In an unusual instance of a female that mated moments prior to her death and subsequently turned to stone, scientists have made an intimate discovery. A fossilized creature that resembles a shrimp was found with fossilized sperm in her reproductive system. The artifact is approximately 16 million years old and comes from the early Miocene epoch.
Lead scientist, Renate Matzke-Karasz, says that this fossil is an example of “ancient sex with gargantuan sperm.” In an e-mail from her post at Ludwig-Maximilian-University in Germany, she goes on to say that she and her team are still excited by the finding of evidence of recent copulation in an ancient time.
Technically, the female specimen is an ostracod, an ancient mussel shrimp. With mussel-like hinged shells, today they thrive in wet locales, such as the ocean and even in mosses. These creatures subsist on water-borne detritus. The fossils were found in a cave in Australia and this cave was home to a large colony of bats perhaps millions of years ago. The inevitable build up of bat guano provided the chemicals required to preserve the finer details of the ostracod’s anatomy.
With about 8,000 species, Ostracoda are one of the most successful groups of crustaceans. Also known as the seed shrimp, their body consists primarily of a large head. Though they are bivalves, they do have tiny appendages and they range in size from smaller than a poppy seed to as large as a meatball.
Four fossilized females were discovered, all containing sperm from recent copulation and the fossilized sperm is some of the oldest ever found. There was also one fossilized male mussel shrimp. When placed under a microscope, the researchers were quite surprised to discover that the fossilized creature’s sperm looked just like its modern counterpart.
Among several unusual sexual features, the modern mussel shrimp, though a small creature, has “giant sperm.” Whatever purpose is served by having sperm four times larger than the animal it comes from, science has yet to figure it out. Some moths and flies also produce the so-called “giant sperm.” Additional intriguing sexual mussel shrimp factoids are that some of the species have three genders, including females that do not copulate with males and that some of these mussel shrimp have two sets of organs for reproducing which can perform parallel to each other.
Appearing in this week’s edition of Proceedings of the Royal Society B: Biological Sciences, a new study demonstrates that the male ostracod could have been spreading giant sperm for over 140 million years. David Horne, a micropaleontologist from Queen Mary University of London, called the fossils amazing and said that the discovery that these creatures have been reproducing using giant sperm for millions of years adds interesting information to the currently unsolved mysteries of why and how.
George Poinar at Oregon State University says that packets of fossilized insect sperm have been discovered in chunks of amber from as far back as the Early Cretaceous period. Other amber pieces, as old as 130 million years, have been found with insects actually mating inside. Fossilized turtles have also been discovered, appearing to be in the act of copulation.
by Stacy Lamy