Nematostella vectensis

Kingdom: Animalia

Phylum: Cnidaria

Class: Anthozoa

Order: Actinaria

Family: Edwardsiidae

Genus: Nematostella

Species: N. vectensis

Below are pictures of Nematostella vectensis (starlet sea anemone) eggs and planula. The life cycle of N. vectensis is egg-->gastrula-->planula-->primary polyp-->adult polyp. They are in the same phylum as jellies and the same class as corals. All these creatures have a polyp phase but, like corals, anemones don't have a medusa phase which is that classic jelly fish image.  

These egg pictures show the fertilized eggs encased in jelly. The sperm penetrates the jelly and it remains until the planula larvae break out of it about 36-48 hours after fertilization (Uhlinger, 1997). The cell masses surrounding the eggs are 'nematosomes' which are made up of nematocytes and flagellated cells (Uhlinger, 1997). These eggs were fertilized 4/18/13 at 13:30 and the photos were taken a few hours later.

Below is a video of a planula that was fertilized on 4/16/13 at 15:00 and was taken on 4/23/13. This looks like a 'late' planula, the Oral-Aboral (OA) axis is elongated. The aboral pole is the end where we see the long apical tuft (lines coming off the planula to the left in the video). The opposite end is the oral pole. The aboral pole is where the apical tuft is and is where the anemone polyp will attach to a substrate and the oral pole is where the tentacles will form around the mouth. Also note the cilia pulsating all around the planula.

1. Uhlinger, Kevin R.(1997). Sexual Reproduction and Early Development in the Estuarine Sea Anemone, Nematostella vectensis Stephenson, 1935. UC San Diego: California Sea Grant College Program. Retrieved from: http://www.escholarship.org/uc/item/6cq8h6f3

-Monica Erviti