Differences in microhabitat,abundance, biomass and body size between oxybiotic and thiobiotic free-living marine nematodes

Summary Analysis of samples from a 15 m deep sandy bottom in the northern part of Øresund, Denmark shows that the nematode fauna comprises 2.9 million individuals per m² down to 20 cm depth which averages of 0.40 g organic carbon. Highest densities are found in the uppermost cm. Biomass attains its highest value at 1–2 cm depth. Three results are discussed: 1) nematodes in the uppermost cm are, on average, three times smaller than those between 1–8 cm depth (60 ng org. C vs. 200 ng org. C ind. weight); 2) a distinct abundance trough is found at 8 cm depth, which correlates with the physical space occupied by the gallery of the lugworm Arenicola marina as well as with its possibly unselective feeding on the interstitial meiofauna at that depth; 3) the thiobiotic (deeper-living) species are significantly more slender than the oxybiotic (surface-dwelling) species, suggesting surface-dependent adaptations to life in oxygen poor and sulphide rich sediments where large amounts of dissolved organic matter occur. This is in contrast to previous assumptions that the body length or body shape reflects adaptations to the physical constraints of interstitial space.     

Interspecific differences in prey items in relation to morphological characteristics among four lutjanid species (Lutjanus decussatus, L. fulviflamma, L. fulvus and L. gibbus)

Clarifying interspecific differences in prey items in relation to morphological characteristics is a fundamental aspect to understand the mechanism enabling the diversity of feeding ecology of fishes. The aim of the present study was to clarify the relationship between prey items and body shape variation, teeth and mandible characteristics for four lutjanid species: Lutjanus decussatus, L. fulviflamma, L. fulvus and L. gibbus. Stomach contents analysis revealed that the main prey items of L. decussatus were fishes, L. fulviflamma were crabs and fishes, and L. fulvus and L. gibbus was crabs. Body shape analysis revealed that L. decussatus and L. fulviflamma had a shallower body depth whereas L. fulvus and L. gibbus had a deeper body depth. The two species with a shallower body had long teeth whereas the other two species with a deeper body depth had shorter teeth. The jaw-lever mechanics were compared and L. decussatus and L. fulviflamma have a faster mouth opening–closing mechanism. Canonical correspondence analysis revealed that fishes was the major prey item for the species having a shallower body depth, higher teeth length and lower ratios of in-lever to out-lever of mandibles, whereas crabs was the major prey item for the species having a deeper body depth, lower teeth length and higher ratios of in-lever to out-lever of mandibles. It is suggested that the interspecific differences in main prey items among the four species are directly related to behavioral differences based on body shape, teeth characteristics and jaw-lever mechanics.     

The role of phylogeny and ecology in shaping morphology in 21 genera and 127 species of Australo‐Papuan myobatrachid frogs

Body shape is predicted to differ among species for functional reasons and in relation to environmental niche and phylogenetic history. We quantified morphological differences in shape and size among 98.5% of the 129 species and all 21 genera of the Australo‐Papuan endemic myobatrachid frogs to test the hypothesis that habitat type predicts body shape in this radiation. We tested this hypothesis in a phylogenetic context at two taxonomic levels: across the entire radiation and within the four largest genera. Thirty‐four external measurements were taken on 623 museum specimens representing 127 species. Data for seven key environmental variables relevant to anurans were assembled for all Australian‐distributed species based on species' distributions and 131,306 locality records. The Australo‐Papuan myobatrachid radiation showed high diversity in adult body size, ranging from minute (15 mm snout–vent length) to very large species (92 mm), and shape, particularly sin relative limb length. Five main morphological and environmental summary variables displayed strong phylogenetic signal. There was no clear relationship between body size and environmental niche, and this result persisted following phylogenetic correction. For most species, there was a better match between environment/habitat and body shape, but this relationship did not persist following phylogenetic correction. At a broad level, species fell into three broad groups based on environmental niche and body shape: 1) species in wet habitats with relatively long limbs, 2) species in arid environments with relatively short limbs (many of which are forward or backward burrowers) and 3) habitat generalist species with a conservative body shape. However, these patterns were not repeated within the four largest genera ? Crinia, Limnodynastes, Pseudophryne and Uperoleia. Each of these genera displayed a highly conservative anuran body shape, yet individual species were distributed across the full spectrum of Australian environments. Our results suggest that phylogenetic legacy is important in the evolution of body size and shape in Australian anurans, but also that the conservative body plan of many frogs works well in a wide variety of habitats.     

The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: the genus Ceratosoma J. E. Gray

The genus Ceratosoma (Nudibranchia: Chromodorididae) is reviewed and seven species, including two new species, are recognized. Species of the genus are known only from the Indo-West Pacific and it is suggested that the external body shape is the most useful character in distinguishing species.     

A new pronocephalid, Pleurogonius tortugueroi n. sp. (Digenea), from the intestine of green sea turtles (Chelonia mydas) in Costa Rica

A new species of trematode, Pleurogonius tortugueroi n. sp. (Digenea: Pronocephalidae) is described from the lower intestine of green sea turtles (Chelonia mydas) from Tortuguero National Park, Costa Rica. The new species differs from all other species of Pleurogonius by having a short oesophagus and oval testes close to lateral posterior limit of the body. It differs from all other species, except P. malaclemys Hunter 1961, by having an ovary between the testes; moreover the latter species is a parasite of freshwater turtles. All others members of the genus have a long oesophagus, testes placed to some distance from the posterior end, and the ovary is pretesticular. The new species appears most closely related to P. linearis Looss, 1901 but differs from it by having a different body shape, lappets of the head collar close at the cecal bifurcation level, a longer vitellarian field, different testis shape and position, ovary intertesticular, and different egg size.     

Morphology and life cycle of a new loriciferan from the Atlantic coast of Florida with an emended diagnosis and life cycle of Nanaloricidae (Loricifera)

Abstract. A new interstitial loriciferan, Nanaloricus gwenae sp. nov., is described from coarse-sand and shell-hash habitats ( Amphioxus sand), at 15–17 m depth, 6–7 miles off the coast of Fort Pierce, FL, USA. The new species is very closely related to the type species Nanaloricus mysticus found off the coast of Roscoff, France in nearly the same kind of sediment ( Dentalium sand). All life stages (Higgins larva, postlarva, and adult) in the life cycle of the new species were found through the 10-year investigation, leading to the conclusion that all species of Nanaloricidae have only a sexual reproductive cycle. The adult of the new species can be distinguished by the different body shape, the lorical spikes and sculpture, and the shape of the scalids. The postlarva has stronger longitudinal ridges on the lorical plates and the Higgins larva has toes with smaller mucrones than those of N. mysticus . An emended definition of the Nanaloricidae is provided based on the new formula of the number of rows and shape of the scalids on the introvert. The associated meiofauna found in the subtidal sand or shell hash is both abundant and diverse. Tardigrades, gastrotrichs, and kinorhynchs are among the most common associates. N . gwenae sp. nov. is represented by only eight specimens collected during a 10-year period of sampling this habitat.     

Plasticity of fish body shape. The effects of diet, development, family and age in two species of Geophagus (Pisces: Gichlidae)

Fish body shape is affected by the genetic makeup of an individual as well as environmental influences, such as diet, development, growth rate and nutrition. Fishes in the family Cichlidae exhibit tremendous morphological diversity in body shape and morphology related to feeding. Certain aspects of cichlid feeding morphology have been shown to be plastic in response to different diets but plasticity in body shape has not been examined previously. Plasticity affects ecological interactions, the direction and rate of evolution, and has ramifications for characters used in systematic studies. I examined the effect of different diets: chironomid larvae (bloodworms) and brine shrimp nauplii, on body shape in two species of the Neotropical cichlid genus Geophagus which differ in the size at which young begin feeding on external food sources. The fry of G. brasiliensis , a substrate spawner, begin to feed on external food sources earlier than the fry of G. steindachneri , a mouthbrooder. I hypothesized that the difference in size at first feeding could lead to a difference in the amount of plasticity inducible in the two species. The magnitudes of changes were mostly similar, although G. brasiliensis responded to the different diets with slightly greater changes in some of the head measurements. The pattern of changes in the two species were also similar, with fish fed ferine shrimp nauplii developing longer and shallower heads and shallower bodies and tails than fish fed chironomid larvae. I also examined the consequences of considering family and age as additional factors besides diet in G. steindachneri. Considering family or age as additional factors in the analyses did not change the conclusion that different diets induce differences, albeit small ones, in body shape. I argue that morphological plasticity is dependent on behavioural flexibility and that it may enhance evolutionary morphological diversification.     

Sexual dimorphism, reproductive biology, and food habits of two species of African filesnakes (Mehelya, Colubridae)

The ecology and general biology of African snakes remains virtually unstudied, even in highly distinctive species such as the filesnakes (genera Mehelya and Gonionotophis ). Our measurements and dissections of preserved specimens provided information on body sizes, sexual dimorphism in size and bodily proportions, clutch sizes, and food habits of two Mehelya species. In both M. capensis and M. nyassae , females attain sexual maturity at the same size as conspecific males, but grow to much larger sizes. Mehelya capensis displays extreme differences in body shape between males and females at the same body length: females have longer and wider heads, thicker bodies, and larger eyes (relative to both head length and head width) than do conspecific males. Dimorphism in body proportions is less marked in M. nyassae. Female reproductive cycles are seasonal in M. capensis , and clutch sizes are larger in this species than in its smaller congener (5-11 eggs in M. capensis , 2-6 eggs in M. nyassae ).
Contrary to popular wisdom, Mehelya are not specialized ophiophages. Mehelya nyassae feeds primarily upon lygosomatine skinks, including many fossorial taxa. Mehelya capensis has a broader diet, feeding on a wide variety of terrestrial lizards (especially agamids and gerrhosaurids) and snakes. Toads are also common prey items. The diversity of prey types taken by M. capensis suggests that these snakes may use ambush predation as well as active foraging. Mehelya is strongly convergent with Asian elapids of the genus Bungarus in its morphology (triangular body shape; powerful jaws; visible interstitial skin), behaviour (nocturnality; reluctance to bite when harassed), and diet (feeding on elongate reptiles, including snakes). Observations of preyhandling and ingestion by captive snakes are needed to clarify possible selective forces for the evolution of the unusual traits shared by these taxa.     

Left-right asymmetry of fly wings and the evolution of body axes.

The body plan of Drosophila, and presumably that of other insects, develops under the control of anterio-posterior and dorsal ventral axes, but no evidence for a left-right axis has yet been found. We used geometric morphometrics to study the wings in three species of flies: Drosophila melanogaster, Musca domestica and Glossina palpalis gambiensis. In all three species, we found that both size and shape showed subtle, but statistically significant directional asymmetry. For size, these asymmetries were somewhat inconsistent within and between species, but for shape, highly significant directional asymmetry was found in all samples examined. These systematic left-right differences imply the existence of a left-right axis that conveys distinct positional identities to the wing imaginal discs on either body side. Hence, the wing discs of Drosophila may be a new model to study the developmental genetics of left-right asymmetry. The asymmetries of shape were similar among species, suggesting that directional asymmetry has been evolutionarily conserved since the three lineages diverged. We discuss the implications of this evolutionary conservatism in conjunction with results from earlier studies that showed a lack of genetic variation for directional asymmetry in Drosophila.     

Convergent evolution of sexual shape dimorphism in Diptera

Several patterns of sexual shape dimorphism, such as male body elongation, eye stalks, or extensions of the exoskeleton, have evolved repeatedly in the true flies (Diptera). Although these dimorphisms may have evolved in response to sexual selection on male body shape, conserved genetic factors may have contributed to this convergent evolution, resulting in stronger phenotypic convergence than might be expected from functional requirements alone. I compared phenotypic variation in body shape in two distantly related species exhibiting sexually dimorphic body elongation: Prochyliza xanthostoma (Piophilidae) and Telostylinus angusticollis (Neriidae). Although sexual selection appears to act differently on male body shape in these species, they exhibited strikingly similar patterns of sexual dimorphism. Likewise, patterns of within-sex shape variation were similar in the two species, particularly in males: relative elongation of the male head capsule, antenna, and legs was associated with reduced head capsule width and wing length, but was nearly independent of variation in thorax length. However, the two species presented contrasting patterns of static allometry: male sexual traits exhibited elevated allometric slopes in T. angusticollis, but not in P. xanthostoma. These results suggest that a shared pattern of covariation among traits may have channeled the evolution of sexually dimorphic body elongation in these species. Nonetheless, static allometries may have been shaped by species-specific selection pressures or genetic architectures.     

The relationship between habitat use and body shape in geckos

Geckos are a highly diverse group of lizards, with more than 1,700 species that exhibit a wide range of behaviors, ecologies, and sizes. However, no study has examined links between habitat use and body shape in pad-bearing geckos. We set out to answer a basic question using a data set of pad-bearing geckos (112 species, 103 pad-bearing, 9 padless, 42 genera): Do geckos that occur in different habitats also differ in body shape? Overall, we found that body shape was surprisingly similar among our sample of pad-bearing species, with the exception of the genus Uroplatus, which was clearly distinct from other geckos due to its depressed body and long limbs. However, the padless geckos differed in body shape from the pad-bearing geckos by having longer arms and legs and less rotund bodies. We found that about half of the pad-bearing species primarily inhabit trees, with the other half, divided approximately equally among rocks, the ground, and mixed habitats. We found no significant links between habitat use and body shape, nor any propensity for larger species to occupy different habitats than smaller species. Padless species tend to inhabit rock and ground substrates. Our results indicate that pad-bearing geckos have a relatively uniform body form, which contrasts with to their diversity in color, size, and behavior. Indeed, our data show that the general gecko body shape is suitable for a wide range of habitats, ranging from arboreal to terrestrial. This pattern is a departure from other ecomorphological studies and suggests that geckos may not easily fit into the mold of adaptive radiation, as suggested by prior studies.     

Holosticha hamulata n. sp. and Holosticha heterofoissneri Hu and Song, 2001, two urostylid ciliates (protozoa, ciliophora) from intertidal sediments of the yellow sea

Two marine urostylid ciliates, Holosticha hamulata n. sp. and Holosticha heterofoissneri Hu and Song, 2001, were investigated using live observation and protargol impregnation. Both species were isolated from Korean intertidal sediments of the Yellow Sea. Holosticha hamulata measures about 150 x 25 mum in vivo, and is characterized by a tripartite body shape with a narrow head, an inflated trunk, and a tail that distally projects ventrally forming a hook-like structure. It is the characteristic body shape that distinguishes H. hamulata distinctly from congeners. Holosticha hamulata differs from H. heterofoissneri, possibly the nearest relative, also by the location of the contractile vacuole (ahead of mid-body versus near posterior body third) and the configuration of the macronucleus (on average, 33 scattered nodules assuming a Y-shape versus 17 nodules that may form a U shape). The average number of the macronuclear nodules is a pronounced feature showing great consistency in populations of each species. However, their arrangement is variable in H. heterofoissneri where the nodules are basically scattered or connected by fine fibers forming an elongate U-shape. The location of the contractile vacuole as a taxonomic feature is discussed and a dichotomous key to the species of Holosticha sensu stricto is provided.     

The effect of phylogeny on interspecific body shape variation in darters (Pisces: Percidae)

We conducted a geometric morphometric analysis of interspecific body shape variation among representatives of 31 species of darters (Pisces: Percidae) to determine whether there is evidence of a phylogenetic effect in body shape variation. Cartesian transformation grids representing relative shape differences of individual species and subspecies revealed qualitative similarities within most traditionally recognized taxonomic groups (genera and subgenera). Canonical variates analysis and a UPGMA cluster analysis were conducted to explore further the relationships among body shapes of species; both analyses revealed patterns of variation consistent with the interpretation that shape is associated with taxonomic affinities. Normalized Mantel statistics revealed a significant positive association between body shape differences and phylogenetic interrelatedness for each of four recent phylogenetic hypotheses, providing evidence of a phylogenetic effect. This result is somewhat surprising, however, given the largely incompatible nature of these four phylogenies. We provide evidence that this result may be due to (1) the inclusion of multiple sets of closely related species to represent the traditionally recognized genera and subgenera within each phylogeny and/or (2) the inclusion of several species with relatively divergent shapes and their particular positions within the phylogenies relative to one another or to the other species of darters.     

Influence of body mass on the shape of forelimb in musteloid carnivorans

In the majority of mammals, the limbs are positioned under the body and play an important role in gravitational support, allowing the transfer of the load and providing stability to the animal. For this reason, an animal's body mass likely has a significant effect on the shape of its limb bones. In the present study, we investigate the influence of body mass variation on the shape of the three long bones of the forelimb in a group of closely‐related species of mammals: the musteloid carnivorans. We use geometric morphometric techniques to quantify forelimb shape; then estimate phylogenetic signal in the shape of each long bone; and, finally, we apply an independent contrasts approach to assess evolutionary associations between forelimb shape and body mass. The results obtained show that body mass evolution is tightly coordinated with the evolution of forelimb shape, although not equally in all elements. In particular, the humeral and radial shapes of heavier species appear better suited for load bearing and load transmission than the ulna. Nevertheless, our results also show that body mass influences only part of forelimb long bone shape and that other factors, such as locomotor ecology, must be considered to fully understand forelimb evolution. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 91–103.     

Nacobbodera chitwoodi,n. gen., n. sp., (Nacobbidae:Nematoda) on Douglas Fir in Oregon

Nacobbodera chitwoodi, n. gen., n. sp., representing Nacobboderinae n. subfam, in the Nacobbidae, is described and illustrated from roots of Douglas fir, Pseudotsuga menziesii near Florence Oregon. This new species, having characters common to Nacobbidae, Heteroderidae, and Meloidogynidae, appears to represent a connecting link between these three families of the Heteroderoidea. Especially, a distinct tail on swollen adult females, vermiform shape of juvenile females, and the shape and sclerotization of the head of the various stages, indicate a Nacobbidae relationship. Certain other characteristics present in this new species are of the Heteroderidae and Meloidogynidae type as follows: Gross shape of adult female in posterior half of body, two ovaries, anterior position of excretory pore as in Meloidogyne females, absence of a bursa, and development of male within a sausage-shaped cuticle as in root-knot and cyst nematodes.     

Ultrastructural data on the spore of Myxobolus maculatus n. sp. (phylum Myxozoa), parasite from the Amazonian fish Metynnis maculatus (Teleostei)

Light and electron microscopy studies of a myxosporean, parasitic in the intertubular interstitial tissue of the kidney of the freshwater teleost fish Metynnis maculatus Kner, 1860 (Characidae) from the lower Amazon River (Brazil), are described. We observed polysporic histozoic plasmodia delimited by a double membrane and with several pinocytic channels and containing several life cycle stages, including mature spores. The spore body was of pyriform shape and was 21.0 microm long, 8.9 microm wide and 7.5 microm thick. Elongated-pyriform polar capsules were of equal size (12.7 x 3.2 microm) and contained a polar filament with 14 or 15 coils. The spore features fit those of the genus Myxobolus. Densification of the capsular primordium matrix, which increased in density from the inner core outwards, differentiating at the periphery into small microfilaments measuring 45 nm each, and tubuli arranged in aggregates and dispersed within the capsular matrix of the mature spores, are described. Based on the morphological differences and specificity of the host, we propose the creation of a new species named Myxobolus maculatus n. sp.     

The morphology and life cycle of Ophryodendron mysidacii sp. nov. a marine suctorian epibiont on a mysid crustacean

A new species of suctorian protist epibiont of the mysid Schistomysis parkeri is described. The individuals show two types of adult form: elongated and flattened, both with 4-8 tentacular lobes. This new suctorian differs from described species of pro-Ophryodendron group by size, number of tentacular lobes, insertion of the tentacles, union of the lorica with the body, shape of the macronucleus, number of micronuclei and the lack of stalk (adult forms). The life cycle of this species is analysed and a succession pattern of its different stages is proposed.     

Quantifying habitat structure: surface convolution and living space for species in complex environments

Habitat complexity is often used to explain the distribution of species in environments, yet the ability to predict outcomes of structural differences between habitats remains elusive. This stems from the difficulty and lack of consistency in measuring and quantifying habitat structure, making comparison between different habitats and systems problematic. For any measure of habitat structure to be useful it needs to be applicable to a range of habitats and have relevance to their associated fauna. We measured three differently‐shaped macrophyte analogues with nine indices of habitat structure to determine which would best distinguish between their shape and relate to the abundance and rarefied species richness of their associated macroinvertebrate assemblages. These indices included the physical, whole‐plant attributes of surface area (SA) and plant volume (PV), the interstitial space attributes of average space size and frequency (ISI), average refuge space from predation (Sp/Pr), and total refuge space (FFV), and the degree of surface convolution at a range of scales (i.e. the fractal dimension at four spatial scales: 7.5×, 5×, 2.5× and 1× magnification). We found a high degree of inter‐correlation between the structural indices such that they could be organised into two suites: one group describing interstitial space and surface convolution at coarse scales, the other describing whole‐plant attributes and surface convolution at fine scales. Two of these indices fell into both suites: the average refuge space from predation (Sp/Pr) and the fractal dimension at 5× magnification. These two measures were also strongly related to macroinvertebrate abundance and rarefied species richness, which points to their usefulness in quantifying habitat structure and illustrates that habitat structure depends not just on shape, but on the space associated with shape.