Wolfgang Sterrer

Investigations into the phylogenetic position of Micrognathozoa using four molecular loci

Micrognathozoa is the most recently discovered higher metazoan lineage. The sole known species of the group, Limnognathia maerski, was originally reported from running freshwater in Disko Island (Greenland), and has recently been recorded from the subantarctic region. Because of the presence of a particular type of jaws formed of special cuticularized rods, similar to those of gnathostomulids and rotifers, the three metazoan lineages were considered closely related, and assigned to the clade Gnathifera. A phylogenetic comparison of four molecular loci for Limnognathia maerski and other newly generated sequences of mainly acoelomate animals showed that Micrognathozoa may constitute an independent lineage from those of Gnathostomulida and Rotifera. However, the exact position of Micrognathozoa could not be determined due to the lack of support for any given relationships and due to the lack of stability in the position of Limnognathia maerski under analysis of different loci and of different parameter sets for sequence comparison. Nuclear loci tend to place Micrognathozoa with the syndermatan/cycliophoran taxa, but the addition of the mitochondrial gene cytochrome c oxidase subunit I favors a relationship of Micrognathozoa to Entoprocta.

Musculature and nervous system of Gnathostomula peregrina (Gnathostomulida) shown by phalloidin labeling, immunohistochemistry, and cLSM, and their phylogenetic significance

AbstractMusculature and nervous system of Gnathostomula peregrina (Gnathostomulida, Scleroperalia) were reconstructed from whole animals by immunohistochemistry and confocal laser scanning microscopy. The F-actin muscular subset, stained with FITC-labeled phalloidin, consists of: (1) eleven pairs (four ventral, one ventrolateral, one dorsolateral, five dorsal) of longitudinal muscles; (2) two types of diagonal muscles (thin fibers throughout the body, and slightly thicker fibers of which seven pairs occur ventrally and two pairs dorsally); (3) evenly spaced thin circular fibers that gird the posterior half of the body, continuing less prominently into the anterior half; and (4) a complex pharyngeal and genital musculature. Dorsoventral muscles are absent. The organization of the FMRFamidergic nervous system shows: (1) a central nervous system with a frontal ganglion and one pair of longitudinal nerves ending in a terminal commissure, and one median ventral nerve; (2) eight to ten unipolar perikarya above, and up to ten bipolar perikarya in front of the brain; (3) a total of five (one unpaired, two paired) longitudinal nerves of the peripheral nervous system with two to four accompanying perikarya; and (4) a buccal ganglion of the stomatogastric nervous system with six to eight perikarya above the pharyngeal bulbus. Our results reveal the musculature and nervous system of Gnathostomula to be more complex than hitherto reported.

An Anatomical Description of a Miniaturized Acorn Worm (Hemichordata, Enteropneusta) with Asexual Reproduction by Paratomy

The interstitial environment of marine sandy bottoms is a nutrient-rich, sheltered habitat whilst at the same time also often a turbulent, space-limited, and ecologically challenging environment dominated by meiofauna. The interstitial fauna is one of the most diverse on earth and accommodates miniaturized representatives from many macrofaunal groups as well as several exclusively meiofaunal phyla. The colonization process of this environment, with the restrictions imposed by limited space and low Reynolds numbers, has selected for great morphological and behavioral changes as well as new life history strategies. Here we describe a new enteropneust species inhabiting the interstices among sand grains in shallow tropical waters of the West Atlantic. With a maximum body length of 0.6 mm, it is the first microscopic adult enteropneust known, a group otherwise ranging from 2 cm to 250 cm in adult size. Asexual reproduction by paratomy has been observed in this new species, a reproductive mode not previously reported among enteropneusts. Morphologically, Meioglossus psammophilus gen. et sp. nov. shows closest resemblance to an early juvenile stage of the acorn worm family Harrimaniidae, a result congruent with its phylogenetic placement based on molecular data. Its position, clearly nested within the larger macrofaunal hemichordates, suggests that this represents an extreme case of miniaturization. The evolutionary pathway to this simple or juvenile appearance, as chiefly demonstrated by its small size, dense ciliation, and single pair of gill pores, may be explained by progenesis. The finding of M. psammophilus gen. et sp. nov. underscores the notion that meiofauna may constitute a rich source of undiscovered metazoan diversity, possibly disguised as juveniles of other species.

Gnathostomulid phylogeny inferred from a combined approach of four molecular loci and morphology

The phylogeny of the obscure metazoan phylum Gnathostomulida has previously only been addressed with cladistic analyses of morphological data. In the present study DNA sequence data from four molecular loci, including 18S rRNA, 28S rRNA, histone H3 and cytochrome c oxidase subunit I, are added to a revised morphological data matrix. The data set represents 23 gnathostomulid species that are analyzed under direct optimization using parsimony as the optimality criterion. The results obtained from analyzing the four molecular loci and combined morphological and molecular data under different parameter sets are generally very congruent, and differ only on minor points. The results clearly support gnathostomulid monophyly, as well as the basal division of Gnathostomulida into Filospermoidea and Bursovaginoidea. Filospermoidea were represented by species of Haplognathia and Cosmognathia, and generic monophyly is supported for both groups. Within Bursovaginoidea, Conophoralia (= Austrognathiidae) and Scleroperalia appear as sister groups. Monophyly of Mesognathariidae was confirmed as well, whereas the relationships between species of Gnathostomulidae and Onychognathiidae were contradicted by the molecular data when compared to morphological observations.

Human economics: A non-human perspective

Abstract Tools (or ‘man-made capital’, i.e., the ‘capital’ of economists) are the exosomatic equivalent of organs. Both are created from ‘natural capital’ (i.e., environmental resources) for the better exploitation of natural capital, promoting net energy flow from the environment to the owner. Current human economic behavior differs from that of non-human organisms in the following ways: 1. 1. Large-scale and quasi-irreversible transformation of natural capital into tools, toys and weapons designed further to speed up this very process. 2. 2. Extensive use of exosomatic energy to fuel such transformation, and to subsidize ecologically non-sustainable economic practices. 3. 3. Storage of energy reserves overwhelmingly exosomatically and not as food, including the accumulation of weapons arsenals. 4. 4. Bequeathing of energy stores, tools, and weapons beyond one generation, leading to the accumulation of wealth and power, which further promote resource transformation. 5. 5. Succesful channeling of interspecific energy interactions between humans and other organisms so as to benefit almost exclusively humans. 6. 6. Standardization of intraspecific energy interactions so as to be reciprocal in the form of business deals. 7. 7. Regulation of intraspecific competition by social agreements such as licenses, tariffs, insurance, pensions, etc. 8. 8. Use and storage of money as a symbol of energy credit in reciprocal intraspecific transactions. 9. 9. Debt, i.e., delayed reciprocity, with unharvested natural capital as the ultimate collateral. 10. 10. Practice of and belief in open-ended economic growth as a solution to economic injustice. In a nutshell, humans are characterized by (1) exploding their economic interactions (i.e., the transformation of natural to man-made capital and its use, storage, accumulation and transmission to the next generation) into the exosomatic sphere; (2) standardizing net energy flow (largely one-way interspecific, and reciprocal intraspecific); and finally by (3) debt which, as todays sale of tomorrows yet unharvested and unowned natural capital, temporarily stretches the worlds carrying capacity while irreversibly corrupting its foundations.

Megamorion brevicauda gen. nov., spec. nov., Ein Vertreter Der Turbellarienordnung Macrostomida aus dem tiefenschlamm eines Norwegischen fjords

Abstract A new marine species of the Turbellaria-Macrostomida, coming from the Norwegian coast (Raunefjorden, off Sletta, mud from 120 m depth) is described. The new genus Megamorion created for this form is characterized by longitudinal nerves situated outside the epidermal muscle sheath, only one genital pore, a testis situated dorsally to the pharynx, a most complex male copulatory apparatus, and a bursa with a cuticular apparatus. Within the family Macrostomidae, the new form is closely related to the genera Dolichomacrostomum and Paromalostomum.

Detailed reconstruction of the nervous and muscular system of Lobatocerebridae with an evaluation of its annelid affinity

BackgroundThe microscopic worm group Lobatocerebridae has been regarded a ‘problematicum’, with the systematic relationship being highly debated until a recent phylogenomic study placed them within annelids (Curr Biol 25: 2000-2006, 2015). To date, a morphological comparison with other spiralian taxa lacks detailed information on the nervous and muscular system, which is here presented for Lobatocerebrum riegeri n. sp. based on immunohistochemistry and confocal laser scanning microscopy, supported by TEM and live observations.ResultsThe musculature is organized as a grid of longitudinal muscles and transverse muscular ring complexes in the trunk. The rostrum is supplied by longitudinal muscles and only a few transverse muscles. The intraepidermal central nervous system consists of a big, multi-lobed brain, nine major nerve bundles extending anteriorly into the rostrum and two lateral and one median cord extending posteriorly to the anus, connected by five commissures. The glandular epidermis has at least three types of mucus secreting glands and one type of adhesive unicellular glands.ConclusionsNo exclusive “annelid characters” could be found in the neuromuscular system of Lobatocerebridae, except for perhaps the mid-ventral nerve. However, none of the observed structures disputes its position within this group. The neuromuscular and glandular system of L. riegeri n. sp. shows similarities to those of meiofaunal annelids such as Dinophilidae and Protodrilidae, yet likewise to Gnathostomulida and catenulid Platyhelminthes, all living in the restrictive interstitial environment among sand grains. It therefore suggests an extreme evolutionary plasticity of annelid nervous and muscular architecture, previously regarded as highly conservative organ systems throughout metazoan evolution.

Gnathostomulida from Fiji, Tonga and New Zealand

Of 54 species of Gnathostomulida known to date, only six have been reported from the Pacific Ocean. This paper describes 18 species of Gnathostomulida from the Pacific islands of Fiji. Tonga and northern New Zealand. Of these, three are species previously described from the northeastern Atlantic and Mediterranean: Haplognathia ruberrima (Sterrer 1966), or the northwestern Atlantic: Haplognathia rosacea (Sterrer 1970) and Pterognathia ctenifera (Sterrer 1970). Fifteen species are new to science, including three that represent two new genera: Cosmognathia arcus gen. et sp.n., Cosmognathia bastillae sp.n., Pterognathia crocodilus sp.n., Pterognathia vilii sp.n., Agnathiella sp., Tenuignathia vitiensis sp.n., Ratugnathia mukuluvae gen. et sp.n., Gnathostomula salotae sp.n., Gnathostomula raji sp.n., Gnathostomula maorica sp.n., Austrognathia singatokae sp.n., Austrognathia nannulifera sp.n., Austrognathia novaezelandiae sp.n., Austrognatharia homunculus sp.n., and Austrognatharia pecten sp.n.

Gnathostomulida from Hawaii

As thc second in a series on Gnathostomulida from the Pacific Ocean this paper describes an additional eight species from Hawaii of which four are new to science. All are accommodated within existing genera: Haplognathia asymmetrica sp.n., Haplognathia ruberrima (Sterrer, 1966), Haplognathia rufa sp.n., Cosmognathia arcus Sterrer, 1991, Cosmognathia manubrium sp.n., Pterognathia ctenifera Sterrer, 1970, Pterognathia hawaiiensis sp.n., and Austrognathia novaeze landiae Sterrer, 1991.

A new species of symbiotic flatworms, Paracatenula galateia sp. nov. (Platyhelminthes: Catenulida: Retronectidae) from Belize (Central America)

Abstract Paracatenula galateia sp. nov. is a mouthless marine catenulid platyhelminth with bacterial intracellular endosymbionts. The worms live in shallow back-reef sands in the Belize Barrier Reef system and are distinguished from the four previously described members of the genus by their large size combined with a ribbon-shaped body and characteristic bipartite inclusions in cells, which are interpreted as sperm. The bacteria are presumed to be sulphur-oxidizing chemoautotrophs. They are found in bacteriocytes which fill the body region (‘trophosome region’) posterior to the brain, whereas the anterior part of the worm (rostrum) is bacteria-free. Phalloidin staining reveals a delicate system of subepitheliar circular and longitudinal muscles and dorsoventral fibres. The serotonergic nervous system consists of a brain at the base of the rostrum and longitudinal fibres extending both anteriorly and posteriorly, the latter being concentrated in a structure called the ‘dorsal cord’.