Ornamentula miyazakii, Minowa & Garraffoni, 2021

Minowa, Axell K. & Garraffoni, André R. S., 2021, Seek and you shall find: new species of the rare genus Ornamentula (Gastrotricha: Chaetonotida) and first record outside of type-locality, Zoologia (e 56781) 38, pp. 1-9 : 2-6

Ornamentula miyazakii sp. nov.

http://zoobank.org/ 33D78328-A59F-4468-8BD9-6999A90C9033

Figs 1–12, Tables 1 , 2

Type material. Holotype. Photographs of one specimen (adult) collected from an urban lagoon in Paulínia, Brazil in October 2017 with floating vegetation. The specimen was examined alive with a compound microscope equipped with DIC, but due to the fragility of its body, it was destroyed and is no longer available ( Garraffoni et al. 2019). The holotype is illustrated in Figs 1–3 and photomicrographs in Figs 5–7 ( Garraffoni et al. 2019) and its digital image data are available at the Museum of Zoology, Universidade Estadual de Campinas, Brazil, under the accession number ZUEC GCH 52; Paratypes: Photographs of two additional specimens (adult and juvenile) collected from the same sampling site, with digital image data available under accession numbers ZUEC GCH 53 to ZUEC GCH 54.

Diagnosis. Ornamentula species 101–193 µm in body length (126–227 µm posterior spines included). Cone-shaped head, small cephalion. Two pairs of extremely long cephalic sensory bristles. Trunk dorsally covered by two columns each made of six large, ornamented scales each with a single spine. Ventral trunk side with small spined scales between ciliary tufts. Posterior end truncated; two pairs of dorsal terminal scales each with a thick spine and a similar terminal ventral scale with a thick spine.

Species-specific characters. A pair of extremely long, lateral cephalic sensory bristles inserted adjacent to the posterior cephalic ciliary tufts. Neck with one transversal row of three spined ornamented scales. Fish-shaped (oval scale with a posterior shallow constriction, and with convexe end) lateral ornamented scale (U44), immediately posterior to the tb spines group. An additional pair of dorsolateral rear spines, inserted on small ornamented scales. All dorsal scales with long, thick slightly curved spines with prominent denticles.

Description. Description based on characters and measurements of two adults (holotype and paratype) ( Table 1 ).

Ornamentula of 101–193 µm length (spines excluded); 126–227 µm (spines included). Elongated-oval dorsoventrally flattened body, with distinct cone-shaped head, and well developed lobes (31 µm wide), with a short and narrow neck region. Sub-terminal mouth ring (8.4 µm diameter), with short tentacle-like projections around the mouth ring. Cephalion 18 µm wide (U04), pleura absent, and hypostomion not observed ( Figs 1, 11). Narrow cylindrical pharynx (62 µm long) ( Figs 6, 9). Intestine with maximum width at its middle (127 µm long, 44 µm wide, U62,) ( Figs 4–9). Truncated posterior end with two thick caudal spines (r1-r2) inserted on dorsolateral scales (U85; U90).

Cephalic ciliation consists of two pairs of lateral tufts (anterior one adjacent to the mouth, U04; posterior one medio-lateral, U06) and a pair of cephalic ciliary transversal bands (U10), bordering the cephalic lateral plates, interrupted in the dorsal and ventral medial region ( Figs 1–3, 9–12). A pair of cephalic sensory bristles extremely long (4.3 µm; U03) inserted between the second lateral cephalic ciliary tuft and lateral cephalic transversal ciliary bands, anteriorly to granular lateral scales (U10) ( Figs 1, 10, 11). Trunk ventral ciliation consists of three paired tufts (U43–U45, U59–U61, U86–U90) associated to lateral trunk spines tb1–3, tc1–2 and r2, respectively ( Figs 3–4). Body dorsum mostly covered with enormous scales with ornamentations described originally as scale reinforcements, probably due to their exaggerated size ( Figs 1, 4–6). Cephalic cuticular armature: Two pairs of anterior lateral cephalic plates on the head (U10), slightly folded in its margin, with finely granulated surface, ( Fig. 7), different from the scales of the trunk. These plates are positioned at both sides of lateral cephalic transverse bands ( Figs 1–3). Several pairs of small rounded scales, each with a fine barbed spine, with fine barbed spines (U08–U12) on the cephalic dorsal space between granulated plates ( Figs 1, 10, 11). Anterior cephalic spines short (3.7 µm, 1.5x the length of inserted scale), lengthen gradually to the posterior longer ones (7 µm, 2.4x the length of inserted scale) ( Fig.1). The lateral cephalic spines (ca) are inserted anteriorly adjacent to the granular plate (17.7 µm long, U03), much thicker at the base and gradually getting thinner distally, until the denticle, where it gets thinnest ( Figs 1–3, 7).

Trunk cuticular armature: Single dorsal anteriormost transversal row with three simple spined scales (U21). The dorsal trunk is covered with two parallel column of six scales each (U24, U30, U43, U58, U76, U90), with varying sizes ( Table 2 ), each scale bears a long, straight, thick, and barbed spine at 4/5 of its length. Laterally, three scales positioned posterior to each spine group (U35, U50, U64), first rounded between ta and tb spine groups; followed by fish-shaped scale, posterior to tb spine group (i.e. rounded anterior half, with middle portion slightly constricted, and posterior half concave, with two pointed edges); posteriormost rounded scale lodged on the concavity of fish-shaped scale. Two pairs of rearmost ventrolateral scales (U67, U96) with r1 and r2 spines inserted, followed by a ventral triangular scale ( Figs 2, 3, 8) with short curved spine (U99).

Ventrolateral trunk with thick and straight spines organized in four groups (ta, tb, tc, td) arranged in 5–3–2–1 spines each (U27, U43, U61, U68), with a conspicuous denticle at 4/5 of its length, and inserted on triangular scales ( Figs 2–3, 8). The ta group is the most laterally inserted, with ta1–2 spines dorsolateral ( Fig. 2).

Ventral trunk anteriorly smooth in interciliar space, and posterior region with 15 small rounded scales (U55–70) between tb, tc, and td spine groups. Anterior scales with longer spines (3.4 µm, 1.5x the length of inserted scale) followed by posterior ones shorter spines (1.7 µm, 1.5x the length of inserted scale) ( Fig. 8).

Sexuality unknown, as we could not observe any specimen with eggs, nor the sexual organs.

Etymology. Species dedicated to animation director Hayao Miyazaki, a highly notorious animator and filmmaker. He animated the fantasy film “Princess Mononoke”, and illustrated the character Forest Spirit (1h01’20” in the original film), that at nighttime turns to Daidarabocchi, resembling the specimen drawn in Fig. 1.

Ecology.Freshwater, periphytic and semiplanktonic among roots of floating vegetation mainly composed by Eichhornia sp.

Remarks.Although the body plan of the taxon Ornamentula seems to be different from other members of Dasydytidae , it shows some common characteristics with other semiplanktonic species. Like its counterparts, Ornamentula species are characterized by a tenpin-shaped body, with evident head and neck constriction, cephalic ciliature arranged by discontinuous tufts and/or bands and body with paired groups of ventrolateral single-barbed spines. Both Atlantic and Amazonian Ornamentula species share several unique morphological features characteristic of the taxon bauplan, such as: i) two parallel columns of dorsal ornamented scales forming a rigid armature, ii) two pairs of lateral cephalic plates (granular scales) on both sides of cephalic transverse ciliary bands, iii) a pair of lateral cephalic spines, iv) two pairs of ventrolateral cephalic ciliary tufts followed by the transverse band, and three ventral ciliary tufts on the trunk, v) four groups of movable ventrolateral spines with a conspicuous denticle inserted on ornamented scales and organized in 5–3–2–1 (ta–tb–tc–td) and vi) two pairs of terminal ventral spines with denticles (r1 and r2).

However, the new species can be distinguished from O. paraensis by some remarkable differences:

1. The dorsolateral cephalic spines (ca) thicker and curved, followed by a pair of long cephalic bristles adjacent to the second cephalic tuft, absent in former species.

2. The group of dorsal cephalic scales provided with spines with prominent denticles, in contrast to simple and shorter spines in former species.

3. The absence of second dorsal transverse rows of scales on the neck, present in O. paraensis .

4. The lateral trunk scale, posterior to tb spine group, fish-like shaped, in contrast to the rounded scale of O. paraensis .

5. Ventral spined scales with rounded uniform shape through the ventrum, unlike O. paraensis , with rounded in anterior portion and posteriorly triangular shaped.

6. A third terminal ventral scale with a short, simple and curved spine, much shorter than r1 and r2 spines,absent in O.paraensis .