Reproductive biology of the endangered percid <i>Zingel asper</i> in captivity: a histological description of the male reproductive cycle

Abstract

Abstract:Abstract: Abstract: Abstract: Abstract: The endemic Rhodanian percid Zingel asper (Linnaeus, 1758), is usually found throughout the Rhône basin, but this fish is now in sharp decline. Understanding its reproductive physiology is important so as to be able to artificially control its reproduction with a view to re-introducing it. This study was carried out on a population obtained by artificial fertilization and bred in external tanks. Fishes were observed from the juvenile stages through to adulthood. Patterns of testicular development were defined from histological observations. Testes of Z. asper were paired, elongated and fusiform dorsocaudal organs. The two lobes of each gonad joined together to form a duct that extended to the urogenital papillae. They showed a lobular structure. The testicular lobules were of the unrestricted spermatogonial type. Up to 10 months-old, most of the males were immature: their testes showed only type A spermatogonia. The appearance of type B spermatogonia in the lobules of a testis indicated the beginning of spermatogenesis in 10 months-old fish. Spermiogenesis occurred 24 months after the fertilization and, in 26 months-old fish, the cyst opened and released spermatozoa into the lumen of lobules. The spermiation belonged to a cystic type. During the third year, histological observations pointed to the same evolution of adult gonads as during the second year. Sexual maturity was reached in captive Z. asper after two years. The spawning occurred in

Spatial and Temporal Changes in Testis Morphology and Sperm Ultrastructure of the Sportfish Sauger (Sander canadensis)

“…Specifically, the zingel (Zingel asper) and Eurasian perch both displayed proliferation and development of sperm cells as early as fall (e.g., October) proceeding the spring breeding season. In contrast to what was seen in walleye (Sander vitreus (Malison et al, 1994)), sauger exhibited a significant proportion of sperm cells in earlier stages of spermatogenesis (i.e., spermatocytes and spermatids) in November (Krol et al, 2006;Chevalier et al, 2011) during this study. Other differences were observed in the testis aside from sperm cell development among seasons as well.…”

Growth variation in the endangered fish Zingel asper: Contribution of substrate quality, hydraulics, prey abundance, and water temperature

“…faster growth at 1 or 1–2 years, larger adult body size (i.e. higher back‐calculated lengths at 3 and 4 years after sexual maturity at 2–3 years; Chevalier, De Conto & Exbrayat, 2011), and longevity of 3–4 years), relative to the Durance (HEN station) and Verdon populations, with overall slow life histories (i.e. slower growth at 1 or 1–2 years, smaller adult body size, and longevity of 4–5 years).…”

“…It is likely that part of the differentiation in growth observed among river catchments can be explained by genetic (i.e. fixed) differences that have accumulated in these populations (Laroche & Durand, 2004) following their geographical isolation over the past century, equivalent to a minimum of 30–50 generations, considering sexual maturity at 2–3 years in this species (Chevalier, De Conto & Exbrayat, 2011).…”

“…From a conservation perspective, the Beaume population of Z. asper appears to be highly vulnerable to extinction as a result of particularly short individual life cycles. The rapid growth rates and low longevities observed in this population, associated with sexual maturity at 2-3 years in Z. asper (Chevalier, De Conto & Exbrayat, 2011), may considerably limit adult reproduction and juvenile recruitment, and reduce resilience to environmental stochasticity. The temperature dependence of growth combined with an emerging trade-off between early growth and longevity may further accelerate individual life cycles, weaken population dynamics and increase the risk of extirpation of the Beaume population in the continuing context of global warming (for an example in lizards, see Bestion et al, 2015).…”

“…Primarily nocturnal, Z. asper has a largely insectivorous diet that changes seasonally from dipteran larvae (Simuliidae and Chironomidae) in autumn and winter to mayfly nymphs (Baetidae and Heptageniidae) and caddisfly larvae (Hydropsychidae) in spring and summer (Cavalli, Pech & Chappaz, 2003; Villsen et al, 2021). Sexual maturity is reached after 2–3 years of development (Chevalier, De Conto & Exbrayat, 2011), and the adult size typically varies from 12 to 20 cm (Labonne & Gaudin, 2005). Zingel asper is Critically Endangered throughout the Rhône catchment, where intensive channel fragmentation, flow regulation, and pollution (Mari, Labonne & Gaudin, 2002) have reduced its native range by up to 80% over the last century (Crivelli, 2006).…”