Delimiting the polymorphic congeners of the genus Oerstedia Quatrefages, 1864 (Nemertea, Hoplonemertea), and descriptions of three new species from the Northwest Pacific

Three new species of the monostiliferous hoplonemertean genus Oerstedia Quatrefages, 1864, are herein described using morphological and molecular data—Oerstedia pseudoculata sp. nov., from Akkeshi Bay and Oshoro Bay, Hokkaido, Japan, and from Aniwa Bay, Sakhalin, Russia; Oerstedia rugosa sp. nov. from Sagami Bay, Misaki, Kanagawa, Japan, and Van Phong Bay, Vietnam; and Oerstedia viridifusca sp. nov. from Manazuru, Kanagawa, Japan. As to the external morphology, O. pseudoculata sp. nov. can be differentiated from O. oculata only by its bright-orange ocelli visible on both sides of the head, and a proboscis pore opening at the ventral tip of the head. These two sister species repeat each other’s color patterns, a phenomenon that can be explained by Vavilov’s law of homologous series. Oerstedia rugosa sp. nov. can be identified by its carmine or deep-red to brownish-red body with several longitudinal, intertwined white lines or wrinkles running from the head to the posterior body, and by 17–23 vaguely bordered white bands composed of variedly sized dots encircling the body, arranged at irregular intervals. Oerstedia viridifusca sp. nov. can be distinguished from other Oerstedia by (i) the entire body flecked with minute greenish-brown dots, especially densely on the anterior portion of the dorsal surface, but sparsely on the posterior half of the ventral surface; (ii) a collar-like portion encircling the body along the posterior cephalic furrow where the greenish-brown dots are absent; (iii) the anterolateral edges of the head lacking the greenish-brown dots; and (iv) the ocelli being brownish-orange in color. Oerstedia phoresiae (Kulikova, 1987) is reported for the first time from Japan, in addition to its previous distribution record in Russia and in South Korea. Phylogenetic analyses based on the 16S, 18S, 28S ribosomal RNA, cytochrome c oxidase subunit I, and histone H3 genes show that the new species are true congeners of the genus Oerstedia with O. pseudoculata sp. nov. and O. viridifusca sp. nov. nested within the clade Paroerstediella whereas O. rugosa sp. nov. in the clade Oerstedia. This taxonomic work emphasizes the importance of DNA barcode sequence in the taxonomy and systematics of the polymorphic congeners of the genus Oerstedia

Molecular Phylogeny of the Genus Nipponnemertes (Nemertea: Monostilifera: Cratenemertidae) and Descriptions of 10 New Species, With Notes on Small Body Size in a Newly Discovered Clade

Nemerteans, or ribbon worms, have been reported from intertidal to hadal depths, often showing bathymetrically wide distribution in genus levels. Although current nemertean systematics practices require to provide DNA sequences and infer phylogenetic relationships with suitable molecular markers, previous molecular systematics on nemerteans are mostly biased toward shallow-water species. Members in the genus Nipponnemertes occur worldwide, from tropical to polar waters and intertidal to bathyal waters. Molecular phylogenetic studies are scarce for the genus; only six shallow-water species of 18 species in the genus were subject to molecular phylogeny. Thus, Nipponnemertes is one candidate that needs to be assessed by genetic approaches. In this study, we performed molecular phylogenetic analyses using 59 specimens in 23 species based on partial sequences of two mitochondrial (16S rRNA and cytochrome c oxidase subunit I) and three nuclear gene markers (18S rRNA, 28S rRNA, and histone H3). Our extensive sampling from intertidal to bathyal waters in the Northwest Pacific significantly updated the fauna of Nipponnemertes in this region from four to 17 species. We herein establish 10 new species and provide an updated species list concisely summarizing all the congeners known from the world. Our phylogenetic tree indicated three major lineages within the genus (herein referred to as “Clade A, B, and C”), each presumably characterized by the combination of morphological characters in the head region. Members in Clade A are: Nipponnemertes pulchra (Johnston, 1837), Nipponnemertes ogumai (Yamaoka, 1947), and several unidentified congeners, characterized by having demarcated head without cephalic patches; members in Clade B are: Nipponnemertes crypta sp. nov., Nipponnemertes jambio sp. nov., Nipponnemertes neonilae sp. nov., and Nipponnemertes ojimaorum sp. nov., species having demarcated head with cephalic patches; members in Clade C are: Nipponnemertes ganahai sp. nov., Nipponnemertes kozaensis sp. nov., Nipponnemertes lactea sp. nov., Nipponnemertes notoensis sp. nov., Nipponnemertes ornata sp. nov., Nipponnemertes sugashimaensis sp. nov., and two unidentified forms collected off Jogashima (Japan) and Guam (USA), species with non-demarcated head lacking cephalic patches. Furthermore, we discuss the evolution of remarkably small body size retained among Clade C

Raymond Gibson (1938–2023): in memoriam

On 29 January 2023, Raymond (Ray) Gibson (Fig. 1), Professor Emeritus of Liverpool John Moores University, died in a hospital on the Wirral. He lived a very busy life, rich in travels and scientific discoveries, and he was one of the most authoritative world experts in the taxonomy of nemerteans. Ray was born on 23 November 1938 in Catterick Village in Yorkshire. He gained his Private Pilot’s License aged 17 and had several adventures in the small plane. In 1965 after leaving the Royal Airforce as a qualified pilot he got his B.Sc. in Zoology First class degree from Leeds University and in 1968 gained his Ph.D. from Leeds University. Ray began his interest in nemerteans when he was a student at Leeds University. His Ph.D. supervisor was Dr. Joe Jennings, who at the time was researching the nutrition and digestion of nemerteans and “turbellarians” (a grade of free-living platyhelminths). Ray’s first articles on the nutrition and biology of Malacobdella grossa were published when he was at Leeds University (Gibson 1967, 1968; Gibson & Jennings 1969). In 1971 Ray joined the Liverpool Regional College of Technology (this became Liverpool Polytechnic and then Liverpool John Moores University), where he worked for 30 years. His first book (Gibson 1972) is an excellent summary of knowledge on nemertean biology at the time and has ‘entangled’ (rather than ‘hooked’) young students worldwide in the following generations into this field. Ray’s exploratory enthusiasm was unmatched. He would come early in the morning and spend the day in concentrated writing, microscopy, or figure preparation. An ashtray was ever present next to his microscope and cigarettes and black coffee were all he needed to sustain him through the long days. For a long time, the histology unit was complete with the all-pervasive smell of xylene. He supervised post-graduates from many countries and backgrounds, teaching them the intricacies of paraffin sectioning and histochemistry.Peer reviewe

Korotkevitschia Friedrich 1968

Genus: Korotkevitschia Friedrich, 1968 Generic diagnosis: Pelagic hoplonemerteans with modified monostiliferous proboscis armature; bulb region and bulb duct not developed; basis, central stylet and diaphragm absent; two accessory stylet pouches with posterior opening; rhynchocoel reaches posterior end of body; rhynchocoel wall with interwoven musculature; mouth and rhynchodaeum open separately; precerebral septum closed; body wall with non­fasciated diagonal muscles; longitudinal musculature not anteriorly divided, with honeycomb fascial substructure; dorso­ventral musculature weakly developed; longitudinal stomach musculature present; frontal organ present; eyes absent; frontal, cephalic and submuscular glands present in precerebral region; cerebral organs lie beside brain and reach behind dorsal ganglia, cerebral organ canals branched, with two distinct kinds of epithelium; cerebral organ furrows lack secondary grooves; cerebral ganglia with neither neurochord cells nor inner neurilemma; lateral nerve cords without accessory nerve, with a thin band of connective tissue with numerous myofibrils; foregut divisible into stomach and pyloric region; intestinal caecum with lateral pouches only; lateral intestinal pouches large and lobed; very long rectum with well­developed sphincter of circular muscle fibres; blood system simple, without pseudometameric transverse connectives; mid­dorsal vessel with single vascular plug; excretory system well developed, opening to exterior in midbody region; testes lie in posterior quarter of the intestinal region, gonadal muscle meshwork not developed. Type species: Cratenemertes pelagicus Korotkevitsch, 1961.Published as part of Chernyshev, Alexei V., 2005, Redescription of Korotkevitschia pelagica (Korotkevitsch, 1961) (Enopla: Hoplonemertea: Cratenemertea), a pelagic nemertean from Antarctica, pp. 1-14 in Zootaxa 862 on page 2, DOI: 10.5281/zenodo.17085

Redescription of Korotkevitschia pelagica (Korotkevitsch, 1961) (Enopla: Hoplonemertea: Cratenemertea), a pelagic nemertean from Antarctica

Chernyshev, Alexei V. (2005): Redescription of Korotkevitschia pelagica (Korotkevitsch, 1961) (Enopla: Hoplonemertea: Cratenemertea), a pelagic nemertean from Antarctica. Zootaxa 862: 1-14, DOI: 10.5281/zenodo.17085

An integrative description of a new Cephalothrix species (Nemertea: Palaeonemertea) from the South China Sea

Chernyshev, Alexei V., Polyakova, Neonila E. (2021): An integrative description of a new Cephalothrix species (Nemertea: Palaeonemertea) from the South China Sea. Zootaxa 4908 (4): 584-594, DOI: https://doi.org/10.11646/zootaxa.4908.4.1

Distribution and Phylogenetic Position of the Antarctic Ribbon Worm <i>Heteronemertes longifissa</i> (Nemertea, Pilidiophora)

To date, a total of 23 valid species of heteronemerteans belonging to 15 genera have been recorded in Antarctic and Subantarctic waters. The ribbon worm Heteronemertes longifissa (Hubrecht, 1887) is the only heteronemertean species reported to have bipolar distribution, but this statement is doubtful. The phylogenetic relationships of H. longifissa to other heteronemerteans remain uncertain. A genetic analysis of specimens from Antarctica has shown that the name H. longifissa refers to two sibling species with an uncorrected p-distance of 5.3% in COI. These species differ in body color: one is whitish, and the other is grayish-pink. The species with the whitish body has been reliably identified from off the Norway coast (as Cerebratulus sp. NemBar1383 (BOLD: ACM5920)), i.e., it has a bipolar distribution. A molecular phylogenetic analysis of Lineidae based on five gene markers (COI, 16S, 18S, 28S, and histone H3) has shown the genus Heteronemertes to belong to Lineage D of Clade 2 sensu Kajihara et al., 2022 (crown Lineidae). The phylogenetic positions of four more species of unidentified lineids are currently under discussion

Exploring the basal topology of the heteronemertean tree of life: establishment of a new family, along with turbotaxonomy of Valenciniidae (Nemertea: Pilidiophora: Heteronemertea)

Kajihara, Hiroshi, Abukawa, Shushi, Chernyshev, Alexei V. (2022): Exploring the basal topology of the heteronemertean tree of life: establishment of a new family, along with turbotaxonomy of Valenciniidae (Nemertea: Pilidiophora: Heteronemertea). Zoological Journal of the Linnean Society 196: 503-548, DOI: 10.1093/zoolinnean/zlac01

Figure 6. A–E in Exploring the basal topology of the heteronemertean tree of life: establishment of a new family, along with turbotaxonomy of Valenciniidae (Nemertea: Pilidiophora: Heteronemertea)

Figure 6. A–E, Baseodiscus takakurai Gibson, 1995, ICHUM 6308, A, anterior end of body, ventral view; B, middle body region, showing appearance of body markings in differently contracted states; C, juvenile, showing dorsal mottling; D, juvenile, with head viewed ventrolaterally, showing two ocelli; E, transverse section of proboscis; F, Baseodiscus komatsui sp. nov., holotype, NSNM NMNS-Ne 1, entire body. Photos by H. Kajihara (A–E) and H. Komatsu (F).Published as part of Kajihara, Hiroshi, Abukawa, Shushi & Chernyshev, Alexei V., 2022, Exploring the basal topology of the heteronemertean tree of life: establishment of a new family, along with turbotaxonomy of Valenciniidae (Nemertea: Pilidiophora: Heteronemertea), pp. 503-548 in Zoological Journal of the Linnean Society 196 on page 524, DOI: 10.1093/zoolinnean/zlac015, http://zenodo.org/record/703795