Ontogenetic variations of thermal optimum for growth, and its implication on thermolabile sex determination in blue tilapia

Abstract

Knowledge of how the optimum temperature for growth (T opt ) varies during ontogeny, and how close it is to the temperatures that induce phenotypic masculinization is fundamental to the understanding of the evolution of thermolabile sex determinism (TSD) in fishes. In blue tilapia Oreochromis aureus, T opt is 32·6 C at the start of exogenous feeding (10 mg fish) and it decreases by c. 1 C each time that the fish body mass increases by an order of magnitude. Temperatures <35 C are not sufficient to induce complete phenotypic masculinization. Based on a multiple-regression model (r 2 =0·938) plotting growth against body mass and water temperature, genotypically female tilapia living at high temperatures during the thermosensitive period (21-28 days) and being reversed into phenotypic males would incur an initial growth disadvantage over fish living at T opt , but not over those living at slightly colder temperatures (27-29 C). This initial disadvantage would be later compensated for by faster growth because of between-sex growth dimorphism to the detriment of phenotypic females. These arguments suggest that there is no definite pressure against the selection of TSD in blue tilapia and probably other Oreochromis spp.

Vertical movements of coastal pike (Esox lucius)—On the role of sun basking

“…The body temperature of pike during autumn was lower than water temperature at the reference station. Optimal temperature also varies depending on ontogeny and physiological processes (Baras, Mpo'N'Tcha, Driouch, Prignon, & Mélard, 2002;Gräns, Rosengren, Niklasson, & Axelsson, 2012), that is optimal temperature for growth does not necessarily conform to T opt for immune defence or reproduction. These areas likely cool down faster compared to areas further from the coast where the reference temperature station was located.…”

Interactions between temperature and size on the growth, size heterogeneity, mortality and cannibalism in cultured larvae and juveniles of the Asian catfish, Pangasianodon hypophthalmus (Sauvage)

“…Studies on how T ° opt varies during the early development (embryonic and larval stages) are much scarcer, and several patterns of ontogenetic variation have been documented. A downward shift of T ° opt with increasing fish size was observed in A. minor (Hansen & Falk‐Petersen 2002), the blue tilapia Oreochromis aureus (Steindachner) (Baras et al . 2002) and the pacu Piaractus brachypomus (Cuvier) (Baras & Florès 2006).…”

“…Indirect effects refer to variable productivity and food availability in natural environments with different thermal conditions (Gross, Coleman & McDowall 1988; Limburg, Pace & Arend 1999), to sexual growth dimorphism in sex‐reversed fish (e.g. Pandian & Sheela 1995; Baras, Mpo'N'Tcha, Driouch, Prignon & Mélard 2002), but also to thermal‐dependent behaviours (Milinski 1993), in particular, the aggressiveness or the propensity to establish dominance hierarchies. In culture environments, most indirect effects of temperature are buffered, and the relationships between temperature and fish growth generally have a parabolic shape (Jobling 1994; Elliott & Hurley 2003).…”

Size‐dependent effects of daily thermal fluctuations on the growth and size heterogeneity of Nile tilapia Oreochromis niloticus

“…In general, small fishes prefer (McCauley & Huggins, 1979; Baras & Nindaba, 1999; Hernández et al , 2002) and perform better at warmer temperatures than larger conspecifics (Pedersen & Jobling, 1989; Imsland et al , 1996, 2006). Cichlids are no exception to this general rule [Mozambique tilapia Oreochromis mossambicus Peters, Mironova, 1976; Nile tilapia Oreochromis niloticus (L.), Mélard, 1986; O. aureus , Baras et al , 2002]. The breadth ( i.e.…”

“…the kurtosis) of the growth‐to‐temperature response also varies during ontogeny [ e.g. stone loach Barbatula barbatula (L.), Elliott et al , 1996; O. aureus , Baras et al , 2002]. Hence, the effect of fluctuating temperatures on growth is also expected to vary during the ontogeny of fishes, but evidence for this is lacking.…”