Abstract
The phylum Annelida exhibits high morphological diversity coupled with its extensive ecological diversity, and the process of its evolution has been an attractive research subject for many researchers. Its representatives are also extensively studied in fields of ecology and developmental biology and important in many other biology related disciplines. The study of biomineralisation is one of them. Some annelid groups are well known to form calcified tubes but other forms of biomineralisation are also known. Herein, we report a new interstitial annelid species with black spicules, Thoracophelia minuta sp. nov., from Yoichi, Hokkaido, Japan. Spicules are minute calcium carbonate inclusions found across the body and in this new species, numerous black rod-like inclusions of calcium-rich composition are distributed in the coelomic cavity. The new species can be distinguished from other known species of the genus by these conspicuous spicules, shape of branchiae and body formula. Further, the new species’ body size is apparently smaller than its congeners. Based on our molecular phylogenetic analysis using 18S and 28S sequences, we discuss the evolutionary significance of the new species’ spicules and also the species' progenetic origin.
Highlights
Annelida is one of the most ecologically and morphologically diverse group of animals known from both marine and terrestrial environments
For its body divided into three regions and absence of lateral eyes[13], the species is designated to the genus Thoracophelia and we describe this species as Thoracophelia minuta sp. nov
It is important to note that the high S peak may be due to the simultaneous emission of sulphur during biomineralization since this species lives in the sand interstices, which suggests that it is susceptible to a reductive condition
Summary
Annelida is one of the most ecologically and morphologically diverse group of animals known from both marine and terrestrial environments. Like many other animal p hyla[2,3,4,5,6], annelids are known to produce biominerals[2]. Groups such as Serpulidae, Sabellidae, and Cirratulidae, forming calcium encrusted tubes[7,8,9], are commonly encountered in the marine environment. The biominerals were reported by Belova & Zhadan (2011) in several species of the genus Ophelia with rod-like inclusions that are produced by cells floating in the coelom. We investigated the mineral composition of the rod-like inclusions. This is the first report of biomineralization in Thoracophelia. We investigated the evolutionary significance of these two topics
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
