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Eleven species of Malmgrenia McIntosh, 1874 are currently recorded from the Northeast Atlantic and Mediterranean Sea. In eight of them, all long notochaetae have stout, entire tips [Malmgrenia andreapolis McIntosh, 1874; M. arenicolae (Saint-Joseph, 1888); M. castanea McIntosh, 1876; M. lilianae (Pettibone, 1993); M. ljungmani (Malmgren, 1867); M. lunulata (Delle Chiaje, 1830), M. mcintoshi Tebble & Chambers, 1982 and M. polypapillata (Barnich & Fiege, 2001)]. They differ by their elytral, parapodial and neurochaetal characters. Three additional species [Malmgrenia darbouxi (Pettibone, 1993), M. marphysae (McIntosh, 1876) and M. louiseae Jourde, Sampaio, Barnich, Bonifácio, Labrune, Quintino & Sauriau, 2015] can be separated from this group by their long notochaetae tapering to a fine, entire tip. Meanwhile, we found two new species in the area, Malmgrenia bicki sp. nov. and Malmgrenia thomsonae sp. nov., both with some long notochaetae showing a fine, bidentate tip (i.e. with subdistal tooth), but differing mainly by the shape of their supra-acicular process and middle neurochaetae. The presence of bidentate notochaetae first led to confusion with Pettibonesia furcosetosa (Loshamn, 1981), originally described as Malmgrenia as well. But in this species, some of the long notochaetae terminate in a fine furcate (i.e. distally split) tip. The discovery of the two new Malmgrenia species led us to re-assess the generic characters of the genera Malmgrenia and Pettibonesia Nemésio, 2006. As a result, we consider the presence of small cephalic peaks as a character of generic importance for Pettibonesia, especially since cephalic peaks are not found in any of the Malmgrenia species described for the area. The bidentate condition of some notochaetae suggests that the two new species could be assigned to Pettibonesia, but the fact that both new species lack cephalic peaks led us to assign them to Malmgrenia. [ABSTRACT FROM AUTHOR]

In this paper we describe three species belonging to the genus Branchiosyllis Ehlers, 1887, collected from different areas of the Socotra Archipelago. Two of them, Branchiosyllis inesae n. sp. and Branchiosyllis camblori n. sp. are new to science. The third species, Branchiosyllis exilis (Gravier, 1900), has been recorded circumtropically but was originally described from the neighbouring country of Djibouti. Branchiosyllis inesae n. sp. is characterized by a dorsoventrally flattened body, lack of branchiae, and a transversal reddish-brown band on the dorsum of each anterior segment, more marked dorsolaterally, bands disappearing after proventricle level, only dorsolateral spots remaining; compound chaetae comprise only falcigers anteriorly, ungulae appear in midbody, in posterior segments only ungulae are present. Branchiosyllis camblori n. sp. is characterized by numerous black spots on the dorsum and on some articles of the dorsal cirri; chaetae are mostly unidentate falcigers in anterior parapodia, and unidentate falcigers and ungulae in posterior parapodia. A description of Branchiosyllis exilis is also included because little information is available from specimens collected close to the type locality. A synoptic table of characters of the three species described herein is also provided. [ABSTRACT FROM AUTHOR]

Members of Polygordiidae Czerniavsky, 1881 are distributed worldwide and are typical inhabitants of coarse grained, marine sublittoral sediments. Species in Polygordiidae are unusual among polychaetes because they lack external segmentation, parapodia, and chaetae as well as external ciliation. Morphological characters for species distinction are thus limited to the shape and minute structures of the prostomium and pygidium. As a result, morphological identification and description of the Polygordius species is difficult. In the present study, we provide new data for species distinction using molecular and morphological methods, i.e., DNA-sequencing ( COI gene), transmission electron microscopy (TEM), and confocal laser scanning microscopy (cLSM). Specifically, we investigated whether the photoreceptor-like sense organs, previously described for Polygordius appendiculatus Fraipont, 1887, could provide additional characters of taxonomic value by examining the ultrastructure of these organs in two additional species, Polygordius erythrophthalmus Giard, 1880 and Polygordius lacteus Schneider, 1868. These organs were found to occur in comparatively large numbers and comprise different types of sensory cells including one rhabdomeric and two ciliary, which are variously combined to form small sensory organs. Structural differences in sensory organs were negligible between P. erythrophthalmus and P. lacteus; however, major differences were observed when compared to P. appendiculatus. These results are in accordance with our molecular data which indicated that P. erythrophthalmus and P. lacteus represent the same species. Thus P. erythrophthalmus is an invalid species and represents a junior synonym of P. lacteus. Furthermore, this study shows that ultrastructural data can significantly contribute to species distinction, especially in morphologically similar species. [ABSTRACT FROM AUTHOR]

The systematic position of Polygordiidae is still under debate. They have been assigned to various positions among the polychaetes. Recent molecular analyses indicate that they might well be part of a basal radiation in Annelida, suggesting that certain morphological characters could represent primitive character traits adopted from the annelid stem species. To test this hypothesis, an investigation of the muscular and nervous systems by means of immunological staining and confocal laser scanning microscopy and transmission electron microscopy was conducted. With the exception of the brain, the nervous system is entirely basiepidermal and consists of the brain, the esophageal connectives, the subesophageal region, the ventral nerve cord and several smaller longitudinal nerves. These are connected by a considerable number of ring nerves in each segment. The ventral nerve cord is made up of closely apposed longitudinal neurite bundles, a median and two larger lateral ones. Since distinct ganglia are lacking, it represents a medullary cord. The muscular system mainly consists of longitudinal fibers, regularly distributed oblique muscles and strong septa. The longitudinal fibers form a right and a left unit separated along the dorsal midline, each divided into a dorsal and ventral part by the oblique muscles. Anteriorly, the longitudinal musculature passes the brain and terminates in the prostomium. There is no musculature in the palps. In contrast to earlier observations, regularly arranged minute circular muscle fibers are present. Very likely, a basiepithelial and non-ganglionic organization of the ventral nerve cord as well as an orthogonal nervous system represent plesiomorphic characters. The same applies for the predominance of longitudinal muscle fibers. [ABSTRACT FROM AUTHOR]

In a collection of polychaetes from the Southwest Atlantic, off the Argentinian coast, ten scale worm species of the family Polynoidae were found. The following nine species are already known to science and their synonymy, diagnostic characters, and distribution are given together with remarks on taxonomy and geographical distribution: Eucranta mollis (McIntosh, 1876), Eucranta notialis Monro, 1936, Harmothoe exanthema (Grube, 1858), Harmothoe magellanica (McIntosh, 1885), Polyeunoa laevis McIntosh, 1885, Halosydna patagonica Kinberg, 1856, Halosydnella australis (Kinberg, 1856), Lepidasthenia esbelta Amaral and Nonato, 1982 and Showapolynoe marmorata (Hartmann-Schröder, 1965) n. comb. Additionally, a new Harmothoe species was discovered and is described in detail. Differentiating characters of the new species and Harmothoe ciliata Monro, 1936 from the Magellan region are discussed. Since two species of Eucranta Malmgren, 1866 out of four known worldwide occur in the Southwest Atlantic and since the genus has never been revised in the past, we discuss the distinguishing characters of the species and present a synoptic table. Furthermore, we raise two subspecies to species level, i.e. Eucranta villosa notialis Monro, 1936 to E. notialis Monro, 1936 and Harmothoe brevipalpa ciliata Monro, 1936 to H. ciliata Monro, 1936. Two new junior synonyms are also recognised: Harmothoe fimbriata Hartmann-Schröder, 1965 is referred to H. ciliata Monro, 1936 and Halosydna brasiliensis Kinberg, 1857 to Halosydnella australis (Kinberg, 1856). An identification key is given to all species found in the considered area. [ABSTRACT FROM AUTHOR]