Author: Daniel Leduc (Marine biologist)

Publisher:

Published: 2023

Total Pages: 0

ISBN-13: 9781991174444

The phylum Nematoda Cobb, 1932, also known as roundworms, is the most abundant metazoan taxon in aquatic sediments worldwide, as well as one of the most diverse. Despite their ubiquitous distribution, our knowledge of nematode taxonomy and diversity in Aotearoa New Zealand, and in particular, free-living species in marine sediments, remains very limited. The nematode fauna of New Zealand's marine environments, ranging from the most accessible beaches to abyssal plains, remains poorly known, with the total biodiversity of the free-living marine nematode fauna in the New Zealand Exclusive Economic Zone estimated at several thousand species. Prior to this work, the total number of free-living marine nematode species known from the New Zealand region was 190 species. Unlike previous recent NIWA Biodiversity Memoirs which focus on a particular taxon group rather than a specific region, this work focuses on the nematode fauna of Pāuatahanui Inlet, a drowned river valley and one of two arms of Te Awarua-o-Porirua Harbour in the Wellington region. The main reason for this regional approach is that the New Zealand marine nematode fauna remains largely uninvestigated, and very few specimen collections are available. The most efficient way to increase our knowledge of free-living marine nematode taxonomy in New Zealand is therefore to begin describing the fauna from an easily accessible environment. Pāuatahanui Inlet was chosen because, while it has high ecological and cultural significance, it is also subject to anthropogenic impacts associated with changes in surrounding land use and pollution. A better knowledge of the nematode fauna will thus bring a more complete understanding of the ecological value of this ecosystem and should facilitate ecological monitoring in the future. A total of 55 nematodes species belonging to two classes, eight orders, 19 families and 41 genera were found. Thirty-nine of the most common species are described here, 26 of which are new to science, four of which are new records for New Zealand, and seven of which [Bathylaimus cf. australis Cobb, 1894; Tripyloides cf. marinus (Bütschli, 1874) de Man, 1886; Chromadora cf. nudicapitata Bastian, 1865; Chromadorina germanica (Bütschli, 1874) Wieser, 1954; Cobbia trefusiaeformis de Man, 1907; Terschellingia cf. longicaudata de Man, 1907; Litoditis cf. marina (Bastian, 1865) Sudhaus, 2011] are cosmopolitan species or species complexes. Together, these species are to be called 'Ngā toke o Parumoana': 'ngā toke' referring to the worms, and 'parumoana' referring to the tidal areas of Te Awarua-o-Porirua which consist of two elements, i.e., the brown mud flats (paru) and the sea (moana). In addition to line drawings and light micrographs, scanning electron micrographs and molecular sequences are provided for 12 and 28 of the species described here, respectively. Eight seemingly cosmopolitan species, some of which are likely to be cryptic species complexes, were found to occur in the inlet, but the identity of the Pāuatahanui Inlet populations could not be confirmed due to a lack of published molecular sequence data. It is highly likely that additional nematode species not listed here will be found in the inlet as sampling continues in the future. Currently, free-living nematodes are estimated to represent about 40% of the total infaunal diversity in Pāuatahanui Inlet.