Pseudostomella cheraensis, Todaro, Antonio, 2007

Todaro, Antonio, 2007, A new species of Pseudostomella (Gastrotricha: Macrodasyida: Thaumastodermatidae) from a sandy beach of Kerala, India, Zootaxa 1616, pp. 61-68 : 62-67

Pseudostomella cheraensis sp. nov.

( Figs 2 , 3 )

Type locality. Cherai beach, (lat. 12° 97′ N, long. 77° 56′ E) Kerala, India. Mid-tide region in clean medium sand, moderately well sorted.

Materials examined. Twelve specimens were examined by light microscopy.

Holotype. One specimen of total length (Lt) 295 Μm collected on 15-12-2005; glycerol wholemounts on microslide, deposited at Marine Biodiversity Museum, CMFRI (Government of India), Kochi, India; ref. No: MBM – 1.1.1.1

Paratype. Two specimens of length 276 Μm and 223 Μm respectively collected from the type locality; glycerol wholemounts on microslides, deposited at the same museum as; ref. No: Paratype 1: MBM – 1.1.1.1.1; Paratype 2: MBM – 1.1.1.1.2

Etymology. Named after the type locality which is a well known sandy beach frequented by both domestic and foreign tourists.

Diagnosis. Pseudostomella up to 295 Μm in total body length, with a distinct anterior pre-buccal apparatus and an elongate bilobed caudum. Buccal palps bearing five dorsal cephalic papillae with sensory hair and four-six minute ventral papillae. Cuticular armature of pentancres extending from the margin of oral cavity to the base of pedicles (caudum) ornaments the entire dorsal surface. Adhesive tubes: pedicles with three distal adhesive tubes (TbP) of unequal length and an adhesive tube at the base. TbA, six in number, in 2+2+2 pattern; TbL, 10-12 per side between U39 and U89. Nine pairs of granular epidermal glands between U25 and U87.5. Sensory hairs on the pre-buccal palps and trunk. Tactile cilia border the margin of the buccal cavity. Caudal organ pear shaped; frontal organ spherical. Oocytes located in the mid body.

Description. The description is based on an adult specimen, 295 Μm in total length. Width at oral cavity, neck (slightly swollen), trunk (6th pair of epidermal gland) and caudal base: 39/ 46/ 40/ 15 Μm at U12, U21, U67 and U93 respectively. Head with well-developed and extended pre-buccal apparatus (pb) incurving anteromedially, characterizing the genus Pseudostomella . Their dorsal margin project out a little beyond the ventral margin. Pre-buccal apparatus has five fleshy dorsal papillae ranging in length from 6 Μm to12 Μm, symmetrically arranged in 2+1+2 pattern. All papillae are with tactile cilia at the tip. Four to six smaller papillae are present along the ventral margin of the buccal palps, arranged in 2+2 or 3+3 pattern. Several sensory hairs (3 Μm) present on the outer lateral margins of pre-buccal apparatus among which, a longer one measured 16 Μm. Sensory hairs or lateral bristles (10 Μm long) of uncertain numbers seen on the lateral margins of the body as well (U22-U91).

Epidermal glands: Eight to nine pairs of granular epidermal glands arranged along the lateral margins of the body originate at about U25 and extent up to U87.5. Their size range between 7.5–10 Μm × 7.5–15 Μm. The middle glands located at 8 Μm apart from each other.

Cuticular armature: The entire dorsal surface from the base of buccal apparatus to the pedicles covered by rows of closely packed pentancres with an average size of 3.5-5 Μm. They are arranged in 13-14 longitudinal columns in the mid-trunk region with each column containing around 58 to 60 pentancres antero-posteriorly. The tines of the ancres project out almost masking the posterior border of the body.

Adhesive tubes: Four of the six anterior adhesive tubes (TbA) seen ventrally at the base of the pre-buccal apparatus in 2+2+2 pattern measure 4 Μm each. The remaining pair at the farthest end are longer. The number and pattern of TbA seem to vary. In one of the paratypes, an additional pair is seen associated with the distal pair, indicating variability in the number of TbA. Eleven pairs of lateral adhesive tubes (TbL) originate at U39 and extent up to U89, with an average length of about 7-8 Μm. Of these, the anterior ten pairs are TbVL, evenly spaced and extent up to U77.6. The last pair, dorso-lateral in position is located at U89. Pedicles (20 Μm long) furnished with three distal tubes (TbP), the median one (8 Μm) directed slightly dorsally, while the others (5 Μm) are directed slightly ventrally. Two posteriorly directed adhesive tubes, 8-9 Μm long, are positioned at the base of the pedicles.

Ventral ciliation: Locomotory cilia form a continuous field of transverse rows from behind the margin of mouth and extent up to the caudal base.

Digestive system: The digestive tract begins with a terminal mouth, covered dorsally by a hood like extension and opens into the pharynx, behind the pre-buccal apparatus. The pharyngeal pores could not be located in the holotype but were seen at the base in the paratypes. The entire digestive tract not well discernable in the holotype. The paratype showed PhIJ at U37- U38. The intestine is broad anteriorly and narrows down posteriorly. The anus opens ventrally at U89.

Reproductive system: Simultaneous hermaphrodites. A single elongate testis on the right side (as seen from above) begins behind the pharyngeo-intestinal junction and leads caudally into a narrow elongate vas deferens. The caudal organ located at U78 is pear shaped and is connected to a spherical frontal organ located at U74.8. The paratype showed two oval oocytes in the mid posterior body, of which the upper larger one measured 38×19 Μm.

Taxonomic affinities. The genus Pseudostomella includes 13 described species; of these four: P. plumosa Ruppert, 1970 , P. klauserae Hochberg, 2002 , P. megapalpator Hochberg, 2002 and P. f a ro e n s i s Clausen, 2004 carry scaled triancres; six: P, ro s c o v i t a Swedmark, 1956, P. m a l a y i c a Renaud-Mornant, 1967, P. indica Rao, 1970 , P. andamanica Rao, 1993 , P. koreana Lee & Chang, 2002 and P. longifurca Lee & Chang, 2002 bear tetrancres whereas the remaining three: P. cataphracta Ruppert, 1970 , Pseudostomella sp. 1 [ Valbonesi & Luporini, 1984] and P. e t r u s c a Hummon, Todaro & Tongiorgi, 1993 have a cuticular armature made up of pentancres. Based on the type of the cuticular covering the new species from India resembles most closely to the latter three taxa.

Pseudostomella cataphracta can be distinguished from the other pentrancres-bearing species, including the new one from India, principally because it possesses a pair of ventral feet (each foot made up of four adhesive tubes), located in posterior region of the trunk. P etrusca is the only one that bears a pair of dorsal adhesive tubes on the base of the pre-buccal palp, moreover it has a much higher number of anterior adhesive tubes compared to P. cheraensis sp. nov. (14 vs 6). Psudostomella sp. 1 from Somalia in contrast with the new species from India shows a pair of ventro-lateral adhesive tubes in the anterior region of the pharynx, a higher number of anterior adhesive tubes, (10 vs 6), shorter caudal pedicles and the dorsal tubes at the end of each caudal pedicle that is shorter of the two tubes that flank it.

The pattern of distribution of the representative species belonging to the genus Pseudostomella hitherto known clearly indicates cosmopolitanism. However, the species as such appear to have a rather narrow range, on the other hand the general absence of biogeograhic records testifying the simultaneous presence of two or more species at a single beach (e.g. as it happens for Tetranchyroderma ) let to hypothesize that biogeography may be influenced also by interspecific competition. In this general framework the finding of three species of Pseudostomella from a North Carolina beach ( Ruppert, 1970) and the occurrence of P. ro s c o v i t a in the Atlantic Ocean (and connected seas) and the Indian Ocean appear particularly interesting and certainly call for further investigations.

Figures

FIGURE 2. Pseudostomella cheraensis sp. nov. – Drawing of the habitus as seen from the ventral side. Scale bar: 100 µm.

FIGURE 3. Pseudostomella cheraensis sp. nov. – DIC optics - A, habitus, dorsal view; B, anterior end, dorsal view, showing the arrangement of the pentancres and papillae of the pre-buccal palps; C, anterior end, ventral view, showing the arrangement of the anterior adhesive tubes. Scale bars: A, 100 µm; B, C, 25 µm.