Recently found accordion worm Pararosa vigarae, a new genus and species of ribbon worms and a comparatively less-known group of invertebrates, has amazed the researchers because of its unique ability to squash up like an accordion to a staggering one-fifth of its normal body length. It was discovered from Ría de Arosa in the Northwest coast of Spain, where it lurks under rocks in the subtidal zone at a depth of 30 metres (98 feet). Combining morphological data with DNA analysis techniques, researchers were able to overcome the taxonomical challenge of identifying this worm.

Classification challenges

According to the study published in Royal Society Open Science, accordion worms belong to the phylum Nemertea, a group of predatory worms that use venom to immobilize their prey. They pose serious challenges for taxonomical studies due to the scarcity of external morphological features.

Taxonomy is the study of the classification and identification of the living world. Traditionally, external morphological features are considered the criteria of this study. However, Nemerteans have very few distinctive visible features to rely on. To overcome this, scientists tried to consider the internal anatomy as a potential marker, but this process turned out to be very complex and inconvenient. Eventually, this process became obsolete, resulting in Nemerteans remaining a lesser-known phylum with currently described 1,350 species.

Genetic Analysis

The study describes that molecular phylogenetic analyses were performed based on partial sequences of 16S rRNA, 18S rRNA, 28S rRNA, cytochrome c oxidase subunit I (COI), and histone H3 gene markers that indicated the newly identified specimens represent a new genus and species of heteronemertean in the family Lineidae.

Imaging experiments revealed that the accordion worm contracts its body to form regular rings that are annular epidermal constrictions that remain visible even when the animal is fully stretched. The number of rings varies with the size of the worm—for instance, the largest specimen collected had 60 rings when fully stretched.