Reproductive biology, multiple paternity and polyandry of the bull shark Carcharhinus leucas

Abstract

To improve understanding of bull shark Carcharhinus leucas reproductive biology, we analysed reproductive traits from 118 bull sharks caught along Reunion Island coasts (Western Indian Ocean), including 16 gravid females. Specific microsatellite loci were used to investigate the frequency of multiple paternity. Males and females reached maturity at c. 234 cm and 257 cm total length (LT), respectively, and litter sizes ranged from 5 to 14 embryos. Analysis of the 16 litters collected in various months of the year indicated that parturition occurs between October and December, with a size at birth c. 60–80 cm LT and that the gestation period is probably c. 12 months. Assuming a 1 year resting period and a period of sperm storage (4–5 months) between mating (in June–September) and fertilisation, the reproductive cycle of bull sharks at Reunion Island would be biennial. At least 56.25% of the litters investigated were polyandrous, sired by 2–5 males. Several males that each sired several litters conceived during the same or distinct mating seasons were detected, suggesting both a seasonal aggregation of sharks to mate and some male fidelity to mating site. Altogether, these findings provide valuable information for both shark risk management and conservation of the species in the Western Indian Ocean.

Intra-specific variation in movement and habitat connectivity of a mobile predator revealed by acoustic telemetry and network analyses

“…natal philopatry). Adult females that stay for longer periods at the reef may be those that are not breeding that year, which is consistent with a previous study on C. leucas in the Western Indian Ocean that suggest this species has a 1 year resting period and a 4-5 month sperm storage period between mating and fertilization (Pirog et al 2019a). Although, it is still unclear why some males also return to these locations.…”

Legacy and emerging organic contaminants in two sympatric shark species from Reunion Island (Southwest Indian Ocean): Levels, profiles and maternal transfer

“…0.2 to 2 km from the shore) using bottom setlines and SMART (shark management alert in real-time) drumlines (Guyomard et al 2019) and were dissected less than 36 h after capture. On the basis of demographic parameters for the two species in RUN (Pirog et al, 2019a(Pirog et al, , 2020, the studied specimens included both mature and immature individuals, including one 82 cm female bull shark specimen considered as offspring of that year (referred to as -young-of-the-year‖ later in the text). Our sampling strategy focused on a wide range of morphometrics for the purpose of studying organic contaminant bioaccumulation as a function of individual size.…”

“…Embryo sizes corresponded to embryo ages of ca. 6 months and 10 months for tiger and bull sharks , respectively (Pirog et al, 2019a(Pirog et al, , 2020Whitney and Crow, 2007), i.e. at the third of total gestation time for tiger shark (Pirog et al, 2020) and at the end of gestation for bull shark (Pirog et al, 2019).…”

“…Among OCPs, mirex concentrations were 2.5 times higher in tiger sharks than in bull sharks (tiger shark: 403 ± 431 pg g -1 ww; bull shark: 180 ± 334 pg g -1 ww, p = 0.028), while dieldrin concentrations were 1.5 times higher in tiger sharks than in bull sharks (tiger shark: 36 ± 14 pg g -1 ww; bull shark: 24 ± 14 pg g -1 ww, p = 0.016). As tiger sharks migrate long distances across the Indian Ocean (Pirog et al, 2019a), these differences suggest that certain insecticides, such as mirex and dieldrin, may be subject to different patterns of use on the Indian Ocean scale, despite the fact that these compounds have been banned in most countries. Although mirex has been detected in air and various matrices in the Indian Ocean, no specific source has been clearly identified (Bouwman et al, 2012;Qiu et al, 2020;Srimurali et al, 2015), while dieldrin may still be in use in Kenya (Barasa et al, 2008).…”

In the intimacy of the darkness: Genetic polyandry in deep‐sea luminescent lanternsharks Etmopterus spinax and Etmopterus molleri (Squaliformes, Etmopteridae)

“…Within elasmobranchs, different reproductive modes have been reported, from viviparity to oviparity (Compagno, 1990; Conrath et al ., 2012; Wourms, 1977), and even parthenogenesis in certain captive animals (Chapman et al ., 2007, 2008; Portnoy et al ., 2014; Robinson et al ., 2011). Elasmobranchs also exhibit seasonal monogamous [ e.g ., Sphyrna tiburo (Chapman et al ., 2004), Galeocerdo cuvier (Holmes et al ., 2018)] or polygamous [ e.g ., Negaprion brevirostris (Feldheim et al ., 2001), Carcharhinus leucas (Pirog et al ., 2015, 2019)] mating strategies. Indeed, multiple paternity seems common within elasmobranchs [see Rossouw et al .…”