Thermal tolerance of paralarvae of Patagonian red octopusEnteroctopus megalocyathus

Abstract

Patagonian red octopus, Enteroctopus megalocyathus, is a merobenthic octopus whose paralarvae have been successfully cultured up to juvenile octopuses. At present, high mortality during the paralarval period prevents the scaling from experimental rearing to commercial aquaculture. The aim of the study was to determine upper (CTMax) and lower (CTMin) thermal tolerance, acclimation response ratio (ARR) and thermal tolerance polygon of paralarvae from different culture conditions and subjected to seven acclimation temperatures (6, 8, 10, 12, 14, 16, 18°C) during the first 5 days of paralarval life. Culture conditions were two types of egg incubation (maternal care and artificial incubators) and two feeding regimes (fed or starved). Fed paralarvae showed thermal preferendum, while unfed paralarvae preferred much higher temperatures than those of acclimation. CTMin and CTMax increased along with the acclimation temperature. Lower values of ARR were obtained in paralarvae from artificial incubation, with this type of paralarva showing the least adaptability to thermal changes. Starved paralarvae showed the lowest values for thermal tolerance range (TTR) and smaller areas of thermal polygon than fed paralarvae. Rearing temperatures above 16°C may be considered suboptimal to paralarvae and affected by the conditions during the embryonic incubation.Rearing temperatures below 8°C may be considered suboptimal for all hatched paralarvae. Therefore, the other temperatures within this range could be used in the context of improving the culture management of paralarvae.

Characterization of cannibalism in early paralarvae of Patagonian red octopus, Enteroctopus megalocyathus (Gould, 1852), grown in a controlled environment

“…In the current work, cannibalism in paralarvae with high prey availability 5 mm in size can be reduced. Besides, the current work showed higher values of cannibalism than reported by Uriarte et al (2013) for E. megalocyathus and similar values to that reported for R. fontaniana by Miranda et al (2011). The difference with the first and similarity with the latter study could because of the small volume of experimental bioassay used in the current work, 1 L against 20 L for Uriarte et al (2013) and 0.5 L for Miranda et al (2011).…”

Assessment of culture density and prey availability for the management of cannibalism in paralarvae of Patagonian red octopus Enteroctopus megalocyathus

“…In other octopus species such as R. fontaniana, cannibalism in paralarvae starts at 7 DAH (Miranda et al, 2011). The management of prey availability can delay the onset of cannibalism, but Artemia is not a balanced food for octopus paralarvae (Uriarte et al, 2018), making the prey quality improvement a priority to avoid cannibalism. Thus, further research is important in the area of E. megalocyathus paralarvae nutrition, including the possibility of using other prey items or formulated feeds.…”

“…The paralarval stage lasts between 90 to 114 days (Uriarte & Farías, 2014), after an embryonic development of 135 to 172 days, depending on the temperature (Uriarte et al, 2014, 2016). Immediately after hatching, the paralarvae are conspicuous predators of Artemia and exhibit an optimal temperature between 11 and 12°C (Uriarte et al, 2018).…”

“…In general, the low survival in the paralarval culture of octopus has been attributed to nutritional deficiencies of the provided preys (Iglesias & Fuentes, 2014). Nutritional quality can be overcome through the selection of wild living foods, or by the Artemia enrichments providing supplementation of essential fatty acids or vitamins (Hernández et al, 2019; Navarro et al, 2014; Roo et al, 2017; Uriarte et al, 2018). In addition, the standardization of prey density and feeding dose, as well as paralarval density, are relevant aspects of the culture system, and should be considered to improve the survival and growth of these planktonic organisms (Iglesias et al, 2007).…”

“…2016). Immediately after hatching, the paralarvae are conspicuous predators of Artemia and exhibit an optimal temperature between 11 and 12°C (Uriarte et al, 2018).…”