Nanaloricus mathildeae, Neves & Kristensen & Møbjerg, 2021

Neves, Ricardo Cardoso, Kristensen, Reinhardt Møbjerg & Møbjerg, Nadja, 2021, New records on the rich loriciferan fauna of Trezen ar Skoden (Roscoff, France): Description of two new species of Nanaloricus and the new genus Scutiloricus, PLoS ONE (e 0250403) 16 (5), pp. 1-42 : 15-24

publication ID	https://doi.org/ 10.1371/journal.pone.0250403
DOI	https://doi.org/10.5281/zenodo.12630837
persistent identifier	https://treatment.plazi.org/id/0396B203-6919-5162-FD9F-FA7AC274F88A
treatment provided by	Felipe
scientific name	Nanaloricus mathildeae
status	sp. nov.

Treatment

Nanaloricus mathildeae View in CoL sp. nov.

( Figs 8–14 View Fig 8 View Fig 9 View Fig 10 View Fig 11 View Fig 12 View Fig 13 View Fig 14 , S 1 View Fig 1 Video).

urn:lsid:zoobank.org:act:953ADF05-F046-4855-A2F8-82F588202999

Material examined. Holotype ( Fig 9 View Fig 9 ). Adult male collected on 8 April 2004 at the type locality at ca. 50 m water depth, mounted in glycerin on a glass slide, and deposited at the Natural History Museum of Denmark under accession number NHMD-678028.

Allotypic paratype ( Fig 11 View Fig 11 ). Adult female collected on 7 February 2013 at the type locality at ca. 45 m water depth, mounted in glycerol on a glass slide, and deposited at the Natural History Museum of Denmark under accession number NHMD-678039 .

Paratypes. 23 adults (6 males, 17 females), 2 tentatively assigned postlarvae and 2 putative postlarval exuvia collected at the type locality between 12 July 1985 and 15 May 2013 at 43–55 m water depths. The 27 paratypic specimens are mounted in glycerin or Fluoromount-G on glass slides, deposited at the Natural History Museum of Denmark under the access numbers NHMD-678022 to NHMD-678027, NHMD-678030, NHMD-678032 to NHMD-678038, NHMD-678040 to NHMD-678051 and NHMD-678053. The specimen registered with access number NHMD- 678044 in shown in Fig 12 View Fig 12 . In addition, an adult male collected at the type locality on 12 July 1985, at ca. 55 m water depth, and mounted on an SEM stub (NHMD-866005) was analyzed for comparative purposes ( Fig 14 View Fig 14 ) .

Additional reference material ( Fig 13 View Fig 13 , S 1 View Fig 1 Video). In addition to the fixed material examined, four non-type specimens (all females), collected at the type locality in April 2019 and August 2020, were observed and photographed alive. Two of these animals were also video recorded alive.

Habitat and distribution. Marine sediments composed of clean shell gravel at type locality.

Type locality. Trezen ar Skoden, Roscoff, France, (48˚45’55”N, 04˚06’45”E).

Etymology. The species is named after Mathilde MØbjerg Boslev Kristensen, who is granddaughter and niece to the middle author and last author, respectively.

The following description will solely focus on adult specimens, as postlarvae have only been tentatively assigned to species (see section below: "Notes on the postlarvae found at Trezen ar Skoden").

Diagnosis. Adults. (1) mouth cone with a telescopic mouth tube and 8 oral ridges of different length. Oral ridges are characterized by posterior sclerotized oral furca and are preceded by cuticularized bars; (2) introvert with 9 rows of scalids; (3) first row with eight clavoscalids that are different between males (multiform, very broad to slender, all branched except for the midventral pair) and females (four-segmented, slender, unbranched); (4) second row with 9 four-segmented, leg-like spinoscalids; (5) third row with 7 two-segmented, feather-like scalids; (6) fourth row with 16 spinoscalids of two types: 8 two-segmented, leg-like scalids (type A) alternate with 8 two-segmented scalids with a feather-like distal segment (type B); (7) fifth to seventh rows all similar, each row with 30 leg-like, three-segmented scalids; (8) eighth row with 30 very long unsegmented spinoscalids whith a small conical base; (9) ninth row with 30 small, teeth-like scalids with four cuspid-like protrusions; (10) neck with 8 single trichoscalids alternating with 7 double trichoscalids, with both the single and each of the double

trichoscalid. (E) Close up of the trichoscalid sensory organ with a small pore (black arrow). Note also a type b basal plate (bpb) of the anterior neck region. (F) Overview of the posterodorsal region of the lorica. Black double arrowheads indicate the cluster of flosculi situated on each dorsolateral plate, while the white double arrowheads point to the small flosculum of the dorsal plate. (G) Detail of a dorsolateral cluster of flosculi arranged in a rectangular pattern. Abbreviations: ac, anal cone; af, anal field; ba, mouth cone bar; cs, clavoscalid; dlp, dorsolateral plate; dp, dorsal plate; fu, oral furca; mc, mouth cone; mt, mouth tube; or, oral ridge; ss, spinoscalid; sp, anterior spike; sr 2-4a/b,7,8, spinoscalid of 2 nd to 4 th (type a and b), 7 th and 8 th rows; vlp, ventrolateral plate; vp, ventral plate. https://doi.org/10.1371/journal.pone.0250403.g014

trichoscalids protruding from a single trichoscalid plate; (11) short sensory organ located anteroproximally to the ventral and ventrolateral double trichoscalids, characterized by serrated margins, anteroproximal pore and a double-square plate; (12) lorica composed of six cuticular plates, with honeycomb sculpturing and bearing 14 large anterior spikes and a very small midventral spike; (13) 9 flosculi (1 dorsal and 4 pairs laterodorsal) present posteriorly on the dorsal side of the lorica (dorsal and dorsolateral plates); (14) posterior region of the lorica characterized by a small anal cone and two pairs of pores: one dorsolateral (gonopores?) and one ventral (gland outlets?).

Description. Body ( Figs 9–14 View Fig 9 View Fig 10 View Fig 11 View Fig 12 View Fig 13 View Fig 14 ). Divided into head (mouth cone and introvert), neck, thorax, and abdomen. The holotypic adult male ( Fig 9 View Fig 9 ) is 283 μm long, including the mouth cone, and 103 μm wide.

Mouth cone (mc; Figs 9–14 View Fig 9 View Fig 10 View Fig 11 View Fig 12 View Fig 13 View Fig 14 ). Long (76 μm long in the holotype), narrow, with three distinct sections. The first, most proximal section is short, broad and characterized by eight large, sclerotized oral furcae (fu) of identical structure; each furca is posteriorly preceded by a cuticularized bar (ba; Figs 10 View Fig 10 and 14B View Fig 14 ). The furcae and the bars are arranged radially. The middle section is long, conical and characterized by a wall reinforced by eight oral ridges of different length ( Fig 10 View Fig 10 ). The four primary oral ridges (or 1) are long and span the whole length of the middle section, while the four secondary oral ridges (or 2) are shorter and span only the posterior three quarters of the middle section. Each of the oral ridges is a continuation of an oral furca. The distal section of the mouth cone is a telescopic mouth tube that ends in a terminal mouth aperture. The mouth tube can be extended, thereby significantly increasing the total length of the mouth cone ( Fig 12 View Fig 12 ). There are no oral stylets.

Introvert (in; Figs 9 View Fig 9 and 10 View Fig 10 ). Round in shape and characterized by nine rows of scalids arranged radially ( Figs 8–14 View Fig 8 View Fig 9 View Fig 10 View Fig 11 View Fig 12 View Fig 13 View Fig 14 ).

First row (sr1; Fig 8 View Fig 8 ) with eight clavoscalids (cs) that differ between males and females ( Figs 9–11 View Fig 9 View Fig 10 View Fig 11 ). In females, all clavoscalids are similar and divided into four segments ( Fig 11 View Fig 11 ). The first, most proximal segment is relatively short and possesses several long papillae arranged anteriorly. It consists of a conical base that projects distally in a curved, cylindrical shape. The second segment, which is the longest segment of the clavoscalid, is club-shaped. The third segment is very short and thin. The fourth segment is also very short and ends as a spinose tip. In males, the clavoscalids are multiform ( Figs 9 View Fig 9 , 10 View Fig 10 and 14 View Fig 14 ). The most ventral pair is exactly as those of the female ( Fig 10 View Fig 10 ). The other six clavoscalids each possess a robust base ( Fig 14B View Fig 14 ) that branches off into primary, secondary and tertiary branches. All branches are very broad and flat, though the secondary branch is the broadest one. This secondary branch has a short, relatively thin base and it branches off halfway through the length of the clavoscalid base ( Fig 10 View Fig 10 ). The primary branch is in turn segmented, possessing distaly two short, slightly curved segments: a thin one followed by a terminal spine-like segment.

The second row (sr 2; Fig 8 View Fig 8 ) consists of nine leg-like spinoscalids (ss), each divided into four segments (sr 2; Fig 10 View Fig 10 ). The first, most proximal segment has a robust, round base with a row of stiff hairs arranged anteriorly (sr 2; Fig 14B View Fig 14 ). The base narrows distally and ends as a cylindrical short portion with a few papillae arranged anteriorly in a row on both sides. The second segment is short and cylindrical, with short hairs arranged posteriorly. The third segment is slightly thinner, represents approximately half of the scalid length, and has serrated margins with several thin hairs. The fourth, most distal segment is slightly curved, terminates as a spinose tip and represents one quarter of the scalid length.

The third row (sr 3; Fig 8 View Fig 8 ) is composed of seven short, two-segmented feather-like spinoscalids ( Figs 10 View Fig 10 , 14B and 14C View Fig 14 ). The proximal segment has a swollen, round base that narrows distally and bears two rows of papillae. The distal segment possesses numerous thick hairs and a small hook-shaped tip.

The fourth row (sr 4; Fig 8 View Fig 8 ) consists of 16 spinoscalids of two types: eight type A leg-like spinoscalids (sr 4a) alternating with eight type B spinoscalids (sr 4b) with thick hairs that are only seen by SEM ( Figs 10 View Fig 10 , 14B and 14C View Fig 14 ). The type A spinoscalids are divided into four segments. The first, most proximal segment has a short, round base that narrows distally and forms a relatively long, cylindrical region characterized by several minute papillae (well discernible by SEM, Fig 14B and 14C View Fig 14 ). This segment represents slightly more than one fourth of the scalid total length and terminates as a large, round knee. The second segment is thin, slightly shorter than the preceding segment, and possesses serrated margins with a few hairs. The third segment is also thin and possesses serrated margins and a few hairs. The fourth, most distal segment lacks the hairs and terminates as a thin tip. Both the third and fourth segments have approximately the same size as the second segment. The type B spinoscalids are two-segmented. The proximal segment is a short, slightly broad base that narrows distally and possesses several short papillae. The distal segment is thin and characterized by numerous thick hairs arranged posteriorly along the segment.

The fifth to seventh rows (sr 5-7; Fig 8 View Fig 8 ) are each composed of 30 three-segmented, leg-like spinoscalids ( Figs 10 View Fig 10 and 14C View Fig 14 ). Each of the three segments comprise approximately one third of the total scalid length. The first, most proximal segment has a short, conical base that narrows distally and forms a cylindrical region with serrated margins that terminates in a small knee bearing papillae. The second and third, most distal segments are both thin; the latter terminates in a slightly curved spine-like tip. These two most distal segments have finely serrated margins and several long hairs scattered along their length, which are only seen by SEM ( Fig 14C View Fig 14 ).

The eighth row (sr 8; Fig 8 View Fig 8 ) consists of 30 unsegmented whip-like spinoscalids with a small conical base ( Figs 10 View Fig 10 and 14C View Fig 14 ). These scalids terminate as a thin tip.

The ninth row (sr 9) consists of 30 very short scalids ( Figs 9D View Fig 9 and 10 View Fig 10 ). Each of these scalids possesses an oval anterior edge and four cuspid-like protrusions, of which three extend backwards from the posterior edge and one from the anterior edge.

Neck (ne; Figs 8 View Fig 8 and 10 View Fig 10 ). Composed of at least five rows of neck flat plates divided into columns by several longitudinal folds ( Fig 10 View Fig 10 ). The anterior neck region is characterized by a row of conspicuous plates situated immediately under the ninth row of spinoscalids ( Figs 9D View Fig 9 , 10 View Fig 10 and 14E View Fig 14 ). Specifically, this row consists of seven triangular plates (bpa), which alternate with eight trapezoid plates (bpb). Both types are characterized by two transverse rows of teeth. Each basal plate is situated in the center of the neck flat plates. The posterior region of the neck is characterized by 15 trichoscalids (tr; Fig 9 View Fig 9 ) arranged radially: eight single (tr 1) alternating with seven double trichoscalids (tr 2) ( Figs 10 View Fig 10 and 14D View Fig 14 ). The trichoscalids are all flat and with a central ridge, serrated margins with few hairs and terminate in either a blunt or a pointy tip. The upper appendages of the double trichoscalids are longer than the lower appendages. In addition, the upper appendages have a pointy tip, while the lower appendages have a blunt tip. The single trichoscalids are broader than the double trichoscalids, and possess a unique blunt end composed of several (ca. 14?) robust finger-like processes. On both sides of the single trichoscalids, the most lateral finger-like process is longer and thus extends further than the more medial ones (only seen by SEM; Fig 14D View Fig 14 ). Both the single trichoscalids and each of the two appendages composing the double trichoscalids protrude from a single trapezoid trichoscalid plate (tp). However, each single trichoscalid composing the midventral pair protrudes from a pentagonal plate. Each of these midventral single trichoscalids is further characterized by two sclerotized plates, one large and one small, located anteriorly to their trichoscalid plate. A short sensory organ is located anteroproximally to the ventral and ventrolateral double trichoscalids (to; Figs 10 View Fig 10 , 14D and 14E View Fig 14 ). The trichoscalid sensory organ protrudes from a plate with a double-square shape ( Fig 10 View Fig 10 ), and is characterized by serrated (toothed) margins and an anteroproximally situated pore ( Fig 14E View Fig 14 ). The putative sensory organs of the dorsal side could not be observed neither by light nor scanning electron microscopy; their presence/absence remains thus to be determined.

Summing up, the number of head and neck appendages (cs = clavoscalids,

ss = spinoscalids, tp = trichoscalid plates, tr = trichoscalids) is given in the following formula ( Fig 8 View Fig 8 ):

Introvert: 8 cs; 9 sr 2; 7 sr 3; 8 þ 8 sr 4; 30 sr 5; 30 sr 6; 30 sr 7; 30 sr 8; 30 sr 9;

Neck: 7a þ 8b bp; 8 þ 14 tp; 8 tr 1 ð single Þ þ 7 tr 2 ð double Þ:

Thorax. Short, surrounded by the lorica and without any appendages or segmentation.

Abdomen. Enclosed in a lorica (lo; Figs 9–14 View Fig 9 View Fig 10 View Fig 11 View Fig 12 View Fig 13 View Fig 14 ) composed of six cuticularized plates with a honeycomb sculpture: one ventral, two ventrolateral, two dorsolateral and one dorsal. The latter plate possesses four anterior spikes (sp), while each of the other plates bears only two. In total, the anterior edge of the lorica is characterized by 14 large spikes of equal length, except for one larger spike on each of the dorsolateral plates. In addition, a very small midventral anterior spike is located between the two large anterior spikes of the ventral plate. The total number of anterior spikes is thus 15 ( Figs 9E View Fig 9 , 10 View Fig 10 and 11D View Fig 11 ).

A cluster of four flosculi ( Figs 11F View Fig 11 and 14G View Fig 14 ) is arranged in a rectangular pattern on each of the dorsolateral plates (dlp; Fig 14F View Fig 14 ). These flosculi are characterized by 4–5 microvilli-like stuctures covered with cuticle ( Fig 14G View Fig 14 ). Additionally, one smaller flosculum with 3 microvilli-like structures is located posteriorly on the dorsal plate ( Figs 11E View Fig 11 and 14F View Fig 14 ).

The postero-dorsal region of the lorica consists of an anal field (af, Figs 9A, 9B View Fig 9 , 10 View Fig 10 and 11A View Fig 11 ). In both males and females this anus-gonopore region is characterized by a small anal cone ( Fig 14F View Fig 14 ) and, close to it, a pair of putative gonopores (go?; Fig 11E View Fig 11 ). These large pores are located on the posterior region of the dorsolateral plates. A cuticularized crest (cc, Fig 9B View Fig 9 ) spans between each of the putative gonopores and the posterior end of the lorica. On the ventral side, a pair of small pores (gland outlets?) is furthermore located posteriorly on each margin of the ventral plate (gl?; Fig 10 View Fig 10 ).

Internal anatomy ( Figs 12 View Fig 12 and 13 View Fig 13 , S 1 View Fig 1 Video). A long buccal tube (bu; Fig 12 View Fig 12 ) extends from the mouth aperture (mo; Fig 10 View Fig 10 )—through the head/thoracic region—to the pharyngeal bulb (pb; Fig 13 View Fig 13 , S 1 View Fig 1 Video). The most posterior region of the buccal tube is characterized by a supporting pre-pharyngeal armature, which is composed of three internal buccal furcae (not shown). In females, the abdominal region is characterized by the presence of two ovaries, each of which may contain oocytes. In a female observed alive, each of the two ovaries (ov) was found containing a large oocyte (oo; Fig 13 View Fig 13 , S 1 View Fig 1 Video). Males are characterized by two large testes, which contain mature spermatozoa in some specimens (not shown).