Saprolegniosis in Amphibians: An Integrated Overview of a Fluffy Killer Disease

Abstract

Amphibians constitute the class of vertebrates with the highest proportion of threatened species, with infectious diseases being considered among the greatest causes for their worldwide decline. Aquatic oomycetes, known as “water molds,” are fungus-like microorganisms that are ubiquitous in freshwater ecosystems and are capable of causing disease in a broad range of amphibian hosts. Various species of Achlya sp., Leptolegnia sp., Aphanomyces sp., and mainly, Saprolegnia sp., are responsible for mass die-offs in the early developmental stages of a wide range of amphibian populations through a disease known as saprolegniosis, aka, molding or a “Saprolegnia-like infection.” In this context, the main objective of the present review was to bring together updated information about saprolegniosis in amphibians to integrate existing knowledge, identify current knowledge gaps, and suggest future directions within the saprolegniosis–amphibian research field. Based on the available literature and data, an integrated and critical interpretation of the results is discussed. Furthermore, the occurrence of saprolegniosis in natural and laboratory contexts and the factors that influence both pathogen incidence and host susceptibility are also addressed. The focus of this work was the species Saprolegnia sp., due to its ecological importance on amphibian population dynamics and due to the fact that this is the most reported genera to be associated with saprolegniosis in amphibians. In addition, integrated emerging therapies, and their potential application to treat saprolegniosis in amphibians, were evaluated, and future actions are suggested.

Oomycete Soil Diversity Associated with Betula and Alnus in Forests and Urban Settings in the Nordic–Baltic Region

“…Our findings indicate that, compared to Pythiales, species of Saprolegniales are more dependent on the potentially more temperate climate of Norway and southern Sweden, which are more strongly influenced by the warm Norwegian Current. This hypothesis is supported by evidence that occurrences of Saprolegniosis in amphibians appear to be associated with temperate coastal zones [47]. The precise climatic or other conditions that underlie this association between Saprolegniales diversity and longitude…”

The importance of quantifying fitness-determining traits throughout life to assess the application of reproductive technologies for amphibian species recovery

“…For example, aquatic oomycetes (known as "water molds") can cause the disease saprolegniosis, which is known to infect wild and captive amphibian embryos. Infertile and dead eggs are readily infected with saprolegniosis postmortem (Costa and Lopes, 2022).…”

“…Developing embryos are also known to be susceptible to infection if they have been exposed to trauma (physical or chemical) to the protective egg jelly capsule, or through contact infection between adjacent eggs (Costa and Lopes, 2022). Reducing the risk of infection during embryonic development is another reason that rearing offspring individually from the point of fertilisation is encouraged.…”

The Taxonomic Status of Physalaemus cuqui Lobo, 1993, with the Description of a New Species of Physalaemus (Anura: Leptodactylidae) from Argentina and Paraguay

“…Cacciali and Buongermini (2022: 68–69). [In part, misidentification] Costantini (2022: their Table 1); Costa and Lopes (2022: 15, their Table 1); Ferraro (2022: their Figs. 1, 3–4, their Appendixes S1–S3, S5–S7); Núñez et al (2022: their Table 1); Oliveira et al (2022: their Table 1); Pontes et al (2022: their Table 1); Peluso et al (2022: 14444, 14448); Sandoval et al (2022: 3441–3443, 3450–3452, their Figs.…”