First record of second‐generation facultative parthenogenesis in a vertebrate species, the whitespotted bambooshark Chiloscyllium plagiosum

Abstract

In this study, two parthenogenetic events within a family of the whitespotted bambooshark Chiloscyllium plagiosum are reported. A captive female produced multiple parthenogens. Unexpectedly, a single specimen of a total of nine parthenogens displayed external claspers characterizing the male sex in chondrichthyans. Upon dissection, internal sexual organs of this specimen were malformed or absent; however, the presence of claspers in this study challenges the as yet assumed sex determination system in this shark species. Even more remarkable was that one of the female parthenogens reproduced asexually again producing viable offspring. As far as is known, this is the first genetically confirmed evidence for second-generation facultative parthenogenesis in vertebrates. These results support the evolutionary significance of parthenogenesis as an alternative to sexual reproduction.

Mixed‐sex offspring produced via cryptic parthenogenesis in a lizard

“…Genetic screening based on microsatellite markers and SNPs derived from ddRAD sequencing, which accuracy was validated by the Sanger sequencing technique, in combination with the mating history of our individuals, proved that facultative parthenogenesis is common in the studied species, being observed in 29 females (Data S1). Altogether, we recorded 194 offspring produced via facultative parthenogenesis (Data S1), which is more than the number of all documented individuals produced via facultative parthenogenesis across all other vertebrates (Booth et al, 2014;Straube et al 2016;Allen, Sanders, & Thomson, 2018). Even the much more accessible mechanism of obligatory parthenogenesis in reptiles-previously assumed not to involve meiosis based on genetic data-had to be reclassified after direct cytological examination (Lutes, Neaves, Baumann, Wiegraebe, & Baumann, 2010), and it is still poorly known in most obligatory parthenogenetic reptiles and can be lineage-specific (Spangenberg, Arakelyan, & Cioffi, 2020).…”

Switch from sexual to parthenogenetic reproduction in a zebra shark

“…Other elasmobranch and snake species have also demonstrated parthenogenetic reproduction in multiple individuals as well as across successive years in captivity369161722. Furthermore, the viability of a vertebrate parthenogenetic offspring has recently been demonstrated in a bamboo shark with a second generation offspring also being produced through parthenogenesis23.…”

Multiple births by a captive swellshark Cephaloscyllium ventriosum via facultative parthenogenesis

“…the offspring had half of the amount of DNA as its parthenogen. The other exception is a putative male C. plagiosum produced via parthenogenesis (Straube et al ., ). The authors speculate that sex determination in the Orectolobiformes may not be a simple XX–XY system as has been proposed for carcharhiniforms (Maddock & Schwartz, ).…”

“…Facultative parthenogenesis has been described in six other captive elasmobranch species: bonnethead shark Sphyrna tiburo (L. 1758) (Chapman et al ., ), blacktip shark Carcharhinus limbatus (Müller & Henle 1839) (Chapman et al ., ), C . plagiosum (Feldheim et al ., ; Straube et al ., ), S . fasciatum (Robinson et al ., ), T .…”

“…This group of five C. ventriosum is the first documented case of offspring born via parthenogenesis in a temperate species of elasmobranch. Facultative parthenogenesis has been described in six other captive elasmobranch species: bonnethead shark Sphyrna tiburo (L. 1758) (Chapman et al, 2007), blacktip shark Carcharhinus limbatus (Müller & Henle 1839) (Chapman et al, 2008), C. plagiosum (Feldheim et al, 2010;Straube et al, 2016), S. fasciatum (Robinson et al, 2011), T. obesus (Portnoy et al, 2014) and A. narinari (Harmon et al, 2015). Additionally, the smalltooth sawfish Pristis pectinata Latham 1794 has recently been reported to do so in the wild (Fields et al, 2015).…”