Report of Epibiont Diatom P. pacificum on the Cyclopoid Copepod D. affinis from the Southwestern Shelf Waters of India (Eastern Arabian Sea)

Pseudohimantidium pacificum, an epizoic diatom has been reported from different parts of the global oceans, however, has not been reported from the shelf waters of India. This symbiotic association of P. pacificum with a specific copepod species (Ditrichocorycaeus affinis) was repeatedly noticed from the shelf waters of the Arabian Sea during the winter monsoon from three locations in the South East Arabian Sea. Our study suggests towards host specificity of P. pacificum and additionally reveals their preference towards male hosts which is consistent with the earlier reports from other regions. Most importantly, this report extends the range of geographic distribution of the epibiont and this is the third report on this epibiont from the Indian Ocean region. It also suggests that epibiosis in marine zooplankton is much frequent phenomenon that has the potential to play an important role in the marine zooplankton population dynamics.

The Sizes, Growth and Reproduction of Arrow Worms (Chaetognatha) in Light of the Gill-Oxygen Limitation Theory (GOLT)

The Chaetognatha are a marine invertebrate phylum including 132 extant, carnivorous species in nine families and two orders, but with unclear protostomian affinities in the animal kingdom. We document the gradual recognition of the distinctiveness of chaetognaths by early taxonomists, with some emphasis on the often-overlooked studies by Chinese marine biologists. The carnivorous arrow worms are understudied relative to their importance in the marine zooplankton, where they rank second in abundance after the herbivorous copepods. Although arrow worms lack gills or other dedicated respiratory organs, we show that the Gill-Oxygen Limitation Theory (GOLT) can be used to explain how temperature and respiration affect their growth and related life-history traits. Notably, we present a reappraisal of evidence for size–temperature relationships between and within chaetognath species, and for the relationship between their temperature-mediated oxygen demand and their growth patterns. Von Bertalanffy weight growth curves of Ferosagitta hispida (family: Sagittidae) based on earlier aquarium experiments by various authors are presented, which suggest (a) a good fit and (b) that the life span of chaetognaths is much lower than suggested by the authors of several published growth curves drawn onto length–frequency samples from the wild. In addition, we show that chaetognaths attain first maturity at a fraction of the maximum length they can attain that is similar to the corresponding fraction in fishes. Overall, we suggest that the manner in which the oxygen they require enters the body of small marine invertebrates, although often neglected, is a crucial aspect of their biology. In addition, based on our result that arrow worms conform to the GOLT, we suggest that this theory may provide the theoretical framework for the study of growth in the other water-breathing ectotherms lacking gills.

Zooplankton diversity monitoring strategy for the urban coastal region using metabarcoding analysis

Marine ecosystems in urban coastal areas are exposed to many risks due to human activity. Thus, long-term and continuous monitoring of zooplankton diversity is necessary. High-throughput DNA metabarcoding has gained recognition as an efficient and highly sensitive approach to accurately describing the species diversity of marine zooplankton assemblages. In this study, we collected 30 zooplankton samples at about 2-week intervals for 1 year. Zooplankton diversity showing a typical four season pattern. Of the “total” and “common” zooplankton, we assigned 267 and 64 taxa. The cluster structure and seasonal diversity pattern were rough when only the “common” zooplankton was used. Our study examined how to maximize the benefits of metabarcoding for monitoring zooplankton diversity in urban coastal areas. The results suggest that to take full advantage of metabarcoding when monitoring a zooplankton community, it is necessary to carefully investigate potential ecosystem threats (non-indigenous species) through sufficient curation rather than disregarding low-abundance operational taxonomic units.

An updated checklist of marine copepoda from Peninsular Malaysia with notes on their functional traits and distributional records

An up-to-date checklist of marine zooplankton copepods from the water of Peninsular Malaysia is presented, there are 235 species of copepods which consists of 89 genera and 44 families. Extensive list of bibliographical references with synonymy, detailed information on their functional groups, and distributional data are provided for each species. The checklist is based on taxonomic and ecological literature until 28 May 2020. Calanoida recorded the most diverse order with 101 species in total, followed by Harpacticoida with 70 species and 61 species from Cyclopoida. As for Canuelloida, Monstrilloida and Siphonostomatoida all recorded with 1 species respectively. There are 192 species of copepod recorded along the west coast (Malacca Strait) and 123 species on the east coast (South China Sea). Endemicity at species level attains 1% for the whole Peninsular Malaysian coast, with 2 genera restricted to the east coast (Kensakia parva and Brachiella malayensis) and one genus to the west coast (Labidocera jaafari). There are six dominant species that can be found along the coast of Peninsular Malaysia (Acartia erythraea, Acartia pacifica, Bestiolina similis, Euterpina acutifrons, Microsetella norvegica, Paracalanus aculeatus, Oithona nana, Oithona simplex and Temora discaudata).