Can Probiotics Affect Reproductive Processes of Aquatic Animals? - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 333

KiSS peptides in zebrafish, medaka and European sea bass (Kitahashi et al. 2008; Felip et al.
2009), but it seems that the KiSS2 gene was lost in placental mammals. A close association
between the GnRH neurons and the kisspeptin fibres present in the median eminence of pri-
mates, as well as of fish, has been discovered in the last few years (Parhar et al. 2004; Shahab
et al. 2005).
In addition, the identification of the adipose hormone leptin, which signals the magnitude of
energy stores to the hypothalamic centres governing reproduction (Goumenou etal. 2003), rep-
resented an important step towards understanding the mechanisms controlling this interplay.
Leptin, at the central nervous system level, induces reproduction by activating kisspeptin neu-
ropeptide production. Leptin produced by adipose tissue also acts at the pituitary and gonadal
levels. In the pituitary, receptors for leptin have been found and a stimulatory action on FSH
and LH production has been described (Zieba et al. 2005). Concomitantly, leptin may also act
at the gonadal level, controlling the gonadal steroidogenesis process (Moschos et al. 2002).
12.5 THE EFFECTS OF PROBIOTIC APPLICATIONS ON FISH
REPRODUCTION
Despite the exponential growth in the interest in, and use of, probiotics in the fish farming
industry, studies concerning their effects on reproduction are scarce. However, a number of
recent studies have reported the beneficial effects of a dietary probiotic supplementation on
the reproductive performances of freshwater species: guppy ( Poecilia reticulate , Ghosh et al.
2007), Mexican molly ( Poecilia sphenops , Ghosh et al. 2007), green swordtail ( Xiphopho-
rus helleri , Ghosh et al. 2007; Abasali and Mohamad 2011), southern platyfish ( Xiphophorus
maculates , Ghosh et al. 2007; Abasali and Mohamad 2011) and zebrafish (Gioacchini et al.
2010a; 2010b; 2010c; 2011; 2012; Giorgini et al. 2010). However, such effects have only been
investigated in one marine species, the killifish ( Fundulus heteroclitus , Lombardo et al. 2011).
Lipid, protein, fatty acids, vitamins and carotenoids contained in the broodstock diet may
influence various reproduction processes such as fecundity, fertilization, hatching and larval
development (Izquierdo etal. 2001). At the same time, hormones, antibiotics, nutrient mixtures
and herbal products usually used as nutrient supplements for broodstock fish might potentially
affect microbial abundance and/or activity in the intestinal tract of the breeders (Nayak 2010;
Wong and Rawls 2012; Sullam et al . 2012; Chapter 4 ). Therefore probiotics could restore and
fortify microbial balance and may be used to repair these reproductive deficiencies by increas-
ing the availability of minerals, and vitamins and producing important digestive enzymes or
metabolites (Holzapfel et al. 1998).
Although the current volume of literature available is limited, the results obtained are so
far are encouraging, clearly demonstrating positive effects of probiotic administration on the
endocrine and paracrine control of the reproductive processes of female broodstock.
12.5.1 Effect of probiotics on the reproduction of poeciliid
livebearing ornamental fish species
Livebearing ornamental fish are amongst the most popular fish with fish hobbyists, because
they are brightly coloured, accept a diverse range of food and breed prolifically to produce live
free-swimming offspring.