The effects of cannibalism on Amazonian poison frog egg and tadpole deposition and survivorship in Heliconia axil pools

This study investigated the influence of cannibalism on egg and larval mortality, and on the deposition strategies of adults, in a tropical anuran breeding in very small leaf axil pools. Patterns of egg and tadpole deposition and mortality in the Amazonian poison frog, Dendrobates ventrimaculatus, were monitored in rainforest near Pompeya in Sucumbios Province, Ecuador. Oviposition and tadpole deposition typically ocurred in leaf axils of Heliconia plants. Pools typically received more than one oviposition. Egg survivorship was low, and significantly lower when eggs were deposited in pools with large tadpoles, indicating that cannibalism is an important source of mortality. Tadpole survivorship was also associated with the presence of other tadpoles: most pools ended with only one surviving tadpole, regardless of the number of tadpoles deposited in the pool. Egg deposition was signifcantly less likely for pools that had a tadpole in them, suggesting that adults can detect the presence of tadpoles and avoid ovipositing in pools that contain them. This hypothesis was tested with a series of pool choice experiments, which revealed that D. ventrimaculatus avoid placing either eggs or tadpoles into a pool which contains a large tadpole. Several hypotheses which could explain multiple deposition in this species are discussed. Received: 14 September 1998 / Accepted: 25 January 1999     

Cu对中国林蛙蝌蚪的急性毒性

试验测定了不同温度条件下Ｃｕ２＋对中国林蛙蝌蚪的急性毒性．结果表明,在水温为９～１３℃、１８℃和２４℃条件下,Ｃｕ２＋对１０ｄ龄中国林蛙蝌蚪９６ｈ的ＬＣ５０分别为５．０１、３．８０和２．９９ｍｇ·Ｌ－１,致死阈浓度分别为４．０、２．５和１．６ｍｇ·Ｌ－１,而在９６ｈ内的无可观察效应浓度分别为２．５、１．６和１．０ｍｇ·Ｌ－１．１８℃条件下Ｃｕ２＋对２０ｄ龄中国林蛙蝌蚪的９６ｈＬＣ５０为２．１７ｍｇ·Ｌ－１．     

Electric currents in Xenopus tadpole tail regeneration

Xenopus laevis tadpoles can regenerate tail, including spinal cord, after partial amputation, but lose this ability during a specific period around stage 45. They regain this ability after stage 45. What happens during this “refractory period” might hold the key to spinal cord regeneration. We hypothesize that electric currents at amputated stumps play significant roles in tail regeneration. We measured electric current at tail stumps following amputation at different developmental stages. Amputation induced large outward currents leaving the stump. In regenerating stumps of stage 40 tadpoles, a remarkable reversal of the current direction occurred around 12-24 h post-amputation, while non-regenerating stumps of stage 45 tadpole maintained outward currents. This reversal of electric current at tail stumps correlates with whether tails regenerate or not (regenerating stage 40—inward current; non-regenerating stage 45—outward current). Reduction of tail stump current using sodium-free solution decreased the rate of regeneration and percentage regeneration. Fin punch wounds healed normally at stages 45 and 48, and in sodium-free solution, suggesting that the absence of tail re-growth at stage 45 is regeneration-specific rather than a general inhibition of wound healing. These data suggest that electric signals might be one of the key players regulating regeneration.     

Scanning electron microscopy of macrophages in the tail musculature of the metamorphosing anuran tadpole,Rana japonica

Summary Scanning electron microscopy was used to investigate the morphological changes of the tail musculature of the metamorphosing anuran tadpole, attention being focused on phagocytosis by macrophages. Muscle fibers were stained en bloc with silver and freeze-fractured during dehydration, or torn after drying. Samples were sputter-coated with gold-palladium and observed in both secondary electron- and back-scattered electron modes with a scanning electron microscope.Various cells were identified by the methods of secondary electron- and back-scattered electron images. Some macrophages lying between muscle fibers at prometamorphic stages possessed numerous finger-like projections and well-developed ruffles. During degeneration of muscle fibers macrophages collected in the degenerating region and invaded the space between the disordering myofibrils. In advanced stages the numbers of macrophages clearly increased on or around the degenerating muscle fibers. At the climactic stage fragmented muscles were entrapped and then engulfed by the macrophages. With the completion of phagocytosis, the macrophages became globular with reduction of the ridge-like ruffles. Macrophages may play a role not only in scavenging the fragmented muscle fibers, but also using their long processes in active formation of the fragments.     

Some observations on the fine structure of the myotendinous junction in myotomal muscles of the tadpole tail

Summary Myotendinous junctions in the myotomal tail muscles of the tadpole of Rana rugosa were examined by electron microscopy. At the site of the myotendinous junction, the sarcolemma is covered on its sarcoplasmic aspect by the connecting filament layer and the attachment layer, and on the extracellular aspect by the intermediary layer and the external lamina, with associated collagen fibrils. The intermediary layer consists of filamentous structures which closely resemble microfibrils (Hanak and Böck, 1971), spine-like or thread-like profiles (Korneliussen, 1973) and intermediary layer (Nakao, 1975a, b) in the myotendinous junctions of other vertebrate skeletal muscles.Particularly interesting is the fact that all the coverings and linings of the sarcolemma, including the external lamina, are completely absent in the terminal segment of the finger-like sarcolemmal invagination characteristic of the myotendinous junction. Furthermore, special types of coupling between a sac of sarcoplasmic reticulum and a part of the sarcolemmal invagination are frequently observed. These couplings always occur along the region of the sarcolemma where the external lamina is absent. The couplings show features similar to those of the triad, such as SR feet , scalloped SR membranes and granular content of the SR sac, suggesting that they are analogous and functionally similar to the triad and other equivalent structures.     

Immunofluorescence of somatostatin-producing sites in the hypothalamus of the tadpole,Alytes obstetricans Laur.

Summary Three sites of somatostatin-synthesizing perikarya, or a related antigen, were determined by immunofluorescence in the hypothalamus of the tadpole, Alytes obstetricans (Amphibia, Anura). Two sites of neurosecretory perikarya were localized in the preoptic nuclei of the anterior hypothalamus; the axons extended either to the anterior diencephalon or to the median eminence and the pituitary. The third site was found in the posterior hypothalamus. These neurosecretory cells showed a strong immunofluorescent reaction; their axons all terminated at the level of the median eminence. Somatostatin cells were only found in intact or hypophysectomized tadpoles given somatotropin (STH). The strong reaction observed in hypophysectomized tadpoles was possibly due to the loss of the terminal portion of the neurosecretory pathway (median eminence and pituitary) by which the agent is transported to the site of discharge.     

The role of amphibian prey in the diet and growth of giant water bug nymphs in Japanese rice fields

Predatory insects that depend upon particular prey animals are commonly regulated by the prey animal’s abundance. Nymphs of the giant water bug Kirkaldyia (=Lethocerus) deyrolli (Heteroptera: Belostomatidae) are predators regarded as specialists in feeding on tadpoles. We studied the ontogenetic diet shift of aquatic nymphs by quantifying instar abundance and by analyzing captured prey and prey relative abundance during the period of rice irrigation in three localities. We also evaluated the contribution of major prey items (tadpoles, frogs, and Odonata nymphs) on specific growth rates of each nymphal stage in a rearing experiment. First to third-instar nymphs of K. deyrolli fed mainly on tadpoles, regardless of differences in prey availability. Nymphs of subsequent fourth and fifth instar stages shifted from tadpoles to other prey animals within each rice field. A rearing experiment demonstrated that giant water bug nymphs provided with tadpoles had greater specific growth rates at all nymphal stages, except for the final stage, than nymphs fed other prey (frogs and Odonata nymphs). The emergence of young K. deyrolli nymphs seemed to coincide with the period during which tadpoles became abundant in the rice fields. Consumption of tadpoles seems important to allow the nymph to complete its larval development in an unstable temporary habitat. An erratum to this article can be found at     

Binucleate trophoblast giant cells in the water buffalo (Bubalus bubalis) placenta

The binucleate trophoblast giant cells (BNC) of the water buffalo, Bubalus bubalis, placenta were studied, with emphasis on the synthesis of BNC-specific proteins. Placentomal tissues of 27 water buffalos (2-10 months of pregnancy) were processed for light and electron microscopy. The frequency of BNCs was 20% of the trophoblastic cells in 2-3-month placentas and increased to 27% in the later stages. Ultrastructurally, binucleate cells displayed a prominent granular endoplasmic reticulum and Golgi apparatus, typical of cells involved with protein synthesis and exportation. The buffalo BNCs contained periodic acid-Schiff (PAS)-positive granules and reacted with antisera against bovine placental lactogen, prolactin-related protein-I, and pregnancy-associated glycoproteins. Lectin histochemistry with Dolichos biflorus agglutinin, Vicia villosa agglutinin, and Phaseolus vulgaris leucoagglutinin showed specific staining of BNCs. Different stages of BNC migration and fusion with uterine epithelial cells were observed. Trinucleate feto-maternal hybrid cells were the typical outcome of cell fusions. These cells underwent degeneration, with typical morphological features of apoptosis. The results revealed a strong homology between water buffalo and cattle BNCs concerning cell morphology, protein expression, glycosylation pattern, and characteristics of cell migration and fusion.     

Relations between development and regeneration of tadpole spinal cord

Summary 1. The developing spinal cords of bullfrogs and transected cords of stage IV tadpoles were subjected to two-dimensional gel electrophoresis and histological analysis. During development, the level of actin,-tubulin or-tubulin in the 7–10th spinal segments increased with time and reached a maximum around stage XIII followed by a decrease, as shown from quantitative assay on protein spots of 2-dimensional gels of cord homogenates. In contrast, the level of 68 kD neurofilament subunit (NF68) was low in tadpoles but high in frog.2. Following a complete transection made at the level of the 8th spinal segment, the cord tissue of the lesion zone degenerated; regeneration from each cut end then occurred, which lengthened for approximate 0.35 mm by 28 days after transection. The content of actin,-tubulin and-tubulin in the cord within 1–2 mm of the transection site was elevated to 124–192% of control values 7–28 days post-transection, whereas NF68 declined to near non-detectable extent.3. The regeneration of each cord stump included outgrowth of neuroepithelial cells and nerve fibers, reconstituting a newly regenerated cord segment. Ultrastructural examination revealed that features of the regrowth of fibers and guidance of neuroepithelial cells to the axonal growth resembled that seen in the developing cord. Thus the biochemical and morphological data support that the regeneration of the nervous system recaptulates its developmental events, providing evidence for molecular mechanisms underlying central axonal regeneration.     

Heterochrony during skeletal development of Pseudis platensis (anura,hylidae) and the early offset of skeleton development and growth

The aquatic frog Pseudis platensis has a giant tadpole, long developmental time, and dissociated metamorphic events that include later offset of larval somatic morphologies. Moreover, when the tadpole metamorphoses, the young frog is nearly the size of an adult, suggesting that this species has low rates of postmetamorphic growth. Herein, we study the development of the skeleton during larval development up to the end of metamorphosis, which is denoted by the complete lost of the tail in P. platensis. Our study revealed heterochronic differences in skeletal development compared with that of most anurans; these involve the complete differentiation of skull bones and the extensive ossification of the postcranial skeleton before completion of metamorphosis. The skull of metamorphosing P. platensis has an ossified sphenethmoid and a fully formed plectral apparatus, thus differing with regard to the pattern observed in most anurans in which both developmental events take place during the postmetamorphic life. Despite the fact that the iliosacral articulation and the urostyle are present at the end of metamorphosis as in most anurans, ossification/calcification of carpus, tarsus, and limb epihyses during metamorphosis of P. platensis suggests that the postcranial skeleton lacks postmetamorphic growth. This study also includes a discussion of the pattern of development of the plectral apparatus, which allows us to propose a new hypothesis regarding pars externa plectri homology. J. Morphol., 2009. © 2008 Wiley‐Liss, Inc.     

Toxicity and effects of mosquito larvicides methoprene and surface film (Agnique® MMF) on the development and fecundity of the tadpole shrimp Triops newberryi (Packard) (Notostraca: Triopsidae)

We investigated the interactions of tadpole shrimp, a mosquito biological control agent, with the juvenile hormone analog methoprene and a monomolecular surface film. In laboratory assays, the tadpole shrimp (TPS) Triops newberryi (Packard) was able to tolerate high concentrations of methoprene without negative impacts on its growth, longevity, and fecundity when exposed to 1 to 10 mg/liter, or 90–900 fold, of the IE₉₀ levels against a laboratory colony of Culex quinquefasciatus Say. The same held true in field trials when the habitats were treated with Altosid® Liquid Larvicide (Altosid® LL, 5% methoprene) at 0.3–1.2 liters/ha. or 1–4 fold of the label rates for mosquito control. However, some significant impacts on the TPS occurred when they were exposed to Agnique® Monomolecular Film (Agnique® MMF) at the label rates for mosquito control ranging from 1.89–9.45 liters/ha. under laboratory and field conditions. To avoid the negative impact of Agnique MMF on tadpole shrimp, it appears that 1.89 liters/ha. would be the maximum rate when Agnique MMF is used to control mosquitoes in the habitats where the TPS is employed as a biological control agent, or prevailing in the aquatic habitats with potential for suppressing mosquito larval populations.     

镉对中国林蛙蝌蚪生长发育的毒性效应

将中国林蛙(Rana chensinensis)蝌蚪分别暴露于加Cd2 的自来水和去离子水中,统计得出24、48、72和96 h的半数致死浓度(LC50)、全致死浓度(LC100)、零致死浓度(LC0)和安全浓度(SC)。结果表明,随着Cd2 浓度的升高和染Cd2 时间的延长,蝌蚪的死亡率增高,Cd2 加入去离子水中对蝌蚪的毒性比在自来水中更强。另外,将26~27期林蛙蝌蚪饲养在含Cd2 0.05、0.1、0.2和0.4 mg.L-1的自来水中直至完全变态,通过对完全变态所需时间、平均体重和长度增长率的测定,研究在SC以下Cd2 对林蛙蝌蚪胚后发育的影响。随着Cd2 浓度的升高,蝌蚪的平均体重和长度的增长率降低,完全变态所需时间增长。说明Cd2 污染在SC以下仍可抑制中国林蛙蝌蚪的生长发育,延缓变态。     

Epicuticular wax of Colletia paradoxa

The composition of Colletia paradoxa epicuticular wax was determined. Hydrocarbons (27%), ketones (22%—mainly taraxerone), free acids (17%), free     

The oral apparatus of tadpoles of Rana dalmatina, Bombina variegata, Bufo bufo, and Bufo viridis (Anura)

The morphology and development of the larval oral apparatus of Rana dalmatina, Bombina variegata, Bufo bufo, and Bufo viridis are described and compared using scanning electron microscopy. The species show different arrangements of the mouthparts. The small oral apparatus of R. dalmatina larvae has three labial tooth rows on the upper labium, while there are four tooth rows on the lower labium with a medial gap in row proximal to the mouth. The margins of the oral apparatus are defined by papillae that encircle the lower labium. B. variegata tadpoles have two upper labial tooth rows and three lower labial tooth rows that are uninterrupted, unlike the ones of R. dalmatina. The mouth is encircled by papillae that are larger than those of R. dalmatina. The oral discs of tadpoles of both B. bufo and B. viridis are similar. They are defined by two upper labial tooth rows (the second of which is interrupted by a medial gap) and by three lower tooth rows that differ in lengths in the two Bufo species. Both species develop papillae on the mouth angles and in two rows on the upper labium. Some morphological differences among the oral discs of R. dalmatina, B. variegata, B. bufo, and B. viridis tadpoles can be attributed to phylogenetic differences, but most can be related to their varying feeding habits and/or to their dietary specializations.     

Modulation of trophoblast stem cell and giant cell phenotypes: analyses using the Rcho-1 cell model

Trophoblast giant cells are located at the maternal-embryonic interface and have fundamental roles in the invasive and endocrine phenotypes of the rodent placenta. In this report, we describe the experimental modulation of trophoblast stem cell and trophoblast giant cell phenotypes using the Rcho-1 trophoblast cell model. Rcho-1 trophoblast cells can be manipulated to proliferate or differentiate into trophoblast giant cells. Differentiated Rcho-1 trophoblast cells are invasive and possess an endocrine phenotype, including the production of members of the prolactin (PRL) family. Dimethyl sulfoxide (DMSO), a known differentiation-inducing agent, was found to possess profound effects on the in vitro development of trophoblast cells. Exposure to DMSO, at non-toxic concentrations, inhibited trophoblast giant cell differentiation in a dose-dependent manner. These concentrations of DMSO did not significantly affect trophoblast cell proliferation or survival. Trophoblast cells exposed to DMSO exhibited an altered morphology; they were clustered in tightly packed colonies. Trophoblast giant cell formation was disrupted, as was the expression of members of the PRL gene family. The effects of DMSO were reversible. Removal of DMSO resulted in the formation of trophoblast giant cells and expression of the PRL gene family. The phenotype of the DMSO-treated cells was further determined by examining the expression of a battery of genes characteristic of trophoblast stem cells and differentiated trophoblast cell lineages. DMSO treatment had a striking stimulatory effect on eomesodermin expression and a reciprocal inhibitory effect on Hand1 expression. In summary, DMSO reversibly inhibits trophoblast differentiation and induces a quiescent state, which mimics some but not all aspects of the trophoblast stem cell phenotype.     

The pattern of collagen degradation in cultured tadpole tissues

A characteristic pattern of selective degradation of isotopically labeled collagen in tadpole tail fin in culture was observed by measuring the amount and radioactivity of degraded collagen fragments released into the culture medium as a function of time of incubation. The changes in specific activity and total amount of hydroxyproline released with time indicated early degradation apparent at 3 hr of incubation of a small fraction of newly synthesized heavily labeled collagen followed by breakdown of the bulk of old lightly labeled fibrils. Collagenase activity rose in the culture medium with the release of collagen breakdown products and continued long afterward. Serum in the medium significantly reduced the release of collagen degradation products to the medium and greatly lowered their specific activity. Possible mechanisms of selective collagen degradation are discussed.