An improved method for the molecular identification of single dinoflagellate cysts

ROV observations reveal infection dynamics of gill parasites in midwater cephalopods

Gill parasites of coleoid cephalopods are frequently observed during remotely operated vehicle (ROV) dives in the Monterey Submarine Canyon. However, little knowledge exists on the identity of the parasite species or their effects on the cephalopod community. With the help of ROV-collected specimens and in situ footage from the past 27 years, we report on their identity, prevalence and potential infection strategy. Gill parasites were genetically and morphologically identified from collected specimens of Chiroteuthis calyx, Vampyroteuthis infernalis and Gonatus spp. In situ prevalence was estimated from video footage for C. calyx, Galiteuthis spp., Taonius spp. and Japetella diaphana, enabled by their transparent mantle tissue. The most common parasite was identified as Hochbergia cf. moroteuthensis, a protist of unresolved taxonomic ranking. We provide the first molecular data for this parasite and show a sister group relationship to the dinoflagellate genus Oodinium. Hochbergia cf. moroteuthensis was most commonly observed in adult individuals of all species and was sighted year round over the analyzed time period. In situ prevalence was highest in C. calyx (75%), followed by Galiteuthis spp. (29%), Taonius spp. (27%) and J. diaphana (7%). A second parasite, not seen on the in situ footage, but occurring within the gills of Gonatus berryi and Vampyroteuthis infernalis, could not be found in the literature or be identified through DNA barcoding. The need for further investigation is highlighted, making this study a starting point for unravelling ecological implications of the cephalopod-gill-parasite system in deep pelagic waters.

Dinoflagellate resting cysts from surface sediments of the Adriatic Ports: Distribution and potential spreading patterns

The ability of microalgae to preserve viable in coastal sediments as resting forms provides a reservoir of biodiversity and a useful tool to determine species spreadings. This study represents the first port baseline survey on dinoflagellate cysts, investigated in nine Adriatic ports during a cross border project. 40 dinoflagellate taxa were detected. The assemblages resulted in all ports dominated by Lingulodinium polyedra and Alexandrium minutum/affine/tamutum group. General separation to the western and eastern side of the Adriatic regarding cysts assemblage composition, partially abundance, was observed. Six taxa were detected as non-indigenous species for the Adriatic. Two taxa are included in the list of harmful aquatic organisms, indicating the potential threat of ballast waters in the Adriatic. Potential spreading of taxa by general circulation and ballast waters, intra- and extra-Adriatic was investigated. The entering in to force of the ballast waters management regulations should enhance prospects to minimize future harmful impacts.

Characterising planktonic dinoflagellate diversity in Singapore using DNA metabarcoding

Dinoflagellates are traditionally identified morphologically using microscopy, which is a time-consuming and labour-intensive process. Hence, we explored DNA metabarcoding using high-throughput sequencing as a more efficient way to study planktonic dinoflagellate diversity in Singapore’s waters. From 29 minimally pre-sorted water samples collected at four locations in western Singapore, DNA was extracted, amplified and sequenced for a 313-bp fragment of the V4–V5 region in the 18S ribosomal RNA gene. Two sequencing runs generated 2,847,170 assembled paired-end reads, corresponding to 573,176 unique sequences. Sequences were clustered at 97% similarity and analysed with stringent thresholds (≥150 bp, ≥20 reads, ≥95% match to dinoflagellates), recovering 28 dinoflagellate taxa. Dinoflagellate diversity captured includes parasitic and symbiotic groups which are difficult to identify morphologically. Richness is similar between the inner and outer West Johor Strait, but variations in community structure are apparent, likely driven by environmental differences. None of the taxa detected in a recent phytoplankton bloom along the West Johor Strait have been recovered in our samples, suggesting that background communities are distinct from bloom communities. The voluminous data obtained in this study contribute baseline information for Singapore’s phytoplankton communities and prompt future research and monitoring to adopt the approach established here.