Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020

We show the distribution of SARS-CoV-2 genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three available genomic nomenclature systems for SARS-CoV-2 to all sequence data from the WHO European Region available during the COVID-19 pandemic until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation. We provide a comparison of the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2.Peer reviewe

When should pearl oyster, Pinctada margaritifera (L.), spat be transferred from the hatchery to the ocean?

Hatchery propagation of pearl oysters is relatively new and optimal hatchery protocols are still being developed. While in the hatchery, pearl oyster spat are supplied a constant and reliable food source and are protected from fluctuations in environmental conditions and predators. This study investigated the hypothesis that retaining blacklip pearl oyster, Pinctada margaritifera (L.), spat in the hatchery for longer periods, prior to transfer to the ocean, would improve growth and survival during early nursery culture. Results showed that the longer spat were retained in the hatchery, the smaller their average size at grading (3.5 months of age). At grading, spat transferred 3 weeks after settlement had a mean dorso–ventral shell height (DVH) of 9.2 ± 0.4 mm with 34% of individuals retained on a 10-mm mesh. However, spat retained in the hatchery until 5, 7 and 9 weeks after settlement, had a mean DVH of 9.0 ± 0.4, 7.8 ± 0.3 and 6.3 ± 0.4 mm respectively. Only 10% of spat transferred 9 weeks after settlement were retained on a 10-mm mesh at grading. The results probably reflect superior nutrition available in the ocean and indicate that pearl oyster spat should be transferred from the hatchery as soon as possible after settlement in order to maximize growt

The influence of algal ration and larval density on growth and survival of blacklip pearl oyster Pinctada margaritifera (L.) larvae

This paper reports on two factorial design experiments conducted to examine the combined effects of algal ration and larval density on growth and survival of black lip pearl oyster Pinctada margaritifera (L.) larvae. In the first experiment, 1-day-old larvae were cultured for 7 days at densities of 1, 2 and 5 mL−1 and fed algal rations of 0, 2.5, 5 or 12.5 × 103 cells mL−1. In the second experiment, 13-day-old larvae were cultured for 7 days at the above densities and fed algal rations of 0, 7.5, 15 and 37.5 × 103 cells mL−1. Algal rations in both experiments were composed of a 1:1 mixture of the flagellates Isochrysis aff. galbana clone T.ISO and Pavlova salina. Response surface contour diagrams were generated from growth and survival data to estimate optimal culture conditions. Results showed that, within a suitable larval density range, growth of P. margaritifera larvae was significantly (P < 0.01) influenced by algal ration. At the end of the first experiment, greatest survival occurred at a ration of 4.5–11.5 × 103 cells mL−1 and at a larval density of ≤ 3 mL−1. Greatest antero-posterior shell length was shown by larvae fed between 4.5 × 103 and 11.5 × 103 algal cells mL−1. In the second experiment, greatest antero-posterior shell length occurred within an algal ration range of 15–32 × 103 cells mL−1. The greatest survival occurred below an algal ration of < 2.5 × 103 cells mL−1; however, this algal ration supported poor algal growth. The results indicate that, to maximize growth and survival, P. margaritifera larvae should be fed at an algal ration of ≈ 8 × 103 cells mL−1 and cultured at a density of three larvae mL−1 up to 8 days of age. Older (13- to 20-day-old) larvae should be cultured at a density of < 2 mL−1 and fed an algal ration of ≈ 25 × 103 cells mL−

Reproductive periodicity and morphometry of Hippopus hippopus and Tridaca crocea

Reproductive periodicity of Hippopus hippopus and Tridacna crocea was examined using a gonad index. Both species showed an annual periodicity. A spawning season extending over several months was indicated for H. hippopus, whereas T. crocea appeared to have a more restricted spawning period. Seasonal changes in the external appearance of the gonads of both species are described. The morphometric relationships between wet mass, dry mass, shell length and shell mass are presented

The effect of binder composition on ingestion and assimilation of microbound diets (MBD) by barramundi Lates calcarifer Bloch larvae

Using 14C-labelled microbound diets (MBD), five different binders were assessed for ingestion, assimilation and assimilation efficiency (AE) when fed to 18 day-old barramundi Lates calcarifer Bloch larvae. MBD bound with alginate and zein were ingested to the highest degree; however, the AE of these two diets was low. Diets bound with gelatin and carrageenan exhibited high AE, although ingestion was significantly lower than for alginate- and zein-bound diets. Combining two binders with different ingestion and assimilation characteristics was investigated as a means of improving diet performance. A diet bound with a 1:1 ratio of gelatin and alginate resulted in greater ingestion than MBD bound with gelatin alone and a higher AE than MBD bound with alginate alone. A third experiment investigated the effects of decreasing binder concentration on ingestion, assimilation and nutrient leaching. Alginate and gelatin were tested at concentrations of 1%, 2% and 3% of the dry weight of the MBD. No significant differences were detected in the ingestion or assimilation rates of the diets bound with different binder concentrations. Leaching losses from MBD containing 1% binder were significantly higher than those bound with 2% or 3% binder. It was concluded that either gelatin or carrageenan at 2-3% inclusion would be a suitable binder in weaning diets for barramundi larvae

Reproductive periodicity and morphometry of Hippopus hippopus and Tridaca crocea

Reproductive periodicity of Hippopus hippopus and Tridacna crocea was examined using a gonad index. Both species showed an annual periodicity. A spawning season extending over several months was indicated for H. hippopus, whereas T. crocea appeared to have a more restricted spawning period. Seasonal changes in the external appearance of the gonads of both species are described. The morphometric relationships between wet mass, dry mass, shell length and shell mass are presented

The combined effects of temperature and salinity on embryos and larvae of the black-lip pearl oyster, Pinctada margaritifera (L.)

This paper reports on a 4 × 4 factorial design experiment conducted to examine the combined effects of temperature and salinity on embryonic development and growth and survival of black-lip pearl oyster, Pinctada margaritifera (L.) larvae. The temperatures used were 20 °C, 25 °C, 30 °C and 35 °C, and the salinities were 25‰, 30‰, 35‰ and 40‰. Response surface contour diagrams were generated from the survival and growth data to estimate optimal conditions. Normal development of embryos occurred only from 25 °C to 30 °C. The optimal conditions for maximum survival and growth were 26–29 °C and 28–32‰. Temperatures of 35 °C or greater were lethal for larvae and, at all temperatures tested, larval growth and survival were lowest at a salinity of 40‰

Ontogenetic patterns of growth and lipid composition changes of blue swimmer crab larvae: insights into larval biology and lipid nutrition

Blue swimmer crab, Portunus pelagicus, is a commercially important crab throughout the Indo-Pacific region, which plays an important role in the food chains of coastal ecosystems. Very limited information is available on larval biology and lipid nutrition of this species. This study investigated survival, growth and ontogenetic changes in lipid composition of P. pelagicus larvae under laboratory conditions. Larvae were fed rotifers (zoea-I), rotifers and Artemia (zoea-II), and enriched Artemia (zoea-III - megalopa), consecutively. Among five larval stages of P. pelagicus, zoea-I and -II had the shortest durations (2.2-2.3 days) while megalopa had the longest duration (4.7 days). As larvae developed, their wet weight, dry weight and carapace length increased exponentially. Lower mortality occurred during zoea-II (12.5%) and âIII (14.3%). Generally, larval fatty acid composition can reflect that of their diets. However, increases in mono-unsaturated fatty acids, 20:4n-6 and 22:6n-3 in megalopa and the first crab compared to zoea-IV might suggest later larvae were still deficient in essential fatty acids, but 20:4n-6 and 22:6n-3 were preferentially accumulated. Therefore, measures of ontogenetic patterns of growth and lipid composition will provide valuable insights for better understanding of larval biology and lipid nutrition of P. pelagicus

Ontogenetic patterns of growth and lipid composition changes of blue swimmer crab larvae: insights into larval biology and lipid nutrition

Blue swimmer crab, Portunus pelagicus, is a commercially important crab throughout the Indo-Pacific region, which plays an important role in the food chains of coastal ecosystems. Very limited information is available on larval biology and lipid nutrition of this species. This study investigated survival, growth and ontogenetic changes in lipid composition of P. pelagicus larvae under laboratory conditions. Larvae were fed rotifers (zoea-I), rotifers and Artemia (zoea-II), and enriched Artemia (zoea-III - megalopa), consecutively. Among five larval stages of P. pelagicus, zoea-I and -II had the shortest durations (2.2-2.3 days) while megalopa had the longest duration (4.7 days). As larvae developed, their wet weight, dry weight and carapace length increased exponentially. Lower mortality occurred during zoea-II (12.5%) and âIII (14.3%). Generally, larval fatty acid composition can reflect that of their diets. However, increases in mono-unsaturated fatty acids, 20:4n-6 and 22:6n-3 in megalopa and the first crab compared to zoea-IV might suggest later larvae were still deficient in essential fatty acids, but 20:4n-6 and 22:6n-3 were preferentially accumulated. Therefore, measures of ontogenetic patterns of growth and lipid composition will provide valuable insights for better understanding of larval biology and lipid nutrition of P. pelagicus