Worms in the water

"Nationalnyckeln" is a multi-volume work in Swedish originally intended to cover all species of living organisms found in Sweden and its adjacent territorial waters. This goal proved too ambitious (mostly due to extremely high production costs for each volume and a surprisingly stingy Swedish government), but the publisher occasionally still ads new volumes to the work. 

This one was published in 2018 and its full title is "Nationalnyckeln till Sveriges flora och fauna. Ringmaskar: Havsborstmaskar. Annelida: Polychaeta: Aciculata". Yes, it´s about worms! 

Aciculata (sometimes Errantia) is a subclass of Polychaeta (bristle worms) which in turn is a class within the phylum Annelida (ringed worms). The most well known annelids are the earthworms and leeches, but there are also thousands of marine species, many of them within Polychaeta. This volume covers 205 species of aciculate bristle worms found in Swedish waters. Somewhat surprisingly, most are illustrated in color, some even with color photos! The English summary has been dropped, but the keys are still bilingual. There is also a general introduction to the annelids. 

Although I can´t say I´m *that* interested in bristle worms, I admit that the species diversity is stunning. Some species are predators, others are "herbivores" (or whatever you call bristle worms which don´t munch on other animals), still others are parasites. These are small and not elongated. Many species in this group are virtually unknown, so the species presentations are sometimes pretty short. And since worms aren´t particularly aesthetically pleasing, I don´t think this is a good collector´s item! That being said, probably indispensable if you are a Swedish nerd with a strange interest in ocean-dwelling invertebrates...