Introduction
Species of the archaeobalanid genus Conopea Say, 1822 are obligate symbionts of cnidarians of the orders Malalcyonacea and Antipatharia and are almost completely covered by host tissue, with only the opercular opening exposed (Figure 1); Conopea currently encompasses 20 valid species in temperate and tropical oceans around the world (Kolbasov et al., Reference Kolbasov, Chan, Molodtsova and Achituv2016; WORMS, 2024).
Figure 1. Conopea (Guinea-Bissau sample with GenBank number PP496555) on Leptogorgia sp. in frontal (A) and lateral (B) views and with host tissue partly removed (C). Scale bar is 1 mm.
Only two species of Conopea were known from the Atlantic Ocean when Carrison-Stone et al. (Reference Carrison-Stone, Van Syoc, Williams and Simison2013) described Conopea saotomensis and Conopea fidelis from gorgonians (Leptogorgia and Eunicella) at São Tomé and Príncipe. Subsequently, Wirtz et al. (Reference Wirtz, Menut, Bérenger, Prat, Louisy and Roquefort2020) reported C. saotomensis from Eunicella sp. at the coast of Gabon (based on examination of specimens by R. Van Syoc). Here we report the first record of C. saotomensis from three islands in the Bijagós archipelago, Guinea-Bissau, extending the known range of the species about 3000 km to the northwest (measured as a straight line from northern Gabon to the Bijagós archipelago) (Figure 2).
Figure 2. Locations where C. saotomensis has been found, namely the Bijagós archipelago (Guinea-Bissau), São Tomé and Príncipe, and the coast of Gabon.
Materials and methods
Four gorgonian fragments with Conopea were collected during an expedition to the Bijagós archipelago, Guinea Bissau, 27.4.-11.5.2023. While scuba diving in a depth range of 3–12 m, we sampled Conopea attached to two unidentified gorgonian species tentatively classified as Leptogorgia spp., and preserved them in 96% ethanol. One specimen from Poilão Island was morphologically examined by RVS and deposited as a voucher specimen at the California Academy of Sciences (collection number CASIZ 422435). A fragment of tissue was isolated from three other specimens – collected near João Vieira and Unhocomo Islands – for DNA barcoding analyses. The cytochrome c oxidase I (COI) sequences of these specimens, available in GenBank (accession numbers PP496555–7), were determined in a single run with a MinIon nanopore sequencer (©Oxford Nanopore Technologies), using a flow cell R10.4, adopting the methodology described by Moura et al. (Reference Moura, Ropa, Magalhães and Gonçalves2022), and demultiplexing sequence reads and assembling DNA barcodes with the ONTbarcoder v2.2 (Srivathsan et al., Reference Srivathsan, Lee, Katoh, Hartop, Kutty, Wong, Yeo and Meier2021). We retrieved all the COI barcodes of Conopea available in GenBank, and aligned these with two sequences of Balanus to serve as outgroup and with the new DNA barcodes of Conopea from Guinea-Bissau. Finally, we generated a maximum-likelihood phylogenetic tree through the PHYML server (http://atgc.lirmm.fr/phyml/; Guindon et al., Reference Guindon, Dufayard, Lefort, Anisimova, Hordijk and Gascuel2010), selecting a standard bootstrap analysis for 1000 repeats and the remaining default settings.
Results
Morphological examination of the specimen and comparison with other specimens in the collection of the California Academy of Sciences Department of Invertebrate Zoology and Geology showed that this specimen was similar to C. saotomensis.
DNA barcoding showed the following results: a COI barcode of one specimen collected at João Vieira Island is 100% similar to the barcode of the Conopea saotomenis specimen from São Tomé with GenBank accession number KC349916. The two other specimens, collected at João Vieira and Unhocomo Islands, had equal COI sequences, representing a distinct haplotype never previously recorded and 99.3% similar to the haplotype of C. saotomensis samples from São Tomé and Principe (GenBank numbers HQ290136, KC349925, and KC349925) (Figure 3).
Figure 3. Maximum-likelihood phylogenetic tree (COI marker) of eastern Atlantic Conopea species.
Thus, both morphology and the COI sequences of the Conopea specimens collected in the Bijagós archipelago agree and indicate that these specimens belong to C. saotomensis, a species hitherto only recorded from São Tomé and Príncipe Islands and the coast of Gabon.
Discussion
The discovery that the same COI sequence is shared between two C. saotomensis samples from places more than 2600 km apart suggests that the species might also be common at other localities, between these two places, along the shores of tropical NW-Africa.
Acknowledgements
The authors thank Sylvie Dias (photography and filming), Nuno Fernandes (diving, health, security), and the IBAP and INIPO (Guinea-Bissau) staff for their help during the expedition. For helpful comments, we are grateful to G. Kolbasov. Study permit: IBAP and INIPO declarations emitted May 2023.
Author contributions
Participation and organization in the Bijagós expedition: C. J. M., P. W., F. T. N., C. B., and E. S. Sample collection: C. J. M. and P. W. DNA barcoding: C. J. M. Morphological analyses: R. V. S. Article writing: C. J. M., P. W., and R. V. S. Funding acquisition: E. S. Article revision and approval: all authors.
Financial support
C. J. M. and the expedition to the Bijagós archipelago were funded by FCT – Foundation for Science and Technology and Aga-Khan Foundation through project MARAFRICA (AGA-KHAN/540316524/2019). The expedition to the Bijagós was also funded by UIDB/04326/2020, UIDP/04326/2020, LA/P/0101/2020, and EU-H20202 854248 (Tropibio).
Competing interests
None.
Data availability
The COI barcodes of C. saotomensis generated are available in GenBank (accession numbers PP496555–7). Other data can be shared on request.
