Oral Papillae Research Articles

Larval morphology in four species of Hylarana from Vietnam and Thailand with comments on the taxonomy of H. nigrovittata sensu latu (Anura: Ranidae)

We describe the tadpole morphology of four species of Hylarana based on larval specimens identified by DNA barcoding. Of these, the larvae of Hylarana attigua and H. maosonensis, two species recently recorded from Phong Nha – Ke Bang National Park, Quang Binh Province, central Vietnam, had not been previously described; in addition, descriptions of the tadpoles of syntopic H. guentheri and H. nigrovitatta are provided as well. The tadpoles of these four species are generalized exotrophic lentic-benthic forms of Orton’s Type 4 with a depressed body shape, dorsolaterally positioned eyes and a moderate height of tail fins. In contrast to the silver-whitish H. guentheri the preserved tadpoles of H. attigua, H. maosonensis and H. nigrovittata are greenish-brown to greyish. The generalized oral discs exhibit a wide gap of marginal papillae on the upper labium and elongated papillae on the lower labium. In general, the keratodont row formulae of the Hylarana species studied herein is 2(2)/3(1) (sometimes 1/3(1) in H. guentheri). Differences between species mainly concern body shape, size in different developmental stages as well as number and shape of oral papillae. H. nigrovittata larvae from near Chiang Mai in northern Thailand mainly differ from Vietnamese specimens in the number and shape of oral papillae. In concert with adult morphological differences and molecular divergences by molecular data this indicates species-level distinctness of the Vietnamese versus the northern Thai populations.

Deep-water Ophiuroidea of the northern Atlantic with descriptions of three new species and taxonomic remarks on certain genera and species

Based on material from the fourth cruise of the RV Akademik Mstislav Keldysh and the MAR-ECO cruise of the RV G.O. Sars, 31 species of Ophiuroidea were identified from the section of the Mid-Atlantic Ridge between the Reykjanes Ridge and the Azores. The taxonomy of the group of genera with reduced arm comb and tentacle pores restricted only to the proximal arm segments is reviewed. It is suggested that the genera Homalophiura H.L. Clark, 1915, Ophiurolepis Matsumoto, 1915, Theodoria Fell, 1961 and Homophiura Paterson, 1985 should be regarded as synonyms of the genus Ophioplinthus Lyman, 1878. From examination of the type specimens, it is demonstrated that the six-armed species Ophiacantha anomala G.O. Sars, 1871 also includes five-armed specimens previously identified as the separate species Ophiacantha cuspidata Lyman, 1878. The latter taxon is considered here as the junior synonym of O. anomala. Previously mentioned ‘deep-water populations of the common shallow water species Ophiacantha bidentata (Retzius, 1805)’ represent a separate species, Ophiacantha fraterna Verrill, 1885, which is well distinguished by the shape of the spicules of the disk, narrow outer oral papilla and narrower tentacle scale as well as a hermaphroditic nature. Three new species, i.e. Ophioplinthus pseudotessellata sp. nov., Ophiocamax patersoni sp. nov. and Ophiophyllum nesisi sp. nov., are described.

The tadpole of Physalaemus henselii (Peters) (Anura: Leiuperidae)

Although Physalaemus frogs are prominent members of Neotropical herpetofauna, larval stages are not known from more than half of the species in this genus. Herein, we describe the tadpole of Physalaemus henselii based on samples collected in Departamento de Rivera, northern Uruguay. General aspect and major external morphological features are similar to most of other known tadpoles of Physalaemus. Remarkable character states are a medial vent tube and the presence of dorsal and ventral gaps in the row of marginal oral papillae. Physalaemus henselii has been successively assigned to the P. cuvieri and to the P. henselii species groups, but no conclusions can be drawn in support of these associations from external larval morphology. Instead, we found that some character states may contribute to relate species, like the presence of a ventral gap in the marginal row of oral papillae which is shared by P. albonotatus, P. cuqui, P. cuvieri, P. fernandezae and P. henselii. This character state is unique among non-bufonid anurans, although it is also present in some species of the related genus Pseudopaludicola. In addition, P. albonotatus, P. cuqui and P. cuvieri tadpoles can be differentiated from P. fernandezae and P. henselii by the presence of two small ventrolateral gaps, which are absent in the latter.

Skeletal characters for identification of juvenile Ophiactis resiliens and Amphiura constricta (Echinodermata): cryptic ophiuroids in coralline turf habitat

Skeletal development of Ophiactis resiliens and Amphiura constricta was examined to determine characters that could be used to identify the juveniles of these species, which co-occur in algal turf habitat. Juvenile O. resiliens recruit to turf after a planktonic larval stage while A. constricta recruit through release from brooding adults. Skeletal development in O. resiliens and A. constricta is typical of most ophiuroids with diagnostic adult characters taking some time to appear. The main characters that can be used to distinguish the two species from an early stage are the number and arrangement of the oral papillae and the presence of disc spines. In O. resiliens diagnostic adult skeletal characters developed at 1.5 mm disc diameter. In A. constricta most identifying adult characters were evident at 700 μm disc diameter. Identification of juvenile O. resiliens is assisted by the presence of disc spines and thorny arm spines, features that disappear as the juveniles grow. Juvenile A. constricta did not develop disc spines or thorns on the arm spines.

The tadpole of Rhinella proboscidea (Anura: Bufonidae) with notes on adult reproductive behavior

The tadpoles of Rhinella proboscidea are described and compared with other tadpoles of the Rhinella margaritifer group. The tadpole of R. proboscidea is characterized by small size (17.8 mm), tooth row formulae 2(2)/3, oral papillae only on lateral margins, jaw sheath V-shaped, spiracle sinistral, vent tube medial, body oval in dorsal view and depressed in lateral view, and color in life light brown. Tadpoles of R. proboscidea are morphologically similar to other species within this group and closely resemble those of R. margaritifer from Cusco Amazónico and R. castaneotica from Pará, Brazil. Rhinella proboscidea is an explosive breeder and reproduction occurs in temporary pools or small headwaters of streams or soaks, during the rainy season.

Exploiting the Keratin 17 Gene Promoter To Visualize Live Cells in Epithelial Appendages of Mice

Keratin genes afford, given their large number (>50) and differential regulation, a unique opportunity to study the mechanisms underlying specification and differentiation in epithelia of higher metazoans. Moreover, the small size and regulation in cis of many keratin genes enable the use of their regulatory sequence to achieve targeted gene expression in mice. Here we show that 2 kilobases of 5' upstream region from the mouse keratin 17 gene (mK17) confers expression of green fluorescent protein (GFP) in major epithelial appendages of transgenic mice. Like that of mK17, onset of [mK17 5']-GFP reporter expression coincides with the appearance of ectoderm-derived epithelial appendages during embryonic development. In adult mice, [mK17 5']-GFP is appropriately regulated within hair, nail, glands, and oral papilla. Tracking of GFP fluorescence allows for the visualization of growth cycle-related changes in hair follicles, and the defects engendered by the hairless mutation, in live skin tissue. Deletion of an internal 48-bp interval, which encompasses a Gli-responsive element, from this promoter results in loss of GFP fluorescence in most appendages in vivo, suggesting that sonic hedgehog participates in K17 regulation. The compact mK17 gene promoter provides a novel tool for appendage-preferred gene expression and manipulation in transgenic mice.

AURICULOSTOMA ASTYANACE N. GEN., N. SP. (DIGENEA: ALLOCREADIIDAE), FROM THE BANDED ASTYANAX, ASTYANAX FASCIATUS (CHARACIFORMES: CHARACIDAE), FROM NICARAGUA, WITH A REEVALUATION OF NEOTROPICAL CREPIDOSTOMUM SPP

Auriculostoma n. gen. (Trematoda: Allocreadiidae) is proposed for Auriculostoma astyanace n. sp. from the intestine of the characid fish Astyanax fasciatus in the Atlantic coastal drainages of Nicaragua. The new genus differs from all papillose allocreadiid genera, except Bunoderella, in possessing 2 pairs of muscular oral papillae (instead of 1 or 3), of which the ventrolateral pair is moderately developed and the dorsolateral papillae are long and auricular. Auriculostoma differs from Bunoderella Schell, 1964, in having lateral vitelline follicles, completely separated or confluent only in the posttesticular region, a uterus limited to the pretesticular region or with a few eggs at the level of the testes, and a long cirrus sac that overlaps the acetabulum or usually reaches posteriorly to the ovarian level. Three other allocreadiid species, all from South American freshwater fishes and each of which had previously been placed in Crepidostomum, are transferred to Auriculostoma based on the presence of the diagnostic muscular oral papillae. These include Crepidostomum platense Szidat, 1954, C. macrorchis Szidat, 1954, and C. stenopteri Mañé-Garzón and Gascón, 1973. Diagnostic features for Auriculostoma also include mainly pretesticular uterus, lateral vitellaria with variation in posttesticular confluence, and tandem testes. The genus appears to be typically associated with neotropical siluriforms (catfishes) and characiforms (tetras).

The feeding behaviour of a deep-sea holothurian, Stichopus tremulus (Gunnerus) based on in situ observations and experiments using a Remotely Operated Vehicle

Using a Remotely Operated Vehicle (ROV) to deploy an in situ cage experiment incorporating fluorescent Luminophore particle tracers, the gut throughput time of the deposit feeding holothurian, Stichopus tremulus (Gunnerus) was determined as 23.73 h (S.D.±2.3). For a range of individuals examined at different depths (350–500 m) and locations, throughput times varied between 19 and 26 h irrespective of animal size or gut tract length. In situ video observations of feeding behaviour showed that this species uses fine oral papillae in a ‘sweeping’ motion to target particles on the seafloor. Following detection of a food source fine-branched digitate tentacles collect a large range of sediment fragments from the seabed. The main types of particles ingested include silica fragments (<20 >500 μm), pelagic foraminifera, benthic foraminifera, fine phytodetrital remains and occasional larger rock fragments (∼1 cm). Ingested sediment consisted mainly of very fine silica fragments (∼50 μm) accounting for over 50% of the total gut contents. Frame-by-frame video analysis revealed that the particle handling time (i.e. the time taken for a tentacle insertion and the subsequent collection of food) was found to be ∼54 s. Only 10 of the 20 feeding tentacles were simultaneously employed during feeding. Use of tentacles appeared to be in sequence, alternating between the reserve and active tentacles. Estimating the rate of movement over the seabed and the total effective capture area of each tentacle, the impact of this animal on the turnover and quality of surface sediment at this deepwater site is potentially substantial. The in situ experiments provided a significant improvement over previous methods used to investigate deep-sea deposit feeders and represent a useful concept for further in situ deep-sea research using an industrial ROV.

Oral Fimbriae and Papillae in Parasitic Lampreys (Petromyzontiformes)

There are 38 species of living lampreys, 18 parasitic and 20 nonparasitic. The parasitic species feed as adults, while the nonparasitic do not. The taxonomy and systematics of the living lampreys is based primarily on dentition characters. Since the number of oral fimbriae and oral papillae have never been systematically investigated in lampreys, we compared them in 17 of the 18 parasitic lampreys to assess their usefulness as taxonomic characters. Both showed little variation with total length and sex within a species, while exhibiting greater variation between species. Parasitic species belonging to the three lamprey families could be distinguished using the number of oral fimbriae: southern hemisphere Mordaciidae (0) and Geotriidae (55–65) and northern hemisphere Petromyzontidae (81–144). However, the taxonomic usefulness of the two characters at the species level was limited. Ten out of the 17 species of parasitic lampreys were placed into four distinct groups based on their numbers of oral fimbriae, and only in two of these was the character diagnostic. Twelve out of the 17 species were placed into two distinct groups based on their numbers of oral papillae and for none of these was the character diagnostic. Blood feeders and intermediate feeders (blood + flesh) were shown to have significantly higher numbers of oral fimbriae than flesh feeders. The higher numbers of oral fimbriae in the former two types of feeders were presumed to be linked to their greater need to create a good seal for feeding purposes. Blood feeders were also shown to have significantly higher numbers of oral papillae than either intermediates or flesh feeders. The higher numbers of oral papillae in the blood feeders were presumed to be linked to their greater need to find suitable attachment sites for feeding purposes.

Brachylaima cribbi (Digenea: Brachylaimidae): scanning electron microscopical observations of the life-cycle stages.

Brachylaima cribbi is a recently described species of terrestrial trematode that infects mammals and birds with helicid land snails as its first and second intermediate hosts. The adult worm is 2.5-6.0 mm long by 0.5-0.8 mm wide being a long slender cylindrical worm with oral and ventral suckers in the anterior quarter and genital pore in the posterior quarter. Scanning electron microscopy shows that there is a dense covering of tegumental spines at the anterior end which diminishes towards the posterior extremities of the worm. Development of spines was observed in juvenile and mature adult worms. In young worms 1-3 weeks post infection (wpi) spines appear as buds with a serrated edge each having 1-4 spikes per spine. As the worm ages the spines broaden and by 5 wpi the number of spikes per spine increases to an average of 8.1. The serial development of oral sucker papillae in the cercaria, metacercaria and adult worm was observed with the finding of an elongated papilla with a bifurcated tip on the cercaria becoming a shorter and thicker elongated papilla with a large central stoma on the metacercaria. In the adult worm, this papilla becomes dome-shaped with a small central stoma. For some of these papillae a cilium could be seen extended from the central stoma. Other life-cycle stages illustrated were the hatched egg with an extruded egg membrane minus an operculum and a portion of the branched sporocyst dissected from the digestive gland of the land snail Theba pisana showing a terminal birth pore. Scanning electron microscopy morphological features of the adult worm observed for the first time in a Brachylaima were the unarmed cirrus extended from the genital pore with released sperm present and the Laurer's canal opening visible in tegumental folds on the dorsal surface approximately 300 microm posterior to the genital pore.

Taxonomic report on some monstrilloids (Copepoda, Monstrilloida) from southeast Mexico with the description of a new species of Monstrilla

During zooplankton surveys carried out between 1987 and 1991 oV the northern coast of the Yucatan Peninsula, southeast Mexico, several monstrilloid copepods were collected. Three species were identified: Cymbasoma chelemense Suárez-Morales and Escamilla, 1997, C. quintanarooense (Suárez-Morales, 1994) and a new species of Monstrilla. Cymbasoma quintanarooense was described from the western Caribbean Sea a few years ago; new and complementary morphological data are added to the original description of this species. Previous to this survey, only one specimen of Cymbasoma chelemense, the holotype, had been collected; an additional specimen is recorded here from the type locality for this species. Monstrilla humesi sp. nov. is described following a set of recently proposed standards for the description of monstrilloid copepods. The new species is quite similar to M. helgolandica Claus, 1863 and to M. gracilicauda Giesbrecht, 1892a. It can be distinguished by the presence of a bilobed fifth leg, the position of the oral papilla, and by the proportional length of its genital compound somite.

Fossil onychophorans from Dominican and Baltic amber: Tertiapatus dominicanus n.g., n.sp. (Tertiapatidae n.fam.) and Succinipatopsis balticus n.g., n.sp. (Succinipatopsidae n.fam.) with a proposed classification of the subphylum Onychophora

Abstract. Tertiapatus dominicanus n.g., n.sp. (Tertiapatidae n.fam.) and Succinipatopsis balticus n.gen., n.sp. (Succinipatopsidae n.fam.) (Lobopodia: Onychophora), the first Tertiary fossils of the Lobopodia, are described from Dominican and Baltic amber, respectively. Both families are characterized by the presence of simple legs lacking foot portions with claws and pads. Tertiapatidae is further characterized by soluble body pigments and oral papillae shorter than the legs. Succinipatopsidae is characterized by non‐soluble body pigments and oral papillae longer than the legs. Nomenclatural changes include the erection of the class Udeonychophora n. nom. for terrestrial onychophorans with a ventral mouth, the order Ontonychophora n.nom. for extant onychophorans possessing legs with a differentiated “foot” portion, and the family Helenodoridae n.nom. for the genus Helenodora from the Carboniferous. The biogeographical significance of these fossils and their phylogenetic relationship with previously described onychophorans are discussed.

Characterisation of the slime gland secretion from the peripatus, Euperipatoides kanangrensis (Onychophora: Peripatopsidae )

The Onychophora display a distinctive mechanism of feeding that involves the entanglement of prey in a sticky secretion. This secretion is produced in the slime glands and ejected as adhesive threads from a pair of oral papillae on either side of the head. Biochemical analyses of the secretion reveals it to be a composite material containing protein, sugar, lipid and a surfactant, nonylphenol. The identification of nonylphenol in the secretion is significant in that this is the first report of this compound from a natural source. The proteins are the principal component of the slime and the amino acid composition of the crude secretion suggests the presence of collagen or a ‘collagen-like’ domain. One or more of the high molecular weight proteins are O-glycosylated where the predominant modification is a single N-acetylgalactosamine (GalNAc). This study adds to our understanding of the chemical and biochemical composition of the unusual onycophoran slime gland secretion.

DDT‐like effects as a result of corticosterone treatment in an anuran amphibian: Is DDT a corticoid mimic or a stressor?

AbstractExposure of tadpoles to dichlorodiphenyl trichloroethane (DDT) induces pathological development of the upper mandible. In the current study, we report a similar pathological development after tadpoles of the Senegal walking frog (Kassina senegalensis: Hyperolidae) were treated with the steroid hormone, corticosterone (CORT) for 5 d at 1.1 μM. Corticosterone‐treated tadpoles developed a “hole” in the snout (mandibular fenestration) with complete loss of the upper keratinized beak, denticles, and oral papillae. Histological analysis revealed a loss of connective tissue, epidermis, and dermis, but remaining dermis, dermal skin glands, and epidermis appeared normal. Analysis of cleared and stained specimens showed that there was no loss of chondrocranial elements but that the cornu trabeculae was eroded, and the cartilago infrarostralis was repositioned and reshaped. The similarities in the effects of CORT reported in the current study and the previously reported effects of DDT suggest that DDT “mimics” CORT or that DDT acts as a “stressor” causing an increase in endogenous CORT. These data are important in defining the effects and mechanisms of pesticide action on anuran larval development.

Ultrastructure of the digestive system of the cercaria of Sanguinicola inermis Plehn, 1905 (Digenea: Sanguinicolidae)

The digenean blood fluke Sanguinicola inermis and the family Sanguinicolidae have previously been described as apharyngeate and sucker-less. Examination of the digestive tract of the cercaria of S. inermis with transmission electron microscopy (TEM), however, has confirmed the presence of a well-developed and complex muscular region immediately adjacent to the sub-terminal mouth. The presence of this muscular region, which may be an oral sucker, emphasises the need for further ultrastructural studies on other members of the family. The adjacent oesophagus, composed of modified tegument, has distinct anterior and posterior regions. TEM shows that the surface of the posterior oesophagus is deeply folded and the apical cytoplasm and sunken cytons become filled with secretory granules, eventually forming a “secretory region” adjacent to the intestine. The dorsal, sac-like intestine is composed of a single layer of epithelial cells, the apical surface of which is drawn into shallow folds. Each cell contains numerous secretory granules, rough ER, and a single basal nucleus. The intestinal lumen, which contains electrondense striated bodies, is filled with fibrous material. Only two sensory oral papillae are associated with the digestive tract, positioned either side of the mouth opening and possibly acting as tango-, stretch- or pressure receptors. The papillae comprise several microtubules lying beneath the apical cytoplasm of the tegument within a nerve process, but there is no connection with the external body surface. The morphology of the alimentary canal of the S. inermis cercaria is discussed in relation to the functioning of the digestive system in preparation for establishment in the final host.

Anomalies in the cephalic area of laboratory-reared larvae and juveniles of the common sole, Solea solea: oral jaw apparatus, dermal papillae and pigmentation

The post-metamorphic common sole, Solea solea, as well as the other Soleidae and Cynoglossidae, are characterized by oral jaw elements without teeth on the ocular side. A relatively large proportion of late sole larvae and early juveniles, routinely reared in the laboratory, showed dentigerous and shape-modified premaxillae and mandibles on the ocular side. Abnormal jaws were associated with dermal papillae and a lack of pigmentation on parts of the ocular side of the head. These features are probably the result of suppressed epigenetic mechanisms normally active during ontogeny. Insights into the morphological evolution of the soleid jaw apparatus are discussed.

TWO NEW MONSTRILLOIDS (COPEPODA: MONSTRILLOIDA) FROM THE COASTAL AREA OF THE MEXICAN CARIBBEAN SEA

ABSTRACT From plankton samples taken in coastal areas of the eastern Yucatan Peninsula, Mexican Caribbean Sea, two new species of Monstrilloida (Copepoda) are described, Monstrilla rebs and Monstrillopsis ciqroi. Monstrilla rebis is distinguished as a new species mainly by the location of the oral papilla and the presence of two setae on both rami of the fifth legs. Monstrillopsis ciqroi differs from all previously known species of Monstrillopsis by the combination of features of the structure and armature of the fifth legs, the armature of the antennule, the proportions of the ovigerous spines, and by its size.

Development of taste organs inRana temporaria

In tadpoles of Rana temporaria two successive generations of taste organs: taste buds (TBs) and taste disks were studied. The TBs are located in the apices of oral premetamorphic papillae. Each TB consists of vertically elongated receptor cells (probably taste) and supporting cells. No basal (Merkel) cells were observed there. Morphologically, two types of receptor cells have been distinguished in a TB. Complete synaptic structures were observed in the TBs between the 30th and 41st of Gosner's (1960) developmental stages, though synaptic vesicles occur already at stage 26. The taste disks consist of taste cells, supporting cells and basal cells. Dense-core synaptic vesicles occur in the gustatory cells at stage 41, but complete synaptic structures were not observed earlier than at stage 45. Synaptic junctions observed at some of the gustatory cells seem to be reciprocal (bidirectional).

Scanning Electron Microscopical Observations of Pellioditis pellio (Nematoda: Secernentia)

Scanning electron microscopical (SEM) observations were made on the surface topography of the lips, papillae, amphids, excretory pore, vulva, anus, caudal alae, cuticular bosses, and annular rings of larvae and adults of Pellioditis pellio. Cobb formula measurements and morphological characteristics agreed with those described previously for this species. SEM reveals for the first time: (1) fleshy appearance of the vulva; (2) spherical excretory pore; (3) crescent-shaped vent; and (4) biradial arrangement of oral papillae, lateral alae, and transverse bosses on the cuticle. Similarities to Caenorhabditis elegans are noted, suggesting that P. pellio may be a useful model for comparative neuroanatomical studies. According to Andrassy (1983), the correct name for Rhabditis pellio is Pellioditis pellio (Schneider, 1866). Morphology, based on light microscopy, and life history of P. pellio were described (Goodchild & Irwin, 1971; Hertwig, 1920; Smyth, 1976; Thorne, 1961), and some studies of reproduction and chemoattraction were conducted (Somers et al., 1977a,b). We report here for the first time surface anatomical features, both of larvae and adults of P. pellio, based on scanning electron microscopical observations. MATERIALS AND METHODS A lumbricid oligochaete, Apporectodea caliginosa (Savigny, 1827), recovered from soil in Long Beach, Los Angeles County, California, U.S.A., was cut into three pieces. Segments 20-40 were severed further into 2-3 mm pieces, which then were placed on 1% nutrient agar (Difco Laboratories, Detroit, Michigan, U.S.A.) in a 100 x 15-mm plastic Petri dish. The anterior and posterior pieces were fixed in 70% ethanol for taxonomic identification. After two days, living rhabditiform larvae appeared on the agar and were transferred to clean dishes. In 2-3 days posttransfer, numerous male and female adults, larvae, and eggs appeared on the surface of the agar. Thereafter, worms were subpassaged twice weekly by transfer into new dishes. Flavobacteria associated with the transferred worms provided nutrients. Goodchild & Irwin (1971) reported that Pellioditis pellio is dioecious, and that Rhabditis anomala and R. maupasi are thelyotokous and parthenogenetic, respectively. To determine the reproductive pattern of our isolate, 10 adult 1 We thank Professor George Poinar, Division of Entomology and Parasitology, University of California, Berkeley, California, for confirming the identification of Pellioditis pellio, and Professor E. G. Easton, Annelida Section of the British Museum for the identification of the annelid Apporectodea caliginosa. TRANS. AM. MICROSC. Soc., 109(1): 85-90. 1990. ? Copyright, 1990, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.162 on Thu, 11 Aug 2016 05:57:47 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC.

Oral papillae of adults of the southern hemisphere lamprey Geotria australis

The morphology, cell types, and innervation of the several small papillae (x̄ = 17) and two larger papillae, which together form a ring just outside the fimbriae surrounding the suctorial disc of adult Geotria australis, have been studied using various histological stains, including silver impregnation, and scanning and transmission electron microscopy. The epithelium of all papillae consists almost entirely of mucigenic cells. The multivillous and oligovillous cells, which are found elsewhere in the lamprey epidermis, were not observed, and Merkel and polyvillous cells are rare. Free nerve endings are common, however, in the basal layers of the epidermis. Unlike the small papillae, the two large papillae contain a core of skeletal muscle and a prominent layer of dermal collagen. In the submucosa of these large papillae, the nerves form a dense, compact layer that contains many large and probably sensory axons. It is suggested that the oral disc papillae of adult G. australis are encapsulated mechanosensory structures that play a role in enabling the animal to locate and attach to a suitable point on host fishes or other surfaces.