Temperature Preference and Sex Differentiation in African Catfish, Clarias gariepinus

Abstract

The African catfish Clarias gariepinus has a genetic sex determination system in which high temperature induces masculinization. The thermosensitive period for sex differentiation is short and occurs very early (from 6 to 8 days posthatching [dph]). As young juveniles can encounter high masculinizing temperature (36.5°C) in African water points, we aimed to determine the thermal preference of sexually undifferentiated juveniles and investigate if they spontaneously move toward high masculinizing temperature. Experiments were carried out in an environmental continuum (28-28-28°C and 28-32-36.5°C) made up of three 50-L aquariums connected together. Four hundred larvae from 10 different full-sib progenies were reared successively from 2 to 14 dph in these facilities. Before and after thermal treatments, fish were reared at 28°C until sex ratio determination at 70 dph. In the control continuum, fish were nearly equally distributed in the three compartments. Conversely, in the thermal continuum, compartment occupation significantly differed with progeny and period. During the highly thermosensitive period, two of five progenies significantly preferred (54.7% and 39.8% occupation) the 36.5°C compartment. All tested progenies reared in thermal continuum and separated 36.5°C aquarium showed a skewed sex ratio toward the male phenotype (78-100%). Nevertheless, no correlation was found between 36.5°C compartment occupation and sex ratio in thermal continuum groups. As masculinization temperature could be encountered in African water points during the spawning season, we discussed the adaptive advantage for the African catfish to display a sex differentiation process controlled by a temperature effect.

Temperature preference of Nile tilapia (Oreochromis niloticus) juveniles induces spontaneous sex reversal

“…niloticus ) 40 hours after transfer into a multichamber device (control at 26.50 ±0.33°C) with a homogeneous distribution occurring throughout the chambers. A previous study using African catfish ( Clarias gariepinus ) in the same device (step temperature gradient continuum with 3 compartments) similarly showed that undifferentiated juveniles spread nearly evenly across the control continuum during the 12 days of the experiment [29]. Other studies conducted on adult zebrafish ( Danio rerio ) also reported an almost random distribution among chambers [30,31].…”

“…niloticus juveniles would spontaneously move to high, potentially masculinizing temperatures, inducing sex reversal. The thermal preference of species exhibiting a GSD + TE sex determining system during the thermosensitive period for sex determination has only been studied in African catfish ( Clarias gariepinus ) [22]. These authors showed that undifferentiated juveniles migrated to high temperatures during the critical period of sex determination (6 to 8 days post hatching), inducing skewed sex ratios toward males (from 78 to 93%).…”

Aspects of reproductive indices and enteroparasitic infestation of Clarias gariepinus (Burchell, 1822) in a tropical reservoir

“…Santi et al (2016) demonstrated that C. gariepinus displayed thermo sensitivity in the sex differentiation process, with a masculizing effect at high temperature, with a sex ratio skewed towards the male phenotype. Santi et al (2017) also reported that C. gariepinus has a genetic sex determination system in which high temperature induces masculinization. The temperature values during the period of study were 27.37 ± 0.03°C in the first year and 27.36 ± 0.03°C in the second year, with no significant difference in the means of the two years (P = 0.083) (Ajala and Fawole, 2016a).…”

Sex-ratio, early sex steroid profiles and cyp19a1b, dmrt1 and foxl2 gene expressions upon high temperature treatment of undifferentiated African catfish juveniles (Clarias gariepinus)

“…Equally important, the highly thermosensitive period is short and extends from 6 to 8 dph, long before the appearance of the first histological signs of sex differentiation at 25 dph. When applied during this period, high temperature frequently masculinized progenies up to 80-100% (Santi et al, 2017(Santi et al, , 2016. We focused the present study on the period before (0 hpf) until shortly after (14 dpf) the highly thermosensitive period, because in African catfish, some progenies were not thermosensitive after 14 dph (Santi et al, 2016).…”