Oregodasys norenburgi, Hochberg, Rick, 2010

Hochberg, Rick, 2010, Two new species of Oregodasys (Gastrotricha: Macrodasyida: Thaumastodermatidae) from Carrie Bow Cay, Belize with ultrastructural observations of the epidermal glandular system, Zootaxa 2660, pp. 1-17 : 3-6

Oregodasys norenburgi new species

(Figs. 1,2)

Diagnosis. Specimens with body lengths of 400 Μm–500 Μm long (mean 448 Μm, n = 8). Maximum body width at mouth, PIJ and midpoint of body is 85/78/95 Μm. Pharynx to 138 Μm long (measured from the tip of the oral hood); oral hood to 50 Μm long; mouth to 80 Μm wide. Red ocelli present on either side of mouth. Cuticle is translucent and covered with ciliated papillae on dorsal and lateral surfaces. Numerous glandular cells fill the dorsal and lateral epidermis. Up to 16 TbA per side, somewhat staggered in position, inserting directly on body surface and leading imperceptibly to the adhesive tubes of the TbVL series. TbVL elongate, 68–82 per side, evenly spaced and sparse in the pharyngeal region, ca. 6–7 per side, becoming clustered in the trunk. TbL shorter than TbVL, to 19 per side, distinctly set off from TbVL and beginning at U80; extending to caudum. TbP 7 per side, fused at their base forming pedicles, with 6 TbP between the pedicles. Locomotory cilia form transverse rows on ventral surface from mouth margin to caudum. Hermaphroditic, with singular testes on right side as seen from below; egg dorsal at mid-body length; caudal organ is muscular; frontal organ not observed.

Type material. The description of Oregodasys norenburgi sp. nov. is taken from twelve specimens from stations CBC10.01, CBC10.04, CBC10.11 and CBC10.24. All specimens were measured in vivo. One specimen from station CBC10.01 was prepared as a permanent wholemount (Holotype: USNM # 1146555, BL = 350 Μm). Red ocelli no longer evident in the type specimen.

Type locality. Holotype station CBC10.01 is an open plain at 10 m depth. Other localities include: CBC10.04, Carrie Bow Cay Reef, sand patches between corals on top of ridge; CBC10.11, Carrie Bow Cay Reef, deep outer slope; CBC10.24, small sand patches on ridge.

Etymology. The species is named after the organizer of the Smithsonian field research workshop, Dr. Jon Norenburg.

Ecology. The new species was present at three stations in moderate abundance. Most specimens with numerous diatoms in gut. Grain size analysis (Table 1) from stations CBC10.04 and CBC10.11 shows a positive skewness, indicating that grain sizes larger than the median predominate; a negative skewness for CBC10.24 indicates a prevalence of grain sizes smaller than the median. All sediment with low amounts of organic detritus.

Description. Specimen length ranged from 350 Μm to 500 long (n=8). The type description is based mostly on an adult specimen of approximately 500 Μm total body length. All animals appear shiny under reflected light (dissection microscope) and opaque under transmitted light due to the highly glandular bodywall epithelium. Ocelli red, approximately 3–4 Μm in diameter, present on either side of the ventral mouth margin and easily observed with a dissection microscope. Red pigments are never present as circular “eyepsots,” but instead are scattered across several cells. Head with papillated oral hood to 50 Μm long. Tip of hood with slightly scalloped margin but void of papillae. Numerous scattered sensory cilia to 7 Μm long across hood margin. Pharynx reaches 138 Μm in length (range: 125 Μm–138 Μm) to tip of oral hood. Body width at mouth/neck/PIJ/trunk are 82/70/74/84 Μm, respectively.

Body covering of papillae to 12 Μm long. Most papillae with a blunt end and a single lateral extension. Several papillae are closely associated with an apparent sensory cilium to 15 Μm long. Papillae completely cover the dorsal body surface except for the tip of the oral hood. The lateral and ventrolateral body surfaces are completely covered with papillae. Most papillae appear to be associated with an underlying epidermal gland of 8– 12 Μm diameter that is highly refractile with transmitted light. Some papillae contained ovoid secretions from the underlying glands ( Fig. 1 A). Some epidermal glands contained ovoid secretions that were colored brown, green or orange. Most epidermal glands were colorless.

Adhesive tubes present in four series. Anterior adhesive tubes (TbA) form a transverse row beneath the ventral mouth margin and arc slightly toward the lateral body margin. Up to 16 TbA per side, inserting directly on body surface, and somewhat staggered in placement. The most medial tubes are approximately 6– –8 Μm long; tubes toward the lateral margins up to 13 Μm long. The ventrolateral adhesive tubes (TbVL) are positioned on either side of the ventral locomotory cilia and extend from approximately U12 to the caudal end. Anteriorly, the TbVL grade imperceptibly with the TbA, but are easily distinguished from them due to their arrangement in a singular column. The TbVL in the pharyngeal region (U12–U28) are shorter (ca. 15 Μm) and less numerous (<15/side) than those in the trunk region. In the trunk, the TbVL are highly elongate (up to 25 Μm) and clustered; numerous tubes insert in proximity to one another along the length of the column. There are up to 70 tubes per side in the trunk region. A distinct set of lateral adhesive tubes (TbL), up to 15 Μm long and 19/side, are set off from the TbVL at ca. U80, where they form a lateral column that leads to the caudum. The caudum is formed of two pedicles, each bearing 7 posterior adhesive tubes (TbP). The two most lateral and medial tubes are shorter (ca. 6–7 Μm) than the three median tubes (ca. 12–15 Μm). Six adhesive tubes, to 12 Μm long, are positioned between the two pedicles.

The ventral ciliature forms a continuous series of transverse rows from the ventral mouth margin to the caudal pedicles. A singular region around the anus, ca. U90, is devoid of cilia. Cilia extend up to 15 Μm long.

The digestive tract begins with a wide mouth, to 82 Μm, covered by an oral hood that extends to U10. The pharynx narrows to ca. 50 Μm at the PIJ. The pharyngeal pores, which were observed in only one specimen due to the opacity of the body wall, were at ca. U26. The intestine is narrow to broad depending on its contents. Several specimens possessed numerous diatom frustules in their guts. The anus opens ventrally around U89.

Animals are simultaneous hermaphrodites. A single testis is present on the animal’s right side (as observed from above) and extends from the PIJ to the caudal organ. Vas deferens opens into a muscular, pearshaped caudal organ on the right side of the body; up to 47 Μm long and 25 Μm wide. Frontal organ not observed. Mature ovum (63 Μm long x 40 Μm wide) dorsal above gut in mid-trunk region.

Figures

FIGURE 1. Habitus of Oregodasys norenburgi sp. nov., multiple specimens. A Dorsal view. Inset: closeup of a papilla containing secretory vesicles. B Dorsal view of head region showing ocelli (oc). C DIC image of the ventral mouth (mo) margin showing the anterior adhesive tubes (TbA). D Dark-field image of the midgut region showing several ova (ov) and numerous diatom frustules (di). E DIC image of the posterior pedicles (pd), ventral view. Lateral adhesive tubes (TbL) are present on either side of the pedicles that bear the posterior adhesive tubes (TbP); locomotory cilia (ci) and ventrolateral adhesive tubes (TbVL) are also shown.