Rainy spring nights bring yellow spotted salamanders (Ambystoma maculatum) out of forested areas where they spend most of their adult lives and down to vernal pools to breed. Like many obligate vernal pool species, spotted salamanders cannot breed in most permanent ponds because fish would eat the salamander eggs and larvae. The fact that vernal pools dry out completely for at least part of the year means they cannot support fish populations and are therefore lack fish predators. 

On these breeding nights, male spotted salamanders deposit spermatophores on leaf debris within the vernal pool. Females will then collect sperm from several spermatophores, fertilizing her eggs internally. Within a few days, the female produces an egg mass, which she attaches to submerged sticks or vegetation near the water’s surface. Often, many salamanders will use the same attachment site, resulting in communal egg mass clusters. 

The entire mass may be mostly clear (like those pictured here) or a cloudy white. Each individual egg mass contains 30 to 250 individual eggs encapsulated by a stiff gelatinous matrix. This gelatinous coating helps prevent the eggs from drying out, but prohibits adequate oxygen exchange required for embryonic development. To overcome this obstacle, spotted salamanders have evolved a symbiotic relationship with a species of alga. Within a few weeks of being laid, the egg masses will become green from the symbiotic alga Oophila amblystomatis. Once the alga has colonized the salamander egg mass, it metabolizes the carbon dioxide produced by the embryos and provides the eggs with oxygen as a product of its own photosynthesis.