Features of the prosimian wrist joint in relation to hominoid specializations.

The wrist joint of lemuroid and lorisoid prosimians is examined in relation to variations among higher primates, particularly the specializations characteristic of hominoids. The lorisines Nycticebus and Perodicticus share a metrically defined primitive morphopattern with other prosimians and cercopithecine monkeys, showing little convergence on apes in carpal bone and distal radius and ulna shape.     

Surface specializations of Fundulus cells and their relation to cell movements during gastrulation

Cell movements in Fundulus blastoderms during gastrulation were studied utilizing time-lapse cinemicrography and electron microscopy. Time-lapse films reveal that cells of the enveloping layer undulate and sometimes separate briefly but remain together in a cohesive layer. During epiboly, the marginal enveloping layer cells move over the periblast as it expands over the yolk sphere. Movement occurs as a result of ruffled membrane activity of the free borders of the marginal cells. Deep blastomeres become increasingly active during blastula and gastrula stages. Lobopodia project from the blastomeres in blastulae and adhere to other cells in gastrulae, giving the cells traction for movement. Contact specializations are formed by the lateral adjacent plasma membranes of enveloping layer cells. An apical junction is characterized by an intercellular gap of 60–75 A. Below this contact, the plasma membranes are separated by 120 A or more. In mid-gastrulae, cytoplasmic fibrils occur adjacent to some apical junctions, and small desmosomes appear below the apical junction. Septate desmosomes also appear at this time. A junction with an intercellular gap of 60 A occurs between marginal enveloping layer cells and periblast. Contacts between deep blastomeres become numerous in gastrulae and consist of contacts at the crests of surface undulations, short areas of contact in which the plasma membranes are 60 or 120 A apart, and long regions characterized by a 200-A intercellular gap. Lobopodia contact other blastomeres only in gastrulae. These junctions contain a 200-A intercellular space. Some deep blastomeres are in contact with the tips of periblast microvilli. The mechanism of epiboly in Fundulus is discussed and reevaluated in terms of these observations. The enveloping layer is adherent to the margin of the periblast and moves over it as a coherent cellular sheet. Periblast epiboly involves a controlled flow of cytoplasm from the thicker periblast into the thinner yolk cytoplasmic layer with which it is continuous. Deep cells move by adhering to each other, to the inner surface of the enveloping layer, and to the periblast.     

Morphological and sensory specializations of five New Zealand flatfish species, in relation to feeding behaviour

The morphology of the feeding apparatus and sensory systems of flatfish species Rhombosolea plebeia (Richardson, 1843), Rhombosolea leporina Günther, 1862, Peltorhamphus novaezeelandiae Günther, 1862, Pelotretis flavilatus Waite, 1911 (f. Pleuronectidae) and Arnoglossus scapha (Forster, in Bloch & Schneider, 1801) (f. Bothidae) are described. The four pleuronectid species have asymmetric jaws and non-toothed gill rakers typical of benthic-feeding flatfish, while the bothid has symmetric jaws and toothed gill rakers typical of midwater-feeding flatfish. R. plebeia, R. leporina and P. novaezeelandiae have extensive external taste bud systems which facilitate non-visual prey location. External tastebuds are lacking in P. flavilatus and A. scapha ; however, these two species have relatively large, prominent eyes which facilitate visual prey location. The lateral line is well-developed in all five species, but R. plebeia, R. leporina and particularly P. novaezeelandiae have additional free neuromasts on their blind sides, which probably assist in prey location.
The feeding habits of these flatfish species closely reflect their morphological and sensory specializations. A detailed feeding study in Wellington Harbour, New Zealand showed that R. plebeia, R. leporina and P. novaezeelandiae have closely overlapping diets consisting of largely sedentary or inactive invertebrates living in the bottom sediments. In contrast, P. flavilatus and A. scapha have specialized diets of one or two species only. While the latter two species differ in that P. flavilatus is a benthic feeder and A. scapha is pelagic feeder, both are visual feeders and therefore more specialist than the other three species.     

Structures and movements of the buccal and pharyngeal jaws in relation to feeding in Diplodus sargus

The present paper studies the possibly different feeding strategies of Diplodus sargus to crustaceans, molluscs, worms, and small fish. The buccal jaws are built strongly and bound together by numerous ligaments. The dentition is heterodont: incisors in front and molars in the middle and hind parts. The principal originality of the musculature of this species is the forward insertion of the adductores mandibulae. These are very thick and insert on both the upper and lower jaws, so that contraction of any individual muscle acts on the buccal pieces as a whole, which thus constitute a remarkable crushing device. The pharyngeal jaws are frail as in primitive perciforms: the lower ones are well separated, being bound only anteriorly, while the upper ones consist of the second and third pharyngobranchials and a posterior toothed plate. When feeding on crabs, Diplodus sargus always sucks in the prey and seizes it with the buccal jaws. Mouth opening is accompanied by extensive protrusion of the mouth, with or without neurocranial elevation. Mouth sucking and seizing movements vary little. Once seized, the prey is usually moved to the molars and crushed. The crushing movements may be fast and ample or slow. In the latter case, deformation of the prey is observable. Crushing usually results in the crab being broken into pieces. The pharyngeal jaws grip one part of the prey and shift it to the oesophagus, then seize the second part. Diplodus sargus adapts its feeding behaviour to the type of prey. A snail, for instance, is crushed by the buccal or pharyngeal teeth, the pieces of shell are ejected, and the soft parts conveyed with difficulty to the oesophagus by the pharyngeal jaws. A fish on the other hand, is sucked tail first into the mouth cavity and quickly shifted to the digestive tract by the pharyngeal bones. Behaviour toward different prey differs by the presence or absence of parts of the sequence of feeding movements (for example crushing) or by the fact that certain movements or parts of the sequence are repeated. The variability of any movement in the sequence is the same whatever the sort of prey. Crushing occurs between the buccal incisors and molars and was observed twice between the pharyngeal teeth. Usually, it seems, the latter are involved in transport only. In transport, the left and right pharyngeal jaws may perform different functions: their movements, unlike the symmetrical movements of the buccal jaws, sometimes differ.     

Morphological specializations of the buccal cavity in relation to the food and feeding habit of a carp Cirrhinus mrigala: A scanning electron microscopic investigation

The buccal cavity of an herbivorous fish, Cirrhinus mrigala, was investigated by scanning electron microscopy to determine its surface ultrastructure. The buccal cavity shows significant adaptive modifications in relation to food and feeding ecology of the fish. The buccal cavity of the fish is of modest size and limited capacity, which is considered an adaptation with respect to the small‐sized food items primarily consumed by the fish that could be accommodated in a small space. Modification of surface epithelial cells, on the upper jaw, into characteristic structures—the unculi—is considered an adaptation to browse or scrap, to grasp food materials, e.g., algal felts, and to protect the epithelial surface against abrasions, likely to occur during their characteristic feeding behavior. Differentiation of the highly specialized lamellar organ on the anterior region of the palate could be an adaptation playing a significant role in the selection, retention, and sorting out of palatable food particles from the unpalatable items ingested by the fish. The filamentous epithelial projections and the lingulate epithelial projections on the palatal organ in the posterior region of the palate are considered to serve a critical function in final selection, handling, maneuvering, and propelling the food particles toward the esophagus. The abundance of different categories of taste buds in the buccal cavity suggests that gustation is well developed and the fish is highly responsive in the evaluation and the selection of the preferred palatable food items. The secretions of mucous cells in the buccal cavity are associated with multiple functions—particle entrapment, lubrication of the buccal epithelium and food particles to assist smooth passage of food, and to protect the epithelium from possible abrasion. These morphological characteristics ensure efficient working of the buccal cavity in the assessment of the quality and palatability of ingested food, their retention and transport toward the esophagus. Such an adaptation may be essential in conducting the function most basic to the survival of the individuals and species—feeding. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Archaeocete-like jaws in a baleen whale

The titanic baleen whales (Cetacea, Mysticeti) have a bizarre skull morphology, including an elastic mandibular symphysis, which permits dynamic oral cavity expansion during bulk feeding. How this key innovation evolved from the sutured symphysis of archaeocetes has remained unclear. Now, mandibles of the Oligocene toothed mysticete Janjucetus hunderi show that basal mysticetes had an archaeocete-like sutured symphysis. This archaic morphology was paired with a wide rostrum typical of later-diverging baleen whales. This demonstrates that increased oral capacity via rostral widening preceded the evolution of mandibular innovations for filter feeding. Thus, the initial evolution of the mysticetes' unique cranial form and huge mouths was perhaps not linked to filtering plankton, but to enhancing suction feeding on individual prey.     

Fuzzy set analysis of the Ethiopian rift valley vegetation in relation to anthropogenic influences

Vegetation data of the Rift Valley have been revisited using fuzzy set theory to give quantitative measures of the links between species and vegetation states. Vegetation is considered as a global indicator of both land use and natural conditions. Human activities in the area have influenced the physiognomy of vegetation so much that an apparently uniform state has developed over most of the Rift Valley floor. Fuzzy set theory has made it possible to interpret the pattern of variation in vegetation on the basis of some reference states corresponding to protected and cultivated sites. The concept of stratocoena is applied to analyse the anthropogenic influences on the tree-shrub and herb layers in order to investigate how they respond to human interference individually.     

Development of T-cell function in relation to T-cell set diversification in nu/nu mice

The differentiation pattern of splenic T-cell populations in germ- and pathogen-free nu/nu mice, as compared to nu/+ littermates, is characterized by two abnormal features: the expression of TL determinants on peripheral T cells and the delayed onset of their differentiation from the predominant Lyt-123:TL+ set into TL- cells of Lyt-1+ and Lyt-123+ phenotype, which, in these mice, does not occur until 10 weeks of age. We report here that the delayed onset of mitogen- or alloantigen-induced interleukin-2 synthesis and T-cell proliferation as well as the development of cytotoxic T-lymphocyte activity of enriched T-cell populations is strictly correlated with the time point of T-cell subset diversification in nu/nu mice and depends in particular on the presence of the Lyt-1 (TL-:Lyt-2-) T-cell set which is lacking in splenic T-cell populations of germ-free young nu/nu mice.     

Seed set in Guayule (Parthenium argentatum,asteraceae) in relation to insect pollination

Guayule (Tarthenium argentatum, Asteraceae) is one of two major plant species grown for natural rubber. Studies were conducted to determine the effect of honey bee (Apis mellifera) pollination and season on seed set and total seed yield/ha. The experiments involved four pollination treatments: plants caged with bees; plants caged without bees; plants open pollinated (uncovered); and plants individually covered. Seeds were harvested monthly July–September 1984, and May–September 1985. Plots with bees produced at least 150% more seeds than plots without bees, and there were no qualitative differences in the seed weights among treatments. Highest seed yield was in May and September. Results indicate that (1) insect pollination in guayule increases seed yield and (2) fewer seeds are produced in the warmest months.     

Development of dietary specializations in a summer community of juvenile fishes

Synopsis Patterns of food use and food availability were analysed in a species rich summer weedbed community of juvenile lake fish to elucidate ontogenetic and ecological adaptations facilitating species co-existence and rapid growth. It was found that: (a) the community was based on the period of high seasonal invertebrate abundance linked to the spring-summer proliferation of macrophytes: food was not limiting; (b) diet separations of individual fish species were high. In mid-July when nine species were present, Schoener diet overlap values exceeded 0.25 in only ten of 36 pairs of combinations. This contrasted with findings from a preceding May-June community of larval fish (Keast 1980); (c) mouth size helped channel the species towards different diets; and (d) diets of the early juveniles were distinct from those of the larvae, and late juveniles and adults of their species. At both the species and community level, ontogenetic and ecological developments have evolved in response to the opportunities created by an annually repetitive resource base.     

Leaf surface specializations of birds and Arthropods in a Panamanian forest

Summary Most species of Panamanian lowland forest birds specialize on leaf undersurfaces when hunting foliage insects. The few species of leaf surface generalists and leaf upper surface specialists are omnivorous gleaners. We estimate that while over 90% of the avian understory insectivory is directed towards leaf undersurfaces, only 50% of canopy foliage insectivory is directed towards the undersides of leaves. In the low understory we found 70–80% of the arthropods on leaf undersides. The excess use of leaf-bottoms by understory birds may be a result of their greater visibility. It is hypothesized that less proficient insectivores are unable to take advantage of the greater effective density of underleaf insects because they can only efficiently attack the closest leaf surfaces; these closest surfaces will usually be the leaf tops from the branch on which the bird is perched. Alternatively, leaf-top specialists may have special foraging adaptations for overcoming the disadvantages of leaf-top foraging. These adaptations may involve attack behavior (Tachyphonus luctuosus) or searching behavior (Dacnis cayana). Dacnis often used leaf damage as a foraging cue; this may be the first report of a bird using leaf damage for searching for insects. The greater use of leaf upper surfaces by canopy birds may be influenced by four factors: greater seasonality of insects in the canopy favoring omnivores which may be less efficient insectivores; more insects on leaf tops; fewer planar leaf arrangements in canopy plants; or the greater visibility of leaf upper surfaces of the outer shell of foliage of massive trees. Based on the greater number of arthropods on leaf bottoms in the dry season, the higher abundance of smaller insects on leaf bottoms, as well as the greater proportion of insects on leaf tops at cooler higher elevations, we suggest that arthropods prefer leaf bottoms in tropical areas for physiological, not predator avoidance reasons.     

A comparative study of allogenic "first set" and "second set" skin rejection in mice.

In our case, where the difference between donor WHT/Ht(H--2d) and recipient C57B1/6 (H--2b) was at the H--2 locus of histocompatibility, the FSg rejection occurred between the 6th and the 10th day, while the SSg rejection was two days earlier. The morphological study emphasized that the cellular infiltrate in the FSg is predominantly lymphocytic, while in the SSg it is predominantly granulocytic. The vascularization settles on the second day postgrafting in the FSg as well as in the SSg, but is scarce and quickly destroyed in the SSg, thus being explained the scanty supply of lymphocytes in the latter graft type. The histochemical reactions demonstrated an increase of the NMPS in skin allograft from the moment of settling till the end of the rejection and a decrease of AMPS, till the complete disappearance, in the rejected graft. Little morphological differences were found between colateral draining nodes and contralateral ones during the reaction to the graft. An important feature described is the presence at the bed graft level of some cells morphologically identical to the IB encountered in great number in the TDA of lymph nodes in the allograft-bearing mice.     

Seed set differs in relation to pollen and nectar foraging flower visitors in an insect-pollinated herb

Assessing the relative contributions to seed sets of each of a plant species' floral visitors provides an indication of the relative influence of these visitors on the plants' reproductive success. In this study we compared the seed set of the gynodioecious Knautia arvensis (Dipsacaceae) in 49 local plant populations in two regions of southern Sweden. We measured the seed set for hermaphroditic and female plant individuals. In both plant sexes and both regions, the seed set was positively related to the abundance of Apidae. The seed set was negatively related to the abundance of pollen-foraging solitary bees (Halictidae, Megachilidae) and beetles (Oedemeridae, Malachidae). The seed set was not related to plant population size, plant density or female frequency. Our results confirm that pollination success in generalised plant–pollinator systems varies between pollinator groups. Flower-visitors foraging for pollen might not contribute to increased pollination success in generalised pollination systems.