Dendrodasys highwaytoheavenensis, Araújo & Hochberg, 2025

Dendrodasys highwaytoheavenensis sp. nov.

Zoobank: urn:lsid:zoobank.org:act:

Material examined. Two adult specimens were examined by light microscopy and measured with an ocular micrometer. Holotype specimen collected from Tobago Island in 2012 deposited in Smithsonian National Museum of Natural History under accession number USNM 1760563 About USNM . Paratype specimen collected from Tobago Island in 2012 deposited in Smithsonian National Museum of Natural History under accession number USNM 1760564 About USNM . Both specimens were mounted alive. Holotype was photographed and video recorded; paratype was only video recorded .

Type locality: Tobago: Highway to Heaven dive spot, 31 m depth: 11º20’154” N, 60º38’539” W. Temperature: 27º C. Grain Size: Mean 0.74 mm ± 0.63 SD; Median 0.58 mm .

Etymology. The species epithet is named after the dive location on the island of Tobago: Highway to Heaven, located in the northwest corner of the island.

Diagnosis

Specimens with body lengths of 240 μm–250 μm long (= 245 μm, n = 2). Maximum body width at head (U5), neck(U16), U50 and caudal end of body (U65) is 32.1/24/33/22 μm. Pharynx to 50 μm long (U20). Triangular head with a blunt terminal mouth and prominent conical cephalic lobes on each side of head. A pair of very small presumed sensorial tubes were present dorsally at U04. A pair of horn-like (triangular) organs medial to cephalic lobes at U05, and a pair of knob-like pestle organs with narrow basis inserted posterior to the cephalic lobes. One pair of TbA arising from a common base per side; TbD, TbV, TbL and TbVL absent. TbP three per side; one tube (per side) at the anterior constriction of the caudal pedicle and one pair at the tip of each pedicle. Eleven pairs of epidermal glands along the body and a single epidermal gland at the base of the bifurcation of the caudal pedicle. Single large mature egg above intestine. Frontal organ with ventral opening present at U51. Putative caudal organ present at U62.

Description

The type description is mainly based on an adult specimen of 250 μm total body length ( Figs. 2 View FIGURE 2 , 3A View FIGURE 3 ). Slightly subterminal mouth positioned in the front of a triangular head. One pair of small tubes (3 μm long), presumed to be sensorial, on the dorsal side of the head at U02. A pair of horn-like (triangular/conical) organs (6 μm) are present at U05 and dorsally to the cephalic lobes ( Figs. 2A, C View FIGURE 2 , 3C, D View FIGURE 3 ). Knob-like pestle organs with narrow base at U08 ( Figs 2 View FIGURE 2 ; 3A View FIGURE 3 ) inserted at lateral body surface and posterior to the cephalic lobes. Trunk widened due to the presence of a mature egg (width range: 19–36 μm) and narrowed at U65 where it extended as a caudal pedicle (70 μm long). The caudal pedicle bifurcated at U88 ( Figs. 2 View FIGURE 2 , 3A View FIGURE 3 ).

Cuticle. The cuticle was smooth across the body and without notable folds or ridges.

Epidermal glands. Round to elliptical epidermal glands of 6–7 μm diameter. A total of eleven glands were present on each side of the body as follows: a refractile pair at U05; an opaque pair at U14; an adjacent pair of refractile/opaque glands at U22/U24, respectively; an adjacent pair of refractile/opaque glands at U28/U30, respectively; an adjacent pair of refractile glands at U42/U44; and three refractile glands at U54, U59, and U64; a single refractile gland present just anterior to the bifurcation of the caudal pedicle at U89 ( Figs. 2A View FIGURE 2 ; 3A, C View FIGURE 3 ).

Adhesive tubes. A single pair of TbA per side arises from a common base at U09; each tube as ca. 11 μm long and completely separated from the other on distal portion ( Figs. 2B View FIGURE 2 , 3B View FIGURE 3 ). Three TbP per side. A single tube to 14 um long was present at the constriction of the caudal pedicle at U75; a thick fiber extended from each tube into the body. The remaining two tubes were positioned at the tip of each pedicle: both tubes 5 μm long ( Figs. 2 View FIGURE 2 , 3A View FIGURE 3 ).

Cilia. Numerous sensory cilia 10–18 μm long projected from the anterior margin of the head and lined the cephalic lobes; cilia ventrally curved over the head margin and were active. The dorsal body wall was also adorned with mobile cilia: some cilia formed a transverse line at U07 ( Fig. 2A View FIGURE 2 ); other cilia were present between the pharynx and lateral body wall ( Figs. 2 View FIGURE 2 ; 3A– C View FIGURE 3 ). Many sensory cilia were adjacent to each other and appeared as pairs (10–15 um long) ( Fig. 2 View FIGURE 2 ; 3A, C View FIGURE 3 ). Two columns of ventral locomotory cilia extended from U03 to U70. The columns merged as transversal band at U18. The columns combined into a single field under the caudal pedicle.

Digestive tract. The narrow mouth (4 μm wide) was subterminal with a trapezoid-shaped cuticular ring at the tip of the head. The buccal cavity expanded slightly as it continues into the pharynx, which was straight and 50 μm long by 10 μm wide.A pair of dorsolateral pharyngeal pores at U17 extended inward as cuticle-lined tubes to the pharynx just anterior of the pharyngo-intestinal junction (PhIJ) at U20. The intestine was 9–12 μm wide and contained small refractile contents along its length; it narrowed to 5 μm wide as it approached the ventral anus at U69.

Muscles. All somatic muscles appeared cross-striated ( Figs. 2 View FIGURE 2 ; 3A View FIGURE 3 ).

Reproductive anatomy. A single large egg was present dorsal to the intestine; the nucleus was 9 μm in diameter ( Figs. 2A, B View FIGURE 2 ; 4A View FIGURE 4 ). Ovary not observed. A frontal organ, somewhat ellipsoidal in shape, was present at U51 close to the left side of the body; allosperm were present inside the organ. An apparent opening of the frontal organ was observed on the ventral body wall where it was surrounded by four raised bumps ( Fig. 2 View FIGURE 2 ; 4A–D View FIGURE 4 ). No testes were observed but a potential caudal organ (10 μm long) was present on the right side of the body at U62. The putative caudal organ was pyriform in shape had a potential ventral opening adjacent to the border of the intestine ( Figs. 4F–G View FIGURE 4 ).