Nuria Sánchez

Phylogeny of Kinorhyncha Based on Morphology and Two Molecular Loci

The phylogeny of Kinorhyncha was analyzed using morphology and the molecular loci 18S rRNA and 28S rRNA. The different datasets were analyzed separately and in combination, using maximum likelihood and Bayesian Inference. Bayesian inference of molecular sequence data in combination with morphology supported the division of Kinorhyncha into two major clades: Cyclorhagida comb. nov. and Allomalorhagida nom. nov. The latter clade represents a new kinorhynch class, and accommodates Dracoderes, Franciscideres, a yet undescribed genus which is closely related with Franciscideres, and the traditional homalorhagid genera. Homalorhagid monophyly was not supported by any analyses with molecular sequence data included. Analysis of the combined molecular and morphological data furthermore supported a cyclorhagid clade which included all traditional cyclorhagid taxa, except Dracoderes that no longer should be considered a cyclorhagid genus. Accordingly, Cyclorhagida is divided into three main lineages: Echinoderidae, Campyloderidae, and a large clade, ‘Kentrorhagata’, which except for species of Campyloderes, includes all species with a midterminal spine present in adult individuals. Maximum likelihood analysis of the combined datasets produced a rather unresolved tree that was not regarded in the following discussion. Results of the analyses with only molecular sequence data included were incongruent at different points. However, common for all analyses was the support of several major clades, i.e., Campyloderidae, Kentrorhagata, Echinoderidae, Dracoderidae, Pycnophyidae, and a clade with Paracentrophyes + New Genus and Franciscideres (in those analyses where the latter was included). All molecular analyses including 18S rRNA sequence data furthermore supported monophyly of Allomalorhagida. Cyclorhagid monophyly was only supported in analyses of combined 18S rRNA and 28S rRNA (both ML and BI), and only in a restricted dataset where taxa with incomplete information from 28S rRNA had been omitted. Analysis of the morphological data produced results that were similar with those from the combined molecular and morphological analysis. E.g., the morphological data also supported exclusion of Dracoderes from Cyclorhagida. The main differences between the morphological analysis and analyses based on the combined datasets include: 1) Homalorhagida appears as monophyletic in the morphological tree only, 2) the morphological analyses position Franciscideres and the new genus within Cyclorhagida near Zelinkaderidae and Cateriidae, whereas analyses including molecular data place the two genera inside Allomalorhagida, and 3) species of Campyloderes appear in a basal trichotomy within Kentrorhagata in the morphological tree, whereas analysis of the combined datasets places species of Campyloderes as a sister clade to Echinoderidae and Kentrorhagata.

On the genus Dracoderes Higgins & Shirayama, 1990 (Kinorhyncha: Cyclorhagida) with a redescription of its type species, D. abei, and a description of a new species from Spain

Abstract The type species of Dracoderes, D. abei, is redescribed based on specimens from several localities in Japan and Korea, and a new species of the genus, Dracoderes gallaicus sp. nov., is described from the coast of Spain in Western Europe. The new species is distinguished by the presence of lateral accessory spines on segment 5. In addition, preliminary diagnostic notes on a yet undescribed species from the Okinawa Region, Dracoderes sp. 1, are provided. Based on new information from D. abei and D. gallaicus sp. nov., an emended genus diagnosis for Dracoderes is proposed. The study includes the first scanning electron microscopical data for species of Dracoderes, and presents for the first time detailed information about head morphology and scalid arrangement, new data about the arrangement of the neck placids, and demonstrates the presence of feebly visible nephridial pores. The new information may be of phylogenetic significance, and is expected to contribute important data for future phylogenetic analyses of the kinorhynch interrelationships.

Morphology disentangles the systematics of a ubiquitous but elusive meiofaunal group (Kinorhyncha: Pycnophyidae)

Kinorhyncha is a group of benthic, microscopic animals distributed worldwide in marine sediments. The phylum is divided into two classes, Cyclorhagida and Allomalorhagida, congruent with the two major clades recovered in recent phylogenetic analyses. Allomalorhagida accommodates more than one‐third of the described species, most of them assigned to the family Pycnophyidae. All previous phylogenetic analyses of the phylum recovered the two genera within Pycnophyidae, Pycnophyes and Kinorhynchus, as paraphyletic and polyphyletic. A major problem in these studies was the lack of molecular data of most pycnophyids, due to the limited and highly localized distribution of most species, often in the Arctic and the deep‐sea. We here overcame the problem by adding a morphological partition with data for 79 Pycnophyidae species, 15 of them also represented by molecular data. Model‐based analyses yielded seven clades, which each was supported by several morphological apomorphies. Accordingly, Kinorhynchus is synonymized with Pycnophyes and six new genera are described for the remaining recovered clades: Leiocanthus gen. nov., Cristaphyes gen. nov., Higginsium gen. nov., Krakenella gen. nov., Setaphyes gen. nov. and Fujuriphyes gen. nov.

Pycnophyes dolichurus sp. nov. and P. aulacodes sp. nov. (Kinorhyncha, Homalorhagida, Pycnophyidae), two new kinorhynchs from Spain with a reevaluation of homalorhagid taxonomic characters

Two new species of the kinorhynch genus Pycnophyes are described from the Atlantic Ocean, Northwest Spain, and the Mediterranean Sea, East of Spain, using differential interference contrast microscopy and scanning electron microscopy (SEM): Pycnophyes dolichurus sp. nov. and P. aulacodes sp. nov. Taxonomic characters from cuticular structures in homalorhagids are discussed and reevaluated. The longitudinal positions of cuticular structures along the trunk are furthermore defined, and the positional terminology is standardized. The distribution of the genus Pycnophyes in European waters is revised, revealing a poor knowledge of kinorhynch biogeography, probably due to incomplete sampling.

Pycnophyes almansae sp. nov. and Pycnophyes lageria sp. nov., two new homalorhagid kinorhynchs (Kinorhyncha, Homalorhagida) from the Iberian Peninsula, with special focus on introvert features

Abstract Two new species of homalorhagid kinorhynchs of the genus Pycnophyes, Pycnophyes almansae sp. nov. and Pycnophyes lageria sp. nov., are described from the Atlantic and Spanish waters of the Mediterranean Sea, using scanning electron microscopy and differential interference contrast microscopy. Pycnophyes almansae sp. nov. is recognized by the presence of middorsal elevations on segments 2–9, pairs of paradorsal setae on segments 3–9 and a single paradorsal seta on segment 2, combined with conspicuous groove-like muscular scars in the subdorsal and ventromedial position on segments 1–10 and a reticulate pattern of cuticular wrinkles in ventrolateral areas on segments 2–10. Pycnophyes lageria sp. nov. is distinguished by its ornamented anterior margin of segment 1, resembling candle wax drops; and its depressed cuticular areas on the ventral region of segment 10, combined with the presence of sensory spots similar to Nanaloricus flosculi, and without middorsal structures or middorsal or paradorsal setae. For the first time, this study presents a detailed description and mapping of the introvert in a species of Pycnophyes based on SEM data, which is compared with the information available on the phylum.

A new kinorhynch genus, Mixtophyes (Kinorhyncha: Homalorhagida), from the Guinea Basin deep-sea, with new data on the family Neocentrophyidae

A new homalorhagid genus and species, Mixtophyes abyssalis gen. et sp. nov., is described from the deep-sea of the Guinea Basin in the Atlantic Ocean. The new genus and species was collected during the R/V Meteor Diva2 M63/2 Cruise, and it is characterized by a trunk with segment 1 consisting of a tergal and a single sternal plate, without any subdivisions or differentiations, segment 2–10 of one tergal and two sternal plates and segment 11 of a tergal and a sternal plate. Lateral terminal spines are present in both sexes. As part of the study of the new taxon, the type material of Neocentrophyes intermedius and N. satyai was re-examined, and new information is provided for both species. Based on the information from Mixtophyes abyssalis gen. et sp. nov. and re-examination of the two Neocentrophyes species, emended diagnoses for Neocentrophyes and Neocentrophyidae are proposed, and an updated identification key to homalorhagid genera and species of Neocentrophyidae is provided. Mixtophyes abyssalis gen. et sp. nov. is tentatively assigned to Neocentrophyidae, but evaluation of our current hypotheses about homalorhagid evolution and phylogeny also indicated that the family most probably is paraphyletic and that revision of homalorhagid classification is required when new results from phylogenetic analyses become available.

Deep-sea Kinorhyncha: two new species from the Guinea Basin, with evaluation of an unusual male feature

Two new species of homalorhagid kinorhynchs from the deep-sea Guinea Basin are described. Pycnophyes nubilis sp. nov. is easily recognized by the presence of paradorsal setae on segment 1; middorsal processes on segments 1–10, progressively increasing in length towards the posterior segments; and middorsal process on segment 10 extending over the last trunk segment. Pycnophyes farinellii sp. nov. is distinguished by middorsal elevations on segments 2–9 and laterodorsal and ventromedial setae on segments 2 and 9 only. Moreover, males of the latter species lack ventromedial tubes on segment 2—a very uncommon feature among the genus. The systematic significance of this character is discussed in detail.

Characteristics of meiofauna in extreme marine ecosystems: a review

Extreme marine environments cover more than 50% of the Earth’s surface and offer many opportunities for investigating the biological responses and adaptations of organisms to stressful life conditions. Extreme marine environments are sometimes associated with ephemeral and unstable ecosystems, but can host abundant, often endemic and well-adapted meiofaunal species. In this review, we present an integrated view of the biodiversity, ecology and physiological responses of marine meiofauna inhabiting several extreme marine environments (mangroves, submarine caves, Polar ecosystems, hypersaline areas, hypoxic/anoxic environments, hydrothermal vents, cold seeps, carcasses/sunken woods, deep-sea canyons, deep hypersaline anoxic basins [DHABs] and hadal zones). Foraminiferans, nematodes and copepods are abundant in almost all of these habitats and are dominant in deep-sea ecosystems. The presence and dominance of some other taxa that are normally less common may be typical of certain extreme conditions. Kinorhynchs are particularly well adapted to cold seeps and other environments that experience drastic changes in salinity, rotifers are well represented in polar ecosystems and loriciferans seem to be the only metazoan able to survive multiple stressors in DHABs. As well as natural processes, human activities may generate stressful conditions, including deoxygenation, acidification and rises in temperature. The behaviour and physiology of different meiofaunal taxa, such as some foraminiferans, nematode and copepod species, can provide vital information on how organisms may respond to these challenges and can provide a warning signal of anthropogenic impacts. From an evolutionary perspective, the discovery of new meiofauna taxa from extreme environments very often sheds light on phylogenetic relationships, while understanding how meiofaunal organisms are able to survive or even flourish in these conditions can explain evolutionary pathways. Finally, there are multiple potential economic benefits to be gained from ecological, biological, physiological and evolutionary studies of meiofauna in extreme environments. Despite all the advantages offered by meiofauna studies from extreme environments, there is still an urgent need to foster meiofauna research in terms of composition, ecology, biology and physiology focusing on extreme environments.

Two new stygophilic tanaidomorphs (Peracarida, Tanaidacea) from Canary Islands and southeastern Iberian Peninsula

Two new species of stygophilic tanaidomorphs are described from El Hierro (Canary Islands) and the Spanish Mediterranean coast from samples collected both at caves and open marine environments. Both species lack autapomorphies but are described based on their unique combination of characters. Pseudotanais isabelae sp. nov. is characterized by the presence of eyes and forcipate chelas, absence of outer seta in article 2 of maxilliped, absence of tubercles on the endite of the maxilliped, presence of 2–6 blade-like spines on the pereopods and presence of one segment on the endopod of the uropod. Zeuxo bimbache sp. nov. is diagnosed by the presence of three aesthetascs on the terminal article of the antennule, laccinia mobilis not articulated on the right mandible, wide and crenulated on the left one; basis of the maxilliped with serrated margin, article 1 of the palp without outer seta, anterior process of the coxa naked, unique chaetotaxy of the pleopods, and endopod of the uropod with three articles. These two species represent the first stygophilic members of the genera Pseudotanais and Zeuxo. Araphura brevimanus (Lilljeborg 1864) and Chondrochelia savignyi (Krøyer 1842) are also reported from our cave samples. An updated checklist of all 24 tanaidaceans recorded in caves is provided, with data on their ecological characterization and degree of troglomorphism. The ecological preferences and affinities of all tanaidaceans present in caves is briefly discussed, and compared with those of other peracarids.

Insights into the diversity of Hormogastridae (Annelida, Oligochaeta) with descriptions of six new species

The earthworm family Hormogastridae is a relatively diverse group in the Western Mediterranean basin. Since 1887, around thirty species have been described and assigned to four genera. However, from 2010 on, molecular, ecological and morphological studies have questioned the validity of those genera. Meanwhile, new species were discovered and assigned to them, pending a formal systematic revision; such a revision has been performed recently by integrating all the existing sources of information. The resulting classification consists of nine genera, including four newly erected ones. This revised systematic background is used in the current work as a base for the description of six new hormogastrid species: Diazcosinia sacrarium Marchán, Fernández, Díaz Cosín Novo, sp. nov., Boucheona martae Marchán, Fernández Díaz Cosín, sp. nov., Boucheona rosae Marchán, Díaz Cosín Novo, sp. nov., Norana emiliae Marchán, Fernández, Díaz Cosín Novo, sp. nov., Norana xylocerasi Marchán, Fernández, Díaz Cosín Novo, sp. nov., and Norana beatrizae Marchán, Fernández, Díaz Cosín Novo, sp. nov. Norana is a new replacement name for the preoccupied Nora Marchán, Fernández, Díaz Cosín Novo, 2018. Likewise, Xanina is proposed to replace the preoccupied Xana Díaz Cosín, Briones Trigo, 1989. We provide an overview of the currently known diversity of the different genera, and we further propose common names in several languages for some of the species of Hormogastridae.