Dragons of the Deep Sea: Kinorhyncha Communities in a Pockmark Field at Mozambique Channel, With the Description of Three New Species

Abstract

Cold seep areas are extremely reduced habitats with spatiotemporal variation of hydrocarbon-rich fluid seepage, low oxygen levels, and great habitat heterogeneity. Cold seeps can create circular to ellipsoid shallow depressions on the seafloor called pockmarks. We investigated two selected pockmarks, characterized by different gas emission, and two sites outside these geological structures at the Mozambique Channel to understand whether and how their environmental conditions affect the kinorhynch fauna in terms of density, richness, and community composition. A total of 11 species have been found living in the studied area, of which three are new species: Fissuroderes cthulhu sp. nov., Fujuriphyes dagon sp. nov., and Fujuriphyes hydra sp. nov. Densities outside the pockmarks are low and regularly decrease from the upper sediment layers, whereas inside the pockmarks, density reaches its highest value at layer 1-2 cm, strongly decreasing along the vertical profile from this depth. Areas under pockmark influence and locations outside pockmarks are similar in terms of species richness, but kinorhynchs showed a significant remarkable higher density at the pockmark sites. Additionally, species composition changes between habitats (inside and outside pockmarks) and between the two sampled pockmarks, with most of the species restricted to one of the studied habitats, except for Condyloderes sp. and Echinoderes unispinosus present both outside and inside the pockmarks. Echinoderes hviidarum, E. unispinosus, and Fi. cthulhu sp. nov., present at sites with gas emission, do not only survive under the specific pockmark conditions (characterized by hydrogen sulfide toxicity, methane high concentration, and low availability of dissolved oxygen) but even profit from a habitat with a likely lower competition for space and resources, flourishing and enhancing the density, most likely through the replacement with specialized species. Contrarily, species that only appear outside the pockmarks do not seem to cope with the presence of hydrogen sulfide and methane. Therefore, environmental factors linked to gas emissions have a major role driving the kinorhynch community composition.

Adult moulting and dimorphism in a new species of Sphenoderes (Kinorhyncha: Kentrorhagata)—Is the exception becoming the rule?

“…For a very long time since the original description, no additional material of S. indicus has been available for examination, but very recently a single specimen identified as Sphenoderes cf. S. indicus was actually reported from Madagascar (Cepeda et al, 2020). This specimen was re-examined for the present study, but the examinations not only confirmed the likely identity as S. indicus, but also showed that the spine morphology of the Madagascar specimen followed the characteristics of stage-2 adults.…”

“…The material was either stored in the collection of the Natural History Museum of Denmark (LM slides with NHMD-catalogue numbers) or in the personal reference collection of the first author (mostly specimens mounted for SEM). Examined material included: For Sphenoderes aspidochelone Sørensen & Landers, 2018: Holotype, four paratypes and one non-type, mounted for LM (NHMD-115833 to 115838) and seven non-types mounted for SEM; for Sphenoderes indicus Higgins, 1969: single non-type specimen, mounted for LM (NHMD-672774), see Cepeda et al (2020) for collecting details; the type material of S. indicus is no longer suitable for examination (see Sørensen, Rho et al, 2010) and was therefore not accessed; for Sphenoderes poseidon Sørensen, Rho et al, 2010: Holotype mounted for LM (NHMD-099618) and three nontypes mounted for SEM.…”

“…Higgins (1969) positively confirms that cuticular hairs are present on segment 1 in S. indicus, but without proving any details about the hair morphology. The Madagascan specimen that is tentatively identified as S. indicus (see Cepeda et al, 2020) clearly shows bamboo leaf-shaped hairs on segment 1, which suggests that such hairs are actually present in this species.…”

Description, redescription and revision of sixteen putatively closely related species of Echinoderes (Kinorhyncha: Cyclorhagida), with the proposition of a new species group – the Echinoderes dujardinii group

“…cthulhu Cepeda et al, 2020. Also, these species showed female papillae, on the sternal plates of segment 7 in F. cthulhu (see Cepeda et al 2020), and on segments 7 and 8 in F. sorenseni (although note that Herranz & Pardos 2013 refer to the papillae as "glandular cell outlets type 2 restricted to females"). Hence, female papillae are present in all species of Fissuroderes.…”

Kinorhynchs from sandy coastal habitats in Turkey, with the description of a new pan- Mediterranean species of Echinoderes (Cyclorhagida: Echinoderidae)

“…and E. charlotteae obviously leaves us with the question whether they should be considered conspecific. For many years species of Echinoderes were all considered to show rather regional and limited distribution patterns, but recent studies have indicated that at least deep-sea species could have much wider, even cross-oceanic, distributions (Sørensen et al, 2018, Yamasaki et al, 2018b, Cepeda et al, 2020, Grzelak et al 2021). However, we still find conspecifity of Echinoderes sp.…”