Fusarium species isolated from post-hatchling loggerhead sea turtles (Caretta caretta) in South Africa

Abstract

Species in the Fusarium solani species complex are fast growing, environmental saprophytic fungi. Members of this genus are filamentous fungi with a wide geographical distribution. Fusarium keratoplasticum and F. falciforme have previously been isolated from sea turtle nests and have been associated with high egg mortality rates. Skin lesions were observed in a number of stranded, post-hatchling loggerhead sea turtles (Caretta caretta) in a rehabilitation facility in South Africa. Fungal hyphae were observed in epidermal scrapes of affected turtles and were isolated. The aim of this study was to characterise the Fusarium species that were isolated from these post-hatchling loggerhead sea turtles (Caretta caretta) that washed up on beaches along the South African coastline. Three gene regions were amplified and sequenced, namely the internal transcribed spacer region (ITS), a part of the nuclear large subunit (LSU), and part of the translation elongation factor 1 α (tef1) gene region. Molecular characteristics of strains isolated during this study showed high similarity with Fusarium isolates, which have previously been associated with high egg mortality rates in loggerhead sea turtles. This is the first record of F. keratoplasticum, F. falciforme and F. crassum isolated from stranded post-hatchling loggerhead sea turtles in South Africa.

Figure 1

Map showing the South African coastline, indicating nesting sites and sites where post-hatchling sea turtles were found along the coastline between Mossel Bay and False Bay.

Figure 2

Maximum likelihood analysis of Fusarium species isolates based on three loci, translation elongation factor 1 α (tef1), large subunit (LSU) and internal transcribed standard (ITS). Numbers within the tree represent the bootstrap values of 1 000 replicates, followed by the posterior probability (italics). Strains isolated during this study are marked with a red asterisk (*).

Figure 3

Maximum likelihood analysis of Fusarium species isolates from other marine animals based on two loci, large subunit (LSU) and internal transcribed standard (ITS). Numbers within the tree represent the bootstrap values of 1 000 replicates, followed by the posterior probability (italics). Strains isolated during this study are marked with a red asterisk (*).

Figure 4

Fusarium crassum, (a) Colony on PDA and (b) reverse side after 7 days incubation at 26 ± 1 °C. (c) areal mycelia presenting microconidia in false heads in situ, (d) Chlamydospores with rough walls in situ, (e–g) macroconidia, (h) microconidia with one septa, (i) macroconidia in situ on carnation leaf agar after 21 days incubation at 26 ± 1 °C, (j–k) hyphal coils observed in situ on carnation leaf agar. All scale bars = 20 µm.