Birger Neuhaus

Ultrastructure, Biology, and Phylogenetic Relationships of Kinorhyncha

Abstract The article summarizes current knowledge mainly about the (functional) morphology and ultrastructure, but also about the biology, development, and evolution of the Kinorhyncha. The Kinorhyncha are microscopic, bilaterally symmetrical, exclusively free-living, benthic, marine animals and ecologically part of the meiofauna. They occur throughout the world from the intertidal to the deep sea, generally in sediments but sometimes associated with plants or other animals. From adult stages 141 species are known, but 38 species have been described from juvenile stages. The trunk is arranged into 11 segments as evidenced by cuticular plates, sensory spots, setae or spines, nervous system, musculature, and subcuticular glands. The ultrastructure of several organ systems and the postembryonic development are known for very few species. Almost no data are available about the embryology and only a single gene has been sequenced for a single species. The phylogenetic relationships within Kinorhyncha are unresolved. Priapulida, Loricifera, and Kinorhyncha are grouped together as Scalidophora, but arguments are found for every possible sistergroup relationship within this taxon. The recently published Ecdysozoa hypothesis suggests a closer relationship of the Scalidophora, Nematoda, Nematomorpha, Tardigrada, Onychophora, and Arthropoda.

Redescription of Cateria gerlachi (Kinorhyncha, Cyclorhagida) from Sri Lanka and of C. styx from Brazil, with notes on C. gerlachi from India and C. styx from Chile, and the ground pattern of the genus.

Cateria gerlachi is redescribed based on specimens from the west coast of Sri Lanka by light microscopical observations of 57 adult and 47 juvenile specimens and by SEM investigations of 33 adult and 10 juvenile specimens. Cateria styx from Brazil is redescribed from 33 adult and 5 juvenile specimens mounted for light microscopy (original material). The original material of C. gerlachi from India and new material of C. styx from Chile have been studied for comparison. Cateria gerlachi can be distinguished from C. styx by leaf-like cuticular hairs dorsally but not laterally on the tergal plate of segment 1 and on the midsternal plate of segments 1-2 vs scales with a posterior process on the entire tergal plate of segment 1 and on the midsternal plate of segments 1-2 in C. styx, fewer lines of leaf-like hairs of the secondary fringe on segments 2-10 in C. gerlachi, broader scales in the central part of the segments in C. gerlachi, the blunt tube on segment 5 in a lateral accessory vs a lateroventral position in C. styx, the lack of a midlateral spine on segment 11 vs its existence on segment 11 of C. styx, the lack of a protrusible dorsal organ at the border of segments 5 and 6 vs its existence in C. styx and type-5 sensory spots and gland cell outlets present on different segments and positions in the two species. We report and document for species of Cateria detailed morphological data, including variability within populations, a female and a male life-history stage, as well as moulting of an adult stage to another adult stage. In contrast to previous records, C. gerlachi occurs in sandy intertidal habitats not only deeply buried in the sediment but also at the surface.

A revision of the Iponematinae (Nematoda: Drilonematoidea) with description of three new species parasitic in tropical earthworms.

The Iponematinae is revised based on the morphological analysis of known and newly described species. Globocephalonema is restored to accommodate three former Iponema species: G. krishnanii, G. hyderabadense and G. timmae. Emended generic diagnoses and keys for species identification are proposed. Three new species, Filiponema javanicum sp. n., F. cylindropharyngatum sp. n. and Tonoscolecinema awakubianum sp. n., parasitic in earthworms deposited in the collection of the Museum fur Naturkunde Berlin, are described and illustrated. Filiponema javanicum sp. n. is closest to F. sarmathicum but is distinguished by its smaller amphids, a cylindroid vs clavate pharynx, the absence of genital sensilla with rounded bases and short bristle in the centre, the lack of somatic sensilla in males, and a differently shaped gubernaculum. From the other three species of the genus, it clearly differs by a rounded vs pointed tail in both sexes. Filiponema cylindropharyngatum sp. n. differs from its congeners by the uniquely short and slim pharynx and fewer eggs with more elongated, finely tuberculate vs smooth, ovoid eggshells. Tonoscolecinema awakubianum sp. n. differs by the presence of a pre-corpal bulb-like pharyngeal swelling, a glandular pharyngeal bulb, a gradually tapering vs conical female tail and cuticularised rectum in females.

New species of Echinoderes (Kinorhyncha: Cyclorhagida) from Mediterranean seamounts and from the deep-sea floor in the Northeast Atlantic Ocean, including notes on two undescribed species

Two new species of Echinoderes from the Eratosthenes Seamount and a deep-sea station near the Sedlo Seamount are described. Echinoderes multiporus sp. nov. from the Eratosthenes Seamount is characterized by a combination of the presence of middorsal acicular spines on segments 4, 6, and 8, ventrolateral tubes on segment 2, lateroventral tubes on segment 5, lateroventral acicular spines on segments 6-9, midlateral tubes on segment 10, and type-2 glandular cell outlets in subdorsal position on segment 2 and in laterodorsal position on segments 4-9. Echinoderes unispinosus sp. nov. from the deep-sea station differs from its congeners by the combination of middorsal acicular spine on segment 4, lateroventral acicular spines on segments 6 and 7, type-2 glandular cell outlets present in midlateral position on segment 1, in subdorsal, laterodorsal, sublateral, and ventrolateral position on segment 2, in lateral accessory position on segment 5, and in sublateral position on segment 8, and densely aligned pectinate fringe teeth of the primary pectinate fringes similar in width on segments 1-10. In addition, the morphological data of two undescribed species from the Anaximenes Seamount and a deep-sea station near the Sedlo Seamount are given. An undescribed species from the Anaximenes Seamount is morphologically similar to Echinoderes unispinosus sp. nov., but differs in the smaller trunk length, the presence of broader pectinate fringe teeth of the primary pectinate fringe on segment 1, and the absence of ventromedial sensory spots on segment 8. Another undescribed species from the deep-sea station differs from its congeners in the pattern of spines, tubes, and type-2 glandular cell outlets and length of middorsal and lateral terminal spines. New names are not given to both undescribed species in this study, because only one specimen is available for each species, and both of the specimens were damaged during the preparation.

Echinoderes pterus sp. n. showing a geographically and bathymetrically wide distribution pattern on seamounts and on the deep-sea floor in the Arctic Ocean, Atlantic Ocean, and the Mediterranean Sea (Kinorhyncha, Cyclorhagida)

Abstract Kinorhynchs rarely show a wide distribution pattern, due to their putatively low dispersal capabilities and/or limited sampling efforts. In this study, a new kinorhynch species is described, Echinoderes pterus sp. n., which shows a geographically and bathymetrically wide distribution, occurring on the Karasik Seamount and off the Svalbard Islands (Arctic Ocean), on the Sedlo Seamount (northeast Atlantic Ocean), and on the deep-sea floor off Crete and on the Anaximenes Seamount (Mediterranean Sea), at a depth range of 675–4,403 m. The new species is characterized by a combination of middorsal acicular spines on segments 4–8, laterodorsal tubes on segment 10, lateroventral tubes on segment 5, lateroventral acicular spines on segments 6–9, tufts of long hairs rising from slits in a laterodorsal position on segment 9, truncated tergal extensions on segment 11, and the absence of any type-2 gland cell outlet. The specimens belonging to the populations from the Arctic Ocean, the Sedlo Seamount, and the Mediterranean Sea show morphological variation in the thickness and length of the spines as well as in the presence/absence of ventromedial sensory spots on segment 7. The different populations are regarded as belonging to a single species because of their overlapping variable characters.