Two new species of the side necked turtle genus,Bairdemys (Pleurodira, Podocnemididae), from the Miocene of Venezuela

The side-necked turtle genusBairdemys (Podocnemididae,Shweboemys Group) from the Miocene of Venezuela and Puerto Rico is revised, and four species are diagnosed on the basis of skull characters; two are de-scribed as new.B. hartsteini Gaffney &; Wood, 2002, from the Cibao Formation of Puerto Rico, is characterized by a higher skull, with a straight labial ridge and a premaxillary notch;B. venezuelensis (Wood &; Díaz de Gamero 1971), from the Urumaco Formation of Venezuela, is characterized by the absence of a premaxillary notch, a high anterior triturating surface convexity, a deep posterior triturating surface concavity, and a short pterygoid mid-line contact;B. sanchezi, new species, from the Urumaco Formation of Venezuela, is characterized by a very low anterior triturating surface convexity and shallow posterior triturating surface concavity, a premaxillary notch, small size, and extensive temporal and cheek emargination;B. winklerae, new species, from the Urumaco Formation of Venezuela, is characterized by an elongate, narrow snout, with a concave labial ridge, and no premaxillary notch. Based on osteological and bone histological results, an additional strongly crushed skull and associated cara-pace fragment of a previously undetermined podocnemidid from the Urumaco Formation of Venezuela can be further referred toPodocnemis or a closely related taxon — again underscoring the importance of this formation as one of the major fossil lagerstätten of turtles in South America.     

Direct and indirect effects of a predatory backswimmer (Notonecta maculata) on community structure of desert temporary pools

Abstract.

• 1 We assessed experimentally the effects of the predatory backswimmer, Notonecta maculata, on naturally colonizing mosquito populations in artificial outdoor pools in the Negev Desert, Israel. A single Notonecta adult per pool (8–15 litres water) had a very large negative impact on populations of Culiseta longiareolata, the most common species found in natural local pools. Notonecta caused large reductions of Culiseta egg rafts and early-instar larvae (instars I and II) and virtually 100% reductions of late-instar Culiseta larvae (instars III and IV) and pupae.
• 2 Notonecta also caused a trophic cascade in the experimental pools; by preying on periphyton-feeding Culiseta larvae, Notonecta indirectly caused significantly higher densities of diatoms, the major component of the periphyton.
• 3 Surveys of nearby natural pools taken between March and May supported the experimental results: a strong negative association between Notonecta and Culiseta among pools occurred as Notonecta increased in numbers and became more widely distributed. Anopheles (occurring only in May) and Culex mosquito immatures were not negatively associated with Notonecta. Culiseta was not associated with surface vegetation whereas both Culex and Anopheles showed strong positive associations with surface vegetation both among and within pools. We attribute the negative association between the predator and Culiseta to local prey extinctions caused by Notonecta in individual pools. Culiseta, being an open water species, is apparently more prone to predation by Notonecta than the vegetation-dwelling Culex and Anopheles.

     

Morphology and development of additional bony elements in the genus Brachycephalus (Anura: Brachycephalidae)

We describe the extra bony elements, plates, and osteoderms present in species of the genus Brachycephalus. Samples of eight species of Brachycephalus, including seven populations of Brachycephalus ephippium, were examined. The large additional elements associated with the skull (parotic plate) and vertebrae (vertebral and paravertebral plates) all comprise intramembranous bone, similar to that of the frontoparietal or nasal bones of the skull of most of frogs. Additionally, in the dermis of one unnamed species, we discovered and described true osteoderms. We discuss the morphological nature and diversity of theses elements and their importance as evidence of phylogenetic relationship within Brachycephalus. In summary, three distinct conditions of extra bony elements occur in the genus Brachycephalus: (1) bony plates may be present or absent in species of the genus; (2) a few, small bony plates may be developed and these may be represented by (a) paravertebral plates small and restricted to the distal ends of the transverse processes of the presacral IV, (b) parotic plates small and not covering the tops of the squamosals, and (c) ornamented spinal plates on all vertebrae; and (3) well‐developed bony plates may be present as (a) paravertebral plates forming a ‘bone‐shield’ on the dorsal surface of the trunk, ornamented, and visible through the integument, (b) parotic plates covering the tops of the squamosals, and (c) spinal plates associated with all vertebrae, and ornamented on vertebrate I–VI. Although the phenomenon of miniaturization may be associated with the appearance of new elements in at least some of the species in the genus, the traditional rule may not be universally applicable. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 752–767.     

The natural diet of the Notonectidae: field trials using electrophoresis

ABSTRACT.

• 1 Field trials were conducted on populations of two sympatic species of the waterbug Notonecta (Hemiptera: Heteroptera), to examine their natural diet using the electrophoretic method of gut contents analysis.
• 2 Fingerprint esterase bands were identified from thirty-three potential aquatic prey types; gut contents of different instars of both species of Notonecta from the field were analysed.
• 3 The level of prey identification possible ranged from 73% in fifth instar N.glauca L. to 100% in third instar N.viridis Delcourt.
• 4 Type A errors, where no prey remains were detected from a full gut, were found in only 3% of the specimens analysed.
• 5 Data on gut states, the number of prey types per gut and details of aquatic prey found in the diet of different instars of field-collected Notonecta are presented.
• 6 These results are compared with previous data on notonectid diets, and the relative merits of different methods of diet analysis are discussed.

     

Cannibalism as the cause of an ontogenetic shift in habitat use by fry of the threespine stickleback

Summary In Crystal Lake, British Columbia, small fry (15 mm SL) of the threespine stickleback (Gasterosteus aculeatus) are concentrated in vegetation while larger fry are not. Because fry in all size classes feed primarily on zooplankton, even when in vegetation, we hypothesized that size-limited predation was responsible for the observed shift in habitat use with size. The major predators on fry in Crystal Lake are adult threespine stickleback, the water scorpion, Ranatra sp. (Hemiptera: Nepidae), backswimmers, Notonecta spp. (Hemiptera: Notonectidae), and dragonfly naiads of the genus Aeshna (Odonata: Aeschnidae). On the basis of distribution and hunting behavior we excluded the insects Ranatra sp., and Notonecta sp. as causal agents for this shift in resource by fry in water >0.25 m deep. Ranatra was found almost exclusively near the shoreline in water <0.25 m deep, and both insects hunted primarily as ambush predators within vegetation. Such predators seemed more likely to drive vulnerable fry from vegetation than to restrict them to it. In contrast, Aeshna naiads and adult stickleback frequently hunted outside of vegetation. In prey preference experiments the naiads did not show the decline in predation efficiency on fry >15 mm SL that would be expected if size-limited predation by this insect was responsible for the observed shift in resource use by fry. Adult stickleback only fed on fry <15 mm SL, and in an experimental situation, consumed fry at a rate 10 times greater than that exhibited by any of the insects. Predation experiments demonstrated that small fry (11–15 mm) spent more time in vegetation in the presence of adult conspecifics than they did in control pools, as would be expected if size-limited cannibalism caused small, vulnerable fry to be restricted to vegetation. Fry >15 mm SL were found outside of vegetation more often than in control treatments. The probable cause of this result is that adults become aggressive toward fry at this size, and often could be seen chasing large fry from vegetation during the experiments. Dragonfly naiads (Aeshna spp.) spent most of their time in vegetation in the experimental pools. Both size classes of fry spent less time in vegetation in the presence of dragonfly naiads than they did in control treatments, an apparent reflection of their similar vulnerabilities to these naiads. The presence of vegetation in pools reduced predation rates by adult stickleback on small fry. Because the experiments presented here indicate that fry are capable of rapidly assessing predation risk and of altering their behavior adaptively, we conclude that small fry occupy vegetation as a refuge from cannibalism. Once fry have reached the size-threshold at which they are no longer vulnerable to adult conspecifics they are able to forage farther from vegetation thereby reducing risk of predation by insects in vegetation and possibly acquiring more abundant food resources.     

Fine morphology of the jaw apparatus of Puncturella noachina (Fissurellidae,Vetigastropoda)

Jaws of various kinds occur in virtually all groups of Mollusca, except for Polyplacophora and Bivalvia. Molluscan jaws are formed by the buccal epithelium and either constitute a single plate, a paired formation or a serial structure. Buccal ectodermal structures in gastropods are rather different. They can be nonrenewable or having final growth, like the hooks in Clione (Gastropoda, Gymnosomata). In this case, they are formed by a single cell. Conversely, they can be renewable during the entire life span and in this case they are formed by a set of cells, like the formation of the radula. The fine structure of the jaws was studied in the gastropod Puncturella noachina. The jaw is situated in the buccal cavity and consists of paired elongated cuticular plates. On the anterior edge of each cuticular plate there are numerous longitudinally oriented rodlets disposed over the entire jaw surface and immersed into a cuticular matrix. The jaw can be divided into four zones situated successively toward the anterior edge: 1) the posterior area: the zone of formation of the thick cuticle covering the entire jaw and forming the electron‐dense outer layer of the jaw plate; 2) the zone of rodlet formation; 3) the zone of rodlet arrangement; and 4) the anterior zone: the free scraping edge of the plate, or the erosion zone. In the general pattern of jaw formation, Puncturella noachina resembles Testudinalia tessulata (Patellogastropoda) studied previously. The basis of the jaw is a cuticular plate formed by the activity of the strongly developed microvillar apparatus of the gnathoepithelium. However, the mechanism of renewal of the jaw anterior part in P. noachina is much more complex as its scraping edge consists not just of a thick cuticular matrix rather than of a system of denticles being the projecting endings of rodlets. J. Morphol. 275:775–787, 2014. © 2014 Wiley Periodicals, Inc.     

Red imported fire ants (Hymenoptera: Formicidae) cover inaccessible surfaces with particles to facilitate food search and transportation

Eusocial insects have evolved diverse particle-use behaviors. A previous study reported that red imported fire ants, Solenopsis invicta Buren, deposited soil particles on substances treated with essential balm, a fire ant repellent. We hypothesized that S. invicta modifies inaccessible surfaces by covering them with soil particles to facilitate food search and transportation. Here, laboratory experiments were conducted to study the particle-covering behavior of S. invicta in response to viscose surfaces or surfaces treated with essential balm or liquid paraffin in the presence of real food (sausage) or non-food objects (acrylic plates). S. invicta workers deposited significantly more soil particles on these three types of treated surfaces than on untreated surfaces. In addition, significantly more particles were relocated on viscose and paraffin-smeared surfaces in the presence of food than in the presence of non-food objects. The particle-covering behavior on viscose surfaces was also observed in the field. Interestingly, when no soil particles were available, ants searched and transported food on viscose surfaces only if the surfaces were artificially covered with sufficient quantities of soil particles but could not do so on viscose surfaces without soil particles or with insufficient quantities of soil particles. In addition, ants actively relocated particles to cover viscose surfaces if the transportation distance was within 200 mm, whereas significantly fewer particles were relocated at longer transportation distances (400 mm). Our study provides a novel example of particle use by fire ants during foraging.     

The proventriculus of some trichopterous larvae

A well-developed proventriculus is present in larvae of the Polycentropodidae and Hydropsychidae. Its structure varies greatly between species but there is a common bilaterally symmetrical pattern based on a pair of posterior ventral folds. These are continuous with the sides of a ventral gap in the fold of foregut that invaginates into the midgut. Modifications of this basic structure to form either triturating or filtering devices occur, and there are others where the mechanism of food treatment is not immediately apparent and may be complex.     

Oviposition habitat selection in response to risk of predation in temporary pools: mode of detection and consistency across experimental venue

Natural selection should favor females that avoid ovipositing where risk of predation is high for their progeny. Despite the large consequences of such oviposition behavior for individual fitness, population dynamics, and community structure, relatively few studies have tested for this behavior. Moreover, these studies have rarely assessed the mode of detection of predators, compared responses in prey species that vary in vulnerability to predators, or tested for the behavior in natural habitats. In an outdoor artificial pool experiment, we tested the oviposition responses of two dipteran species, Culiseta longiareolata (mosquito) and Chironomus riparius (midge), to the hemipteran predator, Notonecta maculata. Both dipteran species have similar life history characteristics, but Culiseta longiareolata larvae are highly vulnerable to predation by Notonecta, while Chironomus riparius larvae are not. As their vulnerabilities would suggest, Culiseta longiareolata, but not Chironomus riparius, strongly avoided ovipositing in pools containing Notonecta. An experiment in natural rock pools assessing oviposition by Culiseta longiareolata in response to Notonecta maculata yielded an oviposition pattern highly consistent with that of the artificial pool experiment. We also demonstrated that the cue for oviposition avoidance by Culiseta longiareolata was a predator-released chemical: Notonecta water (without Notonecta replenishment) repelled oviposition for 8 days. Oviposition avoidance and mode of detection of the predator have important implications for how to assess the true impact of predators and for the use of commercially produced kairomones for mosquito control.     

Reconstruction of the STS 14 (Australopithecus africanus) pelvis

The study reports a reconstruction of the sacrum in STS 14 based on extrapolation from the measurements of the first two sacral vertebrae of STS 14 and of the angle formed by the anterior surfaces of their vertebral bodies. Reconstruction is based on comparisons of, and extrapolation from, sacra of Pan troglodytes, Homo sapiens, and Australopithecus afarensis. The reconstructed sacrum has an anterior sacral curvature of 39°. The two ossa coxae were also completed by mirror imaging of one side by the other. With the pelvis completely reconstructed, the pelvic dimensions for the antero-posterior (AP) diameters of the pelvic inlet, midpelvis, and pelvic outlet are 85, 68, and 69 mm and the corresponding transverse (TR) diameters are 109, 88, and 103 mm, respectively. The posterior sagittal diameters in the three pelvic planes are small compared to the anterior sagittal diameters. This analysis indicates that the STS 14 pelvis is platypelloid in the three pelvic planes; i.e., all the AP diameters are smaller than the corresponding TR diameters. This makes the STS 14 pelvis similar to that to Al 288-1, save for a less pronounced degree of platypelloidy at the inlet in the former. © 1995 Wiley-Liss, Inc.     

Surface topography of the tegument of adult Schistosoma nasale Rao, 1933 from Sri Lanka

Scanning electron microscopical studies of adult male and female Schistosoma nasale are reported. The tubercles on the dorsal and dorso-lateral surfaces of unpaired male S. nasale are devoid of spines. In paired male worms the tubercles on the dorsal surface are large and also are devoid of spines, but some tubercles on the dorso-lateral surface possess spines. Pit-like openings are visible on the surface of the smooth tubercles. The oral and ventral suckers on the male worm are well developed and are invested with spines, as are the gynaecophoric canal and flap. Ciliated sensory receptors are distributed over the surface of the male worm. The oral and ventral suckers of the female worm are much smaller than those of the male: spines occur on both suckers. The surface of the female is non-tuberculate and is thrown into transverse folds. Pit-like openings are visible at higher magnifications. The anterior end of the female is heavily invested in ciliated receptors, whereas the posterior end is heavily spined. The surface topography of S. nasale is discussed in relation to other species of Schistosoma.     

Population turnover and habitat dynamics in Notonecta (Hemiptera: Notonectidae) metapopulations

Simple metapopulation models assume that local populations occur in patches of uniform quality habitat separated by non-habitat. However field metapopulations tend to show considerable spatial and temporal variation in patch quality, and hence probability of occupancy. This may have implications for the adequacy of simple metapopulation models in describing and predicting regional population dynamics of natural systems. This study investigated the effects of habitat characteristics on landscape-scale occupancy dynamics of two species of backswimmer (Notonecta, Hemiptera: Notonectidae) in small freshwater ponds. The results demonstrated clear links between habitat, pond occupancy and population turnover, particularly local extinction. There were considerable changes in the habitat of individual ponds between years, but local changes were not spatially correlated and the frequency distribution of habitat conditions at the landscape level remained similar in different years. Stable occupancy levels of Notonecta species appears to result from a balance of the rates of creation and loss of suitable habitat due to spatially uncorrelated habitat change. Systems such as this, where turnover is driven by habitat dynamics, demonstrate the potential value of incorporating the dynamics of habitat change into metapopulation models. Such developments are likely to improve predictions of landscape-scale occupancy dynamics, whilst also allowing patch-level predictions of occupancy, based on local habitat conditions. Received: 18 August 1999 / Accepted: 3 December 1999     

Effects of predator density and duration of predator occupancy on crustacean abundance and diversity in experimental pools

Keystone predators, by reducing the abundance of competitively superior prey, may have indirect positive effects on weak competitors, possibly increasing their abundance or preventing local competitive exclusion. By analogy to the Intermediate Disturbance Hypothesis, we would expect species diversity to peak at intermediate predator densities. In a replicated artificial pool experiment, we examined the relationships between density of the backswimmer Notonecta maculata (0, 1, 2, and 4 per 30 l pool) and invertebrate taxon diversity over an 11-week period of predator occupancy. Diversity reached high levels at high predator density sooner than at intermediate density. At the end of the experiment, taxon diversity was greatest at densities of 2 and 4 Notonecta per pool. While the overall predator density–diversity curve was in line with the intermediate disturbance hypothesis, the reduction in diversity from intermediate to high predator density was not statistically significant. Density of the preferred prey Daphnia magna decreased with Notonecta density, while densities of the smaller cladocerans Moina brachiata and Ceriodaphnia spp. increased. Suppression of Daphnia at high Notonecta densities may partially explain the increase in Moina and Ceriodaphnia densities. However, most of the relationship between Notonecta and the smaller cladocerans appears to be independent of Daphnia, suggesting complex interactions within the community. Our results suggest that keystone predation plays a strong role in structuring this community. Although diversity did not decrease significantly at the highest predator density as predicted, such a decrease may be more likely for pools with longer durations of predator occupancy or with higher predator densities.     

A note on the number of retinula cells of Notonecta

Summary In each ommatidium Notonecta (Hemiptera) has eight retinula cells of two types in an asymmetrical pattern.     

Significance of head and carapace pores inCeriodaphnia (Crustacea,Cladocera)

Twelve species ofCeriodaphnia were examined by light and scanning electron microscopy for the presence of head and carapace pores. Rostral pores, similar to those in the Scapholeberinae (Dumont & Pensaert, 1983) were found in all species, situated just anterior to or between insertions of the antennules. With two exceptions, the pattern of reticulations around the pores was distinctive for each species. Oval ‘head pores’ or fenestrae occur consistently on the anterior surface of the cervical notch of juvenile and adultC. dubia, cf.dubia (from Australia),lacustris, andreticulata. The patterns of reticulations around a fenestra are unique to each species. It appears thatC. cornuta (s.l.) in the Americas has a fenestra, whereas AustralianC. cornuta (s.s.) has none. Minute pores often occur bilaterally anterior and posterior to the cervical notch in heavily reticulated individuals of several species but are not constant enough to be taxonomically useful. Well-defined small pores are situated within narrow reticulations just medial to the ventral and posterior valve margins ofC. dubia, lacustris, andreticulata. These open into carapace glands of unknown, perhaps secretory, nature. Similar glands have been observed in related taxa. Such glands and marginal pores occur only occasionally or not at all in otherCeriodaphnia. Other small pores sometimes occur among reticulations of the head, fornix, and lateral and antero-ventral surfaces of the valves. They are found more often in juvenile or heavily reticulated individuals. As yet no consistent pattern to their occurrence among species has emerged. Head and carapace pores inCeriodaphnia may be most useful in identifying species rather than in determining species groups or evolutionary patterns within the genus.     

The larval midgut of the cassava hornworm (Erinnyis ello)

Summary Columnar cells of the larval midgut of the cassava hornworm, Erinnyis ello, display microvilli with vesicles pinching off from their tips (anterior and middle midgut) or with a large number of double membrane spheres budding along their length (posterior midgut). Basal infoldings in columnar cells occur in a parallel array with many openings to the underlying space (posterior midgut) or are less organized with few openings (anterior and middle midgut). Goblet cells have a cavity, which is formed by invagination of the apical membrane and which occupies most of the cell (anterior and middle midgut) or only its upper part (posterior midgut). The infolded apical membrane shows modified microvilli, which sometimes (posterior midgut) or always (anterior and middle midgut) contain mitochondria. The cytoplasmic side of the membrane of the microvilli that contain mitochondria are studded with small particles. The results suggest that the anterior and middle region of the midgut absorbs water, whereas the posterior region secretes it. This results in a countercurrent flux of fluid, which is responsible for the enzyme recovery from undigested food before it is expelled. Intermediary and final digestion of food probably occur in the columnar cells under the action of plasma membrane-bound and glycocalix-associated enzymes.     

Ultrastructure of the vegetative organisation and initial stages of silica plate deposition in the soil testate amoebaCorythion dubium

Summary The siliceous body plates ofCorythion dubium are bound by a band of organic cement which is thickest at the lateral margins. The anterior vacuolar cytoplasm is separated by a pigment zone, which forms a dark band in the mid-body region, from the compact posterior region containing a typical vesicular nucleus surrounded by a region of dense endoplasmic reticulum. A pellicular basket of microtubules surrounds the posterior cytoplasm. The large Golgi complex lies between the nucleus and the fundus. Numerous coated and uncoated vesicles from the Golgi cisternae are seen in the peripheral cytoplasm alongside developing plates. These small siliceous plates are enclosed in silicon deposition vesicles lying in surface ruffles of the plasmalemma, often in association with a pair of microtubules. Observations are made on the formation of these vesicles and the early stages of silica deposition. A comparison is drawn between silica deposition inC. dubium and choanoflagellates where there is a similar association between silicon deposition vesicles and microtubules.     

Clonal propagation by the azooxanthellate octocoral Dendronephthya hemprichi

 The azooxanthellate octocoral Dendronephthya hemprichi (Octocorallia, Alcyonacea) is the most abundant benthic organism inhabiting the under-water surfaces of oil jetties at Eilat (Red Sea); however, it is very rare on Eilat’s natural reefs. This soft coral exhibits a newly discovered mode of clonal propagation that results in autotomy of small-sized fragments (2–5 mm in length). They possess specialized root-like processes that enable a rapid attachment onto the substrata. An autotomy event is completed within only 2 days; large colonies can bear hundreds of pre-detached fragments. Temporal fluctuations in the percentage of fragment-bearing colonies indicate that autotomy is stimulated by exogenous factors, probably flow-related events. Recruitment of fragments onto PVC plates placed horizontally adjacent to D. hemprichi colonies, was immediate and remarkably high. Attached fragments were observed 2 days after placement of plates; after 52 days, densities of more than one recruit per cm² were recorded. The negative buoyancy of fragments causes them to land on horizontal surfaces rather than on vertical ones. However, their survivorship on vertical surfaces is much higher. This pattern corresponds with dominance of D. hemprichi on vertical substrata at the oil jetties and on natural vertical reefs of the northern Red Sea. Such a mode of clonal propagation provides an efficient mean for genets of D. hemprichi to exploit food resources within a zooxanthellate-dominated reef community. Accepted: 2 February 1996     

Molecular phylogenetic study of the heterotrophic dinoflagellate genus Protoperidinium (Dinophyceae) inferred from small subunit rRNA gene sequences

In the present study, we investigated the intrageneric and intergeneric phylogenetic relationships of the heterotrophic marine dinoflagellate genus Protoperidinium. Using single‐cell polymerase chain reaction methods, we determined small subunit ribosomal RNA gene sequences for 10 Protoperidinium species belonging to four sections and two subgenera. Phylogenetic trees were constructed using maximum parsimony, neighbor joining and maximum likelihood methods. We found intraspecific variability of small subunit rDNA sequences in Protoperidinium conicum (Gran) Balech, Protoperidinium crassipes (Kofoid) Balech and Protoperidinium denticulatum (Gran et Braarud) Balech, but not in other species. The small subunit rDNA phylogeny revealed that the genus is monophyletic, but its phylogenetic position within the Dinophyceae could not be determined because of ambiguous basal topologies. Within the genus Protoperidinium, species of the subgenus Archaeperidinium with two anterior intercalary plates (2a) were shown to be monophyletic, but species of the subgenus Protoperidinium with three anterior intercalary plates (3a) were resolved as paraphyletic. The sections Avellana, Divergentia and Protoperidinium were shown to be monophyletic, while the section Conica was paraphyletic. Based on the trees obtained in the present study, most of the traditionally defined sections are supported by molecular phylogeny. It was also indicated that the section Avellana evolved from one of the Conica‐type dinoflagellates.