Colonial Entoproct Epibiotic on a Sea Spider

Area of Science:

• Marine Biology
• Invertebrate Zoology
• Molecular Phylogenetics

Background:

• Epibiosis, the interaction where one organism lives on another, is common in marine environments.
• Sea spiders (Pycnogonida) host various epibionts, but entoprocts are rarely reported.
• Entoprocts are small, colonial invertebrates with unique lophophores.

Purpose of the Study:

• To identify and characterize an entoproct found living on a sea spider.
• To determine the phylogenetic relationships of the epibiotic entoproct using molecular data.

Main Methods:

• Morphological examination of the entoproct and host sea spider (Nymphon sp.).
• DNA extraction and sequencing of partial 18S and 28S ribosomal RNA (rRNA) genes from the entoproct.
• Phylogenetic analysis using maximum likelihood based on 18S rRNA gene sequences.

Main Results:

• An epibiotic entoproct, identified as Barentsia sp. (Barentsiidae), was discovered on a Nymphon sp. sea spider.
• The colonial entoproct possessed three zooids, with the largest measuring approximately 0.7 mm and featuring eight tentacles.
• Phylogenetic analysis placed the epibiotic Barentsia sp. as the sister taxon to Barentsia gracilis in an 18S rRNA-based tree.

Conclusions:

• This study documents a novel host-epibiont relationship between a Barentsia entoproct and a Nymphon sea spider.
• Morphological and molecular data confirm the identification of the entoproct and provide insights into its evolutionary placement.
• The findings contribute to our understanding of epibiotic diversity within marine invertebrate communities.