Turbanella hyalina Schultze, 1853

Kolicka, Małgorzata, Kisielewski, Jacek, Kotwicki, Lech, Zawierucha, Krzysztof & Grzelak, Katarzyna, 2014, Checklist of Gastrotricha of the Polish Baltic Sea with the first reports of Heterolepidoderma joermungandri Kånneby, 2011, and Turbanella hyalina Schultze, 1853, Zootaxa 3869 (2), pp. 101-130 : 120-123

Turbanella hyalina Schultze, 1853

( Figs 11–14 ; Table 5 )

Localities: Sites 27, 28, and 29

Materials: 35 specimens (19 adults, 12 subadults, and 4 juvenile), all photographed.

The micro-photographs are available in the Natural History Collections at Adam Mickiewicz University in Poznań and in the collection of the first author.

Short description: Turbanella hyalina Schultze, 1853 , is a medium body-sized species in comparison to other Macrodasyida . The body is slender and tapers towards the posterior end. The head is without distinctly marked conical appendages (palpal organs) and with only a very flat protrusion with a group of sensory cilia on the top and sculptured in front, and a snout-like oral protuberance, bearing a circumcephalic band of cilia. Neck constriction is slight, starting just above the anterior adhesive tubes at U4 and ending at U5. Trunk with a slightly wavy appearance, protruding with every lateral adhesive tube and of approximately uniform width, gradually tapering towards caudal lobes. The caudum is small and narrower than the trunk, with a short medial cone. Epidermal glands are from small to medium (1.1–12.2 Μm), usually distributed in two columns. The anterior adhesive tubes are located on the back of the head on short fleshy hands (at U4). The lateral and dorsal adhesive tubes are predominantly symmetrically distributed around the body on both sides over its entire length. Long sensory cilia and, near the dorsal adhesive tubes, short sensory cilia are connected with each of the lateral adhesive tubes. Additionally, many free sensory cilia (not connected with the adhesive tubes) are located in the trunk region. Posterior adhesive tubes are located on the posterior margin of the caudal lobes. In adults, each caudal lobe bears 5 to 10 adhesive tubes of various lengths. The external tubes are the longest, and the medial tubes the shortest. Sensory cilia are located near the posterior adhesive tubes. Locomotory ciliature runs parallel in two bands from the head to the base of the caudum.

The mouth ring is oval, narrow, protruding, located terminally, and surrounded by sensory cilia. The pharynx is cylindrical and expands slightly towards its posterior end. The pharyngeal pores are distinct and located at U19–U22, near the posterior end of the pharynx. The pharynx is connected via the pharyngeal intestinal junction to a straight intestine.

Taxonomic remarks: Molecular analysis conducted on the specimens from the northern coast of Europe showed that the morphospecies traditionally referred to as T. hyalina Schultze, 1853 , comprises in fact two cryptic species ( Kieneke et al. 2012). Considering the rather small geographic area where the specimens of T. hyalina were collected by Kieneke et al. (2012), it is plausible that a wider sampling area can yield a higher number of cryptic species. Furthermore, T. hyalina displays a wide range of morphological variability within the morphospecies. Different populations of T. hyalina may show completely reduced conical appendages (even without a distinct flat contour) or conical appendages developed to the extent that they resemble those found in T. cornuta while retaining species integrity, as was confirmed by an ultrastructural analysis of their nervous system ( Rothe & Schmidt-Rhaesa 2008).

Differential diagnosis: The genus Turbanella Schultze, 1853 , contains 29 similar species. T. hyalina Schultze, 1853 , most closely resembles T. cornuta Remane, 1925 , T. wiseri Hummon, 2010 , and T. lutheri Remane, 1953 , but differs from:

T. cornuta in terms of: lack of clearly marked conical appendages (palpal organs), the position of the anterior adhesive tubes (the fleshy hands are triangular and longer in T. cornuta ), body shape (the body is not as slender and the base of the caudum is more clearly marked in T. cornuta ), and head shape (the head is shorter and has more oval shape in T. cornuta ).

T. wiseri in terms of: a lack of clearly marked conical appendages (palpal organs) and pharynx shape (the pharynx is straight and equally wide along its entire length in T. wiseri ); in addition, its mouth is surrounded by only one type of short sensory cilia (Hummon 2010).

T. lutheri in terms of: a lack of clearly marked conical appendages (palpal organs) ( T. lutheri has no palpal organs whatsoever), body shape (the cephalic and cervical sections are narrower than the dorsal section in T. lutheri ), head shape (the head is more rectangular in T. lutheri ), a greater number of regularly distributed lateral adhesive tubes (ca. ten pairs of adhesive tubes are in T. lutheri ), a smaller number of posterior adhesive tubes (10–11 adhesive tubes in one caudal lobe are in T. lutheri ), the distribution and length of adhesive tubes in the caudal lobes (the adhesive tubes are located at the end and on the sides of the caudal lobe, and are of equal length in T. lutheri ), and the number and length of the lateral sensory cilia (the lateral sensory cilia are shorter and less numerous in T. lutheri ) ( Remane 1953; Kisielewski 1975; Rothe & Schmidth- Rhaesa 2008).

Distribution: T. hyalina morphospecies is widely distributed in Europe and has been reported in: Belgium ( Jouk et al. 1992), Denmark ( Karling 1954; Kieneke et al. 2012), France ( Müller 2004, Kieneke et al. 2012), Germany ( Kieneke et al. 2012; Schultze 1853), Italy ( Balsamo & Tongiorgi 1995), the Netherlands ( Boaden 1976), Norway ( Kieneke et al. 2012), Romania ( Rudescu 1967), Sweden ( Jansson 1968; Karling 1954; Kieneke et al. 2012), and the United Kingdom ( Howson & Picton 1997; Kieneke et al. 2012).

found among all specimens measured, SD – standard deviation.

Figures

FIGURE 11. Turbanella hyalina Schultze, 1853. Adult specimen—habitus.

FIGURE 12. Turbanella hyalina Schultze, 1853. A—Juvenile specimen, B—Subadult specimen, C—Adult specimen.

FIGURE 13. Turbanella hyalina Schultze, 1853. A—Anterior adhesive tubes, B—Lateral adhesive tubes, C—Dorso-lateral adhesive tubes, D—Dorsal view of caudum, E—Internal view of caudum, F—Ventral view of caudum.

FIGURE 14. Turbanella hyalina Schultze, 1853. A—Pharynx, B, C—Posterior body region with visible epidermal glands.