Parasites of fish larvae: do they follow metabolic energetic laws?

Abstract

Eumetazoan parasites in fish larvae normally exhibit large body sizes relative to their hosts. This observation raises a question about the potential effects that parasites might have on small fish. We indirectly evaluated this question using energetic metabolic laws based on body volume and the parasite densities. We compared the biovolume as well as the numeric and volumetric densities of parasites over the host body volume of larval and juvenile-adult fish and the average of these parasitological descriptors for castrator parasites and the parasites found in the fish studied here. We collected 5266 fish larvae using nearshore zooplankton sampling and 1556 juveniles and adult fish from intertidal rocky pools in central Chile. We considered only the parasitized hosts: 482 fish larvae and 629 juvenile-adult fish. We obtained 31 fish species; 14 species were in both plankton and intertidal zones. Fish larvae exhibited a significantly smaller biovolume but larger numeric and volumetric densities of parasites than juvenile-adult fish. Therefore, fish larvae showed a large proportion of parasite biovolume per unit of body host (cm(3)). However, the general scaling of parasitological descriptors and host body volume were similar between larvae and juvenile-adult fish. The ratio between the biovolume of parasites and the host body volume in fish larvae was similar to the proportion observed in castrator parasites. Furthermore, the ratios were different from those of juvenile-adult fish, which suggests that the presence of parasites implies a high energetic cost for fish larvae that would diminish the fitness of these small hosts.

Modelling seasonal patterns of larval fish parasitism in two northern nearshore areas in the Humboldt Current System

“…While Punta Coloso is an open coastal area with an ocean bottom that mainly comprises sand, gravel, and mud as well as patches of L. trabeculata kelp 24 , in addition to the presence of an upwelling plume and a cyclonic eddy in front of the bay 21 ; conditions that promote the offshore transport of planktonic organisms, decreasing the probability of host-parasite encounters. Parasites in fish larvae could have detrimental impacts on the nutritional and immune response as well as mechanic effects can be caused by parasites via their own body weight 11 . All of these levels could affect the larval growth prior to settlement in fish species 7 .…”

Parasitic copepods affect morphospace and diet of larvae of a temperate reef fish

“…Parasites may cause even major effects on fish larvae, because they are in their early stages of physiological and immunological development (Grutter et al ., ), ectoparasites can induce a reduction of recent growth of fish larvae, as it has been inferred by otolith microstructure analysis (Palacios‐Fuentes et al ., ). From an energetic perspective, presence of parasites in fish larvae implies a high cost that would diminish the fitness of these small hosts by three, non‐exclusive, levels: detrimental nutritional effects induced by parasites; the immune response of the hosts and; mechanic effects caused by parasites via their own body weight (Muñoz et al ., ). All of these levels may cause size‐dependent mortality prior to settlement in fish species showing a bipartite life history (Grutter et al ., ).…”

“…: +56-322507865; email: mauricio.landaeta@uv.cl otolith microstructure analysis (Palacios-Fuentes et al, 2012). From an energetic perspective, presence of parasites in fish larvae implies a high cost that would diminish the fitness of these small hosts by three, non-exclusive, levels: detrimental nutritional effects induced by parasites; the immune response of the hosts and; mechanic effects caused by parasites via their own body weight (Muñoz et al, 2015a). All of these levels may cause size-dependent mortality prior to settlement in fish species showing a bipartite life history (Grutter et al, 2017).…”

Parasitism of Brook Trout (Salvelinus fontinalis) during the first month post-emergence in streams in southwest Nova Scotia

“…Metazoan parasites reported in these studies include directly transmitted monogenean and arthropod ectoparasites as well as food-borne digeneans, cestodes and nematodes, some (or closely related species) of which are known to cause mortalities in host fish held in captivity or at fish farms (Schäperclaus 1991, Woo 1995, Hoffman 1999. In a review of the impact of parasites on young, small-bodied fish, Muñoz et al (2015) concluded that there are three general, not mutually exclusive, impacts: 1) alteration of nutritional budgets; 2) energetic cost of tissue repair and immunological response to invasion; and 3) mechanical disruption and overall reduction in physiological efficiency on such fundamental issues as swimming performance.…”

“…It is known that by the end of the first summer of life, the young cohort of brook trout are exposed to most species of parasites present in older fish in the same streams (Muzzall 2008). We do not know exactly, however, when fry first start acquiring these parasites after they leave the protection of the redd and whether impacts identified by Muñoz et al (2015) contribute to the period of high fry mortality.…”