Tetranemertes antonina (Quatrefages, 1846), by monotypy.

Body long and thin, thread-like; head not demarcated from body; numerous ocelli arranged in four longitudinal rows (two on each side of head, the two rows almost on top of one another); cerebral organs small, located far in front of brain; a pair of shallow oblique or transverse cerebral organ furrows restricted to ventral and lateral surfaces, fused mid-ventrally forming a single furrow; cerebral commissures unusually short and wide; lateral nerve cords with a single fibrous core; longitudinal musculature anteriorly divided by a layer of connective tissue, only the inner layer contributes to proboscis insertion, i.e. precerebral septum lacking; rhynchocoel between 1/5 and 1/3 of body length; proboscis short and thin, with a neural sheath rather than distinct proboscis nerves; anterior proboscis very short, stylets located very close to head, often within a few millimeters of cerebral ganglia. The seven new species described below, as well as Tetranemertes rubrolineata, possess an unusual character of having the central stylet’s basis posteriorly slightly bilobed to deeply forked in fully grown individuals.

The genus includes ten described species: Tetranemertes antonina (Quatrefages, 1846), T. rubrolineata (Kirsteuer, 1965), T. hermaphroditica (Gibson, 1982), T. bifrost sp. nov., T. majinbuui sp. nov., T. pastafariensis sp. nov., T. unistriata sp. nov., T. ocelata sp. nov., T. paulayi sp. nov., T. arabica sp. nov., and one undescribed species (Tetranemertes sp. ETP001). Ommatoplea ophiocephala Schmarda, 1859 from South Africa, previously synonymized with T. antonina by Friedrich (1955), is almost certainly a distinct species, most likely not related to Tetranemertes (see Discussion).

Mediterranean Sea (Banyuls, Trieste, Sicily, Naples, Alborán Island, Almería, Strait of Gibraltar), Caribbean Sea (Bocas del Toro, Panamá; Carrie Bow Cay, Belize; Puerto Rico, USA), western Indian Ocean (Madagascar), Arabian Sea (Dhofar Governorate, Oman), Western Pacific (Heron Island, Australia and Honshu Island, Japan), Eastern Tropical Pacific (Panamá).

The name refers to the number of times the genus Nemertes was re-defined: Nemertes Cuvier, 1817, Nemertes Johnston, 1837, Nemertes Friedrich, 1955, and Nemertes Kirsteuer, 1974.

Type material was never designated, and it is very unlikely that either Quatrefages’ or Bürger’s specimens exist or can be found. With the purpose of improving nomenclatural stability, we designate the following specimen examined by us as the neotype: Indemares-Alborán Campaign Sample TE3-DR23 (Fig. 2), collected by Juan Junoy on 25 September 2011 at the depth of 25 m; 35°55.93'N, 03°02.42'W. This specimen is preserved in Bouin’s and stored in 100% ethanol at the Museo Nacional de Ciencias Naturales (MNCN) in Madrid, Spain (Catalog number MNCN 5.02/28). The anterior portion of another individual (TE4-DR23) collected at the same station is stored in 95% ethanol at the Harvard Museum of Comparative Zoology (IZ-132747), and sequences have been published by Kvist et al (2014). See Table 1 for accession numbers, and Table 2 for collecting information.

Figure 2. 

Tetranemertes antonina A external appearance of T. antonina, after Bürger (1895) B central stylet of T. antonina after Bürger (1895). Tetranemertes antonina neotype (specimen: TR3-DR23, Museum ID: MNCN 5.02/28) C external appearance of living specimen and D head in transmitted light showing distribution and number of ocelli. Abbreviations: ae — anterior end, cg — cerebral ganglion, co — cerebral organ. Scale bars: 4 mm (C); 0.75 mm (D).

Uniformly dark pink (wine) color of the body of living specimens distinguishes T. antonina from most species of the genus except T. hermaphroditica, T. arabica sp. nov. and T. majinbuui sp. nov. Tetranemertes antonina, T. majinbuui sp. nov., T. arabica sp. nov., and T. hermaphroditica are widely separated geographically, and T. antonina, T. arabica sp. nov., and T. majinbuui sp. nov. are also easily differentiated by DNA barcodes (Table 5). Tetranemertes hermaphroditica is a simultaneous hermaphrodite, whereas T. antonina we presume to have separate sexes.

Quatrefages (1846) reported the species between the shells of vermetids, which form a sort of belt around the rocks (presumably, intertidally) along the coast of Sicily. Bürger (1895) reported it as “infrequent” from subtidal depths of 70–100 m at shoals in the Gulf of Naples (Secca di Benda Palumma, Secca di Chiaia), and at the Blue Grotto of Capri. Specimens used in this study were collected from coralline red algae and Ulva at 25 m depth in the western Mediterranean Sea at Alborán Island, Spain.

Mediterranean Sea (Banyuls, Trieste, Sicily, Gulf of Naples, Alborán Island, Almería, Strait of Gibraltar).

Unknown, but appears to be a derivative of a person’s name.

The original description (Quatrefages 1846) is very brief. While Quatrefages (1846) did not observe the stylets, noting that the proboscis is unarmed (“proboscis inerme”), Bürger’s much more detailed redescription (1895) includes an illustration of the stylet region of the proboscis, depicting a cylindrical basis that is rounded posteriorly (Fig. 2B). It is not known whether there is variation in the shape of the basis between individuals of this species to range from rounded to forked, as we have observed among specimens of most of the newly described species. Quatrefages may have missed the stylets because Tetranemertes species have an unusually short anterior proboscis, with stylets often found within millimeters of cerebral ganglia. This proximity of proboscis armature to the brain often makes it difficult to obtain stylet preparations. Stylets of the recently collected specimens have not been examined. Photographs of recently collected live specimens identified as T. antonina and their occurrence records can be found in Herrera-Bachiller et al. (2015) and Herrera-Bachiller (2016). Unfortunately, stylet armature was not observed in the recently collected specimens.

The holotype (in the form of histological sections on slides) deposited at the American Museum of Natural History in New York, USA (AMNH 276) was not examined, as external features and stylet characteristics are not discernible in this material. It is not possible to extract DNA from this material. SAM examined several live specimens from the Arabian Sea (Mirbat, Dhofar Governorate, Oman), which conform to the description of T. rubrolineata. See Table 1 for specimen details and accession numbers, and Table 2 for collecting information.

Body color of living specimens (white or yellowish, with a single, longitudinal, wine-red, dorsal stripe) distinguishes T. rubrolineata from all other described species of the genus except T. unistriata sp. nov. (a look-alike described below). Basis of central stylet thick and bilobed posteriorly (Kirsteuer 1965: fig. 17), twice as long as stylet. DNA sequence data (or tissue for molecular analysis) are not available for T. rubrolineata from the type locality (Madagascar) but are available for material from Oman that we consider potentially conspecific.

At the type locality (Madagascar) relatively common on Acropora cytherea (Dana, 1846) (syn. Acropora corymbosa), Acropora pharaonis (Milne Edwards, 1860), Seriatopora hystrix Dana, 1846 (syn. Seriatopora angulata), and Porites nigrescens Dana, 1846. In southern Oman (Mirbat) among coral and shell rubble at 8–30 m depth.

Madagascar (Tanikely Island, Mozambique Channel), and Arabian Sea (southern Oman).

The species epithet refers to the color pattern of living specimens, specifically the red, mid-dorsal, longitudinal stripe.

SAM collected several specimens resembling T. rubrolineata in southern Oman (vicinity of Mirbat) in January 2022 (Fig. 3). These individuals had stylets with helical sculpting and a posteriorly bilobed to deeply forked basis of central stylet (Fig. 3C) in larger individuals (3–4 cm long). The original description of T. rubrolineata depicts a slightly bilobed basis, but does not mention sculpted stylets (perhaps the likely quality of the compound microscope in the primitive field conditions of Tanikely Island in 1959 would have made that observation difficult). Two smaller individuals (1–2 cm long) with an undersized proboscis and armature had a posteriorly rounded cylindrical basis, similar to that observed in the small individual of T. unistriata sp. nov. from Oman.

Figure 3. 

Tetranemertes rubrolineata from the Arabian Sea (Oman). Individual BOMAN-8038 A external appearance in life B head in transmitted light, showing number and distribution of ocelli, as well as ventral cephalic furrow (arrowheads) C stylet armature. Abbreviations: cg — cerebral ganglion, co — cerebral organ. Scale bars: 4 mm (A); 0.25 mm (B); 50 μm (C).

No specimens of this species were available to us for morphological examination or DNA barcoding. Type material consists of the holotype: mature individual, full series of transverse and oblique sections, deposited at the Australian Museum, in Sydney, Australia (W.5880), collected by R. Gibson, 13 July 1975, western mid-reef flat, Heron Island, Capricorn Group.

Body color of living specimens dusky pink overall with translucent and colorless body margins, resembling T. antonina, T. arabica sp. nov., and T. majinbuui sp. nov. Tetranemertes hermaphroditica is the only species in the genus known to be a simultaneous hermaphrodite. Basis of central stylet is described to be cylindrical and rounded posteriorly, similar to that reported by Bürger (1895) for T. antonina, and unlike the posteriorly bilobed or deeply forked basis in other species of the genus, at least in larger individuals. Wide geographic separation also supports the distinctiveness of this species from all others.

Beneath a large fragment of dead coral (Acropora sp.) partially embedded in clean coral sand.

Heron Island, Australia.

The specific name refers to the fact that specimens of this species are hermaphrodites. Note that both Nemertes and Tetranemertes are of female gender (Nemertes is a Greek nymph, daughter of the god Nereus). Consequently, the correct Latin ending of the specific epithet should be -a, not -us.

Type material in the form of histological sections, anterior end preserved for histology, and tissue in 95% ethanol is deposited with the Smithsonian Institution’s National Museum of Natural History: holotype CB057_18_07 (USNM 1618678), paratype 852_080203_8 (USNM 1156475), paratype CB057_18_01 (USNM 1618745). See Table 1 for additional specimens and accession numbers, and Table 2 for collecting information.

Tetranemertes bifrost sp. nov. differs from all other species of this genus by its distinctive color: purple to black dorsally, with a pattern of bright iridescent longitudinal stripes and spots, which may appear blue, green, yellow and orange, depending on the type of lighting, background, and individual, and blue ventrally. Additionally, it differs from T. antonina, T. hermaphroditica, and T. paulayi sp. nov. by basis of central stylet posteriorly forked, and from the first two species by having stylets sculpted with spiral groves. At the molecular level, COI barcodes of sequenced specimens clearly differentiate it from other species of Tetranemertes (Table 5).

External appearance of live specimens. Long, thin, thread-like body. Can stretch much more than 200 mm long, and up to 0.5 mm wide at the head; body up to 0.7 mm wide. Body slightly compressed dorso-laterally in cross-section throughout most of its length. The caudal end is rounded with no obvious modifications. Tetranemertes bifrost sp. nov. is, perhaps, the most spectacularly colored nemertean in the Caribbean, if not the world (Fig. 4A–F). Larger individuals present a black to deep purple body dorsally, with a discontinuous bright blue mid-dorsal longitudinal stripe running from anterior to posterior tip of body. The blue stripe is flanked by two continuous dorso-lateral stripes that tend to appear orange to yellow in larger individuals, or sky blue to luminescent green in smaller individuals. The flanking stripes begin at the level of the cerebral organ furrow, and continue to the posterior tip of body. The pigment composing the stripes is highly iridescent, so that perceived coloration changes with type and direction of incident light. Ventral side is typically bright blue, pigment scattered over the dark background in a form of numerous tiny speckles (Fig. 4A, D, F). When placed in a dish, worms tangle into a writhing mass, and secrete transparent sticky mucus when handled. Move by ciliary gliding, often with a peristaltic wave passing along the anterior part of the body. When mechanically perturbed, contract into a loose coil. The anterior head region is less contractile, causing an obvious discontinuity in width. Blood is colorless. Remarkably resistant to breaking while being extracted from complex substratum.

Figure 4. 

Tetranemertes bifrost sp. nov. A–C external appearance in life of individuals CBdT0062 (A), CB057_18_01 (B), and CB057_18_07 (C) showing variation in color D ventral view of anterior end of individual SMCP0366 showing cephalic furrow (arrowhead) E, F close up views of head in dorsal (E) and ventral (F) view of individual CB057_18_01 showing distribution of pigment, eyes, and the cephalic furrow (arrowhead on F) G anterior end of individual CB057_18_03 compressed under a glass slide to show number and distribution of eyes H, I stylets of individuals CB057_18_01 (H) and CB057_18_04 (I). Note the sculpted stylets, and the difference in basis shape (forked or rounded posteriorly). Abbreviations: cg — cerebral ganglion, pb — proboscis. Scale bars: 5 mm (A–C); 1 mm (D); 0.5 mm (E–G); 25 μm (H, I).

The head has a characteristic, narrow diamond or spearhead shape, vaguely reminiscent of a viper’s head, its anterior region demarcated from the rest of body both by width and a single ventral cephalic furrow, formed by the midventral fusion of the cerebral organ furrows. The cephalic furrow is located anterior to the cerebral ganglia, runs from the lateral sides toward the ventral midline forming a shallow forward-pointing “V”. Margins of the head are clear, translucent; the anterior-most mid-dorsal part of the head often reddish brown (Fig. 4G). Small yellow-orange iridescent speckles are scattered on the lateral sides of the head at the level of the cephalic furrow (Fig. 4E). Mouth and rhynchopore combine into a single ventral anterior rhynchostomopore. Posterior cephalic furrows lacking.

Numerous small reddish brown ocelli (10–20 on each side of head) are arranged in four longitudinal rows (Fig. 4E–G). The medial rows, which are not visible in ventral view, reach as far back as anterior margin of cerebral ganglia. The lateral rows have fewer eyes, reach slightly past the cephalic furrow and are visible in ventral view (Fig. 4F). Ocelli are somewhat obscured by the dark pigment of the head, and best seen in worms compressed between a slide and a cover-glass (Fig. 4G). When viewed from dorsal side appear to form two rows (because the two rows on each side of head are almost directly on top of each other).

Cerebral organs are small and inconspicuous, difficult to see in living specimens, even when compressed under a glass slide and viewed under a compound microscope. Anterior to the cephalic furrow, the head is dorso-ventrally flattened; posterior to it, there is a dorsal bulge over the brain, and the body is rounder in cross-section than the anterior tip. The anterior margin of the head is bluntly pointed, indented anteriorly by the rhynchostomopore. The cerebral ganglia are clear, and are located at the base of the “spearhead”, connected by fairly wide cerebral commissures (Fig. 4G).

Rhynchocoel and proboscis. Rhynchocoel does not exceed 1/3 of body length. Proboscis transparent, with two distinctive regions separated by a stylet region. The anterior proboscis is much shorter than the posterior, and the stylet bulb has a length to width ratio of ~ 1. The proboscis is armed with a single central stylet and a pair of lateral pouches holding two accessory stylets each. The shaft of the stylet is straight, sculpted with longitudinal grooves, twisted into a slight spiral (Fig. 4H, I). The basis is rod-shaped with an approximate 1:4 ratio of width to length, and is forked posteriorly (Fig. 4H). The smallest individual in which stylets have been examined had a smaller posteriorly rounded basis and a smaller stylet (Fig. 4I). Stylet to basis length ratio is 1.2–1.3 (n = 4). The wall of the rhynchocoel is tinged blue.

Reproduction. Oocytes, measuring 50–80 micron in diameter were noted in specimen CB057_18_03 collected in August 2018.

Free living, benthic marine worms inhabiting coral rubble, gravel, and shell hash. Often found stretched between nooks and crannies of the substratum.

Caribbean Sea: Bocas del Toro, Panamá, also common at Fuerte Sherman, Colon, Panamá; photographed off Puerto Rico, draped over an unknown fan coral (in 1970s by Smithsonian photographer Kjell Sandved).

The name refers to the bright, colorful iridescent stripes and spots characterizing this species. Bifrost, the rainbow bridge in the Norse mythology, reaches between Midgard, the human Earth, and Asgard, the realm of the gods. Some authors state that the name Bifrost means “shimmering path” or “the swaying road to heaven”, and that it might be inspired by the Milky Way.

Type material is deposited with the Smithsonian Institution’s National Museum of Natural History. Holotype CB056_18_01 (USNM 1618677): anterior end preserved for histology, and posterior in 95% ethanol. Paratype 856_080303_3 (USNM 1156478): histological sections of anterior end. See Table 1 for additional specimens, accession numbers, and Table 2 for collecting information.

Pink body color distinguishes T. majinbuui sp. nov. from T. bifrost sp. nov., T. rubrolineata, T. unistriata sp. nov., T. ocelata sp. nov., T. pastafariensis sp. nov., and T. paulayi sp. nov. It differs from T. antonina and T. hermaphroditica by having a posteriorly bilobed basis, and spirally sculpted shaft of stylet. It most resembles T. arabica sp. nov. from which it is widely separated geographically. It is currently unknown whether it has separate sexes; if so, then it would distinguish it from T. hermaphroditica, which is a simultaneous hermaphrodite. DNA barcodes characterize this species unambiguously, clearly differentiating it from all other sequenced species of the genus (Table 5).

External appearance of live specimens. Long, thin, thread-like body. Can stretch much more than 10 cm, and is 0.3–0.5 mm wide at the head. Body rounded in cross-section throughout most of its length, but dorso-ventrally compressed in the head region anterior to the brain. The caudal end is bluntly rounded. Body color is uniform intense pink, paler towards the anterior end (Fig. 5A). As viewed with a microscope most of the pink color is associated with the gut, while the anterior end is pale pink or translucent. The caudal end is paler, and has some dorsal granules of darker color. The anterior part of the head is demarcated from the body by both width and a single transverse ventral furrow (Fig. 5B, C, arrowheads).

Figure 5. 

Tetranemertes majinbuui sp. nov. A external appearance in life of individual CB056_18_01 B–D Close ups of head of a living individual CBdT0058, showing eyes and cephalic furrow (arrowheads) in lateral (B) and dorsal (C) view. Note the cephalic furrow is on the ventral side, but shows through due to transparency of the body at the anterior end D Head compressed under a coverglass to show number and distribution of eyes E stylet armature of individual CB056_18_01 with a typical posteriorly bilobed basis F stylet armature of individual CBdT0058 with a less typical basis (not bilobed or forked posteriorly). Note helical sculpting of stylet shaft. Abbreviations: cg — cerebral ganglion, co — cerebral organ. Scale bars: 5 mm (A); 1 mm (B–D); 25 μm (E, F).

When placed in a dish, tangles into a writhing mass. Secretes transparent, sticky mucus when handled. Moves by ciliary gliding, often with the anterior end of the head raised at an angle from the surface, the inflection point coinciding with the lateral indentation of the transverse cephalic furrow. When mechanically perturbed, contracts forming a loose coil. The head region anterior to the cephalic furrow is less contractile, causing an obvious discontinuity in width when the animal is contracted. Regeneration ability not known. Blood is colorless.

Head is shaped like a narrow diamond or spearhead, vaguely reminiscent of a viper’s head. Anterior to the cephalic furrow, the head is dorso-ventrally compressed; posterior to it there is a dorsal bulge corresponding to the cerebral ganglia. The cerebral ganglia are clearly visible, transparent or very pale pink.

A single transverse cephalic furrow is formed by a pair of the cerebral organ furrows, fused mid-ventrally. The furrow starts laterally and continues toward the ventral midline, forming a very shallow forward-pointing “V”, anterior to cerebral ganglia (Fig. 5B, C). Rhynchostomopore is ventral. Posterior cephalic furrows lacking.

Numerous reddish brown ocelli (~ 24 on each side of head) are arranged in four longitudinal rows (Fig. 5B–D). The medial rows, which are not visible in ventral view, reach anterior margin of the cerebral ganglia. The lateral rows have fewer eyes, reach slightly posterior to the cephalic furrow and are visible in ventral view. When viewed from dorsal side appear to form two rows, because the two rows on each side of head are almost directly on top of each other. Cerebral organs small and inconspicuous, indiscernible even on squeeze preparations.

Rhynchocoel and proboscis. Rhynchocoel does not exceed 1/3 of body length. The proboscis is translucent, with two distinctive regions separated by a stylet bulb. The anterior region is much shorter than the posterior, and the bulb has a length to width ratio of ~ 1. The proboscis is armed with a single central stylet and a pair of lateral pouches holding two accessory stylets each. The shaft of the stylet is straight, sculpted with spiral grooves (Fig. 5E, F). The basis is rod-shaped with an approximate ratio of 1:4 width to length, characteristically bilobed posteriorly in larger individuals (Fig. 5E). Two individuals with much smaller stylets (possibly, due to younger age or regeneration of proboscis) were observed to have a basis posteriorly rounded rather than bilobed (Fig. 5F). Stylet to basis length ratio is ~ 1:1 (n = 1).

Reproduction. No data.

Free living, benthic marine worms inhabiting coral rubble at shallow depths (1–7 m). Can be found stretching between nooks and crannies of the substratum.

Bocas del Toro, Panamá; Puerto Rico, USA.

The species is named after Majin Buu, a male (as far as we can tell) character in the anime Dragon Ball Z, due to its resemblance in color, presence of black dots at the anterior end, and behavior-dependent variability in body width.

Type material is deposited with the Smithsonian Institution’s National Museum of Natural History. Anterior ends are preserved for histology and posterior — in 95% ethanol: holotype CB055_18_04 (USNM 1618675), paratype CB055_18_06 (USNM 1618676). See Table 1 for additional specimens, accession numbers, and Table 2 for collecting information.

Tetranemertes pastafariensis sp. nov. differs from all other described species of this genus, except T. ocelata sp. nov. by uniformly pale yellow to orangish yellow body color. It differs from T. ocelata sp. nov. by having smaller ocelli. Easily differentiated from other species with DNA sequence data (Table 5).

External appearance of live specimens. Long, thin, thread-like body can stretch more than 10 cm in length and is up to 0.5 mm wide at the head; body up to 1 mm wide. Body rounded or slightly compressed in cross-section. The caudal end is rounded. Body color is uniform orangish yellow, paler towards the anterior end (Fig. 6A, B). Blood is colorless.

Figure 6. 

Tetranemertes pastafariensis sp. nov. A external appearance in life of individual CB055_18_04 B anterior end in ventral view of individual CB055_18_06 showing cephalic furrow (arrowhead, cf) C stylets of individual CB055_18_08 showing a posteriorly bilobed basis and sculpted stylets D head of individual CBdT0059 compressed under a glass slide showing number and distribution of eyes, as well as cerebral organs (arrowheads) and pinkish cerebral ganglia. Abbreviations: cg — cerebral ganglion, co — cerebral organ. Scale bars: 5 mm (A); 1 mm (B, D); 25 μm (C).

When placed in a dish, often forms a writhing tangle. When mechanically disturbed it contracts into a knot, and secretes transparent sticky mucus. Moves by ciliary gliding, often with the anterior end of the head raised from the surface, the inflection point coinciding with the lateral indentation of the anterior cephalic furrow. The head region anterior to the anterior furrow is less contractile, causing an obvious discontinuity in width when the anterior end of the animal is contracted. Regeneration ability not known.

The head is somewhat triangular, spear-shaped, resembling head of a snake. The anterior part of the head is demarcated from the body by both width and an anterior ventrolateral cephalic furrow. The body is dorso-ventrally flattened in front of the anterior cephalic furrow; and thicker posterior to it, with a dorsal bulge corresponding to the brain. The cerebral ganglia, tinged pale pinkish orange, are visible through the body wall. The anterior margin of the head is bluntly pointed, slightly indented by the rhynchostomopore.

Cerebral organ furrows are fused ventrally forming a single cephalic furrow (Fig. 6B, arrowhead). The cephalic furrow wraps around the lateral sides of head, and is barely visible from the dorsal side as a pair of lateral indentations. On the ventral side it forms a shallow anteriorly-pointed “V” anterior to cerebral ganglia. Posterior cephalic furrow is lacking. Mouth and rhynchopore are combined into a single anterior ventral rhynchostomopore.

Ocelli (20–40) are arranged in four longitudinal rows, two on each side of the head (Fig. 6B), reaching to posterior margin of cerebral ganglia (Fig. 6D), black in transmitted light. The medial rows are not visible from the ventral side. Cerebral organs present, clearly visible in specimens compressed under a cover slide (Fig. 6D).

Rhynchocoel and proboscis. Rhynchocoel does not exceed 1/3 of body length. The proboscis is transparent, with two distinctive regions separated by a proboscis bulb. The anterior region is much shorter than the posterior, and the bulb has a length to width ratio of ~ 1. Proboscis armed with a single central stylet and two pouches, each holding two or three accessory stylets. The central stylet shaft is straight with spiral grooves. The stylet basis is rod-shaped, with a width to length ratio of ~ 1:4 to 1:5, with characteristic shallow fork posteriorly (Fig. 6C). One individual had a cylindrical basis with rounded posterior (not shown). Stylet to basis length ratio is ~ 1:1 (n = 2).

Reproduction. No data.

Free living, marine benthic species, inhabiting shallow coral reef rubble (1–7 m depth). Tends to stretch in the crannies of the substratum.

Currently only known from Bocas del Toro, Panamá.

The species is named after its resemblance to the Flying Spaghetti Monster, the deity of the Pastafarian religion.

Tetranemertes unistriata sp. nov. differs from most other described species of the genus by its color pattern: a single pale to dark pink mid-dorsal longitudinal stripe on a pale yellow to pale pinkish background. Resembles T. rubrolineata from Madagascar (Kirsteuer 1965) in body color. Although tissue for DNA analysis is not available for T. rubrolineata from Madagascar, DNA sequences from individuals collected by SAM from the Arabian Sea and identified as T. rubrolineata clearly separate the two species. DNA barcodes of T. unistriata sp. nov. are also clearly distinct from those of all other sequenced species of the genus (Table 5).

Type material in the form of histological sections and tissue in 95% ethanol is deposited with the Smithsonian Institution’s National Museum of Natural History. Holotype: 490_071099_2 (USNM 1011574), paratype 490_070999_1 (USNM 1011573). Additional specimens, accession numbers, and collecting information can be found in Tables 1, 2.

External appearance of live specimens. Body thin, thread-like, a few centimeters in length, and less than a millimeter in width. Anterior and posterior ends are gently tapering, bluntly rounded. Color in life varies from pale yellowish orange to pale pink, with a continuous thin reddish or dark pink mid-dorsal longitudinal stripe that reaches from anterior to posterior tip of body (Fig. 7A). Head the same width or slightly narrower than the rest of body, demarcated from the rest of body by a pair of ventral anterior cephalic furrows, nearly fused mid-ventrally to form a shallow anteriorly pointed “V” (Fig. 7B). Rhynchostomopore appears as a short ventral slit, at the anterior tip of head. Small dark ocelli (9–12 on each side of head) are arranged in four longitudinal rows, the two rows on each side of head almost directly on top of one another (Fig. 7D, E). The smaller individual from Oman had fewer ocelli (Fig. 7G, I). Cerebral ganglia large, yellowish or pinkish, partly translucent, show through the body wall (Fig. 7D, E, G). Cerebral organs small, inconspicuous.

Figure 7. 

Tetranemertes unistriata sp. nov. A–E based on sketches from live material (individuals 490_070999_1 through 490_070999_3) from Japan A external appearance in life B diagram of head in ventro-lateral view showing cephalic furrow C stylet and basis D, E anterior end in dorsal (D) and lateral (E) views showing number and arrangement of eyes, and cerebral ganglia E stylet and basis F, G appearance in life of individual BOMAN-07032 from Oman: body shape (F), anterior end in incident light (G) showing size and position of cerebral ganglia and eyes, stylet apparatus (H), and compressed head region in transmitted light to show eye arrangement (I). Abbreviations: cf — cephalic furrow, cg — cerebral ganglion. Scale bars: 1 cm (A); 50 μm (C); 5 mm (F); 1 mm (G); 40 μm (H); 150 μm (I).

Rhynchocoel and proboscis. Rhynchocoel length unknown, but likely restricted to anterior-most region of body. Proboscis short and thin. Stylets were examined in one ~ 8-cm long individual (paratype) from Japan, and the ~ 2 cm long individual from Oman. Central stylet with a straight spirally sculpted shaft, 20–50 μm long. Basis cylindrical, deeply forked posteriorly, 25–75 μm long (Fig. 7E). Two accessory stylet pouches with 2 stylets each. Smaller individual from Oman had considerably smaller stylets and smaller cylindrical basis, rounded posteriorly (Fig. 7H).

Reproduction. No data.

Free-living, marine. Among brown and branched calcareous algae at the depths of 1–2 m in the type locality in Japan. Among coral rubble at 4–9 m depths in Oman.

Type locality is near Seto Marine Laboratory on the Pacific coast of Honshu Island, Japan. One other individual was collected by SAM in the Arabian Sea (Dhofar Governorate, Oman).

Specific epithet reflects the color pattern of living individuals.

Tetranemertes ocelata sp. nov. differs from most other species of the genus by uniformly pinkish orange body color without distinct markings. It most resembles T. pastafariensis sp. nov., from which it differs by having much larger ocelli, and more intense color (pinkish orange as opposed to pale yellow). It differs from T. paulayi sp. nov. by having larger eyes, paler body color, and colorless blood. DNA sequences also clearly differentiate this species from all other sequenced species of the genus (Table 5).

Type material in the form of histological sections is deposited with the Smithsonian Institution’s National Museum of Natural History: holotype 685_061202_2 (USNM1156296), paratype 685_061202_4 (USNM 1156298). See Table 1 for additional specimens, accession numbers, and Table 2 for collecting information.

External appearance of live specimens. Body long and thin, thread-like, tangles easily, up to 12 cm long at rest, but can stretch up to 50 cm. Body width varies from 0.1 mm posteriorly to 0.7 mm in the head region. Head dorso-ventrally flattened; the rest of the body cylindrical in cross-section. Most of the time the worm remains loosely and irregularly tangled and coiled. The head contracts linearly when disturbed. Background color from very pale yellow to salmon color or deep pinkish orange (Fig. 8A). The epidermis appears pale and translucent to transparent, the deepest color associated with the gut. Small specks of darker orange or pale brown pigment scattered throughout the epidermis, others associated with the central nervous system.

Figure 8. 

Tetranemertes ocelata sp. nov. A external appearance in life B proboscis armature showing bilobed basis and sculpted stylets C head compressed under coverslip to show number and arrangement of eyes, cerebral organs and cerebral ganglia D head in ventro-lateral view showing eyes and the cephalic furrow (arrowhead). Abbreviations: cg — cerebral ganglion, co — cerebral organ. Scale bars: 1 mm (A); 50 μm (B); 0.2 mm (C, D).

Head slightly wider than adjacent body, triangular or spear-shaped, reminiscent of the shape of a snake’s head. Anterior tip of head bluntly rounded. Head demarcated from the body by a single shallow ventro-lateral cephalic furrow, formed by a pair of cerebral organ furrows meeting mid-ventrally, and creating an anteriorly directed “V” (Fig. 8D). Posterior cephalic furrow is lacking. Mouth and rhynchopore are combined into a single anterior ventral rhynchostomopore. The head is widest at the level of the cephalic furrow.

Ocelli are proportionally much larger than in other species of the genus, resemble those of cratenemertids and reptant polystiliferans, reddish brown in color, arranged in four rows (two on each side of head, almost directly on top of each other). Eyes of the more lateral/ventral rows are larger than the eyes in the medial/dorsal rows (Fig. 8C, D).

Cerebral ganglia large, translucent, with specks of pinkish pigment, and very wide commissures. Cerebral organs anterior to the cerebral ganglia, visible on squeeze preparations of the head (Fig. 8C).

Rhynchocoel and proboscis. Length of rhynchocoel unknown. Proboscis very short (a few mm long), restricted to the anterior-most part of body. Basis of central stylet long and cylindrical, variably rounded or slightly bilobed posteriorly . Shaft of central stylet straight, sculpted with weakly spiraling groves. Two accessory stylet pouches, each with two accessory stylets (Fig. 8B).

Reproduction. Reproductive specimens collected at Carrie Bow Cay, Belize in June 2002.

Subtidal coral and shell rubble (with significant quantity of orange sponge) at the depth of 20–71 m depth.

Caribbean Sea (Belize) and the Gulf of Mexico.

Specific epithet refers to the size of the ocelli, which are larger than in the other described species of this genus.

Tetranemertes paulayi sp. nov. differs from all other known species of the genus by its orange color, and reddish orange blood vessels. Also, all examined specimens of this species, including the largest, had a pear-shaped rounded basis of central stylet, never bilobed or forked, unlike in larger individuals of most other species of the genus that we have examined. DNA barcoding clearly shows that this species is distinct from the other representatives of the genus (Table 5).

Type material in the form of anterior and posterior preserved for histology, and midbody in 95% ethanol is deposited with the Florida Museum of Natural History. Holotype: BOMAN_07013 (UFID 1055), paratype BOMAN_08291 (UFID 1118). See Table 1 for additional specimens, accession numbers, and Table 2 for collecting information.

External appearance of live specimens. Body is orange-colored (Fig. 9A), with pigment mostly associated with subepidermal layers and the gut. The epidermis pale and translucent, with small specks of orange color throughout. Smaller individuals are paler in color. Body shape is typical for species of the genus: long and thread-like, widest at the level of cerebral ganglia. Anterior tip bluntly rounded. Cerebral organs far in front of the cerebral ganglia (approximately half-way between the cerebral ganglia and anterior tip of head). A single ventro-lateral cephalic furrow is in front of cerebral ganglia, shaped as a shallow anteriorly directed “V” (Fig. 9B). Posterior cephalic furrow is lacking. The head is widest at the level of the cephalic furrow. Blood vessels appear orangish red, and stand out against the background of other internal structures, especially in the posterior region.

Figure 9. 

Tetranemertes arabica sp. nov. and Tetranemertes paulayi sp. nov. from the Arabian Sea (Oman), and Tetranemertes sp. ETP001 from Eastern Tropical Pacific A–C Tetranemertes paulayi. Individual BOMAN-07013, holotype, external appearance in life (A), and head compressed under coverglass (B) to show number and arrangement of eyes, and cephalic furrow (arrowhead). Note orange blood vessels (inset, and white arrowheads). Individual BOMAN-08291, paratype (C), stylets, viewed through the body wall of an individual compressed under coverglass (hence the orange tinge), inset emphasizes sculpted stylets (individual BOMAN-08302) D–F Tetranemertes arabica. Individual BOMAN-09099, external appearance in life (D), proboscis armature (E). Inset on E shows sculpted stylets (individual BOMAN-08030). Individual BOMAN-08050, head compressed under coverslip to show arrangement of eyes (F). Note the pink tinge to the body wall and proboscis wall, and orangish cerebral ganglia G Tetranemertes sp. ETP001 from the Pacific coast of Panamá (individual SMPP0632). Scale bars: 3 mm (A); 0.2 mm (B, F); 50 μm (C and insets on C, E); 100 μm (E); 2 mm (D); 0.5 mm (G).

Rhynchocoel and proboscis. Rhynchocoel limited to the anterior-most part of the body (~ ¼ of body length). Proboscis is very short, with stylet region found immediately posterior to the cerebral ganglia. Basis of central stylet is consistently rounded, never forked or bilobed, even in the largest individuals (4–6 cm long). The stylet shaft is spirally sculpted (Fig. 9C).

Reproduction. No data.

Coral rubble, vermetid-coralline encrustations on rocks, algal holdfasts, barnacles, and algae, at depths of 0–13 m.

Currently only known from the Arabian Sea (Mirbat, Dhofar Governorate, Oman).

Species is named after Dr. Gustav Paulay for his outstanding contributions to studies of marine invertebrate diversity of the world.

Pink body color distinguishes T. arabica sp. nov. from T. bifrost sp. nov., T. rubrolineata, T. unistriata sp. nov., T. ocelata sp. nov., T. pastafariensis sp. nov., and T. paulayi sp. nov. It differs from T. antonina and T. hermaphroditica by having a basis posteriorly bilobed, stylet spirally sculpted. It most resembles T. majinbuui sp. nov. from which it is widely separated geographically. It is currently unknown whether it has separate sexes; if so, then it would distinguish it from T. hermaphroditica, a simultaneous hermaphrodite. DNA barcodes characterize this species unambiguously, clearly differentiating it from all other sequenced species of the genus (Table 5).

Type material is deposited with the Florida Museum of Natural History. Holotype BOMAN_08050 (UFID 1087), in the form of anterior and posterior preserved for histology, and midbody in 95% ethanol, and paratype BOMAN_08300 (UFID 1085) in the form of anterior and posterior preserved for histology, and midbody in 95% ethanol. See Table 1 for additional specimens, accession numbers, and Table 2 for collecting information.

External appearance of live specimens. Body is pale to deep pink. Larger individuals have deeper coloration. Pink specks scattered throughout epidermis, as well in the stylet region of the proboscis. Body long and thin, thread-like, widest at the level of the cerebral ganglia and cephalic furrow (Fig. 9D). Anterior end is least pigmented, semi-translucent. Eyes (25–35) are arranged in four longitudinal rows, two rows on top of each other on either side of head. Anterior tip of head bluntly rounded. A single ventro-lateral cephalic furrow is in front of cerebral ganglia, shaped as a shallow anteriorly directed “V” (Fig. 9F). Posterior cephalic furrow is lacking.

Rhynchocoel and proboscis. Rhynchocoel and proboscis very short (< 1/3 body length), with stylets found within the anterior-most quarter of the body. All examined individuals (n = 8) possessed a posteriorly forked basis and spirally sculpted stylets (Fig. 9E).

Reproduction. Ripe males observed in January 2022.

Coral rubble, shell hash, rocks encrusted with coralline algae and vermetid tubes; between the depths of 2–30 m.

Currently only known from the Arabian Sea (Mirbat, Dhofar Governorate, Oman).

Species epithet refers to the type region of the species, the Arabian Sea (and the coast of the Arabian Peninsula).

A single individual of this species (SMPP0632) was extracted by CE from coral rubble collected by Maycol Madrid on 20 Jan 2020 at Isla Pachequilla (8.67231, -79.0605) from a depth of 5 m using SCUBA. Posterior end of specimen was missing. Partial specimen was 4–5 mm long and ~ 0.3 mm wide. Body uniformly pink with colorless margins and a single mid-dorsal longitudinal stripe, which is light in color and iridescent, similar to that seen in the Caribbean species Tetranemertes bifrost sp. nov. described above, and begins just posterior to the cephalic lobe. Four rows of pre-cerebral ocelli, two on each side, orange-red in reflected light, large in relation to head compared to other eumonostiliferan nemerteans. Head wider than body, diamond-shaped. Stylets not observed. Although we do not have a morphological voucher to designate the holotype and thus formally describe this species, DNA sequences clearly differentiate it from all other species of Tetranemertes (Table 5). See Table 1 for accession numbers.