Heteronemertean Species Research Articles

Distribution and Phylogenetic Position of the Antarctic Ribbon Worm Heteronemertes longifissa (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.

Occasional sexual reproduction significantly affects the population structure of the widespread, predominantly asexually reproducing marine worm Lineus sanguineus (Nemertea: Pilidiophora)

Asexual reproduction by fissiparity has only been described from very few of the approximately 1300 nemertean species that otherwise mainly reproduce sexually. The best studied fissiparous species, Lineus sanguineus (Rathke 1799), is a cosmopolitan heteronemertean species inhabiting intertidal habitats of temperate coasts. Although sexual reproduction has never been described, molecular data suggest that sexual reproduction substantially shapes the genetic structure of the investigated populations. In an attempt to clarify the extent of sexual reproduction, three gene fragments (COI, 16S, ITS) were sequenced for 108 specimens sampled in 8 European localities. The results of a phylogenetic analysis and haplotype network showed no clear distinction between different populations, thus indicating the presence of sexual reproduction. Furthermore, we provide circumstantial evidence for the presence of a comparably long-lived planktonic larval stage as present in the closest relatives of L. sanguineus. To further understand the impact of abiotic factors on sexual reproduction and fissiparity, the effect of different temperature and illumination regimes on reproductive behavior and fragmentation was studied in specimens from a population from Bergen, Norway that share the same haplotype. Experimental setups represented summer (long light period and elevated temperature) and winter (short light and decreased temperature) conditions. Under winter conditions, a higher number of animals remained sexually mature and at least one specimen shed eggs on one occasion. Thus, although short light and/or low temperatures are most likely the influential factors on sexual maturity, the factors that influence fissiparity are less clear. The results of this study further solidify the cosmopolitan status of L. sanguineus and clarify the population structuring of this species. In addition, the study provides first data on the dynamics of sexual and asexual reproduction modes on which future investigations will have to expand, especially regarding genetic and physiological aspects.

Nemerteans from deep-sea expedition SokhoBio with description of Uniporus alisae sp. nov. (Hoplonemertea: Reptantia s.l.) from the Sea of Okhotsk

Approximately 90 nemertean specimens were obtained from the material collected by the SokhoBio expedition 2015 in the Kuril Basin of the Sea of Okhotsk and in the Pacific Ocean between the Bussol Strait and the Kuril-Kamchatka Trench. The collected samples included representatives of five nemertean groups: (1) Palaeonemertea; (2) Heteronemertea; (3) pelagic Hoplonemertea; (4) reptantian Hoplonemertea; (5) eumonostiliferous Hoplonemertea. Tubulanid palaeonemerteans, heteronemerteans, and eumonostiliferous hoplonemerteans dominated the samples. Systematic position of 20 specimens was estimated based on five gene markers (16S, 28S, 18S, COI, and H3). Unknown abyssal and hadal nemerteans from the basal family Carininidae were found near the Bussol Strait, as well as in the Kuril-Kamchatka Trench and the adjacent abyssal plain. Four heteronemertean species without longitudinal cephalic slits were collected from the Kuril Basin. The new records of abyssal Sonnenemertes cantelli in the Sea of Okhotsk and near the Bussol Strait confirm the relationships between the abyssal fauna of the Kuril Basin and parts of the Northwest Pacific fauna. The find of Uniporus alisae sp. nov. in the Sea of Okhotsk, described in the article, is the deepest (3301m) record for the genus Uniporus. The results of a phylogenetic analysis have shown that the new species is referred to Cratenemertea rather than to Polystilifera. A DNA analysis has shown that Nectonemertes major, described from the Sea of Okhotsk, is not a valid species. Gononemertes, obtained from the peribranchial cavity of carnivorous ascidians Culeolus sp. in the Kuril Basin, is closely related to Gononemertes sp. MCZ IZ 45558 from the abyssal plain of the Northwest Pacific, but both do not form a common clade with the shallow-water Gononemertes parasita.

Taxonomy and phylogeny of Lineus torquatus and allies (Nemertea, Lineidae) with descriptions of a new genus and a new cryptic species

The heteronemertean genus Lineus Sowerby, 1806 has been badly in need of revision because of its apparent non-monophyly. In this paper, we focus on Lineus torquatus Coe, 1901, one of the heteronemertean species that occur commonly in waters around the North Pacific, as well as a few other allied species distributed in the western North Pacific, including Lineus alborostratus Takakura, 1898 and Cerebratulus montgomeryi Coe, 1901. Based on phylogenetic analyses using 16S, COI, 28S, 18S, and H3 gene and ITS sequences, we detected a well-supported clade comprised of heteronemerteans with a frontal white band on the head, to which we add Kulikovia gen. nov. This genus is nested within a more comprehensive, highly supported clade, here named the Siphonenteron-clade, which contains Tenuilineus bicolour (Verrill, 1892), Lineus flavescens Coe, 1905, Siphonenteron bilineatum (Renier, 1804), S. cf. bilineatum, Lineus cf. caputornatus, and Lineus sp. from Guam. Our analyses confirmed the presence of a cryptic species of what was formerly known as the cherry-red and reddish forms of Lineus torquatus, herein described as Kulikovia manchenkoi sp. nov. based on some external characters, internal morphology, and the four genetic markers (COI, 16S, H3, and ITS). In contrast to the species pair K. torquata–K. manchenkoi, the reddish form of K. alborostrata does not differ genetically from the typical form of this species. The significance of the external and internal characters for distinguishing cryptic species is discussed.http://zoobank.org/urn:lsid:zoobank.org:pub:9BECBC60-9C82-48EC-AD36-FC564D82A5BChttp://zoobank.org/urn:lsid:zoobank.org:act:D02B2339-4F65-4517-9B13-DD4AAB0C55C5http://zoobank.org/urn:lsid:zoobank.org:act:8D239B62-E655-4721-90F0-A4944DD8A3C7

Redescription of Micrura dellechiajei (Hubrecht, 1879) (Nemertea, Pilidiophora, Lineidae), a rare Mediterranean species

The heteronemertean species Micrura dellechiajei is thus far only known from its type locality in the Gulf of Naples (Italy) and has not been recorded in 120 years. During two oceanographic surveys conducted in Spanish Mediterranean waters, several nemertean specimens were collected, and thorough morphological examination indicated that some of these pertained to the species M. dellechiajei, suggesting that populations may be more widespread than previously thought. Because of the rarity of this species coupled with the fact that its last morphological narrative was given 120 years ago, we here provide a redescription of the species based on the new specimens, complete with illustrations and new data concerning its morphology, and we also place some of the collected specimens in a molecular phylogenetic framework.

Sonnenemertes cantelli gen. et sp. nov. (Heteronemertea)—A new Oxypolella-like nemertean from the abyssal plain adjacent to the Kuril–Kamchatka Trench

Approximately 129 nemertean specimens were obtained in the material collected by the Russian–German KuramBio expedition 2012 to the abyssal plain adjacent to the Kuril–Kamchatka Trench (KKT). Due to deformed, fragmentary condition of most of the collected nemerteans they were identified to the order level only. Both archi- and heteronemerteans were very rare, and tubulanid palaeonemerteans and hoplonemerteans were predominant in the KuramBio epibenthic sledge (EBS) samples. Before the KuramBio expedition, only three species of the World fauna of benthic nemerteans had been known from depths exceeding 3000m; according to data of Vityaz expedition in the KKT, published in 1955, unidentified nemerteans were found in all trawl samples from depths 1000 to 4640m, but only one specimen of unidentified nemertean was collected from depths exceeding 5000m. A reliable estimation of the actual species diversity of the present KuramBio samples could have been made primarily based on molecular genetic analyses; almost all the collected specimens are likely to represent undescribed species. In this study, a new species of the heteronemertean, Sonnenemertes cantelli gen. et sp. nov., from a depth of approximately 4870m is described. This is the deepest record for an identified benthic nemertean, as well as the first species of the subfamily Oxypolellinae from the North Pacific. A single specimen was examined by light microscopy, scanning electron microscopy, and confocal laser scanning microscopy with phalloidin and antibody labeling. Morphologically, this species is similar to those in the genus Oxypolella. A preliminary molecular phylogenetic analysis based on partial 16S rDNA among the selected heteronemertean species indicated that S. cantelli formed a monophyletic group with Oxypolella alba Bergendal, 1903 together as a sister to the genus Baseodiscus. Systematic positioning of Oxypolella, Sonnenemertes, and related genera is discussed.

Oligodendrorhynchus hesperides gen. et sp. n. (Heteronemertea) from the Bellingshausen Sea

Oligodendrorhynchus hesperides gen. et sp. n. (Heteronemertea) from the Bellingshausen Sea A new genus and species of heteronemertean from the Antarctic (Bellingshausen Sea), Oligodendrorhynchus hesperides, is described and illustrated. Some morphological features with major systematic significance are following: the mode of branching of the proboscis and its low number of terminal branches; the lack of horizontal lateral cephalic slits but in their place a pair of shallow epidermal depressions; a gelatinous amorphous connective stratum between the outer longitudinal and circular muscle layers; the presence of a rhynchocoelic nerve; isolated fibres of the rhynchocoel circular muscle layer interwoven with bundles of the adjacent body-wall inner longitudinal muscle fibres in the intestinal region. Other anatomical characters which can also be used to distinguish the new taxon from existing heteronemertean species that have a branched proboscis are also discussed.

Genetics do not reflect habitat differences in Riseriellus occultus (Heteronemertea, Nemertea) from Spain and Wales

The description of the heteronemertean species Riseriellus occultus was based on specimens from Spain, where they live imbedded in sand, and Wales, where the specimens were collected intertidally under stones and rocks. Considering these habitat differences, which are not known from any other nemertean conspecifics, we asked if this instead is an example of two sibling species that could not be separated by morphology. We sequenced specimens for the two mitochondrial genes cytochrome oxidase I (COI) and 16S and estimated an intraspecific phylogenetic network using statistical parsimony. This analysis did not disclose any differences congruent with geography/habitat; neither did the phylogenetic analysis using maximum likelihood. The phylogenetic analysis also included new sequences of Lineus longissimus, a species with many external characters in common with Riseriellus occultus.

On the anatomy of a new species of Oxypolella (Nemertini) and further notes on Oxypolella bergendali Cantell 1975

The anatomy of a new species of heteronemertean from the Mediterranean, Oxypolella banyulensis sp. nov., is described and illustrated. The species is characterized by having a dermis comprising subepidermal longitudinal muscle fibres arranged in characteristic piles, a three-layered proboscis with four main regions, one ciliated pit in the frontal organ, two dorsal nerves and a thin inner circular muscle layer. Further notes on Oxypolella bergendali are given.

Some heteronemerteans (Nemertea) from the Solomon Islands

Three species of heteronemerteans are recorded from the Solomon Islands. Baseodiscus quinquelineatus has previously been reported from the islands, but Notospermus tricuspidatus has not. The third species, Kukumia solomonensis gen. et sp. nov., is fully described and illustrated. We compared the 18S rDNA gene sequence from this species with five other heteronemertean species from which the sequence of this gene is known. Phylogenetic analysis using three palaeonemertean species as outgroup corroborated a relationship with lineid taxa.

Molecular Phylogeny of Some European Heteronemertean (Nemertea) Species and the Monophyletic Status ofRiseriellus, Lineus,andMicrura

The 16S rRNA mitochondrial gene was used to reconstruct the relationships among 10 heteronemertean species (subclass Heteronemertea, phylum Nemertea);Lineus ruberandL. viridisare represented by more than one specimen to assess intraspecific variation in these enigmatic species, and the analysis includes in total 14 terminal taxa incorporating one palaeonemertean species (Tubulanus annulatus) for outgroup rooting. The aligned sequences were subjected to maximum parsimony, maximum-likelihood, and neighbor-joining analyses to estimate the phylogenetic relationship of the species. The results were concordant from all analyses and indicate that neitherLineusnorMicruraare monophyletic taxa, and that there is no support from a phylogenetic point of view to establish the monotypic genusRiseriellus.

A new genus and species of heteronemertean from the Changjiang (Yangtze) River Estuary

A new genus and species of heteronemertean, Yinia pratensis gen. nov. and sp. nov., collected from low salinity waters (salinity 0.2–0.4 ‰) at Changjiang River Estuary, is described and illustrated. The species possesses a proboscis with an outer circular and an inner longitudinal muscle layer, and is placed in family Lineidae sensu Gibson. The following combination of morphological features distinguishes the new species from any other genera in this family: proboscis with two muscle crosses; dermis without connective tissue layer between gland cells and body wall outer longitudinal muscle layer; rhynchocoel wall circular muscles not interweaving with adjacent body wall longitudinal muscles; foregut with circular somatic muscles and subepithelial gland cell layer; neurochord cells present in central nervous system; caudal cirrus missing; blood system developed into alimentary plexus extending almost the full length of the body. Another significant character is that the lobular excretory cells are extremely well developed which may represent adaptation to water of low salinity.

Enzyme electrophoresis, genetic identity and description of a new genus and species of heteronemertean (Nemertea, Anopla) from northwestern Spain and North Wales

Enzyme electrophoresis, genetic identity and description of a new genus and species of heteronemertean (Nemertea, Anopla) from northwestern Spain and North Wales

Praealbonemertes whangateauniensesn. gen. and n. sp., a new heteronemertean from New Zealand

Abstract A new genus and species of heteronemertean, Praealbonemertes whangateaunienses n. gen. and n. sp., is described and illustrated. The species is characterised by inter alia a cephalic lacuna with strands of longitudinal muscle fibres, a proboscis with three muscle layers, and a well-developed muscle plate dorsal to the foregut and anterior intestine. The material was collected in New Zealand.