New observations on the rare physonect Melophysa melo (Siphonophora; Agalmatidae) from the northern Gulf of Mexico.

The rare short-stemmed physonect Melophysa melo typically lives above the thermocline in warm waters of the world's oceans. In the past this species has been described from fragmented or distorted material, with the last two accounts being published in 1931 and 1954. A new description is given herein with pertinent figures based on nine samples recently collected in the Gulf of Mexico (GoM), including the first detailed illustrations of mature nectophores, and of a well-developed corm.

The magnitude of global marine species diversity.

Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered.

Results: There are ∼226,000 eukaryotic marine species described.