Reproduction and development of two angel sharks, Squatina squatina and S. oculata (Pisces: Squatinidae), off Tunisian coasts: semi‐delayed vitellogenesis, lack of egg capsules, and lecithotrophy

Abstract

Distribution, sexual maturity, fecundity, genital asymmetry, cyclic vitellogenesis and gestation are described in the angel sharks Squatina squatina (L., 1758) and S. oculata Bonaparte, I840 from Tunisian waters. With embryonic nutrition being purely lecithotrophic, lack of egg capsules, block of oocyte growth at the beginning of gestation, and inability to ovulate soon after parturition, Squatinidae can be compared to Torpedinidae and to Centroscymnus (Squalidae), except that their vitellogenesis starts again at mid-gestation. This new, special feature has been termed ' semi-delayed vitellogenesis ' with regard to the delayed vitellogenesis of Torpedinidae and Cen rroscymn us.

Maturity, reproductive cycle, and fecundity of spiny butterfly ray, Gymnura altavela (Elasmobranchii: Rajiformes: Gymnuridae), from the coast of Syria (eastern Mediterranean)

“…However, we totally agree with Daiber and Booth (1960) who noted that two such periods of reproduction or a prolonged period of reproductive activity for the species is still an open question, even if we tend to prefer the latter hypothesis, following our observations. Capapé et al (1992) noted that until mid-gestation the vitellogenic activity is blocked and then started again and continued after parturition, considering that it was a case of semi-delayed vitellogenesis similar to those previously described for squatinid species (Capapé et al 1990). In the studied sample vitellogenesis occurred throughout the year in pregnant females proceeding simultaneously with gestation.…”

Sexual development and maturity scale for the angel shark Squatina squatina (Elasmobranchii: Squatinidae), with comments on the adequacy of general maturity scales

“…In cases where more details of clasper development are required, length is a more accurate parameter because it can be clearly defined and measured (Segura et al 2013). Additionally, Capapé et al (1990Capapé et al ( , 2002 used clasper length to separate juvenile, subadult and mature phases. Segura et al (2013) validated that the estimation of the breakpoints and slopes in the total length to clasper length relationship based on a segmented regression model (Muggeo 2003) can discriminate among these phases for S. guggenheim, among others, regardless of the life history strategy or the habitat of the species.…”

“…Despite concerns regarding the conservation status of this species, limited information is available about its life history parameters. For example, the only study on the reproductive biology of S. squatina was by Capapé et al (1990) along the Tunisian coast.…”

“…Additionally, the maturity assessment criteria have not been consistent among the different studies of the genus. Most works considered a juvenile, subadult and mature phase in males and females based on the length and calcification of the clasper and on the condition of the ovaries, oviduct and oviducal gland, following Capapé et al (1990) (Bridge et al 1998, Capapé et al 2002, 2005, Co lonello et al 2007). Other research only included a mature and an immature phase following the former criteria (Awruch et al 2008) or with the distinction of an actively reproducing stage based on the condition of the epididymides and ova and uteri (Shelmerdine & Cliff 2006), as well as sperm smears (Natanson & Cailliet 1986).…”

“…The angel shark Squatina squatina, which has a lecithotrophic viviparous reproduction mode (Budker 1958, Capapé et al 1990, is a bottom-dwelling species of the European and North African continental shelves (Ebert & Stehmann 2013). Because of its life history characteristics and bycatch in fisheries with steadily increasing effort and capacity, its abundance has dramatically declined during the past 50 yr (Morey et al 2006).…”