Redudasys sp.

Kånneby, Tobias & Wicksten, Mary K., 2014, First record of the enigmatic genus Redudasys Kisielewski, 1987 (Gastrotricha: Macrodasyida) from the Northern hemisphere, Zoosystema 36 (4), pp. 723-734 : 728-730

Redudasys sp.

(Figs 1-3; Tables 2, 3)

MATERIAL EXAMINED. — One specimen that is no longer extant. Specimen prepared for sequencing of 18S rRNA and COI mtDNA. GenBank Accession numbers: KJ950121 and KJ950123 .

DISTRIBUTION. — In fine to medium grained sand with some organic content at 3-9 meters. Spring Lake, San Marcos, Texas, USA (29°53’36’’N; 97°55’53’’W), June 17, 2012 .

DESCRIPTION

Redudasys with total body length of 242 Μm. Body width at head (U12), neck (U24), trunk (U76) and base of caudal lobes (U94) is, 47 Μm, 34 Μm, 47 Μm and 21 Μm, respectively. Head with clearly distinguishable sensory cilia. Slight neck constriction present.Trunk of approximate equal width and not wider than widest part of head, narrowing toward the caudal end which indents at U95. Body surface transparent, without cuticular structures.

Apparently only a single pair of TbA present, 9-10 Μm in length, and located at U13. Two pairs of TbP: inner pair 10-12 Μm in length and outer pair 15-17 Μm in length.

Sensory cilia abundant in anterior head region and reach lengths up to 25 Μm. Anteriormost cilia surrounding mouth appear stiffer and are shorter, approximately 10 Μm in length. At least seven pairs of dorsolateral to lateral sensorial hairs observed, posteriormost pair inserted just anterior to caudal indent. Ventral ciliation apparently in somewhat regularly spaced tufts from U8 to U50. Posterior to U50, tufts are medial in distribution.

Mouth terminal. Pharynx 92 Μm long with pharyngeal intestinal junction located at U38. Pharyngeal pores could not be detected in the live specimen but they were subsequently detected in photos, they are located in the posterior part of the pharynx at approximately U33. Intestine straight, narrowing towards its posterior end, with anus at approximately U90.

One egg, approximately 50 Μm in diameter, present dorsally in mid-posterior trunk region. Sperm or accessory reproductive organs not detected.

REMARKS

Compared to other specimens of Redudasys , the most notable difference of the Texan specimen is its smaller size. The shortest total body lengths reported for R. fornerise and Redudasys sp. from Brazil are 300Μm and 280 Μm,respectively ( Kisielewski 1987a;

FIG. 1. — Redudasys sp. found in San Marcos, Texas: A, ventral view of anterior portion of body showing the anterior adhesive tubes (arrow) and the sensorial hairs of the head; B, posterior portion of body showing the caudal lobes with posterior adhesive tubes; C, posterior part of pharynx showing the position of pharyngeal pores (arrows). Scale bars: A, C, 20 µm; B, 10 µm.

Garraffoni et al. 2010), compared to 242 Μm for the Texan specimen ( Table 2). However, our specimen could be a young adult, judging from the presence of only a single egg, and it may attain a larger body size as it matures. The Texan specimen can be separated from R. fornerise based on the following combination of morphological characters: (i) a single pair of anterior adhesive tubes, and (ii) a shorter body length. Although the second pair of anterior adhesive tubes can be hard to detect, they appear absent in our specimen. The only apparent difference from the Brazilian Redudasys sp. reported by Garraffoni et al. (2010) is the shorter body length ( Table 2). The exact distribution of lateral and/or dorsolateral sensorial hairs cannot be justified from the single specimen obtained in this study. However, since the specimen from Texas is geographically far separated from the Brazilian taxa, it is plausible that it is new to science.

The classification of our specimen within the family Redudasyidae and the genus Redudasys is based on the presence of pharyngeal pores in the posterior part of the pharynx and the unequal length of the inner and outer pair of TbP. The Bayesian analysis of the concatenated data set of 18S rDNA and COI mtDNA give maximum support for the inclusion of our specimen within Redudasyidae . The uncorrected pairwise distance based on COI mtDNA, between the Texan specimen and R. fornerise is 0.175. In order to diagnose the Texan specimen, we have provided the position of the ten first unique nucleotides for each taxa for which sequence data is available within Redudasyidae ( Table 3). However, it should be noted that R. fornerise is the only other freshwater macrodasyidan for which sequences are available on GenBank.