Cephalodasys mariannae, Araújo, 2024

Araújo, Thiago Quintão, 2024, A description of a new species of Cephalodasys (Macrodasyida: Gastrotricha) from Florida, USA using an integrative morphological approach, Zootaxa 5463 (4), pp. 581-597 : 582-592

publication ID	https://doi.org/ 10.11646/zootaxa.5463.4.8
publication LSID	lsid:zoobank.org:pub:4ADFD1A8-409A-4E84-8659-83C8778645D4
DOI	https://doi.org/10.5281/zenodo.11952077
persistent identifier	https://treatment.plazi.org/id/B83D87BE-FFB2-8F0F-FF33-FAF9FAF456A6
treatment provided by	Plazi
scientific name	Cephalodasys mariannae
status	sp. nov.

Treatment

Cephalodasys mariannae sp. nov.

urn:lsid:zoobank.org:act:A5F52F5F-8E03-4F42-8AD7-6E09F4986472

Material Examined

Eight adult specimens and one juvenile were examined by light microscopy and measured with an ocular micrometer. All specimens were mounted alive and photographed and/or video recorded. Five adult specimens were prepared for confocal laser scanning microscopy.

Diagnosis

Cephalodasys with a body length up to 630 μm. Body divided into rhombic head, neck, and trunk regions. Tapered posterior end. The rather long buccal cavity has a strengthened cuticular lining. Intestine/midgut linear and without obvious differentiation. Adhesive tubes organized up to six TbA, 11 TbV, 26 TbVL, and 12 TbP on each side of the body. TbA arises from a fleshy hand-like base. TbVL and TbV present in the pharynx and trunk regions; TbD absent. An unpaired ovary is present in a dorsolateral position in the anterior half of the trunk; a pair of long testes is present posterior to the pharyngeal pores and lead to short and caudally directed sperm ducts that fuse ventral to the midgut. An unpaired male gonopore is present at the site of sperm duct fusion. The frontal organ as sperm-storing device is positioned just posterior to the mature oocyte; a small putative caudal organ is located around the anal region.

Etymology:

The newly discovered species is named in honor of Marianne Alexsandra Nerissa Araújo, my beloved sister, who unfortunately passed away in 2019. Marianne played a pivotal role in my life, consistently offering unwavering encouragement and inspiring me to embark on a scientific career. Even after her passing, Marianne’s legacy remains a poignant source of my inspiration, and naming the species in her tribute is a heartfelt acknowledgment of her enduring impact on my scientific journey.

Description

Adult holotype with total body length of 630 μm ( Figs. 1 View FIGURE 1 ; 2 View FIGURE 2 ). Pear-shaped head bearing ovoid muzzle delineated from the neck at U09 by a marked constriction. The trunk region (approximately U11–U100) is slightly wider (ca. 70 μm, U45) than the neck region (45 μm, U09) and ends with a tapered posterior end ( Figs. 1 View FIGURE 1 ; 2 View FIGURE 2 ; 3B View FIGURE 3 ). The body outline appears slightly undulated, which may be a result of the folded integument. Ventral surface flat and dorsal side convex. Smooth cuticle without ornamentation but fine granular patches “cover” the entire body as observed under DIC ( Figs. 1B View FIGURE 1 ; 5D View FIGURE 5 ).

Adhesive tubes. The new species of Cephalodasys has adhesive tubes in an anterior (TbA), ventrolateral (TbVL), ventral (TbV) and posterior (TbP) series. Dorsal tubes are absent. Six TbA per side arranged on fleshy hands at the neck region (U10); tubes are of equal size (8–9 μm) ( Figs. 1C View FIGURE 1 ; 2A View FIGURE 2 ; 3A View FIGURE 3 ). A longitudinal furrow extends down each adhesive tube ( Fig. 3A View FIGURE 3 ), which indicates the presence of a duo-gland adhesive system ( Tyler & Rieger, 1980; Kieneke et al., 2015).. The TbVL are arranged as 26 pairs of tubes from U18 to U89, each 7–13μm in length, and arranged slightly lateral to the TbV ( Fig.4 View FIGURE 4 ). TbV present as 11 pairs of tubes from U28 to U65, each 10–12 μm in length ( Figs. 1C View FIGURE 1 ; 2C View FIGURE 2 ; 4 View FIGURE 4 ). Caudally, 12 pairs of TbP are arranged symmetrically along the posterior margin from U90 to U100, each 5–11 μm in length ( Figs. 1 View FIGURE 1 ; 2A, C View FIGURE 2 ; 3B View FIGURE 3 ).

Cilia. Locomotory cilia arranged in two columns beginning at the anterior ventral head at U04 and extending to the ventral anus at U90 after which two columns fuse in a short uniform field ( Figs. 1C View FIGURE 1 ; 2C View FIGURE 2 ). Seven long sensory cilia present on each lateral margin of the head and ca. 20 sensory cilia laterally arranged between TbVL on each lateral body margin. A ring of spaced cilia covering dorsally and ventrally the head ( Fig. 1 View FIGURE 1 ). Short sensory cilia are present along the lateral body, but their numbers were not determined.

Digestive tract. A circular terminal mouth to 12 μm in diameter. The mouth leads into an expansive cylindrical buccal capsule to 24 μm long with a thicker cuticular wall ( Figs.1B View FIGURE 1 ; 2B View FIGURE 2 ). Cylindrical pharynx with 207 μm long connects to the intestine at the pharyngo-intestinal junction (PhIJ) (U38) ( Figs.1A, B View FIGURE 1 ; 2B View FIGURE 2 ; 3C View FIGURE 3 ; 5A View FIGURE 5 ). The width of the pharynx (ca 30 μm) is the same along most of its length and only increases in width at the pharyngeal pores level which open dorsolaterally at U34 ( Figs.1A, B View FIGURE 1 ; 2B View FIGURE 2 ; 3C View FIGURE 3 ; 5A View FIGURE 5 ). The intestine has an irregular shape, and the width varies considerably along its length. The intestine ends in a ventral anus at U90.

Reproductive organs. Hermaphroditic. The paired testes extend from U38 with each vas deferens projecting caudally and curving medio-ventrally to join a male gonopore at U69 ( Figs. 1B, C View FIGURE 1 ; 2B View FIGURE 2 ; 3C, D View FIGURE 3 ; 5A View FIGURE 5 ). The male gonopore was observed only under DIC as a small circular opening ( Figs. 1B, C View FIGURE 1 ; 5A View FIGURE 5 ). Granular content was observed at the anterior end of each testis, probably representing early cell stages as shown by Kieneke et al. (2015) ( Fig. 3D View FIGURE 3 ). A caudal organ with an irregular ovoid outline and containing granular content is present on the right side of the intestine at the posterior end body at U89 ( Figs. 1B View FIGURE 1 ; 2A View FIGURE 2 ; 5D View FIGURE 5 ). This structure appears to be vesicular, and no obvious muscles were possible to observe.

Unpaired ovary with single mature egg, 75 μm long (U67), is present dorsal to the intestine at U60 with a large nucleus, 20 μm in diameter. Smaller oocytes are present anterior to the egg and oogenesis appears to occur from anterior to posterior ( Figs. 1B View FIGURE 1 ; 2B View FIGURE 2 ; 5A View FIGURE 5 ). Posterior to the mature egg on the left side of the body is a somewhat ovoid frontal organ (FO) at U72. Inside of FO are a few coiled spermatozoa that represents allosperm; anterior end of each sperm is positioned towards an internal pore in the uterus ( Figs. 1B View FIGURE 1 ; 5B View FIGURE 5 ). The frontal organ is connected to the outside by a circular opening surrounded by small granular secretions, a small duct connects this opening with the main chamber of the frontal organ ( Figs. 1B View FIGURE 1 , 2B View FIGURE 2 ; 5B, C View FIGURE 5 ). The female complex (FO + ovary) appears to be surrounded by a putative membrane in one of the specimens analyzed ( Fig. 5B View FIGURE 5 ).

Subadult: Total body length of 400 μm ( Fig. 6A View FIGURE 6 ). Body shape similar to adult specimens, with distinct head pear-shaped head and a tapering posterior end. A small terminal mouth to 10 μm diameter. The mouth leads into an expansive buccal capsule to 11 μm long. Pharynx with total length of 153 μm. PhIJn at U40. Pharyngeal pores at U37 ( Fig. 6A View FIGURE 6 ). Five TbA per side arranged in fleshy hands at the neck region (U12) ( Fig. 6B View FIGURE 6 ), 14–16 TbVL from U23 to U87 (Fig. 56, B) and TbV were not observed. Caudally, seven pairs of TbP are arranged symmetrically along the posterior margin from U89 to U100 ( Fig. 6C View FIGURE 6 ).

Muscular architecture. The muscular architecture consists of longitudinal, helicoidal, circular and semicircular muscles observed in somatic and splanchnic regions ( Figs. 7–9 View FIGURE 7 View FIGURE 8 View FIGURE 9 ). Helicoidal muscles (hm) are present surrounding the entire pharynx and the first third of the intestine, enclosing the circular muscles as well as the ventral, lateral and dorsal longitudinal muscles.

Longitudinal muscles are present in dorsal, lateral, ventrolateral and ventral somatic positions. Dorsally, three pairs of longitudinal muscles (dm) insert in the mouth ring ( Figs. 7A View FIGURE 7 ) and extend posterior to U90 where they fuse close to the anal sphincter ( Figs. 7A View FIGURE 7 ; 8C View FIGURE 8 ). Two longitudinal muscles are observed on each lateral side of the body (lm1 and lm2) ( Figs. 7 View FIGURE 7 ; 8 View FIGURE 8 ). These muscles insert anteriorly into the mouth ring and extend the whole body to insert in the posterior end. Lateral longitudinal muscle 1 (lm1) presents a transversal ventral semicircular connection at U13 and shows a ramification that extends to the lateral region of the head (lm1b) ( Figs. 7 View FIGURE 7 ; 8A, B View FIGURE 8 ; 9C, E View FIGURE 9 ). The thickest longitudinal muscles are the two ventrolateral longitudinal muscles (vlm) ( Figs. 7–9 View FIGURE 7 View FIGURE 8 View FIGURE 9 ). Each muscle inserts at the base of the fleshy hands that bear the TbA; each muscle increases in width as it extends posteriorly, covering most of the lateral longitudinal muscles in a ventral view.

Ventrally, two pairs of longitudinal muscles are present in a somatic position ( Figs. 7B View FIGURE 7 ; 8B, D View FIGURE 8 ; 9D, H, I View FIGURE 9 ). This central pair of longitudinal muscles (cvm) inserts anteriorly in the mouth ring and extends to the anal sphincter at U90. Lateral to these central muscles is an additional pair of longitudinal muscles (vm) that extend from the mouth ring to the posterior body end ( Figs. 7B View FIGURE 7 ; 8B, D View FIGURE 8 ; 9D View FIGURE 9 ). An additional pair of tiny longitudinal muscles (plm) inserts on the mouth ring crossing each other at U03 and extends to PhIJ but the real position remains unclear but appear to be inside the pharynx circular muscles ( Figs. 7B, 7-1 View FIGURE 7 ; 8B View FIGURE 8 ).

Circular muscles are present in somatic and splanchnic positions. The pharynx is composed of only visceral complete circular muscles (pc) from the mouth ring to PhIJ. Each pharyngeal pore has a strong sphincter composed by several circular muscles and a -∞ shape thin muscle connecting both pores ( Figs. 8A View FIGURE 8 ; 9G View FIGURE 9 ). The intestine region has circular muscles in somatic and splanchnic positions. Complete circular muscles (cmi) are present from the PhIJ (U40) to anal region at U90 ( Figs. 7 View FIGURE 7 ; 8C, D View FIGURE 8 ; 9H, I View FIGURE 9 ), where it opens to outside ( Figs. 7-4 View FIGURE 7 ; 9J View FIGURE 9 ), wrapping the intestine tube and developed eggs. An additional independent somatic complete circular muscle (scm) encloses lm1, lm2 and vm from U45 to U91 ( Figs. 7 View FIGURE 7 ; 8C, D View FIGURE 8 ). A small linear branch (cb) ( Figs. 7-3 View FIGURE 7 ; 9H, L View FIGURE 9 ) connecting the visceral to somatic circular muscles is present.

Posterior to the anal region, a series of dorsal semicircular muscles (dscm) are observed covering the complex composed by ventrolateral, laterals and ventral muscles to the posterior end of the body ( Figs. 7A, 7-5 View FIGURE 7 ; 8C View FIGURE 8 ; 9K View FIGURE 9 ). Ventrally, on the anterior region of the body, two other semicircular muscles can be observed ( Figs. 7B View FIGURE 7 ; 8B View FIGURE 8 ; 9E View FIGURE 9 ). The first one (ascm), positioned at U10 surrounding the pharynx and the two lateral longitudinal muscles; the second (lm1c), as mentioned above, connects the lateral longitudinal muscle 1 at U13 ( Fig. 8B View FIGURE 8 ).

Regarding the reproductive apparatus, no fluorescence signal was observed surrounding frontal and caudal organs. However, the frontal organ opening was observed in a single specimen ( Fig. 8C View FIGURE 8 ).

Nuclei. A similar pattern which was described by Wiedermann (1995) for Cephalodasys maximus Remane, 1926 was observed on the new species. A large concentration of nuclei was observed on the dorsal head, probably brain region and along the dorsolateral body regions ( Fig. 9A View FIGURE 9 ). Ventrally, a large number of nuclei are present along the entire intestine length ( Fig. 9B View FIGURE 9 ).

Taxonomic remarks

The genus Cephalodasys is composed of 14 species formally described ( Yamauchi & Kajihara, 2018; Todaro, 2024). The arrangement and numbers of adhesive tubes still is the most valuable morphological characters to distinguish species of Cephalodasys mainly due the lack of more detailed morphology described on the previous works ( Fig. 10 View FIGURE 10 ). The species of this genus can be diagnosed by a distinct head, wider than the neck, and the presence of a furrow demarcating these two regions ( Remane, 1926; Kieneke et al., 2015). Although pear-shaped head is the most common format among the cephalodasyians ( Kieneke et al., 2015), three species displays a slightly to rounded head with lateral projections: C. miniceraus Hummon, 1974 , C. hadrosomus Hummon, Todaro & Tongiorgi, 1993 and C. mahoae Yamauchi & Kajihara, 2018 . Once, the head format is a diagnostic character for the group, the position of these species within the taxon is highly questionable ( Hummon, 1974; Kieneke et al., 2015).

Cephalodasys mariannae sp. nov. is unique and differs from its congeners by the presence of a series of 11 pairs of TbV running from U28 to U65, and C. seagalius is the only known species with two pairs of TbV at U48 ( Fig. 10 View FIGURE 10 ). Beyond that, three Cephalodays species were reported for the same biogeographic region (TNWA) of the new species: C. miniceratus , C. pacificus and C. interinsularis . The new species can be differentiated from C. miniceratus by the head shape: pear-shaped in C. mariannae sp. nov. and rounded with lateral projections in C. miniceratus . Beyond this, these two species can also be differentiated by the number of TbA in the fleshy hands: higher in the new species (6) than C. miniceratus (2). C. pacificus and C. mariannae sp. nov. can be distinguished by number of TbVL: higher in the new species (26) than C. pacificus (5–7); by the shape of the posterior end: tapering in C. mariannae sp. nov. and rounded in C. pacificus . Regarding C. interinsularis , the new species can be differentiated by the arrangement of TbA: fleshy hand-like on new species and arising directly from the body in C. interinsularis ; and by the arrangement and number of TbVL: 26 pairs of TbVL distributed on the pharynx and intestine region of C. mariannae sp. nov. and 5 pairs restricted to the intestine region in C. interinsularis .