Viatcheslav N. Ivanenko

Is the meiofauna a good indicator for climate change and anthropogenic impacts

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research.

Interpreting segment homologies of the maxilliped of cyclopoid copepods by comparing stage-specific changes during development

Abstract Development of the maxilliped of 14 species of cyclopoid copepods from 14 genera in the families Cyclopinidae, Oithonidae and Cyclopidae is described. Segment homologies are inferred from the assumption that homologous setae and arthrodial membranes are added during the same copepodid stage, and from a model of development that patterns the endopod proximally from the proximal of two endopodal segments present at the first copepodid stage. An arthrodial membrane separates the praecoxa and coxa of two Cyclopinidae and two of three Oithonidae. The praecoxa of the Cyclopinidae and the Oithonidae has two groups of setae; the praecoxa of Cyclopidae has no more than one group. The coxa of these copepods has only one group of setae; all Cyclopidae share a coxal lobe with a single seta. The endopod of these three families may include as many as five segments. In general, the distal arthrodial membrane of a segment appears to have been more labile during evolutionary history of the maxilliped than has the ventral seta which inserts on that segment. For purposes of phylogenetic analyses, uncoupling the presence of the distal arthrodial membrane of a segment from the presence of its ventral seta and analyzing each separately may provide a better way of understanding evolutionary transformations of the limb than considering the segment as the basic structural unit of the limb.

Advances in taxonomy, ecology, and biogeography of Dirivultidae (copepoda) associated with chemosynthetic environments in the deep sea.

Background Copepoda is one of the most prominent higher taxa with almost 80 described species at deep-sea hydrothermal vents. The unique copepod family Dirivultidae with currently 50 described species is the most species rich invertebrate family at hydrothermal vents. Methodology/Principal Findings We reviewed the literature of Dirivultidae and provide a complete key to species, and map geographical and habitat specific distribution. In addition we discuss the ecology and origin of this family. Conclusions/Significance Dirivultidae are only present at deep-sea hydrothermal vents and along the axial summit trough of midocean ridges, with the exception of Dirivultus dentaneus found associated with Lamellibrachia species at 1125 m depth off southern California. To our current knowledge Dirivultidae are unknown from shallow-water vents, seeps, whale falls, and wood falls. They are a prominent part of all communities at vents and in certain habitat types (like sulfide chimneys colonized by pompei worms) they are the most abundant animals. They are free-living on hard substrate, mostly found in aggregations of various foundation species (e.g. alvinellids, vestimentiferans, and bivalves). Most dirivultid species colonize more than one habitat type. Dirivultids have a world-wide distribution, but most genera and species are endemic to a single biogeographic region. Their origin is unclear yet, but immigration from other deep-sea chemosynthetic habitats (stepping stone hypothesis) or from the deep-sea sediments seems unlikely, since Dirivultidae are unknown from these environments. Dirivultidae is the most species rich family and thus can be considered the most successful taxon at deep-sea vents.

Asterocheres flustrae n. sp. (Copepoda: Siphonostomatoida: Asterocheridae) associated with Flustra foliacea L. (Bryozoa) from the White Sea

Asterocheres flustrae n. sp. is described from Flustra foliacea L. (Bryozoa) found in the Kandalaksha Bay of the White Sea. This is the first siphonostomatoid copepod to be reported in association with a bryozoan. Distinctive features of the new species are: (1) a female with 21- and male with 18-segmented antennules; (2) five setae on the inner lobe of the maxillule with one much reduced; (3) an aesthetasc on the syncoxa of the maxilla; (4) a 6-segmented maxilliped with a distal claw; and (5) the armature of endopodal segments 2, 1, 1 and 1. Sexual dimorphism was observed not only on the antennules, but also for maxilliped and legs 1–6. By using SEM some new fine structures were revealed, including: one seta on each of antennulary segments 1 to 4, 6 and 8 with a nipple-like tip and an apical pore surrounded at its base by a circlet of cuticular denticles; a rostral region having a circular area ornamented with minute cuticular protuberances; and the labrum ornamented with fine hair-like setules on either side of its apex.

Body Architecture and Relationships Among Basal Copepods

Abstract Most copepods exhibit one of three kinds of body architecture: 1) six broad anterior trunk somites and five narrow posterior trunk somites of gymnopleans; 2) five broad anterior trunk somites and six narrow posterior trunk somites of many podopleans; or 3) four broad anterior trunk somites and seven narrow posterior trunk somites of thaumatopsylloids. A phylogenetic analysis using naupliar and post-naupliar characters, with Mystacocarida as the sister taxon of Copepoda, supports the hypothesis that the thaumatopsylloid architecture is the oldest. No narrow somite is transformed into a broad somite during post-naupliar development of thaumatopsylloids. Podopleans and gymnopleans begin their post-naupliar development with one trunk somite fewer than thaumatopsylloids. Podoplean architecture results when the anterior narrow somite of thaumatopsylloids is transformed to the posterior broad somite of podopleans during the first post-naupliar molt. Gymnoplean architecture, the youngest, results when the anterior narrow somite found on podopleans is transformed to the posterior broad somite during the second post-naupliar molt. These developmental transformations of body somites are assumed to explain the evolutionary origins of podoplean and gymnoplean body architectures.

Early Post-Embryonic Development of Marine Chelicerates and Crustaceans with a Nauplius

Crustaceans that hatch as a nauplius-like larva, as well as xiphosuran and pantopodan chelicerates, are surveyed for five characters: presence or absence of arthrodial membranes separating somites; ventral configuration of the protopod of the second limb; number of transformed (segmented) limbs and limb buds; addition of segments to transformed limbs; fate of limb buds. An arthrodial membrane separates somites 7 and 8 of xiphosurans, a small knob articulates on the protopod of the second limb, and there are nine pairs of limbs but no limb buds. During early development, no arthrodial membranes are added, nor are segments added to limbs 1-9; limbs 10-14 are added as transformed limbs, not as limb buds, after several molts. On the post-embryonic larva of the presumed ancestral pantopodan, arthrodial membranes did not separate adjacent somites, the proximal segment of limb 2 was simple, there were three transformed limbs and no limbs buds. During subsequent molts, arthrodial membranes separated somites 4-7, buds of limbs 4-7 were added in register with each molt, limb buds were reorganized in register into transformed limbs during the following molt, and two segments were added to each transformed limb in register during the next molt. Somites of most crustacean taxa that hatch as a nauplius-like larva are not separated by arthrodial membranes on early post-embryonic stages; exceptions are posterior somites of branchiurans, mystacocaridans and cephalocaridans. Limb 2 (antenna 2) of branchiopods, copepods, thecostracans, mystacocaridans and cephalocaridans bears a naupliar arthrite on the ventral face of the coxa, on branchiurans there is an attenuation, or spine-like outgrowth, on the ventral face, and on 5) Corresponding author; e-mail: ferrarif@si.edu 6) e-mail: johnfornshell@hotmail.com 7) e-mail: avagelli@njaas.org 8) e-mail: ivanenko@mail.bio.msu.ru 9) Co-corresponding author; e-mail: hansdahms@smu.ac.kr

Nauplii of Tegastes falcatus (Norman, 1869) (Harpacticoida, Tegastidae), a Copepod with an Unusual Naupliar Mouth and Mandible

There are six stages in the naupliar phase of development of Tegastes falcatus (Norman, 1869). The labrum is expressed as a simple fold which does not cover the mouth. A poorly-sclerotized mouth tube was observed on some specimens of all stages except NI (= naupliar stage 1); NI and Nil are the only stages without an anus and presumably do not feed. The antennal endopod is a subchela against itself at Nil; its distal endopodal segment becomes bifurcate at NIII. A chela on the naupliar mandible consists of the endopod opposite a distoventral attenuation of the basis on NII-NVI. The segmental elements of a chela are present at NI, although the endopod does not oppose the basis at this stage. The maxillule is a unilobe bud with one seta at NIII that gains a second seta at NV and is transformed into a simple bilobe bud with three setae at NVI. The maxilla and maxilliped are each an asetose, ventral attenuation at NVI. Naupliar stages, found in large numbers along with all six copepodid stages of T. falcatus, apparently feed on suctorian ciliates growing on colonies of the bryozoan Flustra foUacea (Linnaeus, 1758). This is the first description of six naupliar stages for a species of Tegastidae Sars, 1904.

Helioseris cucullata as a host coral at St. Eustatius, Dutch Caribbean

In order to demonstrate how scleractinian corals contribute to marine biodiversity by their host function, information on associated fauna was gathered during a biological survey at St. Eustatius, eastern Caribbean. This knowledge is especially urgent for a host coral such as Helioseris cucullata (Agariciidae), which has undergone strong declines in abundance at various Caribbean localities and has a poor record of associated fauna. New records of H. cucullata as host are presented for the coral gall crab Opecarcinus hypostegus (Cryptochiridae), the Christmas tree worm Spirobranchus giganteus (Serpulidae) and an unidentified serpulid tube worm of the genus Vermiliopsis. A second association record is reported for the coral barnacle Megatrema madreporarum (Pyrgomatidae). Coral-associated copepods were not found on H. cucullata despite a search for these animals. The new records were compared with previous records of other host coral species that showed elements of the same associated fauna. The present findings indicate that new discoveries concerning Caribbean coral reef biodiversity can still be made during field expeditions by targeting the assemblages of associated fauna of specific benthic host species.

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.

Multiple purple spots in the Caribbean sea fan Gorgonia ventalina caused by parasitic copepods at St. Eustatius, Dutch Caribbean

Symbiotic Copepoda comprise a widespread, diverse, and abundant ecological group of small crustaceans associated with various invertebrates, including octocorals. Some copepods, such as Lamippidae, are morphologically highly modified endoparasites found in galls or other cavities of various species of octocorals (Buhl-Mortensen and Mortensen 2004). Despite previous investigations of symbiotic copepods inside Caribbean octocorals (Stock 1973), lamippid copepods associated with the common shallow-water sea fan Gorgonia ventalina Linnaeus, 1758, have not been reported so far. During a marine biodiversity survey around the Dutch Caribbean island St. Eustatius (June 2015) by use of SCUBA (2–21 m deep), numerous colonies of G. ventalina with multiple purple spots (∅ 1–4 cm) were discovered at eight of 40 localities. The spots were outgrowths of the gorgonian tissue, lacking any polyps or noticeable openings (Fig. 1a-c). Dissection of 24 outgrowths revealed chambers typically enclosing one or two adult copepods (female, or female and male) identified as Sphaerippe sp., distinguished by a spherical female body shape and acicules present on legs 1 and 2 (Fig. 1d, e). The GenBank accession number of our copepod 18S rRNA fragment is KT762152. The only known species of the genus, S. caligicola Grygier 1980, was found in galls of the sea fan Callogorgia sp. near Grand Bahama Island at 355 m depth (Grygier 1980). In addition to the adult copepods, the chambers found in G. ventalina contained eggs, spermatophores, and yellow structures representing exuvia of copepods, eggs, and spermatophores covered by a gorgonian secretion. The presence of numerous multiple purple spots on some colonies but their absence in adjacent colonies suggests self-infestation of the gorgonian by offspring of the copepods from first settlement. Our data therefore suggest that endoparasitic lamippid copepods induced the purple spots on G. ventalina colonies. The multiple purple spots with copepods are remarkably similar to those of the multifocal purple spots syndrome (MPSS) of G. ventalina reported from several Caribbean localities since 2006 (Burge et al. 2012). The occurrence of multiple purple spots on G. ventalina around St. Eustatius caused by endoparasitic copepods require Communicated by R. Vonk