Functional morphology of the feeding apparatus of ten species of Pacific butterflyfishes (Perciformes,Chaetodontidae): an ecomorphological approach

Synopsis The functional morphology of the feeding apparatus and the feeding ecology of an assemblage of ten species of butterflyfishes was investigated using a comparative ecomorphological approach. Behavioral observations in situ and in vivo, morphological measurements of fresh-killed specimens, scanning electron microscopy, and kinematic modeling were utilized. The fishes show varying degrees of morphological and behavioral specialization and generalization. The more specialized species group according to how they feed, rather than what they feed on. The feeding guild concept is therefore not very instructive in understanding the functional significance of the feeding apparatus. Many of the morphologically specialized butterflyfishes demonstrate evolutionary convergence in feeding morphology. Whereas the more morphologically specialized species do generally have more ecologically specialized diets, these data do not particularly support the ecomorphological hypothesis in that similar diets do not correspond to similar morphologies.     

Functional morphology of the head of Hawaiian and Mid-Pacific butterflyfishes (Perciformes,Chaetodontidae)

Synopsis The functional morphology of the jaws of six species of butterflyfishes was investigated and related to their feeding behaviors. Utilizing observations and measurements of fresh-killed specimens as well as scanning electron microscopy of their dentitions, interspecific differences in the size, shape, orientation of the mouth, dentition, degree and function of jaw protrusion were related to their different feeding behaviors. The jaws of the six species showed a variety of adaptations for feeding on or over the reef as well as a repertoire of modulated jaw movements hitherto unnoticed in many studies. This radiation in morphologies was believed to be due to relatively simple changes of a few structural elements, changes that could occur relatively rapidly in the evolutionary time scale. The benefit of naturalistic observations in such functional morphological studies was emphasized.     

A review of hybridization in marine angelfishes (Perciformes: Pomacanthidae)

Synopsis Although hybridization of terrestrial and freshwater organisms has been well-studied, very little work has focused on hybridization among coral reef fish species. In the present paper, eleven examples of probable hybrids between marine angelfishes (Pomacanthidae) are reviewed. Evidence is presented which strongly suggests that the nominal speciesApolemichthys armitagei is invalid and that specimens previously identified as this species represent hybrids betweenA. trimaculatus andA. xanthurus. Of the remaining ten probable pomacanthid hybrids, five are inCentropyge (C. eibli x C. flavissimus, C. eibli x C. vrolikii, C. flavissimus x C. vrolikii, C. loricu0lus x C. potteri, andC. multifasciatus x C. venustus); one inHolacanthus (H. bermudensis x H. ciliaris), and four inPomacanthus (P. arcuatus x P. paru, P. chrysurus x P. maculosus, P. maculosus x P. semicirculatus, andP. sexstriatus x P. xanthometapon). An additional five examples of possible pomacanthid hybrids are described, two inCentropyge, two inChaetodontoplus and one inPomacanthus. Examination of hybrids may provide clues on reproductive behavior, dispersal capabilities, and phylogenetic relationships of species. More studies on hybridization in coral reef fish species, particularly those involving molecular techniques, are needed.     

Evolution of high trophic diversity based on limited functional disparity in the feeding apparatus of marine angelfishes (f. Pomacanthidae)

The use of biting to obtain food items attached to the substratum is an ecologically widespread and important mode of feeding among aquatic vertebrates, which rarely has been studied. We did the first evolutionary analyses of morphology and motion kinematics of the feeding apparatus in Indo-Pacific members of an iconic family of biters, the marine angelfishes (f. Pomacanthidae). We found clear interspecific differences in gut morphology that clearly reflected a wide range of trophic niches. In contrast, feeding apparatus morphology appeared to be conserved. A few unusual structural innovations enabled angelfishes to protrude their jaws, close them in the protruded state, and tear food items from the substratum at a high velocity. Only one clade, the speciose pygmy angelfishes, showed functional departure from the generalized and clade-defining grab-and-tearing feeding pattern. By comparing the feeding kinematics of angelfishes with wrasses and parrotfishes (f. Labridae) we showed that grab-and-tearing is based on low kinematics disparity. Regardless of its restricted disparity, the grab-and-tearing feeding apparatus has enabled angelfishes to negotiate ecological thresholds: Given their widely different body sizes, angelfishes can access many structurally complex benthic surfaces that other biters likely are unable to exploit. From these surfaces, angelfishes can dislodge sturdy food items from their tough attachments. Angelfishes thus provide an intriguing example of a successful group that appears to have evolved considerable trophic diversity based on an unusual yet conserved feeding apparatus configuration that is characterized by limited functional disparity.     

Dentition patterns among Pacific and Western Atlantic butterflyfishes (Perciformes,Chaetodontidae): relationship to feeding ecology and evolutionary history

Synopsis The jaw dentition of fifteen species of Pacific and Western Atlantic chaetodontid butterflyfishes was examined in light of their feeding habits and phylogenetic relationships. The ancestral tooth pattern is typical of many of the butterflyfishes, and variations on this basic pattern involve changes in the arrangement, length and number of teeth, and tooth shape to a lesser extent. Many of the more derived conditions can be explained by simple changes in relative jaw shape and size. Despite what appears to be adequate time for evolutionary changes to occur between the Pacific and Western Atlantic faunas, many species retain the generalized tooth arrangement permitting efficient exploitation in a very generalized manner. However, Pacific species as a whole show more specialized morphologies for hard coral feeding than do Western Atlantic species. Cases of parallel and divergent evolution are identified between and among the two faunas. Most morphological change associated with feeding in butterflyfishes is confined to the anterior region of the head, and particularly a few key elements. Suggestions for future morphological studies on the chaetodontids are outlined.     

The influence of prey abundance on the feeding ecology of two piscivorous species of coral reef fish

Despite the potential importance of predation as a process structuring coral reef fish communities, few studies have examined how the diet of piscivorous fish responds to fluctuations in the abundance of their prey. This study focused on two species of rock-cod, Cephalopholis cyanostigma (Valenciennes, 1828) and Cephalopholis boenak (Bloch, 1790) (Serranidae), and monitored their diet in two different habitats (patch and contiguous reef) at Lizard Island on the northern Great Barrier Reef, Australia, over a 2-year period. The abundance of the rock-cods and the abundance and family composition of their prey were monitored at the same time. Dietary information was largely collected from regurgitated samples, which represented approximately 60% of the prey consumed and were unbiased in composition. A laboratory experiment showed that fish were digested approximately four times faster than crustaceans, leading to gross overestimation of the importance of crustaceans in the diet. When this was taken into account fish were found to make up over 90% of the diet of both species. Prey fish of the family Apogonidae, followed by Pomacentridae and Clupeidae, dominated the diet of both species of rock-cod. The interacting effect of fluctuations in prey abundance and patterns of prey selection caused dietary composition to vary both temporally and spatially. Mid-water schooling prey belonging to the families Clupeidae and to a lesser extent Caesionidae were selected for over other families. In the absence of these types of prey, apogonids were selected for over the more reef-associated pomacentrids. A laboratory experiment supported the hypothesis that such patterns were mainly due to prey behaviour. Feeding rates of both species of rock-cod were much higher in summer than in winter, and in summer they concentrated on small recruit sized fish. However, there was little variation in feeding rates between habitats, despite apparent differences in prey abundance. In summary, our observations of how the feeding ecology of predatory fish responded to variation in prey abundance provide potential mechanisms for how predation may affect the community structure of coral reef fishes.     

Home range areas and activity centres in six species of Caribbean wrasses (Labridae)

In six Caribbean wrasse (Labridae) species: Halichoeres bivittatus , Halichoeres garnoti , Halichoeres maculipinna , Halichoeres poeyi , Halichoeres radiatus and Thalassoma bifasciatum , home range area ( A _HR) was positively correlated with fish total length ( L _T) and this relationship was not significantly different among H. bivittatus , H. garnoti , H. radiatus and T. bifasciatum . The data for three of these species ( H. radiatus was excluded because only juveniles were investigated) were pooled and the relationship between L _T and A _HR was analysed for juveniles and initial phase (IP) adults separately. This analysis found that once individuals of these two species become IP adults, the A _HR reached a plateau, despite continued fish growth. In a separate analysis including all six wrasse species, after accounting for differences in L _T using ANOVA, it was found that IP adults required larger areas than juveniles, and terminal phase (TP) adults required larger A _HR than IP adults. Upon analysis of the distribution of activity throughout A _HR for all species studied, it was found that 50% of the observation points (defined as the activity centre) were found in 13 to 24% of the A _HR.     

Reproductive ecology of the three Nordic Pinguicula species (Lentibulariaceae)

Reproductive ecology (pollination biology, breeding systems, and reproductive effort and success) of the three Nordic species of Pinguicula, P. alpina, P. villosa , and P. vulgaris (Lentibulariaceae), was investigated in a subarctic-subalpine area at Abisko, N Swedish Lapland. Additional studies were carried out at Latnjajaure Field Station, a subarctic-alpine tundra site in the Abisko mountains ( P. alpina, P. vulgaris ), and in W Greenland ( P. vulgaris ). At Abisko the species are sympatric and large populations of all three were found within a 50 × 50 m area. The three species are reproduc-tively isolated by internal barriers by occupying different ploidy levels. Pinguicula alpina and P. vulgaris thrive in base-rich habitats, whereas P. villosa is restricted to nutrient-poor Sphagnum bogs, but habitat separation alone is probably not sufficient to prevent illegitimate pollen flow among the species. However, results showed that there are large and consistent differences in pollination biology, flowering phenology, and breeding systems, and these factors interact to create a highly efficient reproductive isolation at all levels, pre-zygotic as well as post-zygotic. Pinguicula alpina is an early-flowering outbreeder, P. vulgaris is an opportunistic late-flowering inbreeder, and P. villosa is quite intermediate between the two extremes. The phenology-based life history strategies of the Pinguicula species were in accordance with a general model developed for arctic flowering plants, predicting maximized fitness through pollen or seed in early- and late-flowering species, respectively.     

The feeding behaviour of New Zealand Dolomedes species (Araneae: Pisauridae)

Abstract

The prey spectrum and predatory behaviour of Dolomedes sp. (‘D. III’), D. aquaticus, and D. minor are described from a series of field and laboratory investigations, the former made around Nelson and on Banks Peninsula, Canterbury, during summer months. All species are large, robust spiders that capture prey by directly seizing it in their mouthparts, not using silk at any stage of predation. Adult aquatic insects are their main prey, but these are available only irregularly during their activity period (night-time), and the spiders are opportunistic in their feeding habits. They will eat virtually any available small animal, and at least the largest species, D. III, is able to capture and ingest small fishes. Dead as well as live organisms are taken. Furthermore, the spiders are capable of feeding infrequently; when feeding on small prey organisms they may capture several sequentially, to increase the size of the meal. Live prey is caught while it is in flight, or on the ground, or at the water surface (rarely submerged), and is detected primarily by touch and airborne sound; vision is unnecessary for normal predation. Prey is captured very rapidly, even though this may initially involve a dash of up to 40 cm across the water surface to locate the organism. Stages in the behaviour of an active spider, from waiting for prey to grooming after ingestion, are described.     

The ontogeny of feeding behavior and cranial morphology in the leopard shark Triakis semifasciata (Girard 1854): A longitudinal perspective

While much is known about the ecological and functional morphology of feeding in lower vertebrates, studies of elasmobranch feeding over ontogeny are broadly lacking. In this study, the ontogeny of feeding behavior and morphology were investigated in neonatal and young-of-the-year leopard sharks Triakis semifasciata using morphometric measurements of growth and high-speed videography in a longitudinal study. Five food types were used during filming sessions to facilitate differentiation of modulation and variation over ontogeny. Functional aspects of muscle and buccal volume scaling were investigated through dissection. Growth over ontogeny was shown to influence numerous kinematic variables, while intra- and inter-individual variability was the dominant factor affecting feeding behavior. Modulation of feeding behavior based on food size and elusiveness was present for timing variables and predator motion during the strike, but not for food motion or the relative extent of buccal expansion. Allometric growth occurred in all aspects of external cranial morphology measured, resulting in a shallower head profile, anterior displacement of the mouth, and relatively larger jaw musculature over ontogeny. While the degree to which morphology constrains or enhances behavior cannot be directly quantified, variability in behavior greatly exceeds variability in morphology over early ontogeny. Maintenance of a behaviorally and morphologically versatile feeding apparatus throughout ontogeny is proposed to enhance the exploitation of resources and facilitate a diverse diet in T. semifasciata under variable environmental conditions.     

Karyotypes of three species of the family Cottidae (Scorpaeniformes)

Karyotypes and cellular DNA contents of three species of the family Cottidae viz.Icelus cataphractus, Gymnocanthus intermedius andAlcichthys alcicornis were analyzed. Structural modifications within the family were supposedly by Robertsonian translocations. The diploid chromosome numbers were determined to be 48 inAlcichthys alcicornis, 44 inGymnocanthus intermedius and 40 inIcelus cataphractus. The DNA contents ranged from 1.46 to 1.50pg/cell in the three species. The karyotype ofIcelus cataphractus is unique in having the smallest chromosome number (2n = 40) and 14 large-sized chromosomes. From the chromosome number and the existence of some large chromosome pairs, Robertsonian translocations seem to have occurred frequently inIcelus cataphractus andGymnocanthus intermedius.     

The ecology of the visual pigments of snappers (Lutjanidae) on the Great Barrier Reef

The visual pigments in the retinal photoreceptors of 12 species of snappers of the genus Lutjanus (Teleostei; Perciformes; Lutjanidae) were measured by microspectrophotometry. All the species were caught on the Great Barrier Reef (Australia) but differ in the colour of the water in which they live. Some live in the clear blue water of the outer reef, some in the greener water of the middle and inshore reefs and some in the more heavily stained mangrove and estuarine water. All the species had double cones, each member of the pair containing a different visual pigment. Using Baker's and Smith's (1982) model to predict the spectral distribution of ambient light from chlorophyll and dissolved organic matter it was found that the absorption spectra of the visual pigments in the double cones were close to those that confer the maximum sensitivity in the different water types. Single cones contained a blue or violet-sensitive visual pigment. The visual pigments in the rods showed little variation, their wavelength of maximum absorption always being in the region 489–502 nm.Abbreviations DOC dissolved organic carbon - DOM dissolved organic material - MSP microspectrophotometry deceased     

Callionymus omanensis,a new species of dragonet from Oman,north‐western Indian Ocean (Teleostei: Callionymidae)

A new species of deep‐living dragonet Callionymus omanensis from Oman is described on the basis of a single male specimen collected in a trawl from 500 m depth off the coast of Oman. The new species is characterized within the subgenus Bathycallionymus by having a small branchial opening; head short (3·9 in proportion to standard length); eye large (2·4 in proportion to head length); preopercular spine with a long, upcurved main tip, with a small antrorse barb and a larger antrorse spine, and with a strong antrorse spine laterally at the preopercular‐spine base, ventral margin smooth; first dorsal fin slightly higher than second dorsal fin (male); second dorsal fin distally straight; 17 pectoral fin rays; distal end of caudal fin slightly pointed, with two median unbranched rays bearing short filaments; first dorsal fin with basal black spot reaching from first to fourth membranes, third membrane with an ocellated distal black blotch; second dorsal fin with vertical dark grey bars; distal three‐fourths of anal fin black; upper half of caudal fin with oblique dark grey bars; pelvic fin dark grey, second ray basally with a black blotch. The new species is compared with similar species. Revised keys to callionymid species of the western Indian Ocean and the Red Sea, as well as species of the subgenus Bathycallionymus, are presented.     

The hyolaryngeal apparatus of three species of Scinax (Scinaxinae: Hylidae: Anura) and comparison with other Hylidae species

The hyolaryngeal apparatus includes the arytenoid, cricoid and hyoid cartilages, and varied sizes and shapes can be distinguished between species. Although the larynx is an important morphological structure for sound production in frogs, few studies describe the structures and processes of its parts in hylids. We studied the hyolaryngeal anatomy of both males and females of Scinax ruber (Laurenti, 1768), using clearing and double staining methods, comparing it with that of Scinax wandae (Pyburn and Fouquette, 1971), Scinax kennedyi (Pyburn, 1973) and other hylid species. We found that S. ruber has the largest arytenoid cartilage of any species of the subfamily Scinaxinae studied to date. We described both the laryngeal differences among three Scinax species and the interspecific variability in the shapes of the projections of the arytenoid in the males of these species. The taxonomic characters (presence/absence of processes of the cartilage of Santorini, oesophageal process or bronchial processes) described here can play a key role in differentiating these species from Scinax species and from other species. In addition, we want to contribute to the natural history and comparison of the larynges in Scinax and within the genus and the Hylidae.     

Arnhemtrachia ramingining: a new genus and species of land snail from Arnhem Land,Australia (Stylommatophora: Camaenidae)

The new, monotypic camaenid genus Arnhemtrachia is described for the new species Arnhemtrachia ramingining from Ramingining, Arnhem Land, Northern Territory, Australia with additional records from the Gove Peninsula in eastern Arnhem Land. This camaenid is characterised by a combination of distinct morphological features, such as a small, discoidal, keeled shell with regular axial ribs, open umbilicus and simple, rounded aperture as well as a reproductive system with a long epiphallus possessing a long flagellum and absence of a penial sheath, with a flap on the penial wall which transverses longitudinal pilasters, and a long, simple bursa copulatrix. Based on comparative morphology, Arnhemtrachia reveals affinities with Trozena morata Iredale, 1838 from NE Queensland.     

Biology and ecology of three species of Australian Dragonets (Pisces: Callionymidae)

Callionymus sublaevis, C. calcaratus and C. calauropomus collected from Moreton Bay and offshore Queensland, were studied biologically and ecologically and the findings compared with other callionymid fishes from Australian waters and other areas. Predominant preys types included penaeid prawns, pelecypods and poly-chaetes. Differences in temporal feeding intensity and prey types eliminated competition in some cases. Through brain pattern analyses, these callionymids were shown to be predominantly sight feeders even at depth, although gustatory feeding also increased slightly with depth. Sex ratios in C. sublaevis were almost even, while C. calauropomus had a predominance of males. C. calcaratus had a predominance of females, but considerable variation occurred on a seasonal basis. Although considerable variation was found in spawning times and spawning period length, the histological changes that occurred in the development of oocytes was similar. The ovarian cycle in C. sublaevis was studied in detail and found to be typical of most teleosts. Length-weight regression coefficients in all species were significantly higher than 3.0, indicating that the weight increased faster than the cube of their length. In all cases females were heavier in older fish with the least difference in length-weight occurring between the males and females of C. calcaratus. Otoliths were found to be satisfactory and reliable for use as a method for age and growth determinations in two of the callionymids studied. Overlap of age groups was found in all species and this was mostly attributed to the length of spawning period. The dragonets studied here all reached age group IV+ and attained maturity usually by the second year. No evidence was found to indicate that males die after spawning as has been shown in C. lyra. Observations on predation by benthic piscivorous fishes and by one avian predator are reported.     

The feeding ecology of Axiothella rubrocincta (Johnson) (Polychaeta: Maldanidae)

The feeding ecology of Axiothella rubrocincta (Johnson) from Tomales Bay, California, is described. This worm inhabits a U-shaped tube of agglutinated sand grains and mucus. Morphological adaptations such as nuchal and anal plaques prevent the tube from becoming clogged. Foreign debris entering the tube is either consumed or incorporated into the tube wall. The proboscis and notosetae are probably used to clean the tube wall. A. rubrocincta combines feeding and burrowing activities to form the funnel and complete the tube: it does not ingest sediment while burrowing. Organic matter deposited into the funnel is buried there by sand slides originating at the rim of the funnel. The concentration of organic matter within the funnel is significantly higher than for non-funnel sediments. A. rubrocincta consumes food from the upper 2 cm of the substratum and is 4.6% efficient as a depositfeeder. It also feeds within the funnel and can ingest large quantities of food. This feeding process is described. A. rubrocincta irrigates its tube at a rate of 5.1 ml sea water/g/h while feeding, and briefly reverses this current to a rate of 0.1 ml/g/h when defaecating. The rhythmic activity patterns are integrated: the mean defaecation and inverse pumping time is 14.4 min at 15 ± 1 C.     

The behavioral ecology of three Indian Ocean surgeonfishes (Acanthurus lineatus,A. leucosternon and Zebrasoma scopas): their feeding strategies,and social and mating systems

Synopsis The relationship between the morphology, feeding strategies and social and mating systems of three surgeonfishes was investigated. Adults of each defend feeding territories, intra-and interspecifically. The largest species, because of its morphological limitation, relies on food that has to be defended against many other species. It forms large colonies in which fishes singly defend small territories containing high standing crop algal mats. Colony formation is a mechanism by which the efficiency and effectiveness of interspecific territory defense is increased. The smallest species, because of its morphological adaptations, is able to rely most on food that other species cannot efficiently exploit. It forms pairs that defend large territories containing a thin algal mat. It is restricted to the poorest quality habitat by the aggressive activities of more dominant species. The third species, which also forms pairs, has an intermediate feeding strategy. The local coexistence of these three and other surgeonfishes results from a combination of (i) their partitioning both habitat and food resources, and (ii) the populations of two of the most dominant species apparently being below the carrying capacity. Territoriality and the absence of parental care facilitates pair formation in surgeonfishes. Permanently territorial species usually form pairs. The colonial species does not form pairs because the colonial habit facilitates interference of males in each other's spawnings.