Functional response of suspension feeding anuran larvae to different particle sizes at low concentrations (Amphibia)

The influence of particle size, initial particle concentration and larval stage on the ingestion rate, ‘retention efficiency’, and filtering rate of anuran larvae with varying filter apparatus anatomy and different life histories was investigated for four species. Larvae of premetamorphic Stages 28 and 32 and prometamorphic Stage 40 were selected for filtering experiments on the basis of their different growth rates. Three different sizes of silica gel particles were offered as mock food. Particle concentration was measured photometrically. The Michaelis-Menten model was used to describe the dependency of ingestion rate, filtering rate, and ‘retention efficiency’ upon initial particle concentration, and to calculate maximum ingestion rate, threshold concentration, and the half-saturation constant. (1) The highest ingestion rates, filtering rates and ‘retention efficiencies’ were achieved by Xenopus laevis larvae, followed by Bufo calamita larvae. Bufo bufo larvae lay at the opposite end of the scale. Rana temporaria larvae were placed between B. calamita and B. bufo larvae. This order is attributed to differences in life histories, especially the different breeding environments in which these larvae occur. (2) The larger the particle size and the older the stage, the greater the tendency toward saturation of the ingestion rate, filtering rate and ‘retention efficiency’. These filtration parameters are graded according to particle size. The ingestion rate (number of particles), filtration rate and ‘retention efficiency’ are greatest for PS3. Ingestion volume is greatest for PS 1. The difference between PS3 and PS2 on the one hand, and PS1 on the other, is often great; for Stage 28 X. laevis it is very great. This shows that larvae ingest large particles more effectively, and that the most effective ingestion takes place at Stages 28 and 32, owing to the growth function of these stages. The ability of larvae to ingest large particles effectively is possibly a very basic phylogenetic characteristic. (3) The threshold concentration is lowest when the particles are at their largest. In accordance with conclusions drawn by other authors, threshold feeding is attributed to regulation by buccal pumping and mucus production. Considerable importance is attributed to threshold feeding with respect to larval adaptation to oligotrophic environments.     

Xenopus laevis larvae (Amphibia,Anura) as model suspension feeders

Larvae of the South African clawed frog, Xenopus laevis (Daudin), are efficient, obligate suspension feeders. We examine the relationship between the ambient particle concentration offered these larvae as food and their filtering, ingestion, and buccal pumping rates. We demonstrate that: (i) the larvae can sense and respond to a broad range of particle concentrations, down to 0.2 mg 1^–1 (dry weight); (ii) their metabolic needs theoretically can be met by particle concentrations as low as 5 mg 1^–1; and (iii) their patterns of regulation of filtering and ingestion fit predictions from certain models used to describe zooplankton feeding dynamics. Two such models are discussed: the modified Monod (Michaelis-Menten) model, with a lower threshold below which the tadpoles do not feed, and an energy optimization model. Both the models and the observed behavior of the tadpoles allow for stability of populations of food organisms. Tadpole feeding dynamics apparently are compatible with both the predictions and assumptions of these models, suggesting similar regulation of feeding by tadpoles and zooplankton. However, the size, morphology, and behavior of X. laevis larvae make their feeding regulation uniquely accessible to direct observation.Contribution No. 223, Center for Great Lakes Studies, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin.Contribution No. 223, Center for Great Lakes Studies, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin.     

The ontogeny of the filter apparatus of anuran larvae (Amphibia,Anura)

Summary The pharynx ofBufo calamita, Rana temporaria andBombina variegata larvae (larval Types IV and III) changes considerably during the latter part of embryonic development. The entodermal regions between the visceral pockets flatten inward to form the anlagen of the filter plates. The ectoderm thrusts forward from the area of the persistent epidermal gills overlying the anlagen of the filter plates. The esophagus pushes dorsolaterally into the pharynx to give rise to the ciliary cushions. Comparison with the development ofXenopus laevis (larval Type I) reveals shared characters: (1) the filter plates are overlapped by the sensory layer of the epiderm and (2) the ciliary grooves are, like the ciliary cushions of larval Types III and IV, anteriorly directed dorsolateral extensions of the esophagus. In all the species studied an ectodermal-esophageal filter apparatus develops. The evolutionary origin of this filter apparatus is discussed. The epidermalization of gills is suggested as a common character with the sister group of Dipnoi, and is therefore a plesiomorphic character in all amphibians. The tendency of filter plate epidermalization is considered to be the end of a process which is also indicated in the epidermalization of the first visceral pouch in lung fish. The ciliary groove is unique in anuran larvae within the Lissamphibia, and is therefore seen as an autapomorphic character within amphibians. On the basis of the different structure of the ciliary cushion inX. laevis and in the other species of this study, two alternative levels of evolutionary ciliary groove origin are discussed. Derivation from the esophagus took place: (1) in a common anuran larval ancestor, or (2) at two independent levels; the first in the Pipidae (-Rhinophrynidae) ancestor and the second in the ancestor of all the other anuran families. Several larval characters and cladistic aspects make the first alternative more probable than the second. Larval Type II anatomy and Larval Type II truncation from the Larval Type IV of Ranoidea do not contradict these considerations. There is disproportionately early commencement of ingestion activity inR. temporaria (G Stage 23),B. calamita (G Stage 23), andB. bufo (G Stage 24) compared toXenopus. Feeding in the former three species precedes the differentiation of the filter plates, their mucus production, and the exhaustion of the yolk supply in the gut tissue. By contrast, the goblet cells and the ciliary cells of the ciliary cushions are already differentiated when feeding starts. This suggests that ingestion in these early stages requires mucus production by the ciliary cushions and transport by their ciliary cells. Presumably in fully formed larvae, the ciliary cushions are the mucus donors, whereas the filter plates are the mucus depositors. By contrast,X. laevis does not begin active food intake by suspension feeding until after the yolk supply has been used up from the entoderm of the buccal cavity to deep in the esophagus.Abbreviations AAC anlage of apical cell - AC apical cell - ACE anlage of cerebrum - ACG anlage of ciliary groove - AD aorta dorsalis - ADV anlage of dorsal velum - AG anlage of glottis - AFP anlage of filter plates - AFR anlage of filter rows - AFPC anlage of epidermal fold of peribranchial chamber (anlage of operculum) - ant. anterior - AMF anlage of middle fold - AO adhesive organ - APEG anlage of persistent epidermal gills - APOP anlage of postnarial papilla - APSF anlage of primary side fold - ASC1 anlage of Type 1 secretory cell - ATE anlage of tuba Eustachii - ATEG anlage of transient epidermal gills - AVV anlage of ventral velum - B branchial arch - BI-IV branchial arches I–IV - BFA buccal floor arena - BFT branchial food trap - BL basal lamina - BRA buccal roof arena - C cilium, cilia - CA cartilage of visceral arch - CC ciliary cushion - CE cerebrum, brain - CG ciliary groove - CH choana - CHY ceratohyale - CIC ciliary cell - CL capillary vessel - CN centriole, basal body - COC cuboidal cells - CT connective tissue - CTC connective tissue cell - d dorsal - DV dorsal velum - DVI–III dorsal vela I–III - E esophagus - e early - ED edge of filter plate - EN endothelium - ENC entodermal cell - EP epiderm - EPC epidermal cell - ER endoplasmatic reticulum - ET erythrocyte - ETZ ectodermal-entodermal transition zone - EV ear vesicle - EX merocrine extrusion - EY eye - EZ zone of extrusion - FP filter plate - FPII filter plate of the 2nd branchial arch - FPIV filter plate of the 4th branchial arch - FPC epidermal fold of peribranchial chamber (operculum) - FC filter cavity - FN filter niche - FR filter row - GL glottis - GS gill slit - 1. GS first gill slit - GZ glandular zone - H heart - HP hypobranchial plate - HY hyoid arch - IC intercellular space, enlarged by fixation and dehydration - L late - LJ lower jaw - LT larval type - LV lipid vacuole - M mitochondrion - MA mandibular arch - MF middle fold - med. median - MS microvillous stubs - MZ zone of microtubes - NAC nucleus of apical cell - NCIC nucleus of ciliary cell - NCL nucleus of capillary vessel - NCOC nucleus of cuboidal cells - NCT nucleus of connective tissue - NENC nucleus of entodermal cell - NEPC nucleus of epidermal cell - NO external nares - NPEC nucleus of periderm cell - NRC nucleus of random cell - NSC1 nucleus of Type 1 secretory cell - NSC3 nucleus of Type 3 secretory cell - NSLC nucleus of sensory layer cell - NSPC nucleus of supporting cell - NSQC nucleus of squamous epithelial cell - OC oral cavity - OS mouth - P papilla - PC peribranchial chamber - PCW peribranchial chamber wall - PE periderm - PEC periderm cell - PEG persistent epidermal gill - PG pigment granule - post. posterior - PS primary side fold - PH pharynx - RC random cell - RO rootlet - SC1 Type 1 secretory cell - SC2 Type 2 secretory cell, goblet cell - SC3 Type 3 secretory cell - SC4 Type 4 secretory cell - SG secretory groove - SL sensory layer - SLC sensory layer cell - SP secretory pit - SPC supporting cell - SQC squamous epithelial cell - SR secretory ridge - SRC secretory ridge cell - SS secondary side fold - ST. stage - STD stomodeum - SU spiculum of hypobranchial plate - T tentacle - TA anlage of tongue - TEG transient epidermal gill - TZ transitional zone of branchial food trap and ventral velum - UJ upper jaw - v ventral - VA visceral arch - VC vacuole - VPI–IV visceral pockets I–IV - VP visceral pocket - VV ventral velum - YV yolk vacuoles Supported by the Deutsche Forschungsgemeinschaft (DFG)     

Growth interactions among blue-green (Anabaena Oscillarioides,Microcystis aeruginosa) and green (Chlorella sp.) algae

The growth interactions amongst the blue-green algal species Anabaena oscillarioides, Microcystis aeruginosa and the green alga, Chlorella sp. were studied both in mixed cultures and in filter cultures separated by a membrane filter in the two arms of an interaction U-tube. The role of nutrients especially phosphate upon the interaction has also been studied. Anabaena and Microcystis both inhibited the growth of Chlorella while Microcystis also inhibited the growth of Anabaena. The inhibitory effect of Microcystis was found to be dependent on high concentrations of the initial algal inocula and independent of the initial concentration of nutrients such as inorganic phosphate, indicating that the nature of the inhibition is probably due to the production of inhibitory extracellular products by Microcystis. On the other hand, the inhibitory effect of Anabaena on Chlorella is the consequence of nutrient competition with Anabaena competing more effectively for the available phosphate.     

Interfacial feeding behavior and particle flow patterns ofAnopheles quadrimaculatus larvae (Diptera: Culicidae)

The interfacial feeding behavior, mouthpart movements, and particle flow patterns of Anopheles quadrimaculatuslarvae were investigated, using videotape recordings, high-speed microcinematography, SEM, and laboratory experiments. While positioned at the water surface, larvae demonstrated 12 behaviors associated with movements of the head. In one of these, a larva rotated its head 180° and directed its mouthparts against the air-water interface. The larva rapidly extended and retracted its lateral palatal brushes (LPBs) at a rate of 5 cycles/s (5 Hz), creating currents and allowing for the collection of particles. Particles moved toward the head at a velocity of 4.31 mm/s, in discrete stops and starts, as the LPBs beat. Our analyses determined that particle movement toward the mouth was governed by very low Reynolds numbers (0.002–0.009). This finding indicated that viscous forces predominated in Anophelesfeeding and no inertial movement of particles occurred. According to this model, the LPBs cannot intercept particles directly, but function as paddles for particle entrainment. We did not observe the pharynx to function in particle filtration but, rather, in food bolus formation. We propose that the maxillary pilose area and midpalatal brush function as interception structures. It appeared that the LPBs do not break the surface film to feed, but collect particles from the surface microlayers. A plume of uningested particles emerged from the sides of the cibarium and descended into the water column. The plume consisted of alternately clear and dark, lenticular laminae formed beneath the larval head during the collecting filtering feeding mode. A comparison of particle sizes from surface microlayers and gut contents of fourth instars showed that larvae ingested mainly small particles in the range of 1.5 to 4.5 pm in diameter. The potential significance of interfacial feeding by anopheline larvae in their aquatic environment is discussed.     

Suspension feeding in Bithynia tentaculata (Prosobranchia,Bithyniidae), as affected by body size,food and temperature

The suspension feeding of Bithynia tentaculata was tested in laboratory experiments. The animals were fed in 1-1 aerated glass beakers, and filtration rates were calculated from changes in cell concentrations during the 6-h experiment. Temperature influenced the filtering rate, with minimum values of 5ml · ind^–1 · h^–1 at 5° C and maxima of 17.2 ml · ind^–1 · h^–1 at 18° C. Three food species of different size, motility and cell surface characteristics (Chlamydomonas reinhardii, Chlorella vulgaris and Chlorogonium elongatum) did not affect filtration rates. Suspension feeding increased with increasing food concentrations up to 12 nl · ml^–1, above which feeding rate was kept constant by lowering the filtering rates. Even the smallest animals tested (<4 mm body length) were found to be feeding on suspended food at a rate of 2.7 ml · ind^–1 · h^–1, and increasing rates up to 8.4 ml were found in the 6–7 mm size class. All size classes of Bithynia showed a circannual fluctuation of their filtration rates. The ecological consequences of Bithynia's ability to switch between two feeding modes, grazing and suspension feeding, are discussed.     

Activity and swimming speed at time of first feeding of halibut (Hippoglossus hippoglossus) larvae

Atlantic halibut larvae show an increase in activity, together with a decrease in swimming speed during active periods, occurring from day 26 onwards, which corresponds approximately to 50% yolk absorption.     

Phylogenetic relationships of Oriental torrent frogs in the genus Amolops and its allies (Amphibia, Anura, Ranidae)

We investigated the phylogenetic relationships among 20 species of Oriental torrent frogs in the genus Amolops and its allies from China and Southeast Asia based on 1346-bp sequences of the mitochondrial 12S and 16S rRNA genes. Oriental species of the tribe Ranini form a monophyletic group containing 11 clades (Rana temporaria + Pseudoamolops, R. chalconota, four clades of Amolops, Meristogenys, three clades of Huia species, and Staurois) for which the phylogenetic relationships are unresolved. The genus Amolops consists of southern Chinese, southwestern Chinese, Thai, and Vietnamese-Malaysian lineages, but their relationships are also unresolved. The separation of southern and southwestern lineages within China conforms to previous morphological and karyological results. Species of Huia do not form a monophyletic group, whereas those of Meristogenys are monophyletic. Because P. sauteri is a sister species of R. temporaria, distinct generic status of Pseudoamolops is unwarranted.     

Genotype versus phenotype variability in Chlorella and Micractinium (Chlorophyta, Trebouxiophyceae)

The most recent revision of the genus Chlorella, based on biochemical and SSU rDNA analyses, suggested a reduction to a set of four "true" spherical Chlorella species, while a growing number of morphologically different species such as Micractinium (formerly Micractiniaceae) were found to cluster within the clade of "true"Chlorella. In this study, the generic concept in Chlorellaceae to Chlorella and Micractinium was evaluated by means of combined SSU and ITS-2 rDNA sequence analyses and biotests to induce development of bristles on the cell wall. Molecular phylogenetic analyses of Chlorella and Micractinium strains confirmed their separation into two different genera. In addition, non-homoplasious synapomorphies (NHS) and compensatory base changes (CBC) in the secondary structures of SSU and ITS-2 rDNA sequences were found for both genera using this approach. The Micractinium clade can be differentiated into three different genotypes. Using culture medium of the rotifer Brachionus calyciflorus, phenotypic plasticity in Chlorella and Micractinium was studied. Non-bristled Micractinium cells developed bristles during incubation with Brachionus culture medium, whereas Chlorella did not produce bristles. Grazing experiments with Brachionus showed the rotifer preferred to feed on non-bristled cells. The dominance of colonies versus solitary cells in the Micractinium culture was not correlated with the "Brachionus factor". These results suggest that morphological characteristics like formation of bristles represent phenotypic adaptations to the conditions in the ecosystem.     

Development and variation of the anuran webbed feet (Amphibia, Anura)

Webbed feet evolved convergently in most groups of aquatic tetrapods. However, extensive webbing is not always limited to an aquatic life style. In Anurans, hind limbs display great variation, including absence, of interdigital membranes, which is explained by differential growth rates of digital and interdigital tissues during early limb development. In order to explore web diversification in anurans, this paper presents analyses of: (1) hind limb early development and its relationship to the expression of interdigital membranes; (2) intraordinal variation of interdigital membranes in adult feet; and (3) intraordinal variation of metatarsal and digit lengths, including comments on metatarsal development. Study of limb development is carried out in larval series of 12 anuran species. Analysis of intraordinal variation comprises a sample of adults of 111 species. We recognize two configurations in the autopodium bud: (1) paddle-like shape with digits differentiated within the confines of interdigital tissues, and (2) pointed autopodium with digits differentiated beyond interdigital tissues. These early differences are conserved in adult morphology, in which allometry and isometry of digit IV (and metatarsal IV) with respect to other digits (and metatarsals) result in asymmetrical and paddle-like autopodium, respectively. The paddle-like autopodium is restricted to fossil and extant pipids and the hylids Pseudis and Lysapsus , whereas the asymmetrical one is present in most anurans. Both configurations seem to represent an early divergence of the autopodium shape. The paddle-like configuration observed in hylids appears as a reversion to an ancient condition that results from a conserved program of limb development.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 39–58.     

Survival, activity and feeding ability of Baltic cod (Gadus morhua) yolk-sac larvae at different salinities

Due to unfavourable conditions (declines in salinity and water oxygen content) in the spawning areas, there has been a considerable decrease in the Baltic cod stock since the beginning of the 1980s, and consequently a decrease in catches. In order to examine the feasibility of introducing yolk-sac larvae in areas of low salinity to improve the stock, laboratory experiments were performed on the effects of salinity on the survival, level of activity and feeding ability of larvae. Yolk-sac larvae from spawning cod caught off northern Gotland, Sweden, were exposed to four different salinities: 10 and 15%○ (salinities of the main spawning areas); and 5 and 7%○ (salinities in the Bothnian Sea and the Baltic proper respectively).
The survival of yolk-sac larvae was high at all salinities, even though there was an indication of higher mortality at low salinities in less viable larval groups. No differences were found in swimming speed or feeding ability at the four salinities, but a significant difference in vertical distribution was recorded. There were significant differences in survival, vertical distribution and feeding ability among larval groups, which indicates that larval quality or viability is of greater importance for larval survival than salinity, in the range of 5–15%○.     

Antioxidant effect of the marine algae Chlorella vulgaris against naphthalene-induced oxidative stress in the albino rats

Alcoholic extract of the marine algae Chlorella vulgaris was examined for its free radical scavenging effect with reference to naphthalene-induced lipid peroxidation in serum, liver, and kidney of rats. Initially, upon naphthalene intoxication (435 mg/kg body weight, intraperitoneally), the lipid peroxidation activity increased significantly (P < 0.001), and in contrast, the enzymic antioxidants (superoxide dismutase, catalase, glutathione peroxidase) and non-enzymic antioxidants (glutathione, ascorbic acid, and α-tocopherol) levels decreased remarkably. When the naphthalene stressed rats were treated with Chlorella vulgaris extract (70 mg/kg body weight, orally), the lipid peroxidation activity reduced significantly (P < 0.001) and the activities of both the enzymic and non-enzymic antioxidants increased reaching near control values. The minimum concentration (70 mg/l) of the extract that exhibited maximum (85%) free radical scavenging activity was chosen for the experimental study. The present results suggest that Chlorella vulgaris extract exerts its chemo-preventive effect by modulating the antioxidants status and lipid peroxidation during naphthalene intoxication.     

O-Dealkylation of coumarin and resorufin ethers by unicellular green algae: kinetic properties of Chlorella fusca and Chlorella sorokiniana

O-Dealkylations of resorufin and coumarin ethers, mediated by microsomal cytochrome P450 mono-oxygenases from animals, plants and microorganisms, are shown here to be performed also by intact cells of the unicellular green algaeChlorella fusca andChlorella sorokiniana. The activity of theO-dealkylation of these ethers was up to tenfold higher withChlorella sorokiniana. Both algae dealkylated methyl-, ethyl-, and pentylethers of resorufin and coumarin. Dealkylation in vivo indicated efficient absorption of methoxy- and ethoxyresorufin, confirmed by the respective absorption kinetics. Piperonylbutoxide and 1-aminobenzotriazole, known inhibitors of plant and mammalian cytochrome P450s, significantly inhibited theO-dealkylase activity of both algal strains. The use of synchronized cultures of both algae revealed that efficiency ofO-dealkylation depends on the stage of the cell cycle: during the growth phase, theO-dealkylase activities increased more than proportional, and the distinct drop in activity during the last hours of the light period indicated the appearance of an endogenous substrate.     

Improving glycogenesis in Streptozocin (STZ) diabetic mice after administration of green algae Chlorella

Chlorella, a type of unicellular fresh water algae, has been a popular foodstuff in Japan and Taiwan. Studies have shown the hypoglycemic effects of Chlorella in alloxan-induced and Streptozocin (STZ)-induced diabetic animals. However, the mechanisms by which Chlorella treatment affects blood glucose homeostasis have not been studied. Diabetes in ICR mice was induced by injection of STZ. Lipogenesis in vivo was measured by incorporating 3H-H2O into lipids in brown and white adipose tissues. Glucose uptake in the liver and soleus muscles was measured by assaying 2-deoxy-D-[1,2-3H] glucose levels. The effects of Chlorella on serum non-esterified fatty acids (NEFA) were measured with commercial assay kits. Insulin-stimulated lipogenic rates in brown and white adipose tissues were unaffected by Chlorella. However, Chlorella increased 2-deoxyglucose uptake in the livers and soleus muscles in normal and STZ mice compared to that in their respective controls (p < 0.01). In addition, fasting NEFA levels were lower in Chlorella-treated STZ mice compared to H2O-treated STZ mice (p < 0.005). The current results suggest that the hypoglycemic effects of Chlorella are due to an enhancement of glucose uptake in the liver and in soleus muscles. The improved insulin sensitivity after Chlorella treatment could be also due to lower NEFA levels, since insulin sensitivity is usually blunted by elevated NEFA in diabetes.     

Morphological aspects of feeding and improvement in feeding ability in early stage larvae of the milkfish,Chanos chanos

The osteological development of elements comprising the oral cavity and fins was examined in early stage larvae of laboratory-reared milkfish,Chanos chanos, from hatching to 200 hours after hatching. Fundamental elements of the oral cavity had developed by the time of initial mouth opening, 54 hours after hatching. The oral cavity was long and cylindrical, with a short, robust Meckel's cartilage, and robust quadrate and symplectic-hyomandibular cartilages. The initial ossification of existing elements and addition of new elements occurred between 120–146 hours after initial mouth opening (HAMO), whereas the cartilaginous basihyal and caudal fin-supports appeared at 37.5 and 61.5 HAMO, respectively. Based on the morphology and developmental patterns of characters examined in this study, the feeding mode of early stage larval milkfish was considered to be “straining,” with an improvement in feeding ability occurring between 120–146 HAMO.     

Cytological evidence for population-specific sex chromosome heteromorphism in Palaearctic green toads (Amphibia,Anura)

A chromosome study was carried out on a number of European and Central Asiatic diploid green toad populations by means of standard and various other chromosome banding and staining methods (Ag-NOR-, Q-, CMA₃-, late replicating [LR] banding pattern, C- and sequential C-banding + CMA₃ + DAPI). This study revealed the remarkable karyological uniformity of specimens from all populations, with the only exception being specimens from a Moldavian population, where one chromosome pair was heteromorphic. Though similar in shape, size and with an identical heterochromatin distribution, the difference in the heteromorphic pair was due to a large inverted segment on its long arms. This heteromorphism was restricted to females, suggesting a female heterogametic sex chromosome system of ZZ/ZW type at a very early step of differentiation.     

The food and feeding habits of Eutropius niloticus (Ruppell), family Schilbeidae (Osteichthyes: Siluriformes) in Lake Kainji,Nigeria

Studies on the food and feeding habits of Eutropius niloticus in Lake Kainji, Nigeria revealed that the fish is omnivorous but fed more on insects than on any other food. The most important insects were Povilla adusta Navas nymphs and imagos and adults of the common grasshoppers. Fish, particularly the clupeids Sierrathrissa leonensis Thys Van den Audernaerde and Pellonula afzeliusi Johnels, also formed an important part of the diet. There was seasonal variation of organisms selected for food and there were variations in the dietary items selected by different age groups. Accumulation of fat was found to correlate with seasonal feeding intensity. E. niloticus serves as food for other fishes.     

Chromosomal rearrangements as the source of variation in the number of chromosomes in Pseudis (Amphibia, Anura)

A cytogenetic study of Pseudis specimens from three localities in Rio Grande do Sul State, the southernmost Brazilian, was performed to identify karyotypic characteristics that could account for differences in vocalization pattern and body size. Individuals from around Tainhas were compared to those of São Jerônimo and Eldorado do Sul. Specimens from these latter two localities were identified as Pseudis minuta, while those from the former were classified as Pseudis sp. (aff. minuta). The populations from São Jerônimo and Eldorado do Sul had 2n?=?24 chromosomes, classified as metacentric, submetacentric and subtelocentric. The population from Tainhas had 2n?=?28 chromosomes, with four pairs of telocentric chromosomes. Modelling of these 28 chromosomes and testing for fusion in the centromeric/telomeric regions yielded a karyotype of 2n?=?24 chromosomes, similar to that of the other populations. The similarity was reinforced by the location of the NORs and heterochromatin. The Tainhas population showed an increase in heterochromatin, as seen by the presence of additional C-bands, especially in the telocentric chromosomes. These data suggest that the two karyotypes described in this work had a common ancestry. There is evidence that the differentiation of these karyotypes may have occurred by chromosome fission and heterochromatin addition. Based on the present karyotype (2n?=?28) and on morphological and vocalization studies by other researchers, we conclude that the Tainhas population may represent a new species.     

Metal concentrations in Sargassum algae from coastal waters of Nha Trang Bay (South China Sea)

The concentrations of metals, viz., Fe, Mn, Cu, Zn, Cd, Pb, and Ni, were investigated in brown algae of the genus Sargassum collected in the coastal waters of Nha Trang Bay (South China Sea). Metal concentrations in algae growing in the zone of influence of the city of Nha Trang were higher than those in macrophytes collected to the south and north of the city. Similar levels of Cu and Fe concentrations were observed in macrophytes from the urbanized coastal areas of Nha Trang Bay and in algae from the Peter the Great Bay (Sea of Japan). This is suggestive of comparable metal inputs from the anthropogenic sources of the cities of Nha Trang and Vladivostok (Peter the Great Bay). However, the concentrations of Pb, Ni, and Cd in algae from the coastal waters of Nha Trang Bay were lower than in macrophytes from the inshore zone of Vladivostok. The high level of pollution of sea water with Zn compounds near Nha Trang was local. The metal levels in macrophytes from background areas reflect the geochemical features of the environment. Sargassum algae from Nha Trang Bay had lower concentrations of Zn, Cd, and Ni and higher concentrations of Mn than algae from Peter the Great Bay. The background concentrations of Cu, Pb, and Fe in macrophytes from both bays were virtually the same.