Good Golly Miss Amazon Molly!

The Amazon molly (Poecilia formosa) is a species of fish found only in the Tuxpan River, the Rio Grande, and the Nueces River in northern Mexico and the southern United States. Within these rivers, P. formosa typically prefers slower moving streams and ditches with plenty of vegetation, and are usually found in freshwater systems.

Amazon mollies are rather small and plain. The body is teardrop-shaped, and adults only grow up to 10 cm (3 in) long. They are mainly silver in color, although they may have rows of small, light brown spots running down their sides. In addition, some individuals may have black spots along their dorsal and tail fins.

Like most other mollies, the Amazon molly is an omnivore. They may feed on algae, seaweed, insects, and mosquito larvae. In turn, they themselves can be prey for larger aquatic insects like giant water bugs, other fishes, alligators, frogs, egrets and herons, and racoons. To avoid predators, P. formosa tends to stay in groups where it is less easy to be singled out.

Perhaps the most interesting feature of the Amazon molly are its reproductive habits. This species is entirely female, and reproduces via a process called gynogenesis. First, females are courted by males from other molly species such as P. latipinna, P. mexicana, P. latipunctata, or P. sphenops. Mating triggers the release of eggs, but the male's sperm is destroyed before it can fertilize them. Instead, the male gets the advantage of increased attractiveness to females of their own species, as these females are more likely to mate with males that have already mated with P. formosa.

After mating, the female broods her eggs for 30-40 days. She then gives live birth to anywhere from 60 to 100 fry, which are all clones of their mother. These young recieve no further parental care, but are fairly independent and are fully capable of reproduction after about 1-6 months, depending on the temperature of the water; warmer waters increase the rate of maturity. Individuals can live anywhere from 1-3 years in the wild.

Conservation status: the IUCN considers the Amazon molly to be Least Concern. However, one of the species that are used to trigger reproduction, the broadspotted molly (Poecilia latipunctata) is Critically Endangered. Primary threats to the Amazon molly include habitat degradation or loss due to construction and damming.

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Photos

Dr. Manfred Schartl

Uncharismatic Fact of the Day

Sometimes, girls will be boys! Female blue-tailed damselflies come in three different colorations, or 'morphs'. Two of these morphs are distinctly female but one, the androchromes strongly resembles male blue-tailed damselflies. Females with this coloring are much less likely to be harassed by males and have more time to allow their eggs to mature before laying.

(Image: A mating pair of blue-tailed damselflies (Ischnura elegans) by Erik Svensson)

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Slip on the Common Slipper Limpet

The common slipper limpet, also known as the boat shell or the fornicating slipper snail (Crepidula fornicata) is a species of sea snail native to the North American coast of the Atlantic Ocean. In addition, it has been introduced to the eastern coasts of Europe and parts of the Pacific Northwest and Japan. They can reside in a variety of habitats including bays, estuaries, island shores, and rocky intertidal zones; their maximum depth tolerance is 70m (229 ft).

Fornicating slipper snails are noted for their unique mating methods. Adults typically live stacked on top of each other, with up to 12 to 14 individuals in a group. The largest, and oldest adults are at the bottom of the stack, while the younger, smaller adults are at the top. C. fornicata is a sequential hermaphrodite; new adults are all male, and will change into females as they get older or if they become the oldest in a stack of all males.

Breeding can occur between Februrary and October, although the peak season is in May or June. Unlike other marine mollusks, which are broadcast spawners, the common slipper limpet utilizes internal fertilization. The male closest to the female at the bottom extends his penis under her shell and fertilize up to 11000 eggs. These eggs hatch after about 3-4 weeks, and the planktonic larvae are released into the water. These larvae take 4-5 weeks to develop into juveniles, at which point they settle either on bare rock or on top of an established limpet chain. If it settles in isolation, the young adult immediately changes into a female; if it settles on a chain, it remains a male. Adults can live on these chains for up to 6 years.

Adult boat shells are rather small, ranging in length from 20–50 mm (0.7-1.9 in). The shell is distinctly arched, with a flat underside that gives it a slipper-like appearance. The shell can be white, pink, or yellow with red or brown streaks; older adults are often covered in algal growth.

Conservation status: The common slipper limpet has not been evaluated by the IUCN. Although they are commonly harvested for food, populations are considered stable. Outside its native range, this species is considered invasive and harmful to other limpet snails.

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Photos

Dr Keith Hiscock

Sytske Dijksen