Narrower Head Research Articles

Fitness consequences of individual specialisation in resource use and trophic morphology in European eels

Individual specialisation can lead to the exploitation of different trophic and habitat resources and the production of morphological variability within a population. Although the ecological causes of this phenomenon are relatively well known, its consequences on individual fitness are less recognised. We have investigated the extent of individual specialisation in resource use and trophic morphology and its fitness consequences through a combination of tagging-recapture, stable isotope analyses and telemetry. The European eel (Anguilla anguilla) was the model species as it displays significant variability in head shape. Independent to their body length, individuals with broader heads displayed a significantly higher trophic position (δ(15)N) than individuals with narrower heads. This corresponded with a significantly higher proportion of prey fish in their diet compared with invertebrates and was associated with the use of a habitat niche located further from the river bank. The European eel therefore provides a rare empirical example of individual specialisation in resource use and trophic morphology in a natural population occurring at a very small spatial scale. Individuals with intermediate head morphology displayed lower body condition (a proxy of fitness) than individuals with extreme head morphology (i.e. narrower and broader headed individuals), demonstrating the existence of disruptive selection associated with individual specialisation.

A New Species and Variety of Senecio (Asteraceae) from Patagonian Argentina

Two novelties in the genus Senecio L. sect. Senecio of Patagonia (Argentina) are described and illustrated: a new species, S. breviramulus Tortosa & Adr. Bartoli belonging to series Xerosenecio (Cabrera) Cabrera & S. E. Freire, and the new variety pinohachense Tortosa & Adr. Bartoli for S. volckmannii Phil. belonging to series Suffruticosi Cabrera subser. Candidi (Cabrera) Cabrera & S. E. Freire. The new species is allied to S. covasii Cabrera and S. pumilus Tortosa & Adr. Bartoli, from which it differs by the smaller, narrowly elliptic leaves and narrower heads with fewer flowers. The new variety of S. volckmannii differs from the typical variety by the presence of female ray florets and the pedunculate capitula.

Lek behavior in hypercephalic Zygothrica dispar Wiedemann (Diptera, Drosophilidae)

In the Neotropical drosophilid secies Zygothrica dispar the males, many of which are hypercehalic, engage in territorial fights on mushrooms. In an attempt to see whether head width effects mating success, lek behavior was videorecorded. Most owners of a territory on the cap of a mushroom are broad-headed, and usually defeat intruders, which in general have a narrower head. Escalation in confrontation to bodily contact is rare and mostly involves opponents of equal head width. Most contests between unequals end after a close head-to-head confrontation, and are thus purely ritual. Females appeared to be courted only on the lek. Although no female was observed to copulate, it can be supposed that male head width influences fitness through its effect on owning a territory on the lek.

Morphometric and Meristic Differences among Bluehead Suckers, Flannelmouth Suckers, White Suckers, and Their Hybrids: Tools for the Management of Native Species in the Upper Colorado River Basin

AbstractHybridization with nonnative fishes is a major factor influencing the status of native catostomids in the Colorado River basin. In Wyoming, hybridization with nonnative white suckers Catostomus commersonii is a particular concern in the conservation of native bluehead suckers C. discobolus and flannelmouth suckers C. latipinnis. The purpose of this study was to describe the meristic and morphometric characteristics of bluehead suckers, flannelmouth suckers, white suckers, and their hybrids from Muddy Creek, Wyoming, for which genotypic data were available to verify the classification of individual fish as pure species or hybrids. We also sought to develop discriminant function models that can be used in the field. Bluehead suckers and flannelmouth suckers had more lateral line scales, shorter and narrower heads, and narrower caudal peduncles than white suckers. Bluehead suckers and bluehead sucker × white sucker hybrids had a cartilaginous biting ridge in their mouth. Important characteristics for discriminating among these taxa included the number of postdorsal lateral line scales and the exterior width of the mouth. The discriminant function correctly classified 100% of the bluehead suckers and bluehead sucker × white sucker hybrids. Flannelmouth suckers, white suckers, and flannelmouth sucker × white sucker hybrids lacked a cartilaginous biting ridge. The number of postdorsal scales, caudal peduncle depth, and ratio of mouth length to the interior width of the mouth discriminated among taxa without a ridge. The discriminant function correctly classified 100% of the flannelmouth suckers, 92% of the white suckers, and 91% of the flannelmouth sucker × white sucker hybrids. None of the white suckers or flannelmouth sucker × white sucker hybrids were misclassified as flannelmouth suckers. Our results suggest that native bluehead suckers and flannelmouth suckers, nonnative white suckers, and hybrids of these species can be accurately identified by a few, easily measured meristic and morphometric characteristics.

Ecomorphology of the Moray Bite: Relationship between Dietary Extremes and Morphological Diversity

The pharyngeal jaws of moray eels function exclusively to transport prey from the oral jaws into the esophagus. This functional innovation in the moray pharyngeal jaw system occurred through the loss of some ancestral functions that presumably included prey processing. Therefore, the oral jaws of morays are used to capture and process prey. Dietary accounts suggest that morays can be categorized as either piscivorous or durophagous in feeding habits. These extreme feeding specializations that select for conflicting biomechanical demands on the oral jaws should result in two discrete clusters of cranial form and diet in morphospace. When functional characters underlying the oral jaws were examined for 10 muraenid species, piscivorous and durophagous morays occupied distinct areas of morphospace. Piscivores exhibited longer jaws, narrower heads, and long recurved teeth, while durophagous morays exhibited shorter jaws, greater dentary depths, and short blunt teeth. Durophagous morays process prey in their oral jaws, and their jaw-opening and jaw-closing ratios, along with their enlarged adductors, revealed jaws modified for force transmission. Pharyngeal jaw characters also separated moray species into different areas of morphospace. For example, Gymnomuraena zebra, a molluscivore, had more teeth on its pharyngobranchials than all other morays, and these teeth were long and thin compared with those of piscivores. The overall patterns of morphological variation corresponded well with moray dietary breadth. In addition, the range of jaw-opening and jaw-closing ratios revealed that for a clade of obligate carnivores, morays exhibit diverse biting behaviors.

The Alabama Bass, Micropterus henshalli (Teleostei: Centrarchidae), from the Mobile River basin

The Alabama Bass, Micropterus henshalli, was diagnosed as a subspecies of Micropterus punctulatus from the Mobile River basin, Alabama, Georgia, and Mississippi, USA, by Hubbs and Bailey (1940). The species has been introduced in the Chattahoochee River, as has the Spotted Bass, Micropterus punctulatus. Micropterus henshalli differs from M. punctulatus, with which it has been aligned, by having higher scales counts, a narrower head, smaller scale width, higher gill raker count, and a smaller tooth patch. It also has a narrower and more elongate body shape than does M. punctulatus. The Alabama Bass is relatively common in streams and rivers throughout the Mobile River basin.

Two new species of large green canopy-dwelling frogs (Anura: Hylidae: Litoria) from Papua New Guinea

Litoria graminea is a large green canopy-dwelling frog originally described from a single specimen from an unknown locality in Papua New Guinea. We demonstrate that this species as currently recognised contains at least three distinct taxa. We restrict the name L. graminea to a population of animals occurring south of New Guinea’s main cordillera and describe two new species of large green arboreal frogs, one from the Kikori River Basin (Southern Highlands and Gulf Province) and one from the Huon Peninsula (Morobe Province). The two new species can be distinguished from each other by differences in iris and sclera colouration, and both can be distinguished from L. graminea by their narrower heads, different iris colouration and by their small round (vs elongate) nuptial pads.

Pseudolaguvia ferula, a new species of sisoroid catfish (Teleostei: Erethistidae) from India

Pseudolaguvia ferula, a new species of erethistid catish, is described from the Brahmaputra River drainage in India. It can be distinguished from congeners in having a terete (vs. depressed) head and body, manifested in the narrower head width (17.1–19.1% SL vs. 19.4–23.4), a smaller anterior fontanel (about one third the length of the frontals vs. at least half the length), and very faint, poorly contrasting cream bands that are sometimes absent on some individuals (vs. sharply contrasting cream bands on a brown body). It can be further distinguished from congeners in having a unique combination of the following characters: dorsal-spine length 17.3–18.7% SL, pectoral-spine length 20.2–24.3% SL, pelvic-fin length 13.0–14.7% SL, length of adipose-fin base 11.5–13.0% SL, caudal peduncle depth 6.9–7.8% SL, body depth at anus 12.1–13.8% SL, eye diameter 8.6–11.7% HL, vertebrae 28–30, and thoracic adhesive apparatus reaching to midway between bases of last pectoral-fin ray and first pelvic-fin ray. with its unculiferous ridges joined at their posterior ends.

A Morphometric Comparison of Island and Mainland Boas (Boa Constrictor) in Belize

Relative to mainland Boa constrictor, boas from islands off the coast of Belize are described as being smaller, having longer tails, more elongate snouts, and proportionately larger eyes. However, no systematic confirmation of these patterns has been made. A morphometric study was initiated to investigate the body size and head shape variation between island and mainland boas in Belize. One hundred twentynine boas from five islands and the mainland were caught and measured. Univariate and multivariate analyses indicated that, in general, previous descriptions are accurate. Island boas are about half the length and one-fifth the mass of mainland boas. In contrast to mainland boas, no sexual size dimorphism is evident in island boas. The head shape of island boas differs from that of mainland boas but this divergence is not consistent among populations. Some island boas have more attenuate snouts compared to mainland boas whereas other island boas have larger eyes and narrower heads. Male island boas have longer tails compared to males from the mainland, but such a difference is not found in females from the two localities. The morphology of island boas is consistent with an arboreal habit and reduced prey size. Because these changes have occurred over an extremely short time interval, this may be another example of the speed and magnitude of adaptation that is possible in squamates.

Variation of Morphology among Juvenile Chinook Salmon of Hatchery, Hybrid, and Wild Origin

AbstractBody morphology differed significantly between juvenile hatchery Chinook salmon Oncorhynchus tshawytscha that have experienced five generations of hatchery culture and juveniles derived from the wild founding stock and cultured in the same environment. All lines tested were raised in a similar hatchery environment. Thin‐plate spline analysis was used to characterize the morphometric variation among these lines of fish. Hatchery fish had a more compressed body, a narrower head, shorter maxillae, and a longer and narrower caudal peduncle than wild fish. Canonical discriminant analysis was able to correctly classify 88% of hatchery fish and 90% of wild fish. Second‐generation hybrids of the two lines were morphologically intermediate to but significantly different from both the hatchery and wild lines, and they appeared to be more similar to the wild line. These results suggest that the differences observed between lines are largely genetic in origin and may be a result of the divergence of the hatchery stock from the founding wild stock. In addition, family of origin had a significant effect on body morphology.

Revision of the Deep-Sea Anglerfish Genus Acentrophryne Regan (Lophiiformes: Ceratioidei: Linophrynidae), with the Description of a New Species from off Peru

The deep-sea ceratioid anglerfish genus Acentrophryne is revised on the basis of all known material. Two species are recognized: the type species Acentrophryne longidens, represented by two specimens collected in the Gulf of Panama and from off the Pacific coast of Costa Rica and a new species described here on the basis of three specimens, all from off Peru. The new species differs from A. longidens in having a much longer distal escal appendage, a longer illicium, a narrower head, and fewer pectoral-fin rays. Diagnoses and descriptions are given for all taxa and a key to the species is provided.

Plasticity in newt metamorphosis: the effect of predation at embryonic and larval stages

Summary1. Some organisms under variable predator pressure show induced antipredator defences, whose development incurs costs and may be associated with changes to later performance. This may be of especial relevance to animals with complex life histories involving metamorphosis.2. This study examines the effect of predation environment, experienced both during embryonic and larval stages, on palmate newt (Triturus helveticus) metamorphosis. Newt eggs were raised until hatching with or without exposure to chemical cues from brown trout (Salmo trutta), and larval development was monitored in the presence or absence of the cues.3. Exposure to predator cues during the embryonic stage resulted in higher growth rates at the larval stage, reduced time to metamorphosis and size at metamorphosis. Metamorphs also had narrower heads and shorter forelimbs than those from predator‐free treatments. In contrast, exposure to predator cues during the larval stage did not affect metamorph characteristics.4. These results indicate that developing embryos are sensitive to predator chemical cues and that the responses can extend to later stages. Reversion of induced defences when predation risk ceased was not detected. We discuss the possible adaptive significance of these responses.

A new Stomatorhinus (Osteoglossomorpha: Mormyridae) from the Ivindo River, Gabon, West Central Africa

Stomatorhinus ivindoensis n. sp. is described from the basin of the Ivindo River, a tributary of the Ogooué River, in Gabon, West Central Africa. This species is characterized by its very small size which is not known to exceed 56 mm standard length. It is distinguished from S. fuliginosus from the Congo basin, the only described Stomatorhinus for which all members of the type series are within the size range of S. ivindoensis, by a smaller caudal peduncle depth to length ratio, a narrower head, a greater number of lateral line scales with visible tubes and pores and by rounded caudal fin lobes. It is distinguished from the similar S. polli, also from the Congo basin, by a longer snout, a smaller eye and a greater interorbital width relative to head length. It is distinguished from S. walkeri, the only other species described from the Ogooué River basin, by its smaller size, smaller snout to pectoral fin distance (relative to standard length) and by its reduced numbers of pectoral rays, vertebrae, and lateral line scales with visible tubes and pores. Stomatorhinus ivindoensis is endemic to the Ivindo River basin of Gabon and is allopatrically distributed with respect to S. walkeri which, although found elsewhere in the Ogooué River basin, has never been recorded from the Ivindo River. Stomatorhinus ivindoensis may be the smallest species of mormyrid fish yet described.Stomatorhinus ivindoensis n. sp. est décrite de la rivière Ivindo, un affluent du fleuve Ogooué, au Gabon, Afrique Centrale. Cette espèce est caractérisée par sa très petite taille, qui ne dépasse pas 56 mm en longueur standard. Elle se distingue de S. fuliginosus du bassin du Congo, la seule espèce de Stomatorhinus décrite dont l’intervalle de taille des spécimens types est compris dans celui de S. ivindoensis, par un rapport largeur sur longueur du pédoncule caudal plus petit, une tête plus étroite, un nombre d’écailles percées le long de la ligne latérale plus grand et une nageoire caudale aux lobes arrondies. Elle se distingue de S. polli, une autre espèce similaire du bassin du Congo, par un museau plus long, un oeil plus petit, et une distance interorbitale plus grande par rapport à la longueur de la tête. Elle se distingue de S. walkeri, la seule autre espèce de Stomatorhinus décrite du

Modeling the Air-Jet Flow Field of a Dual Slot Die in the Melt Blowing Nonwoven Process

An air-jet How field model of the dual slot die in the melt blowing nonwoven process is proposed and solved numerically with the finite difference method. The effects of dual slot die design parameters on velocity and temperature distributions in the melt blowing flow field are investigated. The computation results of the distributions of the x-compo nents of air velocity and air temperature coincide well with our experimental data. The results show that a smaller angle α, a larger slot width e, and a narrower head width f will all result in higher x-components of air velocity and higher air temperatures, which are beneficial to the air drawing of the polymer melt and thus to reduced fiber diameter. The results show the great potential of this research for computer-assisted design in the melt blowing nonwoven technology.

Morphological caste and sex differences in the Taiwanese stingless bee Trigona ventralis hoozana (Hymenoptera: Apidae)

AbstractTo examine morphological differences among queens, workers and males, 14 external body characters were measured in two colonies of the Taiwanese stingless bee Trigona ventralis hoozana. Queens were largest in all of the body parts measured except eye width and mesoscutum length, and values for most variables in queens did not overlap with those of workers and males. In contrast, the worker : male size ratios for 11 variables were close to 1.0, showing that overall body size and shape of workers resembled that of males rather than of queens. Males had the largest eyes and their mesoscutum length was comparable to that of queens. ancova between 14 morphometric variables and mesoscutum width chosen as standard body size showed that allometric growth in most variables was not linear. Plotting of some variables on mesoscutum width showed that queens had a proportionally wider first metasomal tergum and longer antennal scape, but a proportionally narrower head and eye than workers and males. These tests suggest that the morphological caste differences in this species belong to a category of complete dimorphism.

Two new soleid flatfishes (Pleuronectiformes: Soleidae: Soleichthys) from Australian waters, with a re-description of Soleichthys microcephalus (Günther)

Soleichthys microcephalus (Gunther, 1862) occurring in warm temperate waters off New South Wales, Australia, is re-described based on examination of a syntype and additional non-type material. This species differs from congeners in its combination of: low meristic features (43-45 vertebrae, 71-84 dorsal-fin rays, 61-71 anal-fin rays, and 81-89 lateral-line scales); in having two elongated ocular-side pectoral-fin rays of nearly equal length; with small scales present on the ocular-side pectoral- fin base and proximal halves of elongated pectoral-fin rays; in its ocular-side pigmentation consisting of a series of 8-10 mostly complete, bold, wide, dark-brown or blackish crossbands of nearly uniform width throughout their lengths and noticeably wider than the alternating lighter-coloured crossbands; and with two, conspicuous, mid-lateral white spots arranged in horizontal series. Two new species phenotypically most similar to, and with meristic features that largely overlap those of S. microcephalus, are described from specimens collected in tropical waters of northern Australia. Soleichthys serpenpellis n.sp., known from the Gulf of Carpentaria and Delambre Island, Dampier Archipelago, northwestern Australia, is easily distinguished from S. microcephalus and other congeners by its ocular-side head and body pigmentation featuring incomplete, diamond-shaped crossbands broadest in their mid-sections, fewer (about 6) ocular-side body crossbands, and with small, brown spots scattered in the interspaces between the crossbands. Soleichthys oculofasciatus n.sp. occurs off northeast Australia and is distinguished from congeners in its combination of a first elongate ocular-side pectoral-fin ray longer than the second, in lacking scales on the ocular-side pectoral-fin base and elongate pectoral-fin rays, in having a longitudinal series of crossbands (usually 11) on the ocular-side head and body, and with four conspicuous white spots on the body, two of which are arranged in a vertical series at mid-body. The new species differs further from both S. microcephalus and S. serpenpellis in having a longer and narrower head and a longer caudal fin.

Stability in In-Stack Biased CPP SV Heads

In this paper, we present a quantitative micromagnetic modeling analysis of head stability in in-stack biased current perpendicular to plane (CPP) spin valve (SV) heads at deep submicron track widths. It is found that sufficient pinning on the in-stack bias layer is the key for stability. The narrower track-width heads have better stability. For in-stack biased bottom SV heads, the conventional structure has serious stability problem due to weakened or reversed bias field at free layer track edge. Controlling CPP edge profile is crucial for stability. We also studied the effect of current field on head performance. Depending on the current direction, current field can either induce instability or assist head stability.

A new species of the Asian catfish genus Pseudolaguvia from Myanmar (Teleostei: Ostariophysi: Siluriformes: Erethistidae)

A new species of the erethistid catfish genus Pseudolaguvia from Myanmar is described. Pseudolaguvia tenebricosa, new species, from Pathe Chaung, Lower Myanmar, differs from the only congener P. tuberculata (Prashad & Mukerji, 1929) in having an adipose fin not reaching dorsal fin, and a narrower head with a shorter snout.

Kryptopterus geminus, a new species of silurid catfish (Teleostei: Siluridae) from mainland Southeast Asia

Kryptopterus geminus, a new species of silurid catfish is described from the Bang Pakong, Mekong, Mae Khlong and Chao Phraya River drainages in mainland Southeast Asia. Kryptopterus geminus, together with K. cryptopterus, can be distinguished from congeners by the dorsal profile lacking a nuchal concavity and short maxillary barbels extending to the base of the pectoral fin. Kryptopterus geminus can be further distinguished from K. cryptopterus in having a narrower head (9.5– 12.0% SL vs. 12.2–14.2), longer anal fin (62.2–72.7% SL vs. 57.2–62.9) and snout (39.5–45.3% HL vs. 35.1–39.8), and more laterally-placed eyes (only ventral half, vs. ventral two-thirds, of the orbital margin visible when the head is viewed ventrally).

BODY SIZE, SEXUAL DIMORPHISM, AND CLUTCH SIZE IN TWO POPULATIONS OF THE LIZARD SCELOPORUS OCHOTERANAE

Abstract We studied 2 populations of Sceloporus ochoteranae to determine if there were differences in body size, sexual dimorphism, and clutch size. Males were larger and had larger heads than females. Sceloporus ochoteranae from the Canon del Zopilote (elevation 600 m) were smaller, had narrower heads and longer femurs, and had smaller clutches than those from Acatlan (elevation 1,250 m).