Entoprocta: Tetrigidae

A new species of Loxosomella fromthe White Sea (Entoprocta: Loxosomatidae)

S.V. Bagrov & G.S. Slyusarev

Bagrov, S.V. & Slyusarev, G.S. 2002. A new species of Loxosomella from the White Sea (Entoprocta: Loxosomatidae). Zoosystematica Rossica, 10(2), 2001: 281-283.

A new species of Entoprocta, Loxosomella marisalbi sp. n., from the White Sea is de scribed and compared withL. nordgaardi (Ryland, 1961). The distinctions between these species are discussed.

S. V.Bagrov, GS. Slyusarev, Department ofInvertebrate Zoology, Faculty ofBiology and Soil Science, St.Petersburg State University, Universitetskaya nab. 7/9, St.Petersburg 199034, Russia. E-mail: [email protected]

Introduction Both narcotized and non-narcotized animals were fixed with 4% glutaraldehyde in 0.1 M The fauna of Entoprocta from the White Sea is phosphate buffer(pH 7.4) formaking finaldraw very poorly known.Only one short communica ings. The drawings were made using a tion (Krylova, 1986), which treats 11 species, is JENAVAL-7 microscope. published. Krylova (1985) also described two new species. Problems with identification Loxosomella marisalbi sp. n. prompted a review of the literature and revealed (Figs 1-3) that the recently collected material represented an undescribed species. Holotype.Russia, White Sea, Kandalaksha Bay, Chupa The samples were taken by boat dredging and Inlet (66° 17'N, 33°40'E), SW of Marine Biological Sta SCUBA at 5-10 m depth near the Marine Bio tion of St.Petersburg State University, depth 5-10 m, sa logical Station of St.Petersburg State University linity 21-23%0; V.1995, forhabitat see Introduction. Lox02 (White Sea, Kandalaksha Bay, Chupa Inlet, total preparartion of narcotized animal deposited in the ° ° collection of the Department of Invertebrate Zoology, 66 17'N, 33 40'E) during summer (June-Sep St.Petersburg State University. tember) in 1995-1999. The specimens were col Paratype. The same data as in holotype. lected from colonies of several bryozoan spe Description. Body consisting of stalk and ca cies (Scrupocellaria scabra, S. elongata, Den lyx containing all internalorgans (Figs 1-3). Up drobeaniafruticosa, Tricellariagracilis, Eucra per part of body with horseshoe-shaped lopho tea loricata, Tegella armifera,Arctonula arctica) phore with 8 tentacles. Uppermost pair of tenta encrusting fronds of various red algae ( Odontalia cles longer than others (Figs 1-3). In relaxed ani dentata, Ptilota pectinata, Phycodris rustica, mals, lophophore extending beyond calyx. When Phyllophora broduei) that overgrow rhizoids of animal contracts, tentacles are completely re the brown alga Laminaria saccharina. In the tracted into atrial cavity, and lophophore com laboratory, the specimens were placed in glass presses into an almost close ring. Epithelial fold containers with filteredand aerated seawater. located behind lophophorc extending to lateral The live animals under observation were kept sides of calyx. Stalk not longer than calyx. in small glass containers and Petri dishes at the Body covered by thin cuticle. Atrial cavity and temperature from5 to 10 °C. In the study of Lo frontal tentaclesurface formed by ciliated colum xosomella development, we waited forthe buds nar epithelium. Epithelial cells of brood-cham to attach to the bottom of the dish in laboratory. ber flattened. After that, the dishes were installed at the same Alimentary channel opening as slitlike mouth place where the material had been collected, and and passing to oesophagus and stomach; the lat were observed daily. ter followedby oval intestine and rectum, which When it was. necessary, the specimens were opens by anus. Stomach three-lobed (Fig. 3). narcotized in 4.9% aqueous solution of MgC12• Body surfacewith differentsensory elements. & GS. ZOOSYST. ROSSICA Vol. 10 282 S. V. Bagrov Slyusarev: New Entoproctafrom WhiteSea •

Figs 1-3. Loxosomella marisalbi sp. n. 1, lateral view; 2, abfrontal view; 3, frontal view. Abbreviations: b, bud; c, sensory structure; e, embryo;/, epitelial fold; t, tentacle; r, receptor. Scale bar: 100 µm.

Abfrontal surface of each tentacle bearing two Stalk with several muscle fibres.underepithe sensory structures,each with a single cilium: one lium; some of them directed along stalk, others of these structuressituated near tentacle base and twisted in a coil. Muscle fibres of stalk located the other one, near its tip (Fig. 2). Epithelial fold between epithelium and digestive tract and ex of calyx with three pairs of receptors (Fig. 2). tending to calyx. Each tentacle with two longi Uppermost and lowest pair of receptors each tudinal muscles. Base of lophophore with circu formed by a single cell with a tuft of 3-4 cilia, lar muscles. When they contract, the lophophore whereas each middle pair of receptors consist squeezes· to a small ring concealing the tenta ing of three such cells (Fig. 2). cles, so that only the sensory structures situated ZOOSYST. ROSSICA Vol. 10 • S. V.Bagrov & GS. Slyusarev: NewEntoprocta speciesfrom White Sea 283

Table. Morphometriccharacters of Loxosomella nordgaardi and L. marisalbi (standard deviations are given in parentheses)

Measurements L. nordgaardi L. marisalbi Average total length 402 (33) µm 256 (23) µm Maximum total length 475 µm 356 µm Average calyx length 313 (32) µm 162 (14) µm Average stalk length 88 (f 5) µm 95 (8) µm Average ratio of stalk length to calyx length 0.26 (0.05) 0.58 (0.8)

at the tentacle bases remain visible. Mature buds tacle base. The trilobed stomach is situated in have the same capacity. Alimentary channel with the lowest part of the calyx. The budding zone is sphincters; they were never found in histologi on the laterofrontalside of the calyx at the level cal sections, but their effectcould clearly be ob of lowest boundary of the stomach. The maxi served in live animals. mum bud number is 7 (3+4), but usually there A group of 8-10 large cells present in the cen are only 5 (2+3) buds. The bud has a clearly pro tre of foot.In differentspecimens, footshape var nounced pedal gland. ied depending on relief of substratum. For meas Comparison. Using the key given by Nielsen urements see Comparison. (1989), the specimens investigated were initially Data on reproduction and development. Sev identified as Loxosomella nordgaardi (Ryland, eral specimens had two oocytes situated lateral 1961). When the descriptions of L. nordgaardi ly to the ganglion, and only few specimens had by Ryland(1961) and Nielsen (1989) were com 2-4 embryos (Fig. 3). The larvae developed from pared with our material, several differences be these embryos were conical and possessed a ring came apparent: of actively beating cilia at the base of the cone 1. There are no sensory structures in L. nord and a tuft of cilia at the apex. gaardi, as distinct fromL. marisalbi. Asexual reproduction takes place by budding. 2. The maximum number of buds in L. nord A specimen usually has 4-5, sometimes up to 7 gaardiis 5 (more often3), while in L. marisalbi buds. The buds are formedlaterofrontally at the it is 7 (more often5). level of the lower part of stomach (Figs 1-3). The 3. Two species differ in morphometry. We larger (i.e., the older) buds are situated above the measured 20 specimens of L. marisalbi and ob smaller (younger) ones (Figs 1-3). tained the data, clearly distinct from those ·re A completely formed bud has short tentacles ported by Ryland (1961) forL nordgaardi (see and is able to feedindependently. By this time, Table) .. its sensory structures have already been devel oped. At this stage, the buds cat1produce 1-2 of Acknowledgements their own buds. In nature, the bud developed into the adult animal in one week aftersettlement. Our best thanks to Oleg G. Manylov for helpful dis Diagnosis. The maximum registered length of cussion. L. marisalbiis 366 µm. The stalk is never longer than the body. The calyx is slightly flattened References anteroposteriorly. The posterior surfacepossesses Krylova, E.N. 1985. Two new species of the genus a horseshoe-shaped epithelial fold bearing eight Loxosomella (Kamptozoa, Loxosomatidae) fromthe tentacles. The abfrontal tentacle pair is longer White Sea. Zoo!. Zh., 64(8): 1127-1130. (In Russian). than the others. There are three pairs of sensory Krylova, E.N. 1986. Entoprocta of the White Sea. In: structures on the epithelial foldof the calyx. The Sed'moi vsesoyuznyi kollokvium po iskopaemym i sovremennym mshankam [7th All-Union colloquium uppermost and lowest pairs of them consist of on fossil and recent Bryozoa]. Abstracts: 60. Mos one cell with a cilia tuft, while the middle pair is cow. (In Russian). formed by three cells, each of these structures Nielsen, C. 1989. Entoprocts. In: Synopses ofthe British with a tuft of ciliae. Each tentacle has two sen fauna, N. s., 41: 17-57. sory structures represented by a single cilium: Ryland, J.S. 1961. Two species of Loxosomella (Ento one apical and another positioned near the ten- procta) from WesternNorway. Sarsia, 1: 31-38. Received 24 April 2001