File S3. Concatenated 18S+28S sequences used for the maximum-likelihood analysis, reduced to 2440 positions (1–1458 for 18S; 1459–2440 for 28S) by removing alignment-ambiguous sites with Gblocks under “relaxed” parameters. from Flatworm cocoons in the abyss: same plan under pressure

• Main Authors: Keiichi Kakui, Aoi Tsuyuki
• Format: Dataset
• Language: unknown
• Published: 2024
• Subjects: Animal systematics and taxonomy; Plant and fungus systematics and taxonomy; Evolutionary biology not elsewhere classified; Plant cell and molecular biology; Animal cell and molecular biology; deep sea; early development; egg capsule; Japan; ontogeny; platyhelminthes; Pacific; Kamchatka
• Online Access: https://doi.org/10.6084/m9.figshare.24982564.v1; https://figshare.com/articles/dataset/File_S3_Concatenated_18S_28S_sequences_used_for_the_maximum-likelihood_analysis_reduced_to_2440_positions_1_1458_for_18S_1459_2440_for_28S_by_removing_alignment-ambiguous_sites_with_Gblocks_under_relaxed_parameters_from_Flatworm_cocoons_in_/24982564

While knowledge of early ontogeny in abyssal animals is highly limited in general, it was completely lacking for abyssal, free-living platyhelminths. We discovered flatworm egg capsules (or ‘cocoons') on rocks collected at depths of 6176–6200 m on the abyssal slope of the Kuril-Kamchatka Trench, northwestern Pacific. The egg capsules were black and spherical, around 3 mm in diameter, and contained three to seven individuals ( n = 4) at the same developmental stage, either the spherical (putative early embryo) or vermiform (putative late embryo) stages. A molecular phylogenetic analysis based on 18S and 28S rRNA sequences revealed that the flatworms belong in suborder Maricola in Tricladida and suggested that they may have colonized from shallow to deep waters. This study provides the deepest record for free-living flatworms and the first information on their early life stages in the abyssal zone, which were very similar to those in shallow-water forms. This similarity in development between the relatively benign shallow-water and the extreme abyssal environments suggests that triclads adapting to the latter faced primarily physiological and/or ecological adaptive challenges rather than developmental ones.