Developmental changes in oxygen consumption and hypoxia tolerance in the heat and hypoxia‐adapted tabasco line of the Nile tilapia Oreochromis niloticus, with a survey of the metabolic literature for the genus Oreochromis

Abstract

The genus Oreochromis is among the most popular of the tilapiine cichlid tribe for aquaculture.However, their temperature and hypoxia tolerance, if tested at all, is usually tested at temperatures of 20-25 C, rather than at the considerably higher temperatures of 30-35 C typical of tropical aquaculture. We hypothesized that both larvae and adults of the heat and hypoxia-adapted Tabasco-line of the Nile tilapia Oreochromis niloticus would be relatively hypoxia-tolerant. Oxygen consumption rate ( _ MO 2 ), Q 10 and aquatic surface respiration (ASR) was measured using closed respirometry at 2 (c. 0.2 g), 30 (c. 2-5 g), 105 c. (10-15 g) and 240 (c. 250 g) days of development, at 25 C, 30 C and 35 C. _ MO 2 at 30 C was inversely related to body mass: c. 90 μM O 2 g −1 /h in larvae down to c. 1 μM O 2 g −1 /h in young adults. Q 10 for _ MO 2 was typical for fish over the range 25-35 C of 1.5-2.0. ASR was exhibited by 50% of the fish at pO 2 of 15-50 mmHg in a temperature-dependent fashion. However, the largest adults showed notable ASR only when pO 2 fell to below 10 mmHg. Remarkably, p crit for _ MO 2 was 12-17 mmHg at 25-30 C and still only 20-25 mmHg across development at 35 C. These values are among the lowest measuredfor teleost fishes. Noteworthy is that all fish maintain equilibrium, ventilated their gills and showed routine locomotor action for 10-20 min after _ MO 2 ceased at near anoxia and when then returned to oxygenated waters, all fish survived, further indicating a remarkable hypoxic tolerance. Remarkably, data assembled for _ MO 2 from >30 studies showed a > x2000 difference, which we attribute to calculation or conversion errors. Nonetheless, p crit was very low for allOreochromis sp. and lowest in the heat and hypoxia-adapted Tabasco line. K E Y W O R D Shypoxia tolerance, _ MO 2 , Oreochromis, oxygen consumption, Tabasco-line tilapiadevelopment

Ecological adaptations of Amazonian fishes acquired during evolution under environmental variations in dissolved oxygen: A review of responses to hypoxia in fishes, featuring the hypoxia‐tolerantAstronotusspp.

“…Despite several authors using the PO 2 crit as an indicator of hypoxia tolerance in fish (Burggren et al, 2019; Chabot et al, 2016; Claireaux & Chabot, 2016; Regan et al, 2019; Rogers et al, 2016), this hypoxia tolerance indicator has recently been criticized on several grounds. One of the criticisms is because the PO 2 crit values are extremely variable for both hypoxia‐sensitive and hypoxia‐tolerant species (Wood, 2018).…”

Contrasting strategies of hypoxic cardiac performance and metabolism in cichlids and armoured catfish

“…These habitats are often eutrophic and diurnal where chronic hypoxia is common. It is not surprising therefore, that hypoxia and even anoxia tolerance has been documented in a number of cichlid species, allowing them to exploit ecological niches less favorable to hypoxia‐sensitive fish (e.g., Burgreen et al, 2018; Muusze et al, 1998). Cichlids survive severe hypoxia by substantially decreasing their metabolic demand while increasing anaerobic metabolism to maintain energy balance (Table ).…”

“…Nile tilapia ( O. niloticus ) maintained Ṁ O2 down to ≈10% AS but at 6.4% AS, Ṁ O2 declined to just 6.5% of the normoxic rate. Following cessation of measureable Ṁ O2 near anoxia, fish continued to show routine locomotor activity for 10–20 min (Burgreen et al, 2018). In oscar ( Astronotus ocellatus ) Ṁ O2 dropped to 14% of the normoxic rate at 7% AS (Scott et al, 2008) and this species can survive up to 4 h of complete anoxia at 28°C (Muusze et al, 1998).…”

Mortality rate of newly hatched larvae of Nile tilapia (Oreochromis niloticus) submitted to different photoperiods

“…This is because it generates an excellent source of animal protein and because it creates job opportunities and revenues (ROCHA; RODRIGUES, 2015). This industry not only supplies protein-rich foods to a large and growing market but also indirectly reduces the pressure on the least sustainable fish populations from a production standpoint (BURGGREN et al, 2019).…”

“…Initially, in Brazil, Tilapia rendalli was introduced, which was later replaced by Nile tilapia (Oreochromis niloticus) which showed greater weight gain and growth in addition to good meat quality (DRUZIAN et al, 2012). Tilapia are tolerant to heat, thus farming is especially successful in hot climates, with Nile tilapia usually grown in open ponds or hydrographic basins at temperatures of 30 to 35°C (BURGGREN et al, 2019).…”