Type species. Micrura alaskensis Coe, 1901, fixed by original designation.

Etymology. The generic name is feminine in gender, neologized by combining the first part of the Latin maculosus (having spots, spotted) and aura (air, breeze) in reference to the characteristic spotted pigmentation of the thin veil-like amnion surrounding the juvenile inside the pilidium larva, a suspected synapomorphy of this genus (pilidium maculosum morphotype, Fig. 2A).

Diagnosis. Body wall of typical heteronemertean composition with outer and inner longitudinal muscle layers separated by middle circular layer; middle circular muscle layer thickens in posterior esophageal region; outer dermis markedly glandular; sub-epithelial foregut glands—referred to as “accessory buccal glands” by Coe (1901)—associated with buccal cavity and extending into ventral outer longitudinal musculature; proboscis unbranched and unarmed, with four muscle layers including outer and inner (endothelial) circular, longitudinal and, sometimes inconspicuous, diagonal muscle layer—i.e., the musculature is “modified heterotype” according to Chernyshev (2015); two proboscis muscle crosses present, although sometimes thin; outer longitudinal musculature in proboscis absent or present as two muscle strands outside main proboscis nerves; rhynchocoel with outer circular and inner longitudinal muscle layers, not consistently interwoven with body wall musculature; dorsal ganglia separate posteriorly into upper and lower neuropil; neurochord cells absent; inner and outer neurilemma present; external color of live worms pale to dark pink, sometimes white anteriorly; lateral cephalic slits relatively shallow compared to those in other lineids (A. V. Chernyshev, pers. comm.); ocelli lacking at all stages of development as well as in adults; head shape ovate to rectangular, with obtuse apex (Fig. 2B–F), not distinctly marked from the rest of body (i.e. posterior margins of lateral slits linear), except when contracted; body oval in cross-section in foregut region, dorso-ventrally flattened in midgut region; lateral body margins not sharp; worms glide, but do not swim; caudal cirrus present and regenerated easily if lost; gonochoric, with gonads serially arranged and alternating with intestinal diverticula; fertilization occurs externally in water column (i.e. broadcast spawning); oocytes 75–125 µm, with or without chorion; sperm morphology modified or primitive with headpiece size 5–15 µm long (Fig. 3); with planktotrophic pilidium larva of “gyrans” type with conspicuous reddish, black, or brown pigment spots decorating the juvenile amnion (pilidium maculosum).

Composition. This genus includes five species: Maculaura alaskensis comb. nov., Maculaura aquilonia sp. nov., Maculaura cerebrosa sp. nov., Maculaura magna sp. nov., and Maculaura oregonensis sp. nov. (Fig. 2B–F).

Geographic distribution. The geographic distribution of this genus, as confirmed by DNA sequence data, includes the NE Pacific: Alaska (Juneau and Kachemak Bay), Washington (False Bay, San Juan Island), Oregon (Seaside, Coos Bay, Charleston), and California (Crescent City); and the NW Pacific (the Sea of Okhotsk, Russia) (Fig. 1 A). Additional records, awaiting confirmation by DNA sequence data, include various locations in Alaska: Glacier Bay, Sitka, Yakutat, Prince William Sound (Coe, 1901), British Columbia (Coe, 1940), southern California to Ensenada, Mexico (Coe, 1940), and Hokkaido, Japan (Yamaoka, 1940; Iwata, 1954; Gibson, 1995; Roe et al., 2007; Kajihara, 2007). Numerous larvae that were confirmed to belong to this genus have been collected from Coos Bay, OR. Larvae of this morphotype have also been found in plankton near Bamfield, B.C., Canada (Lacalli, 2005).

Micrura alaskensis Coe, 1901, in part.

Etymology. The specific epithet is an adjective (-ensis, -ense), referring to the geographic origin of specimens originally described by Coe (1901).

Type material. Morphological types do not exist. We hereby designate a series of transverse histological sections (18 slides # 1282106) and associated ethanol-preserved material from an individual collected from a mudflat in Charleston, OR by T. Hiebert (Table 1) as the neotype, according to Article 75.3 of the Code (ICZN, 1999). Neotype is deposited at the NMNH. We further designate a partial COI sequence from a different individual collected from the same location as a topogenetype (GenBank accession number KP682055, Table 1).

Material examined. Forty-seven adult individuals (collected from False Bay, San Juan Island, WA as well as locations in or near Gearhart and Charleston, OR) and one wild-caught larva were examined and their identification confirmed by DNA sequence data (see Table 1 for GenBank accession numbers). These included serial transverse histological sections of two individuals (36 slides # 1282107 and 18 slides, neotype, # 1282106), and four whole specimens preserved for histology (#s 1282108–1282111); ethanol-preserved tissue from all six specimens is deposited at the NMNH (Table 1). Ethanol-preserved tissue and/or extracted DNA from remaining individuals are held at the OIMB.

Diagnosis. Maculaura alaskensis comb. nov. differs from M. magna sp. nov. and M. oregonensis sp. nov. by its smaller size, narrower body, and not as pink body color. It most closely resembles M. aquilonia sp. nov. and M. cerebrosa sp. nov. in body shape, color, and size. Maculaura alaskensis differs from M. cerebrosa by having cerebral ganglia of the same general hue as the body (as opposed to having a distinctly pink brain) and a relatively longer caudal cirrus with an abrupt (as opposed to gradual) transition from posterior body (compare Fig. 4B with 4J). Differentiating M. alaskensis from M. aquilonia is challenging and best achieved with freshly collected specimens, as colors can fade in the lab over time. Whereas M. alaskensis is pale anteriorly, M. aquilonia can have a brownish region near the brain (Fig. 4F). The easiest way to distinguish M. alaskensis from M. aquilonia and the other three species is by comparing their eggs and sperm (Fig. 3). At 75 µm in diameter, M. alaskensis eggs are the smallest in the genus (M. oregonensis egg size is not known), and they lack a chorion. Maculaura alaskensis sperm is primitive with a short (5 µm) headpiece, similar to that in M. oregonensis, but distinctly different from the sperm in the other three species, which have variously elongated headpieces.

Habitat, type locality, and distribution. The known range of this species confirmed by DNA sequences extends from False Bay, San Juan Island, Washington to southern Oregon (WA-F1 to OR-C, Fig. 1A), where it is common. Individuals are commonly encountered in the top 10–15 cm of silty, relatively small-grained sand and mud from mid- to low intertidal (e.g. Fig. 1D) in protected bays and estuaries. Although patchy in distribution, several individuals can be found in one shovel-load, stretched like threads between clods and clumps of sand (Fig. 1E). It is quite possible that this species occurs further north and south along the Pacific coast of North America (including Alaska), but none of the individuals from outside Oregon and Washington, that we have sequenced, belong to this species. Coe (1901) did not specify a type locality, but based his description on specimens from a variety of locations in Alaska. Later, Coe (1904, 1940) revised the species range to include southern California and Mexico. The type locality of M. alaskensis comb. nov. is now regarded to be Charleston, OR, as the place of origin of the neotype becomes the type locality of the nominal species-group taxon, according to Article 76.3 of the Code (ICZN, 1999).

Description. External appearance. Largest specimens examined by us were 5 cm in length and 2–3 mm in width, with average length 3–4 cm and width 1–2 mm (Figs. 2B, 4A, B), while gliding. Living worms are, generally, a uniform pinkish or flesh-color. Body is rounded in the foregut region and dorso-ventrally flattened in the midgut region. Sexually mature individuals can appear pale yellow to white due to the color of gametes visible through the body wall between intestinal diverticula. The ventral surface is only slightly lighter than dorsal, if at all. The tip of the head is narrow and rounded, and head is not prominently demarcated from body when worm is gliding. Relatively shallow horizontal cephalic slits extend from anterior tip of the head to about the anterior margin of the mouth. Ocelli are lacking. Mouth is slit-like and elongated. The caudal cirrus is abruptly demarcated from the posterior end of body, and tends to be relatively long and thin compared to that in several other members of the genus (e.g. compare Figs. 2B with 2D, E, and 4B with 4J). Movement is without distinct peristalsis (Fig. 4A). Worms fragment during collection, especially when sexually mature, and posterior end regenerates routinely; anterior regeneration has not been observed. To avoid fragmentation worms should be collected with clumps of sand or mud, and cleaned in the laboratory.

Body wall. The epidermis is ciliated and of uniform thickness, situated on top of a thin dermis; the latter term used here in reference to the thin layer of extracellular matrix underlying the epidermis (Fig. 5E). Gland cells, staining red and blue, are interspersed within the cutis (subepidermal glandular region between the dermis and outer longitudinal musculature, OLM) (Fig. 5A–D). The transition from cutis to the OLM is gradual and visible only by the presence of gland cells that are confined to the cutis anteriorly and extend into the OLM immediately anterior and posterior to the mouth (compare Fig. 5A with 5C, E). The OLM is slightly thinner than the inner longitudinal muscle layer (ILM, e.g. Fig. 5E), but the two layers are of equal thickness in the intestinal region where the circular musculature (CM) is thickest (Fig. 5F). The thick esophageal circular muscle layer (1/2 as thick as body wall CM reported by Coe (1901) was not observed.

Proboscis and rhynchocoel. The rhynchocoel opening is slightly subterminal (ventral); proboscis is long and coiled. The rhynchocoel musculature under the vascular plug is not interwoven with body wall musculature. The proboscis consists of four distinct muscle layers including inner (endothelial) circular, longitudinal, diagonal, and outer circular; two thin muscle crosses were observed in confocal sections (A. Chernyshev, personal communication). The proboscis epithelium sits atop a thin layer of extracellular matrix; glandular ridge present and with red-staining gland cells (Fig. 5E, H).

Digestive system. The mouth is situated ventrally. The opening is a short (80 µm), thin slit that begins immediately posterior to the cephalic slits. Just anterior to the mouth opening, gland cells that open into the foregut (“accessory buccal glands”, following Coe's terminology), become apparent ventrally (Fig. 5D) and remain prominent throughout the anterior esophageal region. At least two types of gland cells are associated with foregut epithelium, one staining orange-red and the other staining purple, and, at times, their bodies may extend into the OLM (Fig. 5D). The foregut is densely ciliated, folded and packed with gland cells. The transition from foregut to intestine is gradual. Intestinal diverticula are not branched. Short, unbranched hindgut opens via a ventral anus anterior to the caudal cirrus.

Excretory system. Relatively large nephridia are found 5 mm from the anterior tip (Fig. 5E) and extend as canals before opening to the outside via two dorso-lateral nephridiopores, one on each side (Fig. 5G) near the transition between foregut and intestine.

Vascular system. Two conspicuous lateral blood vessels flank the rhynchocoel, and a dorsal blood vessel is situated within the ventral wall of the rhynchocoel for the length of the foregut. The mid-dorsal blood vessel enters the rhynchocoel near the brain and forms a single ventral vascular plug. Two lateral cephalic blood lacunae are connected anteriorly via an anastomosing lacuna and, at the level of the brain commissures, surround the ventral rhynchocoel. These blood lacunae are, at times, connected with the blood sinuses surrounding the foregut and become distinct vessels posteriorly. The dorsal blood vessel originates from the commissure between the two lateral vessels just posterior to the ventral brain commissure and is easily observed ventral to the rhynchocoel wall in the intestinal region.

Nervous system. Dorsal and ventral cerebral ganglia are connected via dorsal and ventral commissures, respectively, surrounding the anterior rhynchocoel. The brain is relatively large, and the ventral commissure (Fig. 5A) is nearly twice as thick as the dorsal commissure. The proboscis has two lateral nerves clearly visible anteriorly, which arise from and enter the proboscis anterior to the ventral brain commissure. Lateral nerve chords are situated just outside the CM (Fig. 5F) and consist of a fibrous core and ganglionic region, which are surrounded by blue-staining inner and outer neurilemma, respectively. Two esophageal nerves originate from the inner margin of ventral cerebral lobes at the level of the cerebral organs and are apparent lateral and ventral of the main lateral nerves.

Sense organs. Paired cerebral organs lie just posterior to ventral brain commissure and their canals open into lateral cephalic slits (Fig. 5B). The epithelium of each cerebral organ canal is densely ciliated with underlying conspicuous gland and nerve cells staining orange and fuchsia, respectively (Fig. 5B). Each cerebral organ is connected to the dorsal cerebral ganglion via a cerebral organ nerve. Three apical sense organs were observed in confocal sections (A. Chernyshev, personal communication), but were not observed with histological sections.

Reproduction and development. Reproductive females and males have been collected March-September in OR and WA, with ripest individuals found in summer months. Gonads are arranged laterally between intestinal diverticula. Ovaries contain dozens of oocytes (Fig. 5H). Once dissected into seawater and rounded up, oocytes are 75 µm in diameter and without a chorion (Fig. 3A, Maslakova, 2010). Sperm head pieces (Fig. 3B, Maslakova, 2010) are 5-µm long, cone-shaped i.e. not modified (Stricker and Folsom, 1998). The wild-caught larva, identified as belonging to this species by DNA sequence data, was collected from Coos Bay plankton in October (Fig. 1C). When reared in the lab, first and second cleavage occurs at 2 and 3 hours after fertilization, respectively, at 11–14°C and larvae begin feeding on Rhodomonas lens at 3 days (Maslakova, 2010). They have three pairs of imaginal discs as early as 14 days, and the discs fuse to form a complete juvenile worm by as early as 28 days (Maslakova, 2010). Metamorphosis has been observed in lab culture as early as 35 days after fertilization. Prior to metamorphosis larvae are approximately 500 µm tall and wide (Maslakova, 2010). The larva exhibits the characteristic pilidium maculosum morphotype (Fig. 6), where the amnion surrounding the juvenile worm is pigmented with a polka-dot pattern consisting of red, black, and maroon pigment spots (Maslakova, 2010).

Etymology. This specific epithet is a Latin adjective (aquilonius, -a, -um; “northerly” or “northern”), in reference to the geographic range of this species, reaching the northernmost latitudes for this genus.

Type material. Type material is deposited at the NMNH and includes serial transverse sections of the holotype (male, 20 slides # 1282112) and one paratype (18 slides # 1282113) as well as additional ethanol-preserved tissue. Additional paratypes include four un-sectioned paratypes preserved for histology (#s 1282114–12821117) and associated ethanol-preserved tissue (Table 1). We designate a partial COI sequence from an individual collected from Charleston, OR as a topogenetype (GenBank accession number KP682130, Table 1); ethanol-preserved tissue from this individual is also deposited at NMNH (# 1282118).

Material examined. Forty-three adult individuals, including holotype and paratypes, and four wild-caught larvae were examined and their identification confirmed by DNA sequence data. These individuals were collected from locations near Juneau, AK, and Charleston, OR, USA, as well as from the Sea of Okhotsk near Magadan, Russia (Table 1). COI sequence data from seven individuals collected in Kachemak Bay, AK, by S. Maslakova and J. Norenburg were supplied by J. Norenburg (Smithsonian Institute) from archived specimens (Table 1). Ethanol-preserved tissue and/or extracted DNA from remaining individuals are held at the OIMB.

Diagnosis. Maculaura aquilonia differs from M. magna and M. oregonensis by its smaller size, narrower body, and not as pink body color. It is similar to M. alaskensis and M. cerebrosa in body shape, color, and size. Maculaura aquilonia differs from M. cerebrosa by having cerebral ganglia of the same general hue as the body (Fig. 4C, D) (as opposed to having a distinctly pink brain, Fig. 4G, I) and a relatively longer caudal cirrus with an abrupt (Figs. 2C, 4E) (as opposed to gradual, Figs. 2D, 4J) transition from posterior body. Maculaura aquilonia can be differentiated from M. alaskensis by the presence of a subtle brownish region near the brain, which is best observed in freshly collected specimens (Fig. 4C, D, F). We observed this color in the majority of freshly collected specimens, and it seemed to fade over time in the lab. The most accurate way to differentiate M. aquilonia from M. alaskensis and the other three species is by comparing their eggs and sperm (Fig. 3). Maculaura alaskensis eggs are the smallest in the genus (M. oregonensis egg size is not known), and they lack a chorion (Fig. 3A). The eggs of M. aquilonia also lack a chorion, but are larger, 90–100 µm in diameter (Fig. 3E). M. alaskensis sperm is primitive with a short (5 µm) headpiece (Fig. 3B). Maculaura aquilonia and M. oregonensis sperm are indistinguishable, they both have slightly elongated but not curved headpieces 7–8 µm in length (Fig. 3F, J). In comparison, the sperm headpieces of M. cerebrosa and M. magna are longer (10–15 µm) and slightly curved. Maculaura aquilonia can also be differentiated from the latter two species by body color; it is not as pink (compare Fig. 4C with 4L–Q).

Habitat, type locality, and distribution. Type locality is in Juneau, AK (58.3952°N, 134.7512°W) (AK-J1, Fig. 1B). This species exhibits the largest confirmed range for any species in the genus Maculaura, including eastern Russia, Alaska, and southern Oregon (RU-O1, AK-K1 to OR-C, Fig. 1A). This species is common in silty sand and mud from mid- to low intertidal, sometimes even occurring in black anoxic mud. However, in Juneau, AK, it is found under rocks and within fine mud, where it appears to be the most common nemertean species. In the southern portion of its range, this species is less common than the morphologically similar M. alaskensis and was most abundant at one mudflat along the South Slough estuary near Charleston, OR (OR-C10, Fig. 1C).

Description. External features. Largest specimens were 5 cm in length and 2–3 mm in width, with average individuals on the order of 3–4 cm and 1–2 mm, in gliding (Fig. 4C– F). Head is off-white and body color is pale yellowish pink to brownish ochre. Posterior can be very pale yellow to offwhite in reproductive individuals where gametes are seen through the body wall (Fig. 4F). Body color is the same dorsally and ventrally. Lightly colored brownish pigment near the brain can be seen through the anterior body wall in freshly collected specimens (Fig. 4F). The posterior-most region of the body transitions abruptly to the caudal cirrus (Fig. 4E). Movement is without distinct peristalsis and is led with the head, which often turns dramatically to one side forming a hook or ‘U-shape’ (Fig. 4C, F inset). Fragmentation occurs during collection, especially in sexually mature individuals; posterior end regenerates routinely. Individuals can be rather short and stout when ripe with gametes. External morphology is very similar and sometimes indistinguishable from M. alaskensis (compare Fig. 4A with 4C).

Internal features. Internal anatomy as in M. alaskensis (see Fig. 7A–D).

Reproduction and development. Sexes are separate. Gonads are regularly arranged between intestinal diverticula (Fig. 4F). Reproductive individuals have been collected in March 2013 in southern Oregon. Gametes from both sexes are released when ripe through serially arranged dorsolateral gonopores. Dissected primary oocytes are 90–100 µm in diameter and lack a chorion (Fig. 3E). Sperm headpiece is cone-shaped, 7.5 µm in length (n = 10, Fig. 3F). Wild-caught larvae identified as belonging to this species using DMA sequence data were collected from plankton in Coos Bay in April and May in 2009 and 2012 (Fig. 1C). The amnion surrounding the juvenile worm inside the larva is less pigmented in this species as compared to the others in this genus (Fig. 8). However, we observed pigment spots in the amnion of lab-reared larvae during and immediately following metamorphosis, when the amnion collapses and is swallowed by the juvenile (Fig. 9). When reared in the lab at 12°C, first and second cleavage occur at approximately two and three hours after fertilization, respectively, and larvae begin feeding on Rhodomonas lens at 2 days (Fig. 8A). Pilidia have three pairs of imaginai discs by 2.5 weeks and the trunk and cerebral organ discs fuse by 42 days (Fig. 8C). The larvae reach advanced-proboscis stage by 81 days (Fig. 8D), and metamorphosis was observed as early as 95 days. Metamorphically competent larvae are approximately 550 µm tall (Figs. 8E, F). Metamorphosis is catastrophic, as in other pilidia, and the juvenile nemertean ingests the larval body (Fig. 9).

Etymology. The specific name is a compound unorthodox adjective (cerebrosus, -a, -um) rather freely formed by fusing two Latin words (cerebrum = brain, roseus = pink), in reference to the pinkish brain.

Type material. Serial transverse sections of the holotype (ripe male, 37 slides # 1282119), four paratypes (#s 1282120–1282123) and associated ethanol-preserved tissue are deposited at the NMNH (Table 1). We designate a partial COI sequence from an individual collected in Charleston, OR as a topogenetype (GenBank accession number KP682146, Table 1) and ethanol-preserved tissue from this individual is also deposited at NMNH (# 1282124).

Material examined. Fourteen adult individuals, including holotype and paratypes, and three wild-caught larvae were examined and their identification confirmed by DNA sequence data. These individuals were collected from locations near Charleston, OR, and Crescent City, CA (Table 1). Ethanol-preserved tissue and/or extracted DNA from remaining individuals are held at the OIMB.

Diagnosis. Maculaura cerebrosa differs from M. magna and M. oregonensis by its smaller size, narrower body, and not as pink body color. It is morphologically similar to M. alaskensis and M. aquilonia in body shape, color, and size. Maculaura cerebrosa is distinguishable from the latter two species by having a distinctly pink brain, which is visible through the body wall, and a short caudal cirrus with gradual (as opposed to a relatively longer caudal cirrus with an abrupt) transition from posterior body (Figs. 2D, 4G–J). In addition to the conspicuous pink brain, M. cerebrosa can be differentiated from M. alaskensis and M. aquilonia by comparing their eggs and sperm (Fig. 3). The eggs of M. cerebrosa and M. magna are both surrounded by egg chorions (the eggs of M. oregonensis have not been observed), but the egg diameter is distinctly different: 95 µm in M. cerebrosa and 125 µm in M. magna (compare Fig. 3C with 3G). The sperm headpieces in both species are elongated, but are 10 µm long in M. cerebrosa and 15 µm long in M. magna (Fig. 3D and 3H). The remaining species (for which we know gamete morphology) have eggs without distinct chorions, and “primitive” (not elongated) sperm (see Fig. 3).

Habitat, type locality, and distribution. The type locality is a mudflat near the outer Boat Basin in Charleston, OR (43.3445°N, 124.3215°W) (OR-C15, Fig. 1C). The known range of this species confirmed by DNA sequences extends from southern Oregon to northern California (OR-C to CA–C1, Fig. 1A), although a larger range is expected. This species can co-occur with other members in this genus, particularly M. alaskensis; however, M. cerebrosa is more common under rocks in mid-intertidal gravel and shell hash rather than sand. Individuals are often found intertwined under small rocks along the edges of mudflats (as in Coos Bay, OR or Crescent City, CA) or on the open coast in shell hash and amongst the roots of Phyllospadix sp. (e.g. in Sunset Bay, Middle Cove, South Cove, and North Cove at Cape Arago, OR).

Description. External features. Overall body and head shape as in M. alaskensis and M. aquilonia, but reaching greater lengths than either species. Largest specimens are 10 cm in length and 3–4 mm in width, with average individuals on the order of 5 cm long and 2 mm wide (Fig. 4G–J), while gliding. Head is narrow anteriorly and not prominently demarcated from body when worm is gliding (Fig. 2D). Head shape changes dramatically when contracted, at which time the head tip can be rather pointed. Body is generally a pale pink, rounded anteriorly and dorso-ventrally flattened posteriorly. The posterior of reproductive individuals can be pale pink to yellow, and gametes are visible through the body wall (Fig. 4H). Ventral surface of body slightly lighter colored than dorsal. The most notable exterior feature in this species is a conspicuous pink or rose pigment of the brain (Fig. 4G– I). Caudal cirrus is distinct from those of the other species in the genus as it is rather short and gradually tapers from posterior of body instead of transitioning abruptly, e.g. as in M. alaskensis and M. aquilonia (cf. Fig. 4B, E, J). Movement is without distinct peristalsis and is led with the head, which can contract and taper dramatically. Individuals often seek out and attempt to burrow under objects in glass bowls (e.g. rulers, rocks). Fragmentation occurs during collection, especially in sexually mature individuals, and posterior end regenerates routinely as in M. alaskensis and M. aquilonia.

Internal features. Internal anatomy as in M. alaskensis. (see Fig. 7E–G).

Reproduction and development. Sexes are separate. Reproductive females and males have been collected March through October, with sexually mature individuals mostly found in spring months, slightly earlier than is seen in Maculaura alaskensis. Gametes are arranged serially between intestinal diverticula, as in other Maculaura species. Dissected oocytes are 95 µm in diameter (n = 10) and surrounded by a chorion (Fig. 3C). Sperm headpiece is shaped like the blade of an agricultural scythe and is 10 µm in length (Fig. 3D).

When reared in the lab, first and second cleavage occurs at roughly two and three hours post fertilization (at 12°C), respectively, and larvae begin feeding on Rhodomonas lens at 2–3 days. The cephalic discs and trunk discs develop at approximately one week (Fig. 10A) and polka-dot pigment characteristic of the pilidium maculosum morphotype is apparent on the cephalic discs by 14 days (arrowhead, Fig. 10B). Larvae have all three pairs of imaginai discs as early as 18 days (Fig. 10C) and reach the torus stage (Maslakova, 2010) as early as 25 days (Fig. 10D). In a single cohort (fertilized in March 2014), metamorphosis was observed after approximately 45 days post-fertilization. Metamorphically competent larvae are approximately 500 µm from apical tuft to apex of lateral lappet (Fig. 10E). Metamorphosis is catastrophic, as in other pilidia, and the emerging juvenile devours the larval body. The amnion surrounding the juvenile worm is decorated with red, black, and maroon pigment spots (Fig. 10F). Wild-caught larvae, confirmed to belong to this species by DNA sequencing, were collected from plankton in Coos Bay in August.

Etymology. This specific name is a Latin adjective (magnus, -a, -um; “great” or “large”) in reference to the large size of this species, reaching sizes greater than any other known member of this genus.

Type material. Type material is deposited at NMNH and includes serial transverse sections of the holotype (56 slides # 1282125) and two un-sectioned paratypes preserved for histology and their associated ethanol-preserved tissue (#s 1282126–1282127) (Table 1). We designate a partial COI sequence derived from the holotype as a hologenetype (GenBank accession number KP682147, Table 1).

Material examined. Thirteen adult individuals, including the holotype and paratypes, and 18 wild-caught larvae were examined and in most cases their identification was confirmed by DNA sequence data. All individuals were collected from locations near Charleston, OR (Table 1). Two paratypes lack good quality DNA sequence data, but were confidently identified by morphology alone (#s 1282126– 1282127). Ethanol-preserved tissue and/or extracted DNA from remaining individuals are held at the OIMB.

Diagnosis. Maculaura magna is the largest species in the genus (Fig. 2B–F). It differs from M. alaskensis, M. aquilonia, and M. cerebrosa by a pinkish-red body color (Fig. 4K). Internally the cutis of M. magna has fewer gland cells than in other members of this genus (Fig. 7I). Maculaura magna is morphologically most similar to M. oregonensis because both species have pink body color. However, M. magna is overall larger and its body is more of a dusty rose color compared to M. oregonensis, which is brighter pink or reddish (compare Fig. 4K with 4L–Q). The most accurate way to differentiate species in this genus is by comparing their eggs and sperm (Fig. 3). The eggs of M. magna are large (125 µm in diameter), surrounded by an egg chorion and sperm headpieces are elongated and 15 µm in length (Fig. 3G–H). The only other species that has gametes of similar morphology is M. cerebrosa; however, the gametes of M. cerebrosa are smaller than those of M. magna. The eggs of M.cerebrosa are 95 µm and sperm headpieces are 10 µm in length (compare Fig. 3G–H with 3C–D).

Habitat, type locality, and distribution. The type locality is a mudflat in Charleston, OR (43.3428°N, 124.3218°W) (OR-C1, Fig. 1C). This species is currently only known from southern OR where it is common in sand (e.g. Fig. 1D) and mud from mid to low intertidal. Single individuals are usually found, not occurring in groups, and they can be burrowed quite deep (to 0.75 m). We have found specimens in a variety of sandflats along the shores of Coos Bay, north to Empire, as well as along South Slough estuary near the Charleston Marina. Several individuals have been collected from a sandy beach at North Cove near Cape Arago, OR. However, at these locations it is not nearly as common as M. alaskensis or M. cerebrosa.

Description. External features. Resembles species of Cerebratulus in being rather large, broad, and dorso-ventrally flattened. Largest specimens are up to 30 cm in length and 1 cm in width, and average individuals are approximately 20 cm in length and 3–4 mm wide (Fig. 4K). Head is pale white and body can be rather dark pink (Fig. 4K bottom left inset), with a gradual transition in color from the anterior to posterior. The foregut region is rounded in cross-section, while the mid-body region is flattened dorso-ventrally (Fig. 2F), but rounded in individuals packed with gametes. Dorsal side can be somewhat darker than the ventral side in some individuals, with a sharp lateral transition between the dorsal and ventral color. Head can be pointed and change shape dramatically when contracted (Fig. 2F). The posterior region of the body ends abruptly with caudal cirrus (Figs. 2F inset, 4K upper right inset). Movement is with gentle peristalsis and is led with the head, which can curve from side to side. Fragmentation occurs frequently during collection in the field, due to the large size of this species. The posterior end regenerates easily, but slower than in smaller species (M. alaskensis, M. aquilonia, and M. cerebrosa), and anterior regeneration has not been observed. Regenerated region is typically lighter in color than adjacent (non-regenerated) body.

Internal features. Internal anatomy similar to M. alaskensis (see Fig. 7I–L). Three relatively large apical sense organs are clearly visible just anterior to the proboscis pore in histological sections (Fig. 7H). Mouth is ventral and quite long (up to 1 mm). Transition from foregut to intestinal region is met with a dramatic thickening of the circular musculature (Fig. 7L). The proboscis musculature exhibits two distinct crosses extending from the circular muscle to the proboscis endothelium. The diagonal proboscis muscle layer is thin and less conspicuous in M. magna than in the other four species. The proboscis also contains two outer longitudinal muscle strands outside the main proboscis nerves, which were not observed in the other four species. The nephridial canals are larger in this species than in other Maculaura species, as is, perhaps, fitting, since it is a larger species.

Reproduction and development. Sexes are separate. Ripe females were collected in June, and a reproductive male was collected in January 2012. Gametes are arranged laterally between intestinal diverticula. Dissected oocytes are 125 µm in diameter (n = 10), surrounded by a chorion (Fig. 3G). Sperm headpiece is elongated, 15 µm in length (Fig. 3H). Wild-caught larvae, confirmed to belong to this species by DNA sequence data, were collected from plankton in Coos Bay March through December and exhibit the pilidium maculosum morphotype (Fig. 11). The larval episphere is haystack-shaped and tall with relatively short lateral lappets (Fig. 11B, C).

Etymology. The specific name is an adjective (-ensis, -ense), referring to the type locality and currently known distribution of this species.

Type material. Serial transverse sections of the holotype (female, 39 slides # 1282128), one paratype preserved for histology (# 1282129) and associated ethanol-preserved tissue are deposited at NMNH (Table 1). We designate a partial COI sequence from the holotype as a hologenetype (GenBank accession number KP682159, Table 1).

Material examined. Eleven adult individuals, (all collected from locations near Charleston, OR) including the holotype and paratype were examined and their identification confirmed by DNA sequence data (Table 1). Ethanol-preserved tissue and/or extracted DNA from remaining individuals are held at the OIMB.

Diagnosis. Maculaura oregonensis differs from M. alaskensis, M. aquilonia, and M. cerebrosa by its larger size, wider body, and pink body color. Internally, M. oregonensis differs from these three species further, in that more red and fewer blue staining gland cells are present in the cutis (compare Fig. 7E with 7M). External color in M. oregonensis most closely resembles M. magna; however, the latter species is significantly larger than M. oregonensis and the body color differs slightly between the two species. Maculaura oregonensis is bright pink or reddish in color while M. magna exhibits more of a dusty rose body color (compare Fig. 4K with 4L–Q). The sperm headpiece is shorter in M. oregonensis compared to that in M. cerebrosa and M. magna. The sperm of M. oregonensis has similar morphology to M. alaskensis but is slightly longer (compare Fig. 3B with 3J). Maculaura oregonensis and M. aquilonia sperm are indistinguishable; they both have slightly elongated headpieces (although not as long as M. cerebrosa or M. magna) that are 7–8 µm in length. Instead, these species can be differentiated by body color alone, in that M. oregonensis is significantly darker pink (compare Fig. 4C with 4L–Q). At present we lack information on size and presence of the chorion in oocytes of M. oregonensis.

Habitat, type locality, and distribution. The type locality is a mudflat in Charleston, OR (43.3272°N, 124.3263°W) (OR-C10, Fig. 1C). This species is, at present, only found in southern Oregon where it is relatively rare. Individuals can be found in sand and mud from mid- to low intertidal (e.g. Fig. 1D). Several specimens were collected in north Coos Bay, near the McCullough Bridge, and few individuals were collected with other species of this genus at a variety of mudflats along the South Slough estuary (Fig. 1C). In one instance, several individuals were observed surrounding the hoplonemertean, Paranemertes peregrina.

Description. External features. Largest specimens were 15 cm in length and 5 mm in width, while gliding, with average individuals about 8–10 cm long and 3 mm wide (Fig. 4L–Q). Head is pale white and body color is dark pink. The dorsal side is the same color as ventral side. The body is rounded in cross-section anteriorly and dorso-ventrally flattened posteriorly. Head narrows to a point while worm is gliding (Fig. 4L–O). The proboscis is paler than the background color of the body and can easily be seen through the body wall (Fig. 4O). Brain is pink and shows through the body wall, as a somewhat darker pink at the transition from the pale color of the head to the bright pink of the body. Caudal cirrus present, somewhat intermediate in shape between that of M. cerebrosa and the other species in the genus (Figs. 2E, 4Q). Movement is with gentle peristalsis, as in M. magna, and is led with the head, which can curl dramatically (Fig. 4N). Maculaura oregonensis is often seen retracting its head within its body (Fig. 4M). Fragmentation occurs during collection and posterior end regenerates routinely, but anterior regeneration has not been observed.

Internal features. Internal anatomy as in M. alaskensis (see Fig. 7M–O). The two proboscis muscle crosses are most conspicuous in this species and the nephridia are comparatively larger than in M. alaskensis, M. aquilonia and M. cerebrosa, but smaller than in M. magna (Fig. 7N).

Reproduction and development. Sexes are separate. The gametes of one ripe male were observed on 20 May 2014 (Fig. 3J). Sperm headpiece is approximately 7–8 µm (n = 10) in length. Reproductive females were observed in the Summer 2014, but the size of the oocytes was not recorded. Each ovary of the holotype contained approximately 35 oocytes (Fig. 7O).