Pair Of Tentacles Research Articles

Owenia caissara sp. n. (Annelida, Oweniidae) from Southern Brazil: addressing an identity crisis

ABSTRACT We re-assess the taxonomic status of Owenia Delle Chiaje, 1841 from Southern Brazil based on estuarine specimens from Paranagua Bay (Parana) and Babitonga Bay (Santa Catarina), and literature records. Owenia caissara sp. n. is diagnosed by a branchial crown with five pairs of tentacles, branched close to the base of the crown, rectilinear collar with a pronounced lateral slit, two ventrolateral ocelli partially covered by the collar, up to 23 hooks on a single row in the first abdominal segment, regularly curved nuchal shape, regularly moderate teeth curvature, and long and thin scales with oval transition. The description of Owenia caissara sp. n. reinforces the idea that Owenia fusiformis sensu lato is a complex of closely related species that can be distinguished on the basis of both macro- and micro- morphological traits.

Olfactory Memory Storage and/or Retrieval Requires the Presence of the Exact Tentacle Used During Memory Acquisition in the Terrestrial Slug Limax.

Terrestrial pulmonates can form odor-aversion memories once a food odor is presented in combination with an aversive stimulus. Most of the olfactory information ascends via a tentacular ganglion located in the tip of the two pairs of tentacles, and is then transmitted to the higher olfactory center, the procerebrum. The procerebrum is the locus of memory storage and has been shown to be necessary for odor-aversion learning. However, it is unknown whether the procerebrum is the sole locus in which the memory engram resides. By exploiting the regenerative ability of tentacles, here we investigated whether tentacles function merely in transmitting olfactory information to the procerebrum, or constitute a part of the memory engram. We showed that after removal of the tentacles used during memory acquisition, slugs were unable to retrieve the memory, even if these tentacles were regenerated sufficiently to subserve memory function. Our results support the view that tentacles are more than conduits of odor information; they also participate in the formation of the memory engram.

Two new species of Waldo Nicol, 1966 from sub-Antarctic waters (Bivalvia: Galeommatoidea)

Two new sub-Antarctic Waldo species (Bivalvia) are described: Waldo digitatus and W. paucitentaculatus. Waldo digitatus has a large, elongate–oval shell, with a short, horizontal dorsal margin, the valves showing a wide ventral gape, well separated from the anterior gape, and faint radial sculpture, fading toward shell margin. In addition, in this species the inhalant-pedal aperture is flanked by 5–15 pairs of tentacles. Waldo paucitentaculatus has a small, triangular–oval shell, with anterior and posterior half of dorsal margin long, sloping gently at similar angles, the anterior and ventral shell gapes coalesce to form a single, narrow and elongated gape, and radial sculpture well-marked and visible from beaks to ventral margin. Another distinctive character is the presence of only 1 or 2 pairs of tentacles bordering the siphonal-pedal aperture. Both species were found living as epibionts on the heart sea urchin Abatus cavernosus: W. digitatus is restricted to the perioral area and W. paucitentaculatus is more widely distributed, mainly on the oral surface.

Cambrian lobopodians: A review of recent progress in our understanding of their morphology and evolution

Lobopodians are an important group of organisms which appeared during the Cambrian Explosion. The underlying morphology is invariably a worm-like body bearing multiple pairs of legs. Yet in detail these animals preserve a range of morphologies and have attracted much paleontological attention; particularly since this assemblage probably includes the ancestors of living velvet worms (Onychophora), water bear (Tardigrada) and arthropods (Arthropoda). In recent years, knowledge of Cambrian lobopodians has increased dramatically based on numerous new records. However, there have been few comprehensive reviews of these animals since Ramsköld & Chen's study in 1998. In the present paper, new insights into Cambrian lobopodians are presented. The legs of Aysheaia pedunculata have a strong attachment with the body, like those of lobopodians in the Chengjiang Fauna. Hallucigenia fortis has a pair of eyes, two pairs of tentacles are observed in the ‘neck’ region while a bivalved head shield is unequivocally lacking. Some new characters for, and the orientation of, Hallucigenia sparsa are discussed. Longitudinal wrinkles on the body of Xenusion auerswalde are regarded here as putative muscles. Cardiodictyon sinicum bears doublure structures at the anterior margin of head and a pair of eye spots; the shape of dorsal plates is also reinterpreted. Onychodictyon has a pair of anterior appendages, but no sclerotized head shield. The affinities of Miraluolishania haikouensis are clarified and the proposal that M. haikouensis is a junior synonym of Luolishania longicruris is refuted. The large lobopodians, Kerygmachela, Jianshanopodia and Megadictyon – all with frontal appendages, gill-like limbs and tree-like or lamellate-like branches – may be swimming predators.

Two pairs of tentacles and a pair of procerebra: optimized functions and redundant structures in the sensory and central organs involved in olfactory learning of terrestrial pulmonates

Terrestrial pulmonates can learn olfactory-aversion tasks and retain them in their long-term memory. To elucidate the cellular mechanisms underlying learning and memory, researchers have focused on both the peripheral and central components of olfaction: two pairs of tentacles (the superior and inferior tentacles) and a pair of procerebra, respectively. Data from tentacle-amputation experiments showed that either pair of tentacles is sufficient for olfactory learning. Results of procerebrum lesion experiments showed that the procerebra are necessary for olfactory learning but that either one of the two procerebra, rather than both, is used for each olfactory learning event. Together, these data suggest that there is a redundancy in the structures of terrestrial pulmonates necessary for olfactory learning. In our commentary we exemplify and discuss functional optimization and structural redundancy in the sensory and central organs involved in olfactory learning and memory in terrestrial pulmonates.

Myoanatomy and serotonergic nervous system of the ctenostome Hislopia malayensis: evolutionary trends in bodyplan patterning of ectoprocta.

BackgroundEctoprocta is a large lophotrochozoan clade of colonial suspension feeders comprising over 5.000 extant species. Their phylogenetic position within the Lophotrochzoa remains controversially discussed, but also the internal relationships of the major ectoproct subclades -Phylactolaemata, Stenolaemata, and Gymnolaemata - remains elusive. To gain more insight into the basic configuration of ectoproct muscle systems for phylogenetic considerations, we analysed the adult myoanatomy and the serotonergic nervous system as well as myogenesis in budding stages of the ctenostome Hislopia malayensis.ResultsIn adults, the serotonergic nervous system is restricted to the lophophoral base with a high concentration in the cerebral ganglion and serotonergic perikarya between each pair of tentacles. Prominent smooth apertural muscles extend from the basal cystid wall to each lateral side of the vestibular wall. The musculature of the tentacle sheath consists of regular strands of smooth longitudinal muscles. Each tentacle is supplied with two bands of longitudinal muscles that show irregular striation. At the lophophoral base several muscles are present: (i) Short muscle fibres that proximally diverge from a single point from where they split distally into two separate strands. (ii) Proximally of the first group are smooth, longitudinal fibres that extend to the proximal-most side of the lophophoral base. (iii) Smooth muscle fibres, the buccal dilatators, traverse obliquely towards the pharynx, and (iv) a circular ring of smooth muscle fibres situated distally of the buccal dilatators. Retractor muscles are mainly smooth with short distal striated parts. The foregut consists mainly of striated ring musculature with only few longitudinal muscle fibres in the esophagus, while the remaining parts of the digestive tract solely exhibit smooth musculature. During budding, apertural and retractor muscles are first to appear, while the parietal muscles appear at a later stage.ConclusionsThe apertural muscles show high similarity within Ectoprocta and always consist of two sets of muscles. Gymnolaemates and Phylactolaemates show clear differences within their digestive tract musculature, the former showing smooth and longitudinal muscles to a much greater extent than the latter. The complex musculature at the lophophoral base appears promising for inferring phylogenetic relationships, but sufficient comparative data are currently lacking.

PLoS Neglected Tropical Diseases Issue Image | Vol. 4(3) March 2010

This snail subspecies belongs to the family Pomatiopsidae (Mollusca: Gastropoda), and is the intermediate host of Schistosoma japonica in China. The ribs on the shell and varix surrounding the aperture are clearly visible, and a pair of eyes and a pair of tentacles are also visible on the head, with a strong contour of the foot below. This subspecies is found only in China, and has a relatively wide distribution in regions in the middle and lower reaches of the Changjiang (Yangtze) River, where schistosomiasis is still a health problem in provinces such as Hubei, Hunan, Jiangxi, and Anhui (see article by Zhao et al., doi:10.1371/journal.pntd.0000611). Image Credit: Qin Ping Zhao (Department of Parasitology, School of Basic Medical Science, Wuhan University, Wuhan, Hubei Province, China).

Ctenophores

Ctenophores

Two new trochids of the genus Antimargarita (Gastropoda: Vetigastropoda: Trochidae) from the Bellingshausen Sea and South Shetland Islands, Antarctica

Two new trochids of the genus Antimargarita, A. powelli and A. bentarti, from the Antarctic waters are described here. A. powelli, from the Bellingshausen Sea, is distinguished by its rounded whorls, numerous spiral cords, a radula with seven lateral teeth at each side of the rachidian, and an epipodium with eight pairs of tentacles. A. bentarti, from the South Shetland Islands, is characterized by having a shell outline gradated by prominent primary spiral cords, a radula with five lateral teeth at each side of the rachidian and an epipodium with six tentacles on the left side. The diagnostic features for Antimargarita are redefined considering both shell and anatomical features and its suprageneric placement is discussed.

Redundancy of olfactory sensory pathways for odor-aversion memory in the terrestrial slug Limax valentianus

Terrestrial slugs have the ability to learn and remember a food odor paired with an aversive stimulus. Olfaction in slugs involves the tips of two pairs of tentacles, the superior and the inferior tentacles. Sensory nerves in both pairs of the tentacles transmit olfactory information to the structure in the CNS, the procerebrum where learning and memory formation occur. We investigated the role of each pair of tentacles in odor-aversion learning, and examined the ability of slugs to recall memory after selective surgical amputation. Our results show that memory formation was not altered by the amputation of either one of the pairs before or after odor-aversion learning, while the odor sensibility of the slugs was maintained. These data suggest that either pair of tentacles is sufficient for the acquisition and retrieval of aversive olfactory memory.

New observations of the lobopod-like worm Facivermis from the early cambrian Chengjiang Lagerstätte

Facivermis yunnanicus (Hou & Chen, 1989), from the Early Cambrian Chengjiang Lagerstatte, a worm-like fossil with 5 pairs of tentacles and a perceived shrunken end, has been regarded as related to polychaetes, later it has been variously interpreted as lobopods, Pentastoma and lophophorates. Newly discovered complete specimens by the ELI field team show that the taxon has, in addition to the 5 pairs of appendages, a pear-shaped trunk end bearing two or three circles of hooks. Accordingly, based on these important morphological characters, reconsideration of its affinities is provided and the taxonomy is remedied herein. Because the five pairs of appendages of Facivermis yunnanicus resemble the appendages of the fore-trunk of lobopod Miraluolishania (Liu & Shu, 2004), it seems that they are homologous structures. Therefore, the affinities of Facivermis are regarded here as being close to the lobopods, in addition, the lobe-like appendages of Facivermis are very crucial to exploring the origin of the appendages of lobopods and arthropods.

Protein Patterns and Synthetic Profiles during Distal Regeneration in Hydra oligactis: (Hydra/regeneration/protein/mesoglea).

Protein patterns and synthetic profiles were examined during distal regeneration in Hydraoligactis. Electrophoretic and radioactive tracer analyses revealed qualitative changes in the general protein profile during regeneration, with a heightened period of protein synthesis between 27-30 hr of regeneration, immediately preceding emergence of the first pair of tentacles. Following this, an increase in collagen-rich mesogleal protein secretion was observed coincident with tentacle initiation. Inhibition of collagen secretion with the proline analog L-azetidine-2-carboxylic acid (LACA) inhibited tentacle formation, and resulted in the development of unique "hypostome buds" at the distal regeneration surface. At the cellular level LACA did not inhibit the nerve cell differentiation that normally precedes tentacle growth, although some predicted decline in cnidocyte production was noted. It is proposed that mesogleal collagen secretion and structural organization may play a major role in the mechanical aspects of Hydra tentacle morphogenesis.

Larval development and metamorphosis of Sabellaria cementarium Moore, 1906 (Polychaeta: Sabellariidae)

The development of the polychaete Sabellaria cementarium Moore, 1906 proceeds at 10–14 °C, as follows: 23 h, early trochophore with prototroch and apical tuft; 65 h, 1 pair of provisional setae; 3.5 days, feeding trochophore; 18 days, metatrochophore; 4 weeks, metatrochophore with tentacle buds; 5–6 weeks, nectochaeta competent to metamorphose; 6–8 weeks, settlement and metamorphosis. Larval behavior is described. Tube sand of adult sabellariids (S. cementarium, Phragmatopoma lapidosa, ldanthrysus ornamentatus) and beach sand induced metamorphosis. Larvae exhibit a low degree of substrate specificity in their settlement, but sand is essential. Metamorphosis involves a loss of provisional setae, anterior rotation of tentacles and opercular cirri, and reduction of episphere. Following these changes, the juvenile secretes a mucoid tube to which sand grains are attached. Metamorphosis is considered complete when the caudal appendage has formed; this occurs 7–10 days postsettlement. Juveniles were kept in the laboratory for 38 days. During this time, they develop three pairs of tentacles, lose all larval pigment, and form a second thoracic segment. Within the opercular crown, primary opercular paleae replace settling paleae.

EFFECTS OF BROWSING PREDATORS: ACTIVITY CHANGES IN INFAUNA FOLLOWING TISSUE LOSS

Effects of tissue loss on defecation and/or tube building are documented for three infaunal species of polychaete annelids, Abarenicola pacifica, Axiothella rubrocincta, and Spiophanes bombyx. Abarenicola and Axiothella feed head down and expose their tails while defecating; their tail tips were experimentally ablated. Spiophanes feeds on the sediment surface with its pair of tentacles and its head. One or both of its tentacles were experimentally removed. The tissues removed in the experiments are those often lost to browsing predators in field populations. Defecation frequency and amount were significantly reduced in the experimental individuals relative to controls in all three species. In Spiophanes tube building was also significantly reduced; in Axiothella it was not. These results indicate that rates of biogenic sediment modification can be strongly affected by tissue losses of infauna to browsing predators.

Microarchitecture and function of the lophophore in the bryozoan Cryptosula pallasiana

The architecture and function of the lophophore of the marine bryozoan Cryptosula pallasiana (Moll) are described, including some new features not previously discovered in bryozoans. The nature of fluid movements within the lophophoral coelom during feeding activities is postulated on the basis of the arrangements of epithelia and muscles. Epithelial cells at the tentacle bases are blastemic in nature, and there is a ciliated pit of unknown function in the angle between every pair of tentacles. There are 6 nerves in each tentacle, including a pair of single-axon subperitoneal nerves. Neurosecretory-like vesicles and glycogen occur in some neurons of the ganglion. The basal lamina collagen has a diameter smaller than that previously recorded for an invertebrate. Filament dimensions are given for several different muscles. Tentacle muscles and lophophore retractor muscles are smooth. Thick paramyosin-like filaments up to 75 nm diameter occur in two muscle types. A new set of muscles is described: the basal transverse muscles of the tentacles.

Tentacle morphogenesis in hydra : I. The morphological effect of actinomycin D.

Hydra oligactis exposed to 3 μg/ml actinomycin D for 24 hours regenerated only the first pair of tentacles (the mid-laterals). If left uncut, actinomycin D treated animals underwent a reduction of the normal number of tentacles to two or less.Inductive activity was retained in the 2-tentacled hypostomes. However, the tentacles present exhibited reduced capacities to capture and manipulate prey.Histological studies showed that the tentacles of actinomycin D treated hydra were morphologically identical to those of the controls. The interstitial cell (I-cell) population of the treated animals, however, became depleted. Replacing the hypostome of an actinomycin D treated hydra with a normal hypostome reversed the cellular effects of actinomycin D treatment.The modifications in tentacle morphogenesis occurring after actinomycin D treatment are consistent with an impairment of hypostomal function in the animal. It is suggested that the morphological site of this malfunction may be in the nervous system.

Feeding and tube-building in the Fabriciinae (Annelida, Polychaeta)

Sabellid worms use their branchial crowns to collect and sort suspended particles for feeding, and in the majority of cases for tube-building. Two examples from the subfamily Fabriciinae are considered. In Fabricia sabella the pinnules borne on the three pairs of gill filaments possess three rows of cilia. The two rows of latero-frontal cilia move water through the crown and also trap particles from this current and deposit them on the frontal cilia. These transport the particles to ciliated grooves in the gill filaments, where a little preliminary sorting occurs as they move towards the centre of the crown. The final sorting occurs at the centre of the crown: large particles are rejected whilst the small ones are carried to the mouth. The medium-sized particles are either mixed with mucus and incorporated into the tube or, when the animal is not tube-building, they are rejected. In Manayunkia aestuarina the four pairs of gill filaments and the pair of tentacles are devoid of pinnules, but bear three rows of cilia. Usually two pairs of gill filaments are moved over the surface of the substratum and particles are collected from it by the latero-frontal cilia. The particles are then deposited on the frontal cilia in the gill-filament groove; this is deposit feeding. Particles disturbed during deposit feeding become suspended in the water and are then trapped by the latero-frontal cilia on the remaining gill filaments and the tentacles; this is secondary suspension feeding. Particles already in suspension are also utilized; this is suspension feeding. Particles collected by these three methods are moved down the gill-filament grooves, where a little preliminary sorting occurs. As in Fabricia, the particles are completely sorted in the centre of the crown. The large particles are rejected, small particles move to the mouth and the medium-sized particles travel to the ventral lip where they are coated with mucus and incorporated into the tube or, as in Fabricia, rejected. The development of the abfrontal cilia, the sorting mechanism in the gill filaments and the presence of mucous glands in the pinnules and other gill-filament structures of the larger sabellids, are considered in the discussion.

Phoronidea from Brazil

Phoronidea from Brazil