 |
| Pectinereis strickrotti Villalobos-Guerrero, Huč, Tilic, Hiley & Rouse, 2024 |
Abstract
Nereidid polychaetes are well known from shallow marine habitats, but their diversity in the deep sea is poorly known. Here we describe an unusual new nereidid species found at methane seeps off the Pacific coast of Costa Rica. Specimens of Pectinereis strickrotti gen. nov., sp. nov. had been observed dating back to 2009 swimming just above the seafloor at ~1,000 m depth but were not successfully captured until 2018. Male epitokes were collected as well as a fragment of an infaunal female found in a pushcore sample. The specimens were all confirmed as the same species based on mitochondrial COI. Phylogenetic analyses, including one based on available whole mitochondrial genomes for nereidids, revealed no close relative, allowing for the placement of the new species in its own genus within the subfamily Nereidinae. This was supported by the unusual non-reproductive and epitokous morphology, including parapodial cirrostyles as pectinate gills, hooked aciculae, elfin-shoe-shaped ventral cirrophores, and elongate, fusiform dorsal ligules emerging sub-medially to enlarged cirrophores. Additionally, the gill-bearing subfamily Dendronereidinae, generally regarded as a junior synonym of Gymnonereidinae, is reviewed and it is here reinstated and as a monogeneric taxon.
 |
| Pectinereis strickrotti gen. nov., sp. nov. male anatomy. A, B, D-F. Paratype (SIO-BIC A9889), epitokous male: A, whole body of living specimen in dorsal view; B, anterior region of living specimen in dorsal view; D, prostomium of preserved specimen in frontal view; E, posterior end of preserved specimen in dorsal view; F, post-natatory chaetigers and pygidium of preserved specimen in dorsolateral view. C. Holotype (SIO-BIC A9836), epitokous male: anterior region of preserved specimen in dorsal view. Scale bars: A, ~20 mm; B, ~5 mm; C, 5 mm; D, 1 mm; E, 3 mm; F, 0.5 mm. Credits: A, B, Ekin Tilic; C, Tulio Villalobos; D-F, Greg Rouse. |
 |
| Pectinereis strickrotti gen. nov., sp. nov. in life. A, B, D. Several epitokous males swimming near methane seeps of Mound 12 (~1,000 m depth) of the Costa Rica margin and videoed via the submersible DSV Alvin. A. A frame grab from a video taken on Alvin dive 4503 on Feb. 4, 2009. B and D. Frame grabs from video taken on Alvin dive 4987 on Nov. 2, 2018. C. A fragment of an atokous infaunal female was collected at the same depth and locality via sediment pushcore on Alvin dive 4984 on Oct. 30, 2018. A white egg ~350 μm in diameter is visible on the exterior. Scalebar 1 mm. E. An epitokous male swimming near methane seeps of Parrita Scar (~1,000 m depth) of the Costa Rica margin. The specimen was initially caught via slurp with the ROV SuBastian (dive S0218, Jan. 11, 2019) but escaped. Images A, B, D, courtesy of Woods Hole Oceanographic Institute. E, courtesy of Schmidt Ocean Institute. |
Family NEREIDIDAE de Blainville, 1818
Subfamily NEREIDINAE de Blainville, 1818
Pectinereis Villalobos-Guerrero, Huč, Tilic, Hiley & Rouse gen. nov.
Diagnosis: Prostomial anterior region entire. Esophageal caeca absent. Anterior parapodial cirrostyles as comb-like gills. Dorsal cirrostyles attached sub-distally and dorsal ligule attached sub-medially to expanded cirrophores. Notopodial prechaetal, neuropodial postchaetal and inferior lobes present. First two chaetigers without notoacicula. Neuropodial spinigers and falcigers very long, homogomph. Epitoke males divided into four body regions, with distally-bilamellated dorsal cirrophore, elfin-shoe shaped ventral cirrophore, pre-pygidial hooked aciculae, and ensiform spinigers.
Etymology: This genus is named by combining the Latin word pectinis (= ‘comb’) with the name of the type genus of the family, Nereis. The name emphasizes the pectinate (i.e., comb-like) parapodial cirrostyles (gills) in the first anterior chaetigers formed by digitiform filaments. The gender is feminine, as the stem genus-group name.
Pectinereis strickrotti Villalobos-Guerrero, Huč, Tilic, Hiley & Rouse sp. nov.
Etymology: The species is named in honor of Bruce Strickrott, Group Manager and lead submersible pilot of the DSV Alvin (Woods Hole Oceanographic Institution), who chased these worms for many years before finally skillfully succeeding in their capture.
Tulio F. Villalobos-Guerrero, Sonja Huč, Ekin Tilic, Avery S. Hiley and Greg W. Rouse. 2024. A remarkable New deep-sea nereidid (Annelida: Nereididae) with gills. PLoS ONE. 19(3): e0297961. DOI: 10.1371/journal.pone.0297961
