Spinther bohnorum Tilic & Rouse sp. nov.

Spinther n. sp.: Andrade et al. (2015): fig. 1 E, tables 1, 2.

Spinther sp.: Tilic et al. (2022): fig. S 2.

Materials

Type status: Holotype. Occurrence: catalogNumber: A 2846; recordedBy: K. White; individualCount: 1; sex: female; lifeStage: adult; occurrenceStatus: present; preparations: fixative: formalin 8 %; preservative: ethanol 50 %; disposition: in collection; previousIdentifications: Spinther sp.; occurrenceID: CE88DCFA-8FEF-5D1B-9FF9-3D51F42F3DCC; Taxon: scientificName: Spinther bohnorum Tilic & Rouse; kingdom: Animalia; phylum: Annelida; class: Polychaeta; family: Spintheridae; genus: Spinther; specificEpithet: bohnorum; taxonRank: species; scientificNameAuthorship: Tilic & Rouse; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: Oceania; waterBody: South Pacific Ocean; islandGroup: Society Islands; island: Mo'orea; country: French Polynesia; countryCode: FP; locality: between Opunohu Bay and Cook's Bay; verbatimDepth: 10-15 m; minimumDepthInMeters: 10; maximumDepthInMeters: 15; verbatimCoordinates: 17.4768°S, 149.8316°W; verbatimLatitude: 17.4768°S; verbatimLongitude: 149.8316°W; decimalLatitude: - 17.4768; decimalLongitude: - 149.8316; Identification: identifiedBy: Greg Rouse; Event: eventDate: 14-11 - 2010; year: 2010; month: 11; day: 14; verbatimEventDate: 11 / 14 / 2010; Record Level: institutionID: http://biocol.org/urn:lsid:biocol.org:col:14844; collectionID: http://grbio.org/cool/t8vy-919z; institutionCode: SIO; collectionCode: BIC; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: catalogNumber: SMF 32994; recordedBy: K. White; individualCount: 1; lifeStage: juvenile?; occurrenceStatus: present; preparations: fixative: formalin 8 %; preservative: ethanol 50 %; disposition: in collection; otherCatalogNumbers: SIO: BIC: A 18597; previousIdentifications: Spinther sp.; occurrenceID: ADD7BF30-2295-5EAA-A693-60F159B03765; Taxon: scientificName: Spinther bohnorum Tilic & Rouse; kingdom: Animalia; phylum: Annelida; class: Polychaeta; family: Spintheridae; genus: Spinther; specificEpithet: bohnorum; taxonRank: species; scientificNameAuthorship: Tilic & Rouse; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: Oceania; waterBody: South Pacific Ocean; islandGroup: Society Islands; island: Mo'orea; country: French Polynesia; countryCode: FP; locality: between Opunohu Bay and Cook's Bay; verbatimDepth: 10-15 m; minimumDepthInMeters: 10; maximumDepthInMeters: 15; verbatimCoordinates: 17.4768°S, 149.8316°W; verbatimLatitude: 17.4768°S; verbatimLongitude: 149.8316°W; decimalLatitude: - 17.4768; decimalLongitude: - 149.8316; Identification: identifiedBy: Greg Rouse; Event: eventDate: 14-11 - 2010; year: 2010; month: 11; day: 14; verbatimEventDate: 11 / 14 / 2010; Record Level: institutionID: http://biocol.org/urn:lsid:biocol.org:col:34838; institutionCode: SMF; basisOfRecord: PreservedSpecimen

Type status: Other material. Occurrence: catalogNumber: —; recordedBy: K. White; individualCount: 1; lifeStage: adult; occurrenceStatus: present; preparations: fixative: RNAlater; disposition: used up; previousIdentifications: Spinther sp.; associatedSequences: https://www.ncbi.nlm.nih.gov/sra/SRR2005641, https://www.ncbi.nlm.nih.gov/nuccore/PV053298; occurrenceID: E1001A2A-E6ED-5124-8821-EA1AA88EEEA4; Taxon: scientificName: Spinther bohnorum Tilic & Rouse; kingdom: Animalia; phylum: Annelida; class: Polychaeta; family: Spintheridae; genus: Spinther; specificEpithet: bohnorum; taxonRank: species; scientificNameAuthorship: Tilic & Rouse; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: Oceania; waterBody: South Pacific Ocean; islandGroup: Society Islands; island: Mo'orea; country: French Polynesia; countryCode: FP; locality: between Opunohu Bay and Cook's Bay; verbatimDepth: 10-15 m; minimumDepthInMeters: 10; maximumDepthInMeters: 15; verbatimCoordinates: 17.4768°S, 149.8316°W; verbatimLatitude: 17.4768°S; verbatimLongitude: 149.8316°W; decimalLatitude: - 17.4768; decimalLongitude: - 149.8316; Identification: identifiedBy: Greg Rouse; Event: eventDate: 14-11 - 2010; year: 2010; month: 11; day: 14; verbatimEventDate: 11 / 14 / 2010; Record Level: institutionID: http://biocol.org/urn:lsid:biocol.org:col:14844; collectionID: http://grbio.org/cool/t8vy-919z; institutionCode: SIO; collectionCode: BIC; basisOfRecord: PreservedSpecimen

Type status: Other material. Occurrence: catalogNumber: 1430143; recordedBy: K. White; S. El-Tourky,; individualCount: 1; occurrenceStatus: present; preparations: fixative: Ethanol; disposition: used up; previousIdentifications: Spinther sp.; associatedSequences: https://www.ncbi.nlm.nih.gov/nuccore/PV054334; occurrenceID: 1B25BF80-5028-5638-8626-CBCF147EB326; Taxon: scientificName: Spinther bohnorum Tilic & Rouse; kingdom: Animalia; phylum: Annelida; class: Polychaeta; family: Spintheridae; genus: Spinther; specificEpithet: bohnorum; taxonRank: species; scientificNameAuthorship: Tilic & Rouse; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: Oceania; waterBody: South Pacific Ocean; islandGroup: Society Islands; island: Mo'orea; country: French Polynesia; countryCode: FP; locality: Society Islands, Moorea, In front of Hilton; verbatimDepth: 15-17 m; minimumDepthInMeters: 15; maximumDepthInMeters: 17; verbatimCoordinates: -17.4756, -149.842; verbatimLatitude: - 17.4756; verbatimLongitude: - 149.842; decimalLatitude: - 17.4756; decimalLongitude: - 149.842; Identification: identifiedBy: Christopher Meyer; Event: eventDate: 05-12 - 2009; year: 2009; month: 12; day: 5; verbatimEventDate: 5 Dec 2009; fieldNotes: BIZ- 230; Record Level: institutionID: http://biocol.org/urn:lsid:biocol.org:col:34871; institutionCode: USNM; basisOfRecord: DNAExtraction

Description

Holotype adult female with nine chaetigers, body 0.95 mm long, 0.63 mm wide at the widest point (excluding parapodia and chaetae). Paratype, possibly juvenile, with seven chaetigers (Fig. 3 E). Body dorsoventrally flattened, oval. Live animals bright orange / red speckled with small white spots dorsally (Fig. 3 A). Preserved specimens in alcohol white, with faint white spots visible on delicate fan-like notopodial lamellae (Fig. 3 C). Notopodial fans covering the dorsum, except for the anteroposterior mid-line.

Eyespots not visible. Prostomium small, spherical lobe situated dorsally between notopodial fans of chaetiger 2 (Fig. 3 A). Mouth ventral, located posterior to chaetiger 1. Proboscis protruded, long (0.84 mm), with a mid-ventral groove and ventrally folded tip (Fig. 4 A). Notopodia dorsally radiating, with thin, delicate lamellae between notochaetae (Fig. 3 A, Fig. 4 A). Most notochaetae bifid, with only a few entire ones irregularly distributed amongst them (Fig. 4 G), all similar in thickness, distal parts of bifid notochaetae spread (Fig. 4 C). Neuropodia cylindrical with slightly enlarged tips, without parapodial extensions (Fig. 4 D). A single, compound neuropodial hook projects distally from each neuropodium. Neuropodial hooks strongly curved, with a prominent lateral tooth (Fig. 4 F); 3-4 distally pointed aciculae embedded in neuropodia (Fig. 4 D). Pygidium with two elliptical pygidial cirri (Fig. 4 A).

Spherical oocytes (diameter ± 30 µm) visible through the body wall and attached to neuropodia (Fig. 3 D, Fig. 4 D, E).

Type material

Holotype (SIO BIC A 2846) and one paratype (SMF 32994). Both specimens were collected between Opunohu Bay and Cook’s Bay, Mo'orea, Society Islands, French Polynesia, at depths of 10–15 m on 14 November 2010. The holotype is a female adult; the paratype is likely a juvenile.

Material examined

Holotype (SIO BIC A 2846), paratype (SMF 32994) and two additional specimens:

one specimen collected at the same type locality on 14 November 2010 (unregistered, adult); one specimen collected in front of the Hilton, Mo'orea, Society Islands, French Polynesia (17.4756°S, 149.842°W), at 15–17 m depth on 5 December 2009 (USNM 1430143; associated with DNA extraction).

Type locality

South Pacific Ocean, Society Islands, French Polynesia, between Opunohu Bay and Cook’s Bay, Mo'orea (17.4768°S, 149.8316°W), at depths of 10– 15 m.

Diagnosis

Small species (ca. 1 mm) with bright red-orange colouration and white speckles dorsally. Ventral surface generally smooth. Neuropodia lacking parapodial extensions, with neurochaetae as falcate compound hooks bearing a marked lateral tooth. Notochaetae comprising both entire and bifid forms, with bifid chaetae having spread distal ends.

Etymology

Spinther bohnorum sp. nov. is named after Brenda and Jeffrey Bohn and their family in appreciation of their steadfast support for marine invertebrate taxonomy and biodiversity research.

Distribution

Known only from Mo'orea, French Polynesia.

Taxon discussion

Spinther is a small and easily recognised group of polychaetes, comprising only 12 accepted species reported worldwide, though half have been named from the North Pacific (Table 2). While the taxonomic history of Spinther is not extensive, it has been notably convoluted. Similarly, its phylogenetic affinities and placement within the annelid tree of life have long been a subject of debate (Rouse et al. 2022). Despite advances in molecular approaches, the placement of Spinther within the annelid tree of life remains unresolved. Andrade et al. (2015) included the transcriptome of Spinther bohnorum sp. nov. in their phylogenomic study, but their results were inconclusive, likely due to long-branch effects (see also Tilic et al. (2022)). Spinther is a monotypic genus, classified as Aciculata incertae sedis with uncertain affinities (Rouse et al. 2022), rendering the family name Spintheridae redundant.

Most Spinther species live on the surface of sponges, clinging to their hosts using their hooked neurochaetae. Their bright colouration often matches the sponge, providing camouflage. Whether Spinther is parasitic or a highly adapted commensal remains unclear. In the case of Spinther bohnorum sp. nov., it is also likely to associate with red sponges, given its colouration. However, this species was not collected directly on a sponge, but rather found in washings of coral rubble, suggesting a possible association yet to be confirmed.

Johnston (1845) introduced the name Spinther oniscoides Johnston, 1845 for specimens from Ireland. A few years later, Sars (1851), unaware of Johnston’s work, described Oniscosoma arcticus Sars, 1851 from northern Norway. Oniscosoma is now considered a junior synonym of Spinther (Sars 1862). Stimpson (1854), apparently unaware of both Johnston’s and Sars’ studies, described Cryptonota citrina Stimpson, 1854 from the Bay of Fundy, Canada, which was also later regarded as a junior synonym of Spinther (Sars 1862). Grube (1860) described S. miniaceus Grube, 1860 from the Adriatic Sea. Wirén (1883) subsequently used the name S. arcticus (Sars, 1851) for a species from the Bering Sea, considering it sufficiently similar to Sars’ species. However, Augener (1928), page 672, disputed this, asserting that Wirén’s specimen, collected during the Vega expedition, was distinct enough to warrant a new species. Augener proposed the name S. vegae Augener, 1928 for Wirén’s material, but only mentioned it in passing, without a formal description. Subsequently, Graff (1888) re-described the same specimen under the name S. arcticus. Augener criticised this approach, stating that it was inadmissible for Graff to retain the name S. arcticus for what he considered a different species. Despite this, S. vegae was never properly validated. Adding to the confusion, Hartman (1948) incorrectly interpreted Wirén (1883) as having created a homonym and replaced the name S. arcticus Wirén, 1883 with S. wireni Hartman, 1948. However, this replacement name was unnecessary and is now considered invalid. Riddell (1909) re-described S. oniscoides and highlighted that Graff had misidentified it, showing that Graff’s specimens actually belonged to S. citrinus. Levinsen (1883) ' s Spinther major Levinsen, 1883 is also treated as a junior synonym of S. oniscoides by McIntosh (1900). Augener (1913) introduced S. australiensis Augener, 1913 from Western Australia. Hartman (1948) listed six species as valid within Spinther, including her new species, S. alaskensis Hartman, 1948. She treated S. miniaceus Grube, 1860 as a junior synonym of S. arcticus (Sars, 1851). In the western Pacific, S. hystrix Uschakov, 1950 was described from the Sea of Okhotsk, while S. japonicus Imajima & Hartman, 1964, S. ericinus Yamamoto, 1985 and S. sagamiensis Imajima, 2003 were described from Japan. Hartman (1967) also added S. usarpia Hartman, 1967 from the Antarctic. These contributions, alongside S. bohnorum sp. nov., bring the total number of nominal species to 15. A detailed and integrative investigation of Spinther species, combining morphological and molecular data, is needed to confirm or reject some of the proposed synonymies.

Spinther bohnorum sp. nov. most closely resembles S. australiensis in having falcate neurochaetae with a lateral tooth and no parapodial extension. However, S. bohnorum sp. nov. differs in possessing both bifid and entire notochaetae, whereas S. australiensis only has bifid notochaetae. Additionally, S. bohnorum sp. nov. exhibits a striking red-orange colouration with white speckles, while S. australiensis was originally described by Augener (1913) as “ dull ochre-yellowish with whitish, colourless skin fans ” (matt-ockergelblich mit weißlich farblosen Hautkämmen). Finally, S. bohnorum sp. nov. is much smaller, with the largest specimen having only 13 chaetigers and the mature female holotype having just nine chaetigers (± 1 mm body length), compared to S. australiensis, which was described with 23–31 chaetigers (> 4.5 mm body length).

The COI sequence obtained for a Spinther bohnorum sp. nov. specimen (USNM 1430143; GenBank: PV 054334) matches the COI from the published transcriptome sequence (GenBank: PV 053298) and was one of several generated as part of the Mo'orea Biocode project. The other two Spinther COI sequences generated (extractions catalogued as USNM 1430144; GenBank: PV 054335 and USNM 143322) are arguably for different Spinther species, being 8–9 % divergent from Spinther bohnorum sp. nov. and from each other. Unfortunately, there is no voucher material directly associated with these sequences. There are additional Spinther specimens collected as part of the Moorea Biocode project held at SIO-BIC and at the Florida Museum of Natural History, but the former were all fixed in formalin and those from the latter have not been sequenced. The presence of sympatric species of Spinther at Mo'orea warrants further investigation.

Methods

Specimens were obtained from coral rubble collected via SCUBA which was then treated with suspension-decantation and sieving. Live specimens were imaged using a LEICA MZ 9.5 stereomicroscope with a CANON Rebel T 1 i camera. The formalin-fixed holotype was transferred from 70 % ethanol to a 1: 1 mixture of 99.5 % undenatured ethanol and 98 % glycerine prior to imaging. Over several days, the solution was gradually replaced by glycerine to allow a gentle transition from ethanol. This clearing step improves tissue transparency and enhances visualisation of chaetae for imaging. The specimen was photographed in dorsal and ventral views using a motorised NIKON SMZ 25 stereomicroscope, equipped with a NIKON Digital Sight 10 camera, with image stacks processed using NIKON NIS Elements Basic Research software (v. 5.42. 04). Confocal laser scanning microscopy (CLSM) scans were performed without staining (autofluorescence) using a LEICA DM 2500 microscope, 405 nm excitation wavelength, a LEICA ACS APO 10 × objective (dry) and LAS X (v. 3.5. 7.23225) software. Image stacks were processed in Fiji (v. 1.54 f). Distal ends of noto- and neurochaetae were imaged without differential interference contrast using a NIKON Eclipse Ni microscope at 40 × magnification.

For molecular analyses, a COI sequence was obtained via Sanger sequencing for a Spinther bohnorum sp. nov. specimen (USNM 1430143) GenBank: PV 054334, for which only the extraction remains. This was generated as part of the Moorea Biocode project (https://ocean.si.edu/ecosystems/coral-reefs/welcome-moorea-biocode-project).

The transcriptome assembly of Spinther bohnorum sp. nov. was used as a BLAST database. The Spinther COI sequence was used as a BLAST query to identify and mine the COI barcode sequence, which was subsequently uploaded to GenBank (accession number PV 053298).

Specimen data for this description were (in parts) gathered and processed via the Discovery Laboratory of the SENCKENBERG OCEAN SPECIES ALLIANCE.

Repository: Type material are deposited at the Benthic Invertebrate Collection, Scripps Institution of Oceanography (SIO), Senckenberg Research Institute and Natural History Museum, Frankfurt (SMF) and Smithsonian National Museum of Natural History (USNM).