR 15) in Patagonian fjords and channels of southern Chile between 46 degrees S and 53 degrees S. Zooplankton sampling was conducted at 82 stations with Bongo (60 cm diameter, 300 mu m mesh size) and Tucker (1 m(2) diameter, 300 mu m mesh size) trawl nets. The paralarvae were preliminarily identified by morphology and pigment patterns. Subsequently, their identity was confirmed through mitochondrial DNA (16S rRNA and COIII) analysis comparing them with the common adult octopus species from Chile which also have planktonic paralarvae (Octopus mimus, R. fontaniana and Enteroctopus megalocyathus) by phylogenetic analysis. We obtained 12 octopus and 1 squid paralarvae in 2008 and 16 octopus and 1 squid paralarvae in 2009. The paralarvae were caught exclusively in areas with higher oceanic influence and were absent in areas with greater freshwater discharge and/or ice melting. Southern Chile is characterized by geomorphological discontinuity due to fragmentation of the south coast starting at 41 degrees 30'S, where there is a large freshwater influence in estuaries promoting fjord-like characteristics. Thus, it is not surprising that cephalopod paralarvae were not found in such places, because they are stenohaline. Both morphometric and molecular data confirmed that 26 paralarvae belonged to R. fontaniana; one paralarva was identified as Enteroctopus megalocyahtus; Doryteuthis gahi and Onychoteuthidae were also collected. Our results expand the known range of cephalopod paralarvae to areas where they have never have been reported in the southern tip of Chile. The presence of paralarvae in these fjords supports the hypothesis of their use as spawning grounds for many species of squid and octopus of different families.