Cephalodella ungulata, Fischer, Claus & Ahlrichs, Wilko H., 2006

Fischer, Claus & Ahlrichs, Wilko H., 2006, Cephalodella ungulata n. sp. (Monogononta: Notommatidae), a new rotifer species from North-West Germany, with notes on C. tenuiseta (Burn, 1890), Zootaxa 1378, pp. 49-59 : 50-58

publication ID	https://doi.org/ 10.5281/zenodo.175031
DOI	https://doi.org/10.5281/zenodo.6263974
persistent identifier	https://treatment.plazi.org/id/03D5B41C-FF81-FFAC-FEA8-B3FBFD0DFE21
treatment provided by	Plazi
scientific name	Cephalodella ungulata
status	sp. nov.

Treatment

Cephalodella ungulata View in CoL n.sp.

( Figures 1–4 View FIGURE 1 A – D View FIGURE 2 A – F View FIGURE 3 View FIGURE 4 A – D )

Material and methods: Live samples were taken form the type locality. After extensive examination of the living individuals, some individuals were taken for the trophi preparation (after De Smet 1998a) but with SDS/DTT (modified after Kleinow et al. 1990, without proteinase K). Other specimens were narcotized with carbonated water and fixed with Picricacid formaldehyd, 240 mOsm (after Melone 1998). Dehydration was carried out in a graded ethanol series followed by critical point drying. Scanning electron microscopy was performed with a Zeiss DSM 940, operated at 10 kV.

Holotype: A parthenogenetic female in a permanent, glycerin glass slide mount deposited at Museum für Naturkunde, Berlin, ( ZMB) Generalkatalog freilebende Würmer ZMB Vermes 11217. Paratypes: Two parthenogenetic females mounted for SEM deposited as ZMB Vermes 11218 – 11221 (two individuals from other species on this stub) and a trophi preparation with SDS/DTT for SEM with four trophi as ZMB Vermes 11222–11225 deposited at ZMB, Germany.

Type locality: A ditch near Leer Lower Saxony, Germany. November 2005 (53°14’25.82” N, 7°31’15.88” E).

Diagnosis: Short claw-bearing toes, usually slightly retracted, approximately 1/5 of the total length and bent dorsally; double keeled tail; hyaline, without eyespots or lenses; trophi type D (after Wulfert 1937 & 1938) with asymmetrical unci with two uncinal teeth and a toothlet on the left and one uncinal tooth on the right uncus; three pairs of salivary glands: one lateral (small), one ventral and one dorsal (both large).

Description: Habitus ( Fig. 1 View FIGURE 1 A – D & 4 View FIGURE 4 A – D ): Elongate, slightly laterally compressed body with hyaline soft lorica and ill-defined plates. Head set off. Short dorsally bent toes bearing claws usually slightly retracted. They are approximately 1/5 of total length. Convex corona nearly terminal and without lips. Head and foot relatively long in comparison to trunk. Double-keeled tail nearly covers foot.

Corona: Nearly terminal, convex.

Dorsal antenna-bearing pseudosegment: Rectangular, dorsal antenna near caudal margin. A fold as continuation of lateral sulcus of trunk. In SEM two parallel folds on either side of dorsal and ventral median line. Distinct constriction between dorsal antennabearing segment and trunk.

Trunk pseudosegment: Widening towards lateral antennae in dorsal or ventral view. Lateral antennae in caudal third of trunk. Dorsally with wide sulcus. Lateral sulcus narrow and difficult to observe in a light microscope.

Tail: Nearly covering foot laterally and posteriorly. Delimited from foot and trunk. Double keel as continuation of dorsal sulcus of the trunk.

Foot pseudosegment: Dorsally and ventrally nearly parallel-sided. Towards trunk narrower than tail from the side. Inconspicuous groove between toes.

Toes: Approximately 1/5 of total length, usually slightly retracted, continuously tapering to tip, with septum near tip and claws. Lateral view: dorsally bent; dorsal view: toes a little bit apart, proximal parts slightly convergent but tips divergent; toes a little bit narrower than when viewed from the side.

Digestive system (without trophi, Fig. 1B & 1D View FIGURE 1 A – D ): Mouth opening in beginning of ventral part of corona. Ephipharynx consists of two pairs of rod like structures, one pair shorter than the other. Mastax length roughly ¾ of dorsal antennae-bearing segment with three pairs of salivary glands: two large pairs dorsally and ventrally and one smaller pair laterally. Oesophagus clearly visible. Stomach cells with small inclusions. Stomach after ¾ of trunk continued by small intestinum. Stomach sometimes coloured yellow. Anus directly under tip of tail.

Trophi ( Fig. 2 View FIGURE 2 A – F & 3 View FIGURE 3 ): Tilted against body axis by angle of roughly 30° with fulcrum pointing ventrally.

—Fulcrum: Lateral view: dorsally straight, ventrally broadening towards rami, rodlike in middle and spatulate at caudal end; with basal apophysis. Dorsal view: rodlike, spatulate at caudal end.

—Rami: With conspicuous ridges. Frontal median margin with toothlike lamella. Ventral caudal margin nearly rectangular to fulcrum. Behind dorsal and lateral margin subunci. 6–7 smaller teeth follow one large tooth on each inner margin of subbasalchambers.

—Manubria: Clava with two lamellae: ventral one broadening towards cauda of manubria and with wide opening; dorsal one first broad, then tapering towards cauda of manubria and without opening. Medium rodlike part with opening. Cauda broader than medium part of clava at base and narrowing towards end. Caudal end curved ventrally with tip tilted dorsally and inwards.

—Unci: Two uncinal teeth one after another and a toothlet above them on left uncus with a gap between these in which the right uncinal tooth fits ( Fig 2E View FIGURE 2 A – F & 3 View FIGURE 3 ), both unci with broad lamellae.

Musculature (not figured): Some parts of ring-muscles and some retractors in front region visible.

Epidermis: Without secondary structure; smooth and hyaline.

Glands ( Fig 1B & 1D View FIGURE 1 A – D ): Two large oval pairs of salivary glands dorsally and ventrally of mastax with smooth surface. Additionally, one pair of small round salivary glands laterally of mastax. Gastric glands nearly round and short stalked. A pair of subcerebral glands present. Footglands large: approximately 1/3 of foot.

Nervous system and sense organs: Large ganglion, one part innervating dorsal antenna, with a pair of small subcerebral glands. No eyespots. A small round retrocerebral organ at the end of ganglion visible. Dorsal antenna near caudal margin of dorsal antennabearing segment, consisting of a small number of cilia ( Fig 4B View FIGURE 4 A – D ). Lateral antennae consisting of two diverging cilia inserted in caudal third of trunk ( Fig 4A View FIGURE 4 A – D ). Between retracted toes a very small caudal antenna with only one cilium visible with SEM ( Fig. 4D View FIGURE 4 A – D ).

Reproductive system ( Fig 1B & 1D View FIGURE 1 A – D ): Vitellarium with eight nuclei. Parthenogenetic egg oval and parts of it in foot and tail.

Protonephridial system: Fluid of protonephridial bladder is emptied into the terminal portion of intestinum (cloaca).

Differential diagnosis: The three taxa with reportedly type B trophi but a manubrial end similar to the new species show otherwise clear differences to the new species. The body of C. boettgeri is reminiscent of C. gibba (Ehrenberg) . The plates are not discernable, the toes are tapering uniformly and only four salivary glands are reported. C. lindamaya has characteristic toes with fairly large terminal claws. These claws are curved with acute tips and four distinct spinules are inserted in a row on the inner edge of the claw. The habitus of C. theodora is much more compact and the toes are shorter and of a characteristic shape.

Only three of the seven species with type D— C. tenuiseta , C. stenroosi Wulfert, 1937 and C. gigantea Remane, 1933 — have no eyspots as is the case in the new species. But C. stenroosi and C. gigantea show clear differences in habitus to the new species. This for example is seen in the toes, which are much longer in C. gigantea and in C. stenroosi have a dorsal lump (also in the older synonym C. bertonicensis Manfredi, 1927 ) or a blunt tooth in the middle, so there is no confusion possible. However, Donner (1972 & 1978) described the variant C. stenroosi austriaca with smooth toes. As far as the salivary glands lacking as in C. stenroosi and the tophi ( Fig. 5 View FIGURE 5 ) are concerned, this variant can easy be distinguished from C. ungulata n. sp.

The new species differs from C. tenuiseta in morphology and relative position of the toes. In C. tenuiseta the toes are closer together, thinner, longer and without claws. Additionally, the trophi of C. ungulata n.sp. differ from those in C. tenuiseta in having asymmetrical unci with two uncinal teeth on the left and one on the right uncus. The variation americana has been described by Donner (1950) who considers the earlier descriptions of C. tenuiseta by Harring & Myers (1924) and Wulfert (1937) to be other descriptions of this variation. But they vary in the description of trophi, toes and body shape. Harring & Myers (1924) variation americana was found in brackish and saltwater ditches — a habitat completely different from habitats reported by other authors and also not the habitat of the new species. They found no retrocerebral organ such as we found in the new species. Unfortunately they give no figure of the trophi. The proportions and shape of the pseudosegments as given by Wulfert (1937) are almost identical to our new species. However, the species described by Wulfert (1937) is characterized by a shorter, not double keeled tail and a more convex corona. On the inner margin of the rami one large tooth is followed by ten to twelve smaller teeth as opposed to six to seven small teeth in C. ungulata n.sp. Furthermore, the basal apophysis of the fulcrum is lacking as well. The toes described by Donner (1950) are sturdier than those in the other descriptions of C. tenuiseta americana but still longer and closer together than in the new species. In this description, the right ramus bears a striped lamella and a single tooth, the left one two unequal teeth. This again is different from C. ungulata n.sp. where the inner margins of the rami are symmetrical. In C. tenuiseta americana the ends of the manubria are bent dorsally, whereas in C. ungulata n.sp. they are bent ventrally. All other species of the genus Cephalodella are clearly different from our new species.

Measurements (n = 5): Total length 268–286 µm, toe 51–59 µm, trophi 34–40 µm, Manubria µm 29–32, Fulcrum 18–22 µm.

Distribution and ecology: Found in moderate numbers in the periphyton of a ditch with many plants near Leer, Lower Saxony, Germany (53°14’25.82” N, 7°31’15.88” E). This ditch with neutral pH harbours a great diversity of rotifers such as C. ventripes (Dixon-Nuttall) , C. intuta Myers, Lophocaris oxysternon (Gosse), L. salpina (Ehrenberg), Mytilina trigona (Gosse) , M. ventralis (Ehrenberg) , Itura aurita (Ehrenberg) , Dicranophoroides caudatus (Ehrenberg) , Trichocerca tenuior (Gosse) and Plationus patulus ( O.F. Müller) . The diet consists at least partly of autotrophic flagellates.

Etymology: The species-name is derived from the Latin word ungula meaning claw because of the characteristic claws at the end of the toes.

Discussion. Although C. ungulata n.sp. strongly resembles C. tenuiseta , it shows some clear differences in key diagnostic features such as trophi, toe-shape and relative toe length to C. tenuiseta . So it seems justified to give it the status of a new species and not only that of a variation of C. tenuiseta . It is not clear whether the old descriptions of C. tenuiseta by Burn (1890) and Dixon-Nuttall (1903) are only early descriptions of C. gigantea ( Wulfert 1937, Nogrady et al. 1995). Given this, the variation americana would be the only description of C. tenuiseta and should be given species rank. But there is still the problem that the descriptions assigned to C. tenuiseta var. americana by Donner (1950) are considerably different. Harring & Myers (1924) found this species in brackish and saltwater ditches whereas the other two descriptors found it in freshwater. Therefore, it is unclear whether these can be the same species. Even the descriptions of Donner (1950) and Wulfert (1937) show clear differences in the shape of the toes and trophi, e.g. the inner margin of the rami and the presence or absence of a basal apophysis of the fulcrum. So can they be the same variation, are they different variations or are they even different species?

This also applies to C. tenuiseta simplex Berzins, 1976 . Answering this question, however, presupposes a careful re-examination such as De Smet (1998b) carried out for C. catellina ( O.F. Müller) and related species.