Ostracods are small, bivalve crustaceans that can inhabit underwater caves. The ostracod genus Spelaeoecia is know only from marine caves and occurs in Bermuda, the Bahamas, Cuba, Jamaica and Yucatan (Mexico).
FOR THE AGES Single-celled foraminifera helped to create the materials used in some of the world’s great monuments, and are also very valuable in telling Earth’s history because they produce shells that make good fossils.
Spirula is the only genus of squid with an internal shell, a relic of their ammonoid ancestors. When spirula die their fragile shells float to the surface and are collected on the beaches as "rams' horn shells." This one is encrusted with barnacles.
Coloured scanning electron micrograph (SEM) of a passion flower (Passiflora caerulea) pollen grain. Pollen grains are the male gametes (sex cells) of a plant. Magnification: when printed 10 centimetres wide.
Diatoms are microscopic algae composed of separate halves, with delicate siliceous cell walls. They're usually single-celled organisms, though some live colonially. They inhabit fresh and salt waters and are among the most abundant of all phytoplankton.