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When the light is shining through the collar, it is possible to make out the individual egg capsules within it. Sand collars are the characteristic egg masses of one family of sea snails, the moon snails, marine gastropod mollusks in the family Naticidae. These egg masses are often found washed up either whole, or sometimes in fragments, on ...
Naticidae, common name moon snails or necklace shells, is a family of medium to large-sized predatory sea snails, marine gastropod molluscs in the clade Littorinimorpha. The shells of the species in this family are mostly globular in shape.
The sand collar egg mass of Euspira catena. The rounded shell is thin and polished and brownish-yellow, with a row of reddish markings just below the suture of the last whorl. It can grow to about 3 cm (1 in) and has a short spire and seven rounded whorls separated with distinct sutures. The lowest whorl occupies about 90% of the volume.
The gonopore acts as an opening through which eggs are deposited. The opening leads into the mantle tubule, in which eggs flow from the oviduct and ovary. The mantle tubule produces three things, yolk; carries most of the nutrients needed to develop a healthy offspring, egg capsule formation, and sperm reception and storage; where fertilization ...
The yolk sac is an ancient structure. It is found in fish and probably the last common ancestor of vertebrates. The fish structure was innovated upon by the amniotes (reptiles, birds, and later mammals), which evolved bigger yolks and tougher eggs for life on land. The placental mammalian yolk sac is a further elaboration of the amniote ...
Male genitalia of Lepidoptera. The main component of the male reproductive system is the testicle, suspended in the body cavity by tracheae and the fat body.The more primitive apterygote insects have a single testis, and in some lepidopterans the two maturing testes are secondarily fused into one structure during the later stages of larval development, although the ducts leading from them ...
Researchers in the UK and the US have taken human eggs in their most early stage and developed them to maturity in a lab for the first time. It's a big achievement that could open up new avenues ...
The human allantois is a caudal out-pouching of the yolk sac, which becomes surrounded by the mesodermal connecting stalk or body-stalk. The vasculature of the body-stalk develops into umbilical arteries that carry deoxygenated blood to the placenta . [ 12 ]