Maikon Di Domenico

Phylogeny and systematics of Protodrilidae (Annelida) inferred with total evidence analyses

Protodrilidae is a group of small, superficially simple‐looking annelids, lacking chaetae and appendages, except for two prostomial palps. Originally considered to be one of the primitive “archiannelid” families, its affinity within Annelida is still highly debated. Protodrilids are found worldwide in the interstices of intertidal and subtidal marine sediments. Despite their simple appearance they constitute one of the most species‐rich interstitial families, with 36 described species in two genera, Protodrilus and the gutless Astomus. Here we present the first phylogenetic study of Protodrilidae employing five gene fragments, 55 morphological characters and 73 terminals (including seven outgroups) analysed under direct optimization and parsimony as well as model‐based methods. The large data set includes all 36 described species of Protodrilidae (17 of which are represented only by the morphological partition) as well as 30 undescribed or uncertain species (represented by both morphology and molecules). This comprehensive, inclusive and combined analysis revealed a new perspective on the phylogeny of Protodrilidae: the family is shown to contain six cosmopolitan subclades, each supported by several morphological apomorphies, and with the genus Astomus consistently nested among the other five clades rather than next to these. Consequently, the diagnosis of Protodrilus is emended, Astomus remains unchanged and the four remaining lineages are diagnosed and named Megadrilus n. gen, Meiodrilus gen. nov., Claudrilus n. gen and Lindrilus gen. nov. Character transformations showed that large size and presence of pigmentation, oviducts and eyes are plesiomorphies of the family, retained in Protodrilus, Megadrilus gen. nov. and Lindrilus gen. nov. These features are secondarily lost in the gutless Astomus with epidermal uptake of nutrients, as well as in Meiodrilus gen. nov. and some species of Claudrilus n. gen, with smaller size correlated to life in interstices of finer sediments.

Franciscideres gen. nov. – a new, highly aberrant kinorhynch genus from Brazil, with an analysis of its phylogenetic position

A new genus and species of Kinorhyncha, Franciscideres kalenesos gen. et sp. nov., is described from tidal and subtidal sandy habitats in Brazil. The new genus and species is characterized by an extremely flexible trunk without pachycycli that appears perfectly circular in cross-section, segments 1, 2 and 11 consisting of closed rings and 3 to 10 of single, bent plates with midventral articulations, a neck without placids that resembles an additional segment, densely packed scale-like, cuticular hairs, and a terminal segment with a middorsal spine and two sets of lateral terminal spines, but no midterminal spine. Phylogenetic analyses of 18S rRNA of Franciscideres kalenesos gen. et sp. nov. and 47 other kinorhynch ingroup taxa suggest that the new genus is a basal homalorhagid, whereas comparison of morphological characters indicates affinities between the new genus and the peculiar cyclorhagid Cateria. http://zoobank.org/urn:lsid:zoobank.org:pub:64E29D97-DE1D-4511-8683-C969DD2EED43

Evolution of cave Axiokebuita and Speleobregma (Scalibregmatidae, Annelida)

The evolutionary history of Axiokebuita and Speleobregma, two poorly known lineages of annelids exclusive from deep‐sea or marine caves but always from crevicular habitats, is explored here. Speleobregma lanzaroteum Bertelsen, 1986, and Axiokebuita cavernicola sp. n. are described from anchialine and marine caves of the Canary Islands using light and electron microscopy. Speleobregma lanzaroteum is previously known only from a single specimen from the water column of an anchialine cave in Lanzarote. Emended diagnosis, details on the ciliary patterns and behavioural observations are provided based on newly collected material and in situ observations. Axiokebuita cavernicola sp. n. is found in Pleistocene gravel deposits in a shallow water marine cave in Tenerife (Canary Islands). The new species is characterized by the presence of dorsal ciliary bands and short knob‐like neuropodial cirri from segment two. The porosity and permeability of the gravelly environment of A. cavernicola sp. n. are shown to be equivalent to the water column or crevices of Speleobregma and other Axiokebuita spp. Phylogenetic analyses of five gene fragments and 44 terminals using maximum‐likelihood and Bayesian methods support a derived position of A. cavernicola sp. n. within Axiokebuita and confirm a sister‐group relationship of Axiokebuita with Speleobregma with high nodal support. The Axiokebuita–Speleobregma clade is morphologically characterized by a globular pygidium with adhesive glands and ventral ungrooved ciliated palps. Our results support two independent cave colonization events, favoured by the preadaptation of the members of Axiokebuita–Speleobregma lineage to crevicular habitats.

In situ ingestion of microfibres by meiofauna from sandy beaches

Microfibres are widespread contaminants in marine environments across the globe. Detecting in situ ingestion of microfibres by small marine organisms is necessary to understand their potential accumulation in marine food webs and their role in marine pollution. We have examined the gut contents of meiofauna from six sandy beaches in the Atlantic Ocean and the Mediterranean. Out of twenty taxonomic groups, three species of the common sandy beach annelid Saccocirrus displayed in situ ingestion of microfibres in all sites. Laboratory observations showed that species of Saccocirrus are able to egest microfibres with no obvious physical injury. We suggest that their non-selective microphagous suspension-feeding behaviour makes Saccocirrus more prone to ingest microfibres. Although microfibres are rapidly egested with no apparent harm, there is still the potential for trophic transfer into marine food webs through predation of Saccocirrus.

Description of three new species of Protodrilus (Annelida, Protodrilidae) from Central America

Abstract Three new species of Protodrilus are described from the shallow Western Atlantic waters of Belize and Panama: P. smithsoni sp. nov., P. draco sp. nov. and P. hochbergi sp. nov. Protodrilus smithsoni sp. nov. resembles P. jägersteni and P. submersus from New Zealand, differing by (i) the presence of a dorsal ciliated area on segments 5–6 of males, (ii) lateral organs extending only to segment 15 (versus 16) and (iii) the smaller size of body and palps. Protodrilus draco sp. nov. is similar to the European P. hypoleucus and P. helgolandicus, but differs in (i) each pygidial lobe possessing a short cirrus and (ii) the posterior-most lateral organ extending dorsally. Protodrilus hochbergi sp. nov. resembles P. purpureus and P. schneideri from the Eastern Atlantic, but differs in (i) the extension of the salivary glands to segment 15 (versus 6) and (ii) the presence of paired lateral ciliary bands on the prostomium. This first exploration of Protodrilus along the Caribbean coast of Central America revealed five new species (three described here), but not P. corderoi, a species described from Brazil and recorded at Dominica. The findings indicate a putative high diversity of Protodrilus species in the Western Atlantic, comparable to the well-sampled Eastern Atlantic (18 reported species). The close resemblance to described species stresses the importance of detailed morphological studies, preferably including scanning electron microscopy, as well as DNA data, in order to describe and identify species of Protodrilus.

Protodrilus (Protodrilidae, Annelida) from the southern and southeastern Brazilian coasts

Protodrilus corderoi, Protodrilus ovarium n. sp. and Protodrilus pythonius n. sp. are reported from beaches in southern and southeastern Brazil and described combining live observations with light and electron scanning microscopy studies. Protodrilus corderoi is redescribed from new collections at the type locality, and a neotype for the species is assigned since the original type material no longer exists. New information on reproductive organs, segmental adhesive glands and unpigmented ciliary receptors as well as morphometrics is provided. Protodrilus ovarium n. sp. and P. pythonius n. sp. are formally described. Protodrilus ovarium n. sp. is diagnosed by the presence of separated lateral organs on segments 7–12, three spermioducts of segments 10–12 and salivary glands in segments 1–9. Protodrilus pythonius n. sp. is defined by the presence of separated lateral organs on segments 7–16, long pygidial lobes and body tapering toward the pygidium. The distribution of the different species in more or less spacious habitats seems to be correlated with their gross morphology. Protodrilus pythonius n. sp., with relatively long and wide body and long palps with ciliary bands, was collected in very coarse sandy sediments at a reflective sheltered beach. Conversely, P. corderoi and P. ovarium n. sp., both possessing more slender bodies with shorter, less ciliated palps, occurred in medium-coarse, well-sorted sediments in the more energetic swash zone of exposed intermediate-reflective beaches. The finding of P. pythonius and P. corderoi in nearby beaches corroborates other studies showing a higher morphological variability among species in different habitats within the same geographical area than among species in the same habitat in different geographical areas.

Saccocirridae (Annelida) from the southern and southeastern Brazilian coasts

Pharyngocirrus gabriellae (Du Bois-Reymond Marcus 1946) and Saccocirrus pussicus Du Bois-Reymond Marcus 1948 are redescribed based on newly collected material from the south and southeastern Brazilian coasts. Neotypes are designated, since no type material was formally indicated in the original descriptions. New morphological information on the muscular ventral pharynx, ciliation, chaetae and pygidium is provided. Pharyngocirrus gabriellae is additionally characterised by the presence of mouth ciliary patches, capillary lyrate chaetae with a single median tooth and equally bifid medium chaetae with denticulate prongs. The novel diagnostic characters of Saccocirrus pussicus include the absence of a pharynx and the presence of 1–3 pygidial, adhesive ridges and 20 fertile segments. The two species live in very distinct interstitial habitats, with varying hydrodynamics. Pharyngocirrus gabriellae is found at sheltered intertidal and shallow areas in sediments with a redox layer, whereas Saccocirrus pussicus prefers the swash zone of exposed, oxygenated, reflective beaches. Morphology and habitat preferences of P. gabriellae and S. pussicus are consistent with other Saccocirridae species from the ‘Pharyngocirrus’ and ‘Saccocirrus’ genera, respectively.

Patterns of diversity in marine Gastrotricha from Southeastern Brazilian Coast is predicted by sediment textures

Broad spatial variations of biodiversity are associated with patterns and processes at different scales, and are well known for large terrestrial animals. For the interstitial microscopic fauna a wide distribution conception is accepted for several phyla. This assumption is being revised since more information has become available on their biogeography and general macroecological threats. This study analyzed the variability of marine Gastrotricha diversity among benthic habitats and localities along the Brazilian coast. We tested the hypothesis that sediment textures, location, tidal zones, and their interactions, are potential explanatory variables that affect the Gastrotricha diversity. Richness estimates, species composition, and beta diversity were used as response variables of biodiversity. The number of gastrotrichs, macrodasyids, and chaetonotids species was mostly explained by sediment sorting and the highest richness was detected in poorly sorted sediments. Species composition and beta diversity were correlated with tidal zone, location, and average grain size, and the highest turnover of species was expected on islands. The general diversity patterns observed in our study that were explained by sediment textures, tidal zones, and localities, are expected to be observed along other marine coastlines in the world and may be correlated with sediment transport and deposition processes.

A taxonomic overview of marine and estuarine oligochaetes from Brazil

Aquatic oligochaetes from South America are still poorly known. As a basis for a general survey of marine oligochaetes from the southwestern Atlantic, we present here a critical overview of the available taxonomic information on marine and estuarine oligochaetes from Brazil. Only 13 of the 600 described species are currently known from Brazil, and 8 exclusively from their type locations. The enchytraeid Marionina cf. nevisensis is newly reported from São Sebastião (São Paulo State). The distribution range of the naidid Tectidrilus gabriellae is expanded to the Paranaguá Bay (Paraná, S Brazil).

Editorial: diversity of marine meiofauna on the coast of Brazil

After a first bout of primarily taxonomical effort, meiofauna studies in Brazilian waters remained virtually neglected until the 1990s. At the end of the last century, taxonomical and ecological studies on meiofauna taxa were again published regularly, especially for Nematoda and Copepoda. In this issue, 18 new species are described and ten species are redescribed from seven Phyla. The five ecological articles cover the spatial distribution of forams and amoeba in a lagunar system, the meiofauna associated with biogenic structures, the relationship between nematodes and granulometry, and the response of sandy-beach meiofauna to a natural, short-term pulse of diatoms. All these contributions show the potential of the Brazilian coast for revealing new species and testing small to large-scale hypotheses about ecological processes.