Dutch Christmas card
Best wishes for the season from The Netherlands
From Henk Mooijman
At the eve of a New Year, a New Century, even a New Millennium, a train of thought is going through my mind. At that Eve, I am thinking on the many unique, peaceful moments and events, when I was in the opportunity of scuba diving in the Eastern Schelde. All this is flowing through my mind; at the same time with the difficulty making a choice for that special moment which affected me the most. As a picture many times is the best way to share such a wonderful moment, I like to express my Best Wishes in the form of my last piece of work in this Century, with the birth of a new under-water life cycle.
Psammechinus milians during the reproduction phase
The Echinoidea (sea urchins) belong to 1 of the 5 major classes of the echinoderms. The Echinoidea consist of 2 subclasses, 14 orders and 40 families. There are regular and irregular forms. The regular form of the sea urchins prefer a hard rocky bottom, on which they find their food. They don’t have a special preference for their food, they consume what is available, botanical as well as animal. They occur in all climatic regions, and from the littoral zone, where they are abundant, till the edge of the continental plate with the depth of 200 m. Also some other forms occur and prefer depths of 1000–4000 m. The record is for the family Pourtalesia which is found at a depth of 7200 m. The outer difference between the sex is very difficult to establish. Reproduction takes place when the male emits his sperm, which result in the fact that the female emit their yolk-poor eggs with a diameter of 0.19–0.22 mm. The free-swimming eggs then can be fertilised. During the development phase the larva is swimming like a ciliate near the water surface, while it is feeding itself with microscopical plankton. It develops in 4–6 weeks to a sea urchin of less than 1 mm. He or she grows in one year till a diameter of 20 mm and becomes ready for reproduction. The average life cycle is 6–8 years with a dimension of approximately 39 mm.
Macrofoto op duikiocatie Levensstrijd Zienkzee (Oosterschelde) Diepte 6.2 m, water temp. 17°C, luchttemp. 20°C.
Equipement: Semi Drysuit, Eon, Camera type: zoeker. Merk: Sea & Sea type MM2 met macrolens 1:2. Flitser: Y550.
Foto en tekst door H.Th.J. Mooijman L.v.M en Member of the Q.M.C.
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