Dorsolateral Trunk Research Articles

Description of a new karst-adapted species of the subgenus Japonigekko (Squamata: Gekkonidae: Gekko) from Guangxi, southern China

Abstract A new species of the genus Gekko Laurenti, 1768, Gekko paucituberculatussp. nov., is described here, based on two specimens from Tianyang District, Baise City, Guangxi Zhuang Autonomous Region, China. It was placed in subgenus Japonigekko on the basis of morphological and molecular phylogenetic analysis and can be distinguished from all congeners in this subgenus by significant divergences in the mitochondrial 16S and ND2 genes and by a combination of the following morphological characters: Moderate body size, SVL 77.2 mm in the adult male and SVL 85.9 mm in the adult female; tubercles only present along dorsolateral trunk and absent on other regions; fingers and toes with weak webbing; continuous precloacal pores 12 in the male, absent in the female; a single postcloacal tubercle on each side; a light-coloured vertebral line from nape to tip of tail; dorsum greyish-brown, with 7–8 dirty-white bands between nape and sacrum. Meanwhile, the distribution of G. palmatus in China has been confirmed as occurring in Guangxi and Guangdong Provinces. This study brings the total species of the subgenus Japonigekko in China to 19.

Convergent evolution of dark, ultraviolet-absorbing cuticular pigmentation in a new Afro-Oriental Echiniscus brunus species complex (Heterotardigrada: Echiniscidae)

Abstract Green, brown and black pigments are uncommon in the otherwise typically yellow to orange Echiniscidae. Viridiscus, a genus currently represented by a handful of species, in which cuticular coloration varies from a light green through dark green to almost black, has been an exception. Here, we uncover a new echiniscid lineage from the primeval subtropical and tropical rainforests of India and Tanzania, comprising three species with a caramel/brown body. Given that both Viridiscus and the new species complex lack dorsolateral trunk appendages and share dark cuticular pigmentation, they may be mistaken for each other. However, a closer inspection of the dorsal cuticular sculpture and molecular phylogenetic analyses indicate that the new complex belongs within the Echiniscus spinulosus morphogroup. Thus, the presence of dark pigments in two indirectly related lineages is evidence for the convergence of dark cuticular coloration in limno-terrestrial heterotardigrades. We detected three species in the new complex: Echiniscus brunus sp. nov., from the Western Ghats (Tamil Nadu, India), and two other candidate species, Echiniscus aff. brunus sp. can. 1 and Echiniscus aff. brunus sp. can. 2, from India and Tanzania, respectively. We refrain from describing the two latter species formally because they exhibit little or no morphological differences, which is yet another clear case of the crucial role of DNA barcoding in an accurate estimation of tardigrade species richness.

Promising Pharmacological Activities of Ziziphus Herbal Extract and its Formulations

The aim of the present research is to study the potential pharmacological activities of herbal extract of Ziziphus and its formulations. It is observed that the plant extracts of different species of Ziziphus have a variety of pharmacological activities. Due to antibiotic resistance, it is necessary to discover new sources of antibiotics. New technologies are used for the development of antimicrobial and antioxidant drugs with enhanced pharmacological activities. Also, scientists are concentrating on herbal medicines because of their numerous advantages over synthetic drugs. Now-a-days many of these herbal formulations, sold over the counter, are not properly standardized for quality and toxicity. In this research work the sub-chronic dermal toxicity study of Ziziphus oenoplia leaf extract containing Carbopol hydrogel formulation is evaluated on adult male Albino Wister rats. Here, the extract containing hydrogel in 3 doses, and 0.9% NaCl solution (negative control) has been applied on the shaved area of dorsolateral trunk of different groups of rats once a day for 28 days for the study. After conduction of the experiment, it has been observed that the control as well as the test groups of animals did not possess any mortality/ morbidity, clinical signs of toxicity or skin reactions such as edema or erythema. There has been no significant change in food consumption or any notable elevation in body weight in the animal groups throughout the experimental period. Thus, in this study the Ziziphus extract incorporated Carbopol hydrogel has been successfully evaluated for dermal toxicity which reveals that the formulation can be safely applied dermally for wound healing purpose.

The embryology, metamorphosis, and muscle development of Schizocardium karankawa sp. nov. (Enteropneusta) from the Gulf of Mexico

Schizocardium karankawa sp. nov. has been collected from subtidal muds of the Laguna Madre, Texas, and the Mississippi coast, Gulf of Mexico. The Texas population is reproductive from early February to mid-April. Gametes are liberated by a small incision in a gonad. Oocyte germinal vesicle breakdown is increased in the presence of sperm, and the highest fertilization success was in the artificial seawater Jamarin U. Manually dechorionated embryos develop normally. Development was asynchronous via a tornaria larva, metamorphosis and maintained to the juvenile worm 6 gill-pore stage. Phalloidin-labeled late-stage tornaria revealed retractor muscles that connect the pericardial sac with the apical tuft anteriorly, the oesophagus ventrally, and muscle cells of the early mesocoels. The muscle development of early juvenile worms began with dorso-lateral trunk muscles, lateral trunk bands, and sphincters around the gill pores and anus. Adult worms are characterized by a stomochord that bifurcates anteriorly into paired vermiform processes, gill bars that extend almost the entire dorsal to ventral branchial region resulting in a narrow ventral hypobranchial ridge, and an elaborate epibranchial organ with six zones of discrete cell types. The trunk has up to three rows of liver sacs, and lateral gonads. The acorn worm evo-devo model species Saccoglossus kowalevskii, Ptychodera flava, and Schizocardium californicum are phylogenetically distant with disparate life histories. S. karnakawa from S. californicum are phylogenetically close, and differences between them that become apparent as adult worms include the number of gill pores and hepatic sacs, and elaborations of the heart–kidney–stomochord complex. An important challenge for evolutionary developmental biology is to form links from phylogenetically distant and large-scale differences to phylogenetically close and small-scale differences. This description of the embryology, development, and adult morphology of S. karankawa permits investigations into how acorn worm development evolves at fine scales.

Necrotiserende eosinofiele dermatitis bij drie honden

In dit artikel wordt bij drie honden necrotiserende eosinofiele dermatitis beschreven met een acuut ontstaan en snel verloop. De eerste huidletsels werden gekenmerkt door intens jeukende erythemateuze en stevig aanvoelende intacte papels en plaques. De letsels werden snel groter en evolueerden tot samenvloeiende targetoïde nodulen met centrale exsudatie, ulceratie en necrose. De letsels kwamen hoofdzakelijk voor op de hals en op de dorsolaterale romp. Eén hond vertoonde ook orale letsels. Het histopathologisch beeld toonde in de drie gevallen eosinofiele dermatitis en panniculitis gericht op de dermale en subcutane bloedvaten met secundaire aantasting van de haarfollikels. Een overgevoeligheidsreactie op medicatie of op andere lichaamsvreemde antigenen kunnen mogelijk de oorzaak zijn geweest.

Preexpanded Perforator Flaps of the Dorsolateral Trunk in Pediatric Patients

Contractures and broad scars of the axilla, anterior chest wall, and neck have detrimental effects on functional, physical, and psychological development of children. Perforator flaps have already been shown to be reliable options for the reconstruction of contractures, but there have been no reports demonstrating the value of preexpanded perforator flaps of the dorsolateral trunk region in the treatment of extensive contractures and scars of pediatric patients. The purpose of this study was to demonstrate these techniques by a case series formed of pediatric patients with broad scars and contractures of the anterior chest wall, axilla, neck, and breasts. Seven pediatric patients (mean age, 11.6 years) who were treated by preexpanded perforator flaps are presented. By this means, clinical experience regarding the intercostal artery perforator, thoracodorsal artery perforator, circumflex scapular artery perforator, and lumbar artery perforator flaps was shared. Flaps as large as 21 × 11 cm could be successfully transferred in pediatric patients. Broad scar tissues were resurfaced with broad flaps carrying similar characteristics with the uninjured anterior chest wall and neck skin in six of the authors' patients. In one patient with partial necrosis, a full-thickness skin graft was used for the residual defect. The mean duration of postoperative (after flap transfer) follow-up was 17.2 months. The preexpanded thoracodorsal artery perforator, intercostal artery perforator, and circumflex scapular artery perforator flaps are useful and effective reconstructive options for the treatment of scars and contractures of the anterior chest wall, axilla, neck, and breast in pediatric patients. : Therapeutic, IV.

CD3+ and BLA.36+ cells do not occur in the epidermis and adnexal epithelia of normal skin from the dorsolateral trunk of cats.

A small population of resident T-lymphocytes is present in the normal epidermis of humans, mice, and rats. However, resident epidermal lymphocytes have not been reported in the normal skin of the cat. Skin-biopsy specimens from the normal skin of the dorsolateral trunk from 30 cats were examined histologically and immunohistochemically for the presence of lymphocytes, CD3+ cells, and BLA.36+ cells in epidermis and adnexal epithelia. All examinations were negative. It appears that lymphocytes occur rarely, if at all, in the epidermis and adnexal epithelial of normal cat skin. Hence, the presence of lymphocytes in these structures should be considered abnormal.

Bone morphogenetic protein-4 and Noggin signaling regulates pigment cell distribution in the axolotl trunk

Wild-type (dark) and white mutant axolotl ( Ambystoma mexicanum) embryos were used to investigate the role of the secreted growth factor bone morphogenetic protein-4 (BMP-4) and its antagonist, Noggin, in dorso-lateral trunk neural crest (NC) migration. Implantation of a BMP-4-coated microbead caused a melanophore-free zone around the bead, reduction of the dorsal fin above the bead, and disappearance of myotome tissue. We established a novel method that allows controlled induction of protein synthesis and release. Xenopus animal cap (XAC) cells injected with heat shock-inducible constructs for BMP-4 and Noggin were implanted into axolotl embryos and protein expression was induced at defined time points. With this approach, we could demonstrate for the first time that Noggin can stimulate melanophore migration in the white mutant. We further showed that implantation of BMP-4 expressing XAC cells alters pigment cell distribution without affecting muscle and dorsal fin development.

Ramificação e distribuição dos nervos frênicos no músculo diafragma do gato doméstico

A ramificação e a distribuição dos nervos frênicos direito e esquerdo foram estudadas em 30 músculos diafragmas de gatos domésticos sem raça definida, 7 machos e 23 fêmeas, conservados em solução de formaldeído a 10%. Mediante fixação e dissecção, observou-se que os nervos frênicos se ramificaram para as respectivas partes carnosas do músculo diafragma, pars lumbalis, costalis e sternalis, e terminaram em maior freqüência em tronco dorsolateral e ramo ventral (63,33%). Notou-se ainda os seguintes arranjos: ramos dorsal, lateral e ventral (25,0%); ramo dorsal e tronco ventrolateral (6,66%); troncos dorsolateral e ventrolateral (3,33%); tronco dorsolateral, ramos lateral e ventral (1,66%). Os nervos frênicos se distribuíram simetricamente em 11 exemplares (36,66%), exibindo somente a terminação em tronco dorsolateral e ramo ventral. Os ramos dorsais inervaram a pars lumbalis (73,33% à direita e 56,66% à esquerda) e a pars costalis (13,33% à direita e 10,0% à esquerda). O ramo dorsal direito supriu a crus mediale dexter do pilar direito (100,0%) e o ramo dorsal esquerdo inervou a crus mediale sinister do pilar direito e o pilar esquerdo (100,0%). Os ramos laterais inervaram a pars lumbalis (23,33% à direita e 33,33% à esquerda), a pars costalis (96,66% à direita e 100,0% à esquerda) e a pars sternalis (3,33% somente à direita). Os ramos ventrais inervaram a região ventral da pars costalis (46,66% à direita e 43,33% à esquerda) e a pars sternalis (96,66% à direita e 100,0% à esquerda). Quatro animais fêmeas (13,33%) exibiram cruzamento de fibras provenientes do ramo ventral esquerdo para o antímero direito sendo que em um desses exemplares (3,33%) ocorreu conexão entre o ramo ventral esquerdo e o direito.

Ganglion cyst of the cervical spine presenting with Brown-Sequard syndrome

Ganglion cysts of the spine are uncommon. They occur mostly in the dorsolateral trunk and arise with the greatest frequency in the lumbar spine. However, they are rarely symptomatic. We report a rare case of a patient with a ganglion cyst of the lower cervical spine presenting with acute Brown-Sequard syndrome. The patient had no history of trauma. Magnetic resonance imaging of the cervical spine showed a cystic lesion connecting to the synovial joint C6–7 and compressing the posterior aspect of the spinal cord. The patient underwent emergent C6–7 laminectomy with total removal of the cyst. Neurological function recovered completely 4 months after operation. Ganglion cysts should be considered in the differential diagnosis of an extradural mass of the cervical spine. Magnetic resonance imaging provides a rapid and correct diagnosis, and laminectomy with removal of the cyst results in good neurological recovery.

Natural infestation of the chewing lice (Werneckiella equi) on horses and treatment with imidacloprid and phoxim

Infestation with the chewing louse (Werneckiella (Damalinia) equi) can be found on horses world-wide. Louse infestations, including clinical signs of louse-derived dermatitis, are known from Icelandic horses. A clinical field investigation was conducted in Iceland using horses with natural louse infestations to evaluate the efficacy of imidacloprid in a 10% solution in comparison with phoxim in a 0.05% solution. A total of 27 horses received a single imidacloprid treatment using 16 ml of the 10% solution along the mane and on the dorso-lateral trunk. A further 43 horses were treated twice, 14 days apart, with phoxim, using 2 x 50 ml solution applied along the mane and the dorso-lateral trunk. At the final evaluation on day 28, complete control of the lice was obtained for the imidacloprid treated horses and only a single moribund louse was found on two horses treated with phoxim.

Enhanced wound contraction in fresh wounds dressed with honey in Wistar rats (Rattus Novergicus).

Due to reports that honey accelerates wound healing, an investigation on its role in wound contraction in fresh wounds inflicted on wistar rats was carried out. Twenty adult male wistar rats had 2cm by 2cm square wound inflicted on their right dorsolateral trunk. They were divided into two groups. The experimental group had their wounds dressed with honey while the control group had normal saline dressing. Wound dressing was done every five days and measurements taken at each dressing. Wound morphology was also assessed. Dressing with honey significantly enhanced percentage wound contraction on day 10 with value of 79.20+/-2.94 compared to control value of 53.50+/-4.32. p=0.0. The mean wound measurement on day 10 reduced significantly in honey group, 1.15+/-0.18 compared to control group 2.38+/-0.28. p=0.002. However, there was no significant difference in fibroblast count per high power field in honey group 68.0+/-2.59 compared to control 90.2+/-17.40, p=0.242. Honey dressing increased mean blood vessel count per high power field, 18.8+/-3.77 albeit non significantly when compared to control value of 13.4+/-2.44, p=0.264. Also honey dressing caused increased granulation tissue formation in wounds dressed with honey compared to control group. Our study suggests that honey dressing enhances wound contraction in fresh wounds which is one of the key features of wound healing.

Groenlandaspidid placoderm fishes from the Late Devonian of North America

Two new taxa of groenlandaspidid fish (Placodermi: Arthrodira) from non-marine deposits of the Catskill Formation (Upper Devonian) at Red Hill, Clinton County, Pennsylvania, USA, are the first to be described from North America outside of Greenland. Groenlandaspis pennsylvanica n.sp. is known only from isolated trunk elements that are quite similar to Groenlandaspis antarctica Ritchie, 1975. Groenlandaspis pennsylvanica n.sp. is characterized by distinct features of the median dorsal (MD), posterior dorsolateral (PDL), and anterior dorsolateral (ADL) plates. Turrisaspis elektor n.gen. and n.sp. is a smaller form with a high median dorsal plate (MD) and tall, narrow elements of the dorsolateral trunk shield, particularly the PDL, giving this taxon a distinctively short, high trunk shield. The head shield of Turrisaspis elektor has a divided pineal plate and the postmarginal plate makes contact with the postorbital plate, excluding the marginal plate from the lateral margin of the head shield. Groenlandaspis pennsylvanica n.sp. is a rare faunal component at the Red Hill site whereas Turrisaspis elektor is very common. The large sample size of Turrisaspis elektor provides a glimpse at ontogenetic and individual variation within this taxon.

Anatomical study of the diaphragm of the opossum (Didelphis albiventris).

The anatomical characteristics of the South American opossum diaphragm were described. Five male and seven female adult opossums, weighing between 700 and 1110 g, were used. Animals were killed by ether inhalation saturation. The abdominal and thoracic walls were dissected and opened, the viscerae were removed and the diaphragm anatomy was described and photographed in situ. After diaphragm removal, some dimensional data were taken and tabled. Primary branches of the phrenic nerves were dissected under a surgical microscope. The secondary branches were studied and described by transillumination after clarification in acetic acid. The opossum diaphragm is domed and has a mean area of 54.33 +/- 3.8 cm2. Well-identified costal, sternal and lumbar parts form the peripheral muscular region. The central tendinous region presents with a V-like form. Three folioles comprise the phrenic centre and present different dimensions. The caudal vena cava passes through its foramen between the ventral and right dorsal folioles. Both right and left phrenic nerves present one ventral branch and one dorsolateral trunk in 50.0% and 66.67% of the cases, respectively.

Changes in neuronal receptive field characteristics in caudal brain stem following chronic spinal cord injury.

Chronic spinal cord injury pain is poorly understood and, thus, not effectively relieved by traditional treatments. In the present study, a variety of partial, severe and sham chronic spinal lesions were made in 31 male rats at spinal level T8. During routine care/handling and brief behavioral testing of the animals throughout the 30-day recovery period, the majority of those with severe contusion injuries (verified histologically) showed signs of mechanical hypersensitivity on the dorsolateral trunk just rostral to the level of injury (i.e., upper thoracic territory). Terminal electrophysiological experiments were performed on all rats (urethane anesthesia). Single unit recordings were made at two supraspinal locations within the caudal brainstem, the nucleus reticularis gigantocellularis and nucleus reticularis gigantocellularis pars alpha. Neurons in these areas normally receive bilateral nociceptive somatovisceral inputs from many parts of the body. Seventy-three percent of the animals with severe contusion injuries developed novel low-threshold neuronal responses to stimulation of the dorsolateral trunk (upper thoracic territory). This amount was significantly greater than for animals with more moderate spinal lesions (dorsal or lateral hemisection; 29% and 25%, respectively) or sham controls (0%). These data suggest (1) that the spinal contusion is a reliable model for studies of the neural mechanisms that underly central spinal cord injury-related pain and (2) that the caudal brainstem is one supraspinal location where neurons undergo significant changes in responsiveness following severe chronic spinal cord injury. The observed plasticity is likely part of the central reorganization producing the multitude of sensory disturbances that surface following spinal cord injury.

Analysis of Embryonic Chick Periderm by Monoclonal Antibody Specific against Periderm1 : (periderm/ectoderm/monoclonal antibody/cytokeratin/chick embryo).

The monoclonal antibody, 6H11, specific against embryonic chick periderm, was produced and found capable of recognizing polypeptides with 45 Kd in cytoskeletal fractions of skin and limb buds. These polypeptides were separated into two and one isoelectric variant, respectively, by two dimensional gel electrophoresis, and assigned to the acidic subfamily of cytokeratin. The ectoderm of the limb buds at stage 24 stained with 6H11. At stages 25 to 26, the experession of 6H11 in the ectoderm could no longer be detected except in a limited number of 6H11-positive cells present in the ectoderm. These positive cells were subsequently noted on the periphery of the ectoderm. They increased in number to finally form the periderm. Periderm in the dorsolateral trunk was also formed similarly by 6H11-positive cells but the timing of formation differed in the dorsal and lateral trunk. In the formation of skin integuments, such as feathers and scales, no regionality of 6H11-expression was found. The expression of 6H11 eventually decreased and ceased to be evident at about the time of hatching. Its expression in the basal epidermis during embryogenesis could not be detected. In the following, a possible mechanism of the periderm formation is discussed.

Contribuição ao estudo da inervação do diafragma em eqüinos da raça Puro Sangue Inglês

The results obtained through the study of 30 diaphragms of adult throughbred horses, extracted from 15 male and 15 female animals from the Jockey Clube de São Paulo and the Jockey Clube Brasileiro, allowed us to come to the following conclusions: 1) The phrenic nerves terminate in a ventral branch and in a dorsolateral trunk on the right (96.7%) and on the left (26.7%), or in a dorsal branch and a ventrolateral trunk on the left (66.7%) and on the right (3.3%). Trifurcations in ventral, lateral and dorsal branches are also found on the left (6,6%). Right and left phrenic nerves are simetrically arranged in a ventral branch and a dorsolateral trunk (26.7%) and a dorsal branch and a ventrolateral trunk (3.3%). 2) The dorsal branches of the phrenic nerves innervate the lumbar portion on the left (86.6%) and on the right (83.3%) respectively. They provide fillets to the tendinous center of the diaphragm either on the right or on the left (6.6%). They also provide fillets to the dorsal leaflet on the right (6.6%), and to the vena cava caudal on the left (6.6%), and only in one case they provide branches to the right lumbar portion (3.3%). 3) The lateral branches of the phrenic innervate the costal portion on the left (90.0%) and on the right (56.6%), more precisely the dorsal and lateral portion. They provide fillets to the dorsal leaflet on the right (20.0%) and on the left (3.3%), they go towards the ventral portion of the costal part on the left (6.6%). 4) The ventral branches of the phrenic nerves innervate the ventral portion of the costal part and the sternal part on the left (86.6%) and on the right (76.6%), respectively. They send branches to the ventral leaflet on the right and on the left (6.6%). They transverse the ventral leaflet which is responsable for the innervation of the heteronomous sternal part on the left (3.3%). They innervate only the ventral portion of the costal part on the right (3.3%). They form a small trunk which extends into two fillets, one to the ventral portion of the costal part, and other to the sternal part of the right (3.3%). They also send branches to the dorsal leaflet of the right (3.3%). They send fillets to the wall of vena cava caudal on the right (3.3%). They send a branch which goes to the tendinous center of the diaphragm on the right (3 3%). 5) The homolateral conexions ("anastomosis") were found on the right (40.0%) and on the left (3.3%) among the following fillets* of the right dorsal and lateral branches (30.0%) the right lateral branch (33%), of the right ventral branch (3.3%), and of the left lateral and dorsal branches (3.3%). 6) The statistical analysis does not show a significant difference, at the level of 5.0%, concerning several aspects of innervation o f the diaphragmatic muscles, when both sexes are compared.

Formation of pigment cell patterns in Triturus alpestris embryos

The distribution of melanophores and xanthopores in developing tailbud stages of Triturus alpestris was investigated. In stage 27 embryos (curved tailbuds), melanophores are distributed evenly but sparsely over the entire dorsolateral trunk. With progressive development melanophores arrange themselves into compact dorsal and lateral bands present in stage 34 embryos (9 to 10-mm-long larvae). On the inner surface of detached pieces of skin from early tailbuds which were investigated in the scanning electron microscope xanthophores were discovered in addition to and mixed with melanophores. Unlike melanophores they are invisible from outside. Later in development they occupy the zone between the melanophore bands and also the dorsal fin. Thus, formation of pigment cell patterns in Triturus embryos is a process which seems to depend on the differential sorting out of two populations of neural crest-derived chromatophore cell types.

Changes in the distribution of melanophores and xanthophores inTriturus alpestris embryos during their transition from the uniform to banded pattern.

The change in distribution of melanophores from stage 28+ (uniform melanophore pattern) to stage 34 (banded melanophore pattern) and the participation of xanthophores in these changes has been investigated inTriturus alpestris embryos by studying the social behaviour of single cells. While melanophores are clearly visible from outside the embryo at stage 28+, xanthophores cannot be recognized from the outside until after stage 34. In ultrathin sections of stage 34 embryos, xanthophores are observed alternating with melanophores in a zonal distribution (Epperlein 1982). Using detached pieces of dorsolateral trunk skin, which retain their chromatophores after detachment, the entire distribution of melanophores and xanthophores can be visualized in a scanning electron microscope (SEM). In ambiguous cases (early stages), cells were reprocessed for transmission electron microscopy (TEM) and the presence of the characteristic pigment organelles was assessed. In addition, xanthophores were specifically identified by pteridine fluorescence with dilute ammonia. Pteridines were also identified chromatographically in skin homogenates. The combination of these methods allowed precise identification and quantitative determination of melanophores and xanthophores. Both cell types were present as codistributed, biochemically differentiated cells at stage 28+. Changes in the pattern up to stage 34 were due to the rearrangement at the epidermal-mesodermal interface of a relatively fixed number of melanophores which became preferentially localised at the dorsal somite edge and at the lateral plate mesoderm, and to the distribution of an increasing number of xanthophores to subepidermal locations in the dorsal fin and between the melanophore bands. Concomitant was an increase in the thickness of the epidermal basement membrane and a change in shape of chromatophores from elongate via stellate to rosette shaped, which may be correlated with a shift from migratory to sessile phases.

STUDIES ON AMPHIBIAN METAMORPHOSIS

The dermal plice or folds of newly-metamorphosed Rana pipiens, as is well known, constitute a striking and characteristic development for this species. Although minor folds have been described, the most distinct plicae are those of'the dorso-lateral trunk and lateral upper jaw regions. The former consists of two folds, one on each side of the trunk, running from the dorsal-posterior border of the eye back to a point just lateral to the urostyle prominence. The latter likewise consists of two folds, one on each side of the upper jaw, running from a point just anterior and ventral to the external nares posterior on a level just ventral to the tympanic membrane to a point just dorsal to the origin of the fore-limb. The folds are usually about 0.5 mm. in width at this time and are white in color in sharp contrast to the black or dark-greenish coloration of the adjacent integument. Histologically, the folds are seen to be composed of integument having a much thickened stratum spongiosum in which are found mucous and unusually large poison glands. It is the concentration and abnormal size of these glands in this particular region which result in the formation of an actual ridge or fold as viewed externally. The development of the dermal plica during metamorphosis may be roughly estimated by external observation. In the normal larva, just prior to the onset of involution, no indications of plicae formation are visible. During the early stages of transformation, however, broad though very indistinct bands of integument are noticeable in the dermal plicae regions. These are at first of a dull, grayish-white shade. Later, however, towards the close of metamorphosis, they become lighter in color, as the bands appear to narrow, and more sharply demarcated from the adjacent integument. Following larval transformation, the plicae become increasingly whiter and very distinct, after which they undergo relatively little change during the early growth period of the young frog. 11