From Egg to Embryo to Juvenile to Adult...

     The life cycle of Photeros annecohenae includes five juvenile instars The life cycle of an ostracod in the genus Vargula (now Photeros); Used with permission from Jim Morin, separated by molts (that occur via the process of ecdysis) as well as an
adult instar that is followed by a final molt. Females become receptive after this terminal molt (Morin 1986). Sexual dimorphism begins to become apparent in the size and shape of the fifth instar and is even more pronounced in the final adult stage. Each juvenile instar lasts ten-27 days; therefore, it takes about three months for the juvenile to fully develop (Gerrish 2009). Photeros annecohenae grows by determinate growth, meaning it reaches a conclusive size.

A sequence of photos showing the gestation of a female Photeros annecohenae; Used with permission from Gretchen Gerrish

     Eggs are located inside the body of the ostracod and, when fertilized, are moved out into the brood pouch in the carapace. Females have multiple broods The life cycle of Photeros annecohenae; Used with permission from Gretchen Gerrishand give birth following a 26 +/- 1.6 day incubation period in which their embryos develop (Gerrish 2009). This is evidence that females put in more parental investment than males (a factor in sexual selection). Two to three days into development the embryos appear cloudy. Faint, pigmented eye spots begin to develop by day 15 which leads to fully-formed compound eyes by day 18 (Gerrish and Morin 2008). The light organ is also apparent by this time. On average, a female deposits 13 offspring per brood. After brood deposition, a female normally takes 7.84 +/- 1.05 days to mate again (Gerrish and Morin 2008).
    
     Females are capable of producing more than one brood without This photo shows the morphological differences between a female with a brood, a female without a brood and a male; Used with permission from Jim Morin remating. This indicates that they must be able to store sperm, which further increases the sex ratio toward males (Gerrish Personal Communication).

     Photeros annecohenae demonstrate a long lifespan for crustaceans of their size (potentially nine and a half months) (Cohen and Morin 1990). This may be due to the fact that there is little known pressure from predators to mature quickly because this species resides in the benthos. Since the organism is more protected from predators by residing at the bottom in the ocean in the grassbeds instead of in the open sea, they do not need to adapt to protect themselves from predators as rapidly. Photeros annecohenae develop slowly, taking three months to become a mature adult. Speed of development and size of final adult form are thought to be related to water temperature, salinity and habitat (Cohen and Morin 1990).

The life span of Photeros annecohenae, showing juvinilie stages and the adult stage; Used with permission from Gretchen Gerrish The life span of Photeros annecohenae, showing juvinilie stages and the adult stage; Used with permission from Gretchen Gerrish

In order to grow and develop into healthy adults, ostracods must be properly nourished. To learn more about this, investigate the Nutrition page!

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