Abstract
Decapod crustaceans, such as those from the Homarus genus, are key benthic representatives supporting very valuable fishing and aquaculture industries. Those commercially caught, such as the European lobster (H. gammarus) can be stored in live facilities for short (few days) to long periods (up to 6 months) before being traded. Conditions in captivity are not standardized, including holding temperatures or feeding regimes. Herein, the physiological condition during long-term starvation (24 weeks) in H. gammarus was assessed at three temperatures (4, 8 and 12°C). Our results indicate that, H. gammarus have the capacity to endure long-term starvation. Principal component analysis (PCA) of measured parameters showed two main components (Eigen value>1). Fasted animals kept at 12°C separated from all others experimental groups due to higher total phenoloxidase (PO) activity in the hemolymph and water content in the muscle, suggesting that keeping H. gammarus un-fed at this higher temperature is physiologically more demanding and detrimental. This was later confirmed by significant changes particularly in this group in histology and lipid class composition of the hepatopancreas. These data call into question the suitability of current accepted in-vivo condition markers (e.g. hemolymph protein concentration) for determining the physiological condition and welfare of decapods such as H. gammarus.
Highlights
Crustacean species such as those of the family Nephropidae experience starvation periods as part of their molt-dependent growth process. The capacity of these and other decapod species to cope with long periods of starvation has been widely reported in the literature (Stewart et al, 1972; Jones and Obst, 2000; Sacristan et al, 2016)
Long periods of starvation do not result in a reduction in body weight, the loss of specific organ mass such as the hepatopancreas (Watts et al, 2014), referred to as the midgut gland, perigastric organ or digestive gland (Cervellione et al, 2017b), can occur
Total hemocyte counts (THCs) for instance have been shown to decrease in H. americanus during starvation (Stewart et al, 1967), which could affect key immune parameters such as phenoloxidase (PO) activity, a response reported to change in other marine invertebrates (Matozzo et al, 2011; Coates et al, 2012), but which has not yet been measured in the Homarus genus
Summary
Crustacean species such as those of the family Nephropidae (the clawed lobsters) experience starvation periods as part of their molt-dependent growth process. The hepatopancreas, and in particular its lipid reserves, play a major role in the long-term survival of decapod crustaceans during starvation This is an observation supported by the high percentage of lipids reported in the hepatopancreas of several species, and by their decrease in starvation studies (Jones and Obst, 2000; Ciaramella et al, 2014; Watts et al, 2014; Sacristan et al, 2016). Total hemocyte counts (THCs) for instance have been shown to decrease in H. americanus during starvation (Stewart et al, 1967), which could affect key immune parameters such as phenoloxidase (PO) activity, a response reported to change in other marine invertebrates (Matozzo et al, 2011; Coates et al, 2012), but which has not yet been measured in the Homarus genus. The recent study of Clark et al (2017) illustrated how these and other diverse analytical techniques can increase the understanding of nutritional status in lobsters
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