New genus and two new species of the family Ethmolaimidae (Nematoda: Chromadorida), found in two different cold-seep environments

This study describes a new genus Dystomanema gen. nov. with two new species, D. cadizensis sp. nov. and D. brandtae sp. nov. within the family Ethmolaimidae, subfamily Neotonchinae, based on specimens from two low-activity cold-seep environments at distant geographical locations. The new genus was first identified in samples from the Darwin mud volcano (1100 m depth) in the Gulf of Cadiz and later on also found in samples from a low-activity seep in the Larsen B embayment (820m depth) off the eastern Antarctic Peninsula. Until now, the family Ethmolaimidae contained nine genera: Ethmolaimus and Paraethmolaimus in the subfamily Ethmolaiminae, and Comesa, Filitonchoides, Filitonchus, Gomphionchus, Gomphionema, Nannolaimus, and Neothonchus in the subfamily Neotonchinae. The most important family characteristics are: an annulated cuticle bearing transverse rows of dots, cephalic sensilla arrangement of 6+6+4, a spiral amphid, an oesophagus with muscular posterior bulb, paired gonads and males with cup-shaped precloacal supplements. The new genus resembles Comesa and Neotonchus, but is typified by a ventrally displaced oral opening with three very small teeth that are easily overlooked. D. cadizensis gen. nov. sp. nov. is characterized by the 1401-2123 mu m long body; cuticle transversally striated with fine punctation; head conical; low lips; amphid spiralled 3 turns, oral opening ventrally displaced, male with outstretched testes; spicules of equal size; gubernaculum plate-like and ten to twelve conspicuous cup-shaped precloacal supplements with external longitudinal articulated flange. D. brandtae gen. nov. sp. nov. can be distinguished by the 2438-3280 mu m long body; cuticle transversally striated with fine punctuation; head conical; low lips; amphid spiraled 3+ turns; oral opening ventrally displaced; male with anterior testes outstretched and posterior one smaller and reflexed; spicules of equal size; gubernaculum plate-like and twenty conspicuous cup-shaped precloacal supplements with external longitudinal articulated flange. Notes on the ecology and habitat of the new genus are provided in light of its discovery in cold-seep environments.

Family-level AMBI is valid for use in the north-eastern Atlantic but not for assessing the health of microtidal Australian estuaries

Analysis of benthic macroinvertebrate samples at a higher taxonomic level than species, e.g. family, potentially provides a more cost-effective protocol for environmental impact assessments and monitoring as it requires less time, funds and taxonomic expertise. Using the AMBI database, species ecological group scores are shown to be coherent within families. Faunal data from a wide range of environmental impact scenarios in the north-eastern Atlantic demonstrate that AMBI, calculated from mean values for families, exhibits a strong linear relationship with species-level AMBI, the correlation improving by using square-root transformed rather than untransformed abundances. In many regions of the world, however, the sensitivity of benthic macroinvertebrates to environmental perturbations is unknown, precluding the use of AMBI for environmental assessments. Yet the families are essentially the same as in the AMBI database. The utility of family-level AMBI is tested using data for four south-western Australian estuaries previously subjected to environmental quality assessments, but where only 17 species of the 144 taxa are included in the AMBI database. Although family-level AMBI scores reflect differences in environmental quality spatially and temporally within an estuary, they do not follow variations in environmental quality among estuaries. Indeed, south-western Australia estuaries are numerically dominated by families with high AMBI scores, probably due to the detrimental effects of natural accumulations of organic material in estuaries with long residence times. As taxonomic distinctness follows trends in environmental quality among estuaries, as well as temporally and spatially within a system, it provides an appropriate substitute for assessing the 'heath' of microtidal estuaries.