The biology and ecology of lotic Tardigrada

• 1 Tardigrades comprise a micrometazoan phylum that is a sister group of the arthropods.
• 2 They are components of the meiobenthos in lotic habitats, and ≈ 50–70 species have been reported in such habitats world‐wide. Approximately 800 species have been identified from all marine, freshwater, and terrestrial habitats.
• 3 Taxonomy is based primarily on the morphology of the claws, buccal‐pharyngeal apparatus, cuticle and eggs.
• 4 Reproductive modes include sexual reproduction (amphimixis) and parthenogenesis. The sexual condition of individuals may be either gonochorism, unisexuality, or hermaphroditism. Moulting occurs throughout the life of the tardigrade.
• 5 Latent states (cryptobiosis, including encystment, anoxybiosis, cryobiosis, osmobiosis and anhydrobiosis) enable tardigrades to withstand unfavourable environmental conditions.
• 6 Population densities, life histories, dissemination and biogeography of freshwater species are poorly known.

     

Distribution patterns of interstitial freshwater meiofauna over a range of spatial scales,with emphasis on alluvial river-aquifer systems

Spatial distribution patterns of the interstitial meiobenthos are examined across a range of scales. A global interstitial highway model is presented with the alluvial aquifer system as its central core. Spatially discontinuous hypogean entities, such as karstic aquifers, springs, anchialine waters and the psammolittoral, have limited interconnections except through the alluvial aquifer system and are contiguous with epigean waters. The global interstitial highway is viewed as an evolutionary pathway and long-term dispersal route for meiobenthic forms. The distribution of interstitial animals in alluvial river-aquifer systems is examined at longitudinal (altitudinal), reach, floodplain, gravel bar, and vertical (depth) scales. Geomorphic and hydrogeologic features and interactions emerge as major determinants of the spatially heterogeneous nature of alluvial aquifers that structure the patchy distribution patterns of hypogean fauna across a range of scales.Invited summary of Symposium on the Biogeography of Subterranean Crustaceans: the Effects of Different Scales. Prepared for print by D. C. Culver.Invited summary of Symposium on the Biogeography of Subterranean Crustaceans: the Effects of Different Scales. Prepared for print by D. C. Culver.     

The musculature of Draculiciteria tessalata (Chaetonotida, Paucitubulatina): implications for the evolution of dorsoventral muscles in Gastrotricha

The muscular system of the marine interstitial gastrotrich Draculiciteria tessalata (Chaetonotida, Paucitubulatina) was analyzed with fluorescent phalloidin. Muscles in circular, longitudinal, helicoidal and dorsoventral orientations were found. Circular muscles were present as discreet rings on the pharynx only. Five pairs of longitudinal muscles were found in dorsal, lateral and ventral positions. One of the two pairs of lateral muscles is newly described for the species. Helicoidal muscles, external to the circular muscles and some longitudinal bands, spiraled around the pharynx and anterior portion of the intestine. Two pairs of segmentally-arranged dorsoventral muscles were also present. Lateral dorsoventral muscles extended from the base of the pharynx to the anterior part of the caudal furca. Medial dorsoventral muscles extended from the pharyngeal-intestinal junction into each ramus of the caudal furca. A hypothesis on the evolution of dorsoventral muscles in D. tessalata is proposed which includes a splitting of circular muscles into separate somatic and splanchnic components with a further displacement of both muscle sets into a dorsoventral orientation.     

Is Diurodrilus an annelid?

Interstitial marine meiofaunal worms of the genus Diurodrilus have always been considered part of Annelida, either as basal or derived, though generally with reference to Dinophilidae. New evidence shows that Diurodrilus has a unique anatomy, and lacks key annelid features, possibly even segmentation. We assessed the systematic position of Diurodrilus among other protostome animals via light microscopy, confocal laser scanning microscopy, and transmission electron microscopy studies of anatomy, focusing on musculature, the nervous system, as well as molecular sequence data. We show that there is little morphological or molecular evidence to support a relationship with Dinophilidae or any other annelids. Diurodrilus has some similarities to Micrognathozoa, though the latter shows complex jaws. On the basis of the configuration of the nervous system and the cuticle we regard Diurodrilus to belong to Spiralia, possibly close to Annelida; however, until further evidence is acquired it should be regarded as incertae sedis in this large animal clade. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

The current knowledge on centipedes (Chilopoda) in Slovenia: faunistic and ecological records from a national database

In spite of Slovenia’s very high biodiversity, it has only a few animal groups that have been significantly investigated and are well known in this area. Slovenian researchers have studied only about half of the species known to be living in the country (Mršić 1997), but among well investigated species are centipedes. All available data about centipedes in Slovenia collected from 1921 to 2014 have been consolidated and constitute a general electronic database called “CHILOBIO”, which was created to provide an easy overview of the Slovenian centipede fauna and to allow entry and interpretation of new data collected in future research. The level of investigation has been studied with this database, in conjunction with a geographic information system (GIS). In the study period, 109 species were identified from 350 localities in 109 of the 236 UTM 10 × 10 km quadrants which cover the study area. The south-central part of the country has been the subject of the best investigations, whereas there is an absence of data from the south-eastern, eastern and north-eastern regions The highest number of species (52) has been recorded near the Iška valley (Central Slovenia, quadrant VL68). In 48% of the UTM quadrants investigated fewer than 10 species were recorded and just 5 species were found in one locality. Seventeen species were reported only in the Dinaric region, 4 in the Prealpine-subpannonian region and 7 in the Primorska-submediterranean region.     

A new interstitial ostracod species of the genus Paracobanocythere from Vietnam,with mitochondrial CO1 sequence data of three Asian species

This study is a first report of an interstitial ostracod from Southeast Asia. The ostracod species, Paracobanocythere vietnamensis sp. n., was found in the marine interstitial environment of Phu Quoc Island, Vietnam. Thus far, three species of this genus have been described. The morphology of the carapace as well as the appendages of this new species are quite similar to Paracobanocythere hawaiiensis and Paracobanocythere watanabei. However, we found that they could be easily distinguished according to the morphology of the male copulatory organ. Additionally, we estimated the evolutionary distances among these three species based on nucleotide and amino acid sequences of the mitochondrial CO1 gene. Similar morphologies of carapaces and appendages, and relatively small evolutionary distances according to CO1 between Paracobanocythere vietnamensis sp. n. and Paracobanocythere watanabei suggest that these two species are very closely related.     

天津近海自由生活线虫多样性分析

2007年4月在面临高度开发的天津近岸海域,对沉积物中自由生活的线虫样品进行了采集,并分析了其多样性,为生物多样性研究和环境监测提供科学数据.结果表明,该海域自由生活线虫有80余种,生物丰度以拉氏矛咽线虫Dorylaimopsis rabalais的优势最突出.调查海域的沉积物虽然受到了一定的污染,但其污染状况并不恶劣.垂直的层次分析表明一些多样性指数受采样深度影响,分析时应关注采样深度.     

Troglochaetus beranecki Delachaux (Polychaeta, Archiannelida) in esker groundwaters of Finland: a new class of limnic animals for northern Europe

The presence of Troglochaetus beranecki is reported in the phreatic groundwater of eskers in southern Finland within the area covered by glaciers during the last glacial epoch. The hitherto known distribution of this species includes central and southern Europe and parts of northern America, but it has not previously been found in northern Europe, where groundwater invertebrates have generally been assumed to be lacking. The limit of distribution of this species is now moved 1500 km to the north-east. This revised version was published online in July 2006 with corrections to the Cover Date.     

土壤动物研究综述

土壤动物是当今生态学研究的热点,其对环境的指示作用已经受到越来越多生态学家的重视.对土壤动物学的发展历史,以及我国土壤动物的研究现状和现代土壤动物学研究的一些热点领域进行了综述.     

Marine gastrotrichs from the sand beaches of the northern Gulf of Mexico: species list and distribution

In this meio-faunistic survey along the northern coast of the Gulf of Mexico, gastrotrichs were found in sand collected mostly from beaches on barrier islands. Sediment from Florida and Alabama contained the largest species number. South Texas collecting sites also hosted a very diverse gastrotrich fauna. Paucitubulate Chaetonotida, previously unreported from the area, accounted for about one half of the 45 species encountered. After comparing local specimens also with high resolution videosequences of individuals collected from distant geographic regions, the amphi-Atlantic and/or cosmopolitan distribution of 27 of these species, is confirmed.     

New data on freshwater psammic Gastrotricha from Brazil

Current knowledge of freshwater gastrotrich fauna from Brazil is underestimated as only two studies are available. The present communication is a taxonomic account of the first-ever survey of freshwater Gastrotricha in Minas Gerais State. Samplings were carried out yielding six species of three Chaetonotidae genera: Aspidiophorus cf. pleustonicus, Ichthydium cf. chaetiferum, Chaetonotus acanthocephalus, Chaetonotus heideri, Chaetonotus cf. succinctus, Chaetonotus sp., and also an undescribed species belonging to the genus Redudasys (incertae sedis): this is the first finding of specimens of Redudasys outside of original type locality. These preliminary observations suggest that the knowledge of the biodiversity of Gastrotricha in the Minas Gerais State, as well as in the whole Brazil, will certainly increase as further investigations are undertaken, and that freshwater Macrodasyida may be more common than previously thought.     

Graphical Presentation of the African Tardigrade FaunaUsing GIS with the Description of Isohypsibius malawiensis sp. n. (Eutardigrada: Hypsibiidae) from Lake Malawi

The tardigrade fauna of the African continent is reviewed and presented graphically using Worldmap, a Geographical Information System (GIS) developed for exploring geographical diversity patterns in large biological datasets. References to the African tardigrade fauna have been gathered from published literature and supplemented with unpublished species information from the collection of Prof. Reinhardt M. Kristensen (RMK), Zoological Museum, University of Copenhagen. 156 species belonging to 36 genera of tardigrades are present. They consist of 105 eutardigrade species and 51 heterotardigrade species, of which 42 species are semiterrestrial and 9 species are marine. The presence of tardigrades are reported from 20 countries, but of these 9 are represented by a single reference. Marine tardigrades in particular have been neglected, with only a single report from the shores of the African continent. Data from the RMK collection of samples from Egypt is included in the analysis.

The scattered and sparse knowledge of the African tardigrade distribution makes general conclusions difficult, but emphasises the large regions which require further investigation. The current distribution patterns corresponds with easy accessible or ‘tourist’ locations. Regions where GIS could be used to illustrate ecological preferences are also pointed out by the analysis.

Isohypsibius malawiensis sp. n. is described from Lake Malawi. It has a smooth body surface and lacks eyes. The heteronych claws are without lunulae, but below the claws a double arched cuticular bar is present. The dorsal and ventral apophyses of the buccal tube have a large drop-shaped swelling. The first macroplacoid is the largest followed by the second, which is only slightly larger than the third; microplacoid is absent. Males are smaller than females. Females lay only one to two very large eggs in the exuvium. The Malpighian tubules are clover-shaped. The new species is interstitial in coarse sediment and no other tardigrade species were present.     

A new marine cyclopoid copepod of the genus Neocyclops (Cyclopidae,Halicyclopinae) from Korea

A new cyclopoid species of the genus Neocyclops Gurney, 1927 is described. Type specimens were collected from a beach on south-western coast of the Korean Peninsula by rinsing intertidal coarse sandy sediments. Neocyclops hoonsooi sp. n. is most characteristic in showing the conspicuous chitinized transverse ridges originating from the medial margins of the coxae of all swimming legs. The new species is most similar to Neocyclops vicinus, described from the Brazilian coast, and Neocyclops petkovskii, from Australia. All three species share a large body size (more than 750 µm long), the presence of an exopodal seta on the antenna, two setae on the mandibular palp, the same seta/spine armature on the third endopodal segment of leg 3 (3 setae + 3 spines), and the fairly long inner distal spine on the third endopodal segment of the female leg 4. However, Neocyclops hoonsooi sp. n. differs from both species by the much shorter caudal rami (less than 1.7 times as long as wide) and the shorter dorsal caudal seta VII. Furthermore, Neocyclops hoonsooi is clearly distinguished from Neocyclops vicinus by the 10-segmented antennule (vs 12 segments in Neocyclops vicinus), and from Neocyclops petkovskii by the elongate inner distal spine on leg 5 exopod and the 3-segmented leg 5 in male (vs 4-segmented in Neocyclops petkovskii). A tabular comparison of characters separating Neocyclops hoonsooi from its closest allies and a key to Neocyclops species from the Indo-Pacific Ocean are provided. This is the first record of the genus Neocyclops from the northern Pacific.     

Evolution of interstitial Polychaeta (Annelida)

An update of the systematics is given for the eight most important interstitial polychaete families: Diurodrilidae, Nerillidae, Protodrilidae, Protodriloididae, Saccocirridae, Parergodrilidae, Polygordidae and Psammodrilidae. Additional information and new observations are presented for the Diurodrilidae, Nerillidae and Psammodrilidae. Three new supplementary evolutionary hypotheses for these families are here suggested: (I) basal position of Diurodrilidae in Polychaeta, (2) evolution of Nerillidae in mud, and (3) evolution from meio- to macrofaunal forms of Psammodrilidae.