Spatial and trophic niche differentiation in two sympatric lizards (Tropidurus torquatus and Cnemidophorus ocellifer) with different foraging tactics

Abstract In a ‘restinga’ habitat of southeastern Brazil, we studied the food habits and the microhabitat use of two lizards with distinct foraging modes: the tropidurid Tropidurus torquatus, a sit-and-wait predator, and the teiid Cnemidophorus ocellifer, a wide forager. The diet of the two species differed strongly, indicating a low level of similarity in their trophic niche. The sit-and-wait predator fed mainly on mobile prey, whereas the wide forager fed mainly on sedentary prey (larvae). The spatial niche breadth of T. torquatus was larger than that of C. ocellifer. Despite interspecific differences, the two species overlapped greatly in micro-habitat use. The data indicate that at Linhares the two lizard species differed more in food resources than in microhabitat, and that most of the food differences reflect the foraging patterns of the species.     

Morphology,performance, fitness: functional insight into a post-Pleistocene radiation of mosquitofish

Bahamas mosquitofish (Gambusia hubbsi) colonized blue holes during the past approximately 15 000 years and exhibit relatively larger caudal regions in blue holes that contain piscivorous fish. It is hypothesized that larger caudal regions enhance fast-start escape performance and thus reflect an adaptation for avoiding predation. Here I test this hypothesis using a three-pronged, experimental approach. First, G. hubbsi from blue holes with predators were found to possess both greater fast-start performance and greater survivorship in the presence of predatory fish. Second, using individual-level data to investigate the morphology–performance–fitness pathway, I found that (i) fish with larger caudal regions produced higher fast-start performance and (ii) fish with higher fast-start performance enjoyed greater survivorship in the presence of fish predators—trends consistently observed across both predator regimes. Finally, I found that morphological divergence between predator regimes at least partially reflects genetic differentiation, as differences were retained in fish raised in a common laboratory environment. These results suggest that natural selection favours increased fast-start performance in the presence of piscivorous fish, consequently driving the evolution of larger caudal regions. Combined with previous work, this provides functional insight into body shape divergence and ecological speciation among Bahamian blue holes.     

Characterization of RyR1-slow, a ryanodine receptor specific to slow-twitch skeletal muscle

Two distinct skeletal muscle ryanodine receptors (RyR1s) are expressed in a fiber type-specific manner in fish skeletal muscle (11). In this study, we compare [(3)H]ryanodine binding and single channel activity of RyR1-slow from fish slow-twitch skeletal muscle with RyR1-fast and RyR3 isolated from fast-twitch skeletal muscle. Scatchard plots indicate that RyR1-slow has a lower affinity for [(3)H]ryanodine when compared with RyR1-fast. In single channel recordings, RyR1-slow and RyR1-fast had similar slope conductances. However, the maximum open probability (P(o)) of RyR1-slow was threefold less than the maximum P(o) of RyR1-fast. Single channel studies also revealed the presence of two populations of RyRs in tuna fast-twitch muscle (RyR1-fast and RyR3). RyR3 had the highest P(o) of all the RyR channels and displayed less inhibition at millimolar Ca(2+). The addition of 5 mM Mg-ATP or 2.5 mM beta, gamma-methyleneadenosine 5'-triphosphate (AMP-PCP) to the channels increased the P(o) and [(3)H]ryanodine binding of both RyR1s but also caused a shift in the Ca(2+) dependency curve of RyR1-slow such that Ca(2+)-dependent inactivation was attenuated. [(3)H]ryanodine binding data also showed that Mg(2+)-dependent inhibition of RyR1-slow was reduced in the presence of AMP-PCP. These results indicate differences in the physiological properties of RyRs in fish slow- and fast-twitch skeletal muscle, which may contribute to differences in the way intracellular Ca(2+) is regulated in these muscle types.     

Henneguya cartilaginis n. sp. (Myxozoa: Myxosporea) in the head cartilage of masu salmon Oncorhynchus masou masou

Henneguya cartilaginis n. sp. (Myxozoa: Myxosporea) is described from wild masu salmon Oncorhynchus masou masou in Hokkaido, Japan. H. cartilaginis n. sp. produced white cysts, up to 3mm in size, in the head of masu salmon. Infected fish exhibited cranial protrusion due to the cysts. Spores (11.4 × 8.6μm) of H. cartilaginis n. sp. were egg-shaped with the posterior end more pointed and possessed two caudal appendages (34.2μm average length). Histological observations revealed that large plasmodia possessing fine fibrous pseudopodia on the surface developed in the head cartilage. H. cartilaginis n. sp. resembles H. cerebralis, which was described from the cranial cartilage of Kosogol grayling Thymallus nigrescens in Mongolia. However, they were distinguishable by spore morphology. Molecular analysis of the 18S rDNA sequences indicated that H. cartilaginis n. sp. was most closely related to Henneguya zschokkei, H. nuesslini and H. salminicola of salmonid fish, with genetic similarities of 95.3%, 95.1% and 93.9%, respectively. Based on these differences in spore morphology, molecular data, the site of infection and geographical distribution, the present species is considered to be a new species.     

Length-weight relationships of eleven fish species captured in 18 streams of the Capim River basin,Brazil

The length-weight relationship is important for the study of populational dynamics. This study aimed to describe the length-weight relationships (LWR) of 11 fish species sampled on 18 streams of the Capim river basin on eastern Amazon. Specimens were captured in 2014, 2015 and 2017, using sieve nets with 2 mm of mesh size. Fixed specimens were fixed in 10% formalin and conserved in alcohol 70%, measured for standard length (SL, 0.1 cm) and total weight (W, 0.01 g). The 11 species analysed were: Hemigrammus bellottii, Hemigrammus ocellifer, Hyphessobrycon heterorhabdus, Iguanodectes rachovii, Copella arnoldi, Nannostomus trifasciatus, Apistogramma regani, Apistogramma agassizii, Gymnorhamphichthys rondoni, Hypopygus lepturus, Anablepsoides urophthalmus.     

MORPHOLOGICAL EVOLUTION MEDIATED BY BEHAVIOR IN THE DAMSELFLIES OF TWO COMMUNITIES

Behavior can play a mediating role in determining the selective pressures that influence the evolution of morphological structures. To examine this, I quantified patterns of morphological variation among larvae of Enallagma damselfly species (Odonata: Coenagrionidae) that use different behaviors to avoid the major predators found in each of two communities, lakes with and without fish. Specifically, I quantified the sizes and shapes of the abdomens and caudal lamellae (used for swimming) and legs for three species from fishless lakes and six species from lakes with fish. A preliminary cladistic analysis indicates that species within each lake type are not members of a single clade, which supports the conclusions of previous odonate taxonomists. Previous studies have shown that species in fishless lakes are very active, running and swimming frequently and at high rates of speed in the absence of predators, and they avoid their primary predators, large dragonflies, by swimming. These species have the widest abdomens, the largest caudal lamellae relative to overall body size, and the longest legs of the species studied, which should make them powerful swimmers and runners. Furthermore, species in fishless lakes are morphologically very similar to one another and differ greatly from fish-lake species, although each is more closely related to species in fish lakes. In contrast, species from lakes with fish move very slowly and infrequently in the absence of predators and do not attempt to evade attacking predators. However, despite their behavioral similarity, large interspecific variation in morphology exists among the fish-lake species, and the only morphological patterns were differences associated with membership in the two primary clades identified in the cladistic analysis. A modification of Felsenstein's (1985) method of evolutionary contrasts which allows character change to be isolated along single branches is introduced and is used to reconstruct the evolutionary histories of these characters. This analysis suggests that large increases in caudal lamella size, abdominal segment lengths and widths, and leg length accompany speciation events associated with habitat shifts from fish-lakes to fishless lakes. Following habitat shifts selection pressures exerted by dragonfly predation apparently favored swimming as an escape tactic, which mediated selection pressures onto morphologies used in swimming to increase swimming performance; morphological patterns in extant species reflect this adaptation to a new environment. Mechanisms by which behaviorally mediated selection could have accelerated evolutionary dynamics following founder events are discussed.     

Two new species of Nippostrongylinae (Nematoda,Trichostrongylina) parasites of Cricetomys gambianus and Arvicanthis niloticus (Muridae) from Senegal

Two new Nippostrongylinae (Heligmosomoidea, Heligmonellidae) originating from Senegal are described. Heligmonina bioccai n. sp., a parasite of Cricetomys gambianus (Cricetomyinae) found in the surroundings of Dakar and Neoheligmonella bai n. sp., a parasite of Arvicanthis niloticus (Murinae) from the Province of Richard Toll. H. bioccai n. sp. is related to H. hybomysi (Durette-Desset, 1966) a parasite of Hybomys univittatus from the Central African Republic by some characteristics of the caudal bursa and of the synlophe. They are the only two species with the same pattern of caudal bursa: type 1-3-1 for the right lobe, 2-3 for the left lobe, and with the same number and disposition of the cuticular ridges at mid-body in the female. The two species are differentiated by the size (three times smaller in H. hybomysi), the ratio of spicule length on body length (7.6% versus 17% in H. hybomysi) and by a different synlophe in male and posterior part of female. N. bai n. sp. is differentiated from the closely related species N. dielmensis Diouf, Ba and Durette-Desset, 1997, also a parasite of Arvicanthis niloticus from Senegal by rays 8 arising asymmetrically on the dorsal ray and by the deirids situated at the same level as the excretory pore.     

Niche differences between two sympatric whiptail lizards (Cnemidophorus abaetensis and C. ocellifer, Teiidae) in the restinga habitat of northeastern Brazil.

Differences among sympatric lizard species usually result from differences in the use of three resources: space, time and food or some combination of these three. However, differences in resource utilization among sympatric species may simply reflect their specific ecological needs rather than competitive pressures. In this study, we analyzed the temporal, spatial and food niche of two congeneric teiids (Cnemidophorus abaetensis and C. ocellifer) living sympatrically in the "restinga" habitat of Abaeté in the Salvador Municipality, Bahia State, Brazil to assess the degree of niche differentiation among them. The whiptail species overlapped considerably in an hourly activity (Ojk = 0.93), in microhabitat use (Ojk = 0.97) and in the prey items consumed (Ojk = 0.89). Differences in amount of vegetation in the microhabitats used by both lizard species may have contributed to differences in the activity period and in the distribution of the main prey eaten by these lizards which may, in turn, facilitate their coexistence in Abaeté. Although sympatric C. ocellifer and C. abaetensis in Abaeté differed only slightly in their use of microhabitats, period of activity and diet, the most important niche dimension segregating the two species seemed to be the food niche.     

Functional morphology of the caudal skeleton in teleostean fishes

The basic function of the caudal skeleton in teleostean fishes is to support the caudal fin, but its parts contribute to this function in somewhat different ways. The main axis for this support is the upturned terminal end of the vertebral column, which ends at the base of the uppermost principal rays. The uroneural struts just ahead of this axis provide support for it. The parts of the caudal skeleton behind and below this upturned axis, the hypurals and parhypural, not only support the caudal rays but also provide a means for differential movements between the upper and lower parts of the fin base. This basic caudal skeleton varies with the position of the fish in the sequence of teleosten evolution, the way in which the fish uses its caudal fin, and to some extent with the shape of the fin.     

Moravecia australiensis n. g., n. sp. (Dracunculoidea: Guyanemidae) from the gills of the green porcupine fish Tragulichthys jaculiferus (Cuvier) in Australia

A new dracunculoid genus and species, Moravecia australiensis, is described from gill-filaments of the green porcupine fish Tragulichthys jaculiferus (Cuvier) (Tetraodontiformes: Diodontidae) from Moreton Bay, Queensland, Australia. Abundant mobile larvae and a few adult males with females occurred in the gill-filament between the epithelial basement membrane and efferent artery. Gills of all 69 fish examined contained larvae. Eleven harboured adult nematodes of a previously undescribed species belonging to the family Guyanemidae. The new species is placed within a newly proposed genus because it differs from the four existing genera in the family in possessing fine cuticular transverse striations, two forward protruding cephalic elevations, a circumoral elevation, a small triangular mouth surrounded by six cephalic papillae arranged in two lateral clusters of three each and a pair of large lateral amphids. Males have two pairs of pedunculate caudal papillae supporting the caudal alae. A key to the genera of the Guyanemidae is presented.     

Heritability and genetic correlation of abdominal versus caudal vertebral number in the medaka (Actinopterygii: Adrianichthyidae): genetic constraints on evolution of axial patterning?

Variation in the number of abdominal vs. caudal vertebrae is an important source of morphological diversification of fish. It is not clear, however, whether abdominal and caudal regions evolve independently. Regressions of offspring on parents demonstrated substantial additive genetic variation within populations, i.e. heritability, in both abdominal and caudal vertebral numbers of the medaka ( Oryzias latipes ). However, the heritability of caudal vertebrae tended to be smaller than that of abdominal vertebrae in some estimations, suggesting that abdominal and caudal regions are controlled by separate developmental modules. Furthermore, genetic correlation between abdominal and caudal vertebral numbers, estimated using full-sib family means, was negative but weak, supporting independent evolution. In addition, substantial genetic differentiation among populations was demonstrated in abdominal vertebral numbers, but not in caudal numbers. These results support our view that Jordan's rule, a geographical tendency for fish from higher latitudes to have more vertebrae, in this fish reflects local adaptations of abdominal vertebral numbers. In contrast, the low heritability of caudal vertebrae may reflect the intrinsic invariability of genes associated with a change in caudal vertebral numbers. This genetic constraint may have restricted morphological diversification of not only the medaka, but also the Order Beloniformes as a whole.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 867–874.     

Latitudinal variation in axial patterning of the medaka (Actinopterygii: Adrianichthyidae): Jordan's rule is substantiated by genetic variation in abdominal vertebral number

Because the body axes of fish consist of two anatomically distinct vertebrae, abdominal and caudal, one type may be more variable in number than the other and thus contribute more to morphological diversification. Jordan's rule, a geographical tendency for fish from higher latitudes to have more vertebrae, has not been examined in terms of numbers of abdominal and/or caudal vertebrae, despite its prevalence. Vertebral observations of wild populations of the medaka ( Oryzias latipes ) revealed that the latitudinal increase in vertebral number is caused by an increase in abdominal vertebrae; caudal vertebrae did not vary systematically across latitudes. Laboratory experiments revealed that this latitudinal cline in abdominal vertebral number persists in a range of common environments, demonstrating a genetic basis. Phenotypic plasticity was also evident: lower developmental temperatures resulted in more abdominal vertebrae. This indicates that greater numbers of abdominal vertebrae in higher latitude individuals in the wild may be caused not only by genetic factors but by lower habitat temperatures, although the contribution of the former to Jordan's rule is assessed to be much greater. The genetic basis of the latitudinal variation in abdominal vertebral number suggests that selection on functions associated with abdominal regions is the probable explanation for Jordan's rule in this fish.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 856–866.     

An organizer controls the development of the "sword," a sexually selected trait in swordtail fish

SUMMARY Male swordtail fish of the genus Xiphophorus (Poeciliidae) possess a "sword" that is composed of several colored elongated ventral fin rays of the caudal fin. The sword is a secondary sexual trait that evolved through sexual selection by female preference. To uncover the developmental mechanisms underlying the metamorphosis from a juvenile caudal fin to the sword, we have devised a transplantation protocol to assay the fate of single transplanted fin rays and their interactions with flanking rays. These experiments provide evidence for the existence of a previously unrecognized inductive signal that originates in those rays that develop into the two longest sword rays. This "sword organizer" causes adjacent fin rays to grow and become integrated into the sword and induces the development of an additional, typically pigmented sword in grafts to the dorsal part of the caudal fin. We show that the potential to develop a sword is restricted to certain parts of the caudal fin. Our findings suggest that the evolution of swords in swordtails required the acquisition of two developmental mechanisms: the establishment of signaling competence in prospective sword rays in the embryo or early larva, and its activation through androgen signaling in adult male fish.     

The caudal appendage of the cladoceran Bythotrephes cederstroemi as defense against young fish

Rainbow trout (Onchorhynchus mykiss), 40–80 mm in length,were fed the cladoceran Bythotrephes cederstroemi with and withoutits caudal appendage (spined or despined) to determine if theappendage makes ingestion of the zooplankter difficult for smallfish. Handling time was measured as the period of opercularand buccal activity as fish ingested prey. In 980 observationsfor 13 trout, fish spent 8 s longer or 800% more time handlingspined Bythotrephes than despined. Fish ultimately rejectedsignificantly more spined prey than despined prey. Average handlingtimes of spined prey were negatively correlated with fork lengthand smaller fish rejected spined prey more often. All fish handleddespined prey equally well. Eight of 13 fish changed their handlingefficiency over time. However, only two fish decreased handlingtime on spined prey, while two fish increased handling timeon spined prey. Four fish decreased their handling time on despineditems. Bythotrephes' caudal appendage increases the likelihoodthat it will be rejected after capture by fish and decreasesfish predation rate by increasing handling time. This is newevidence of a freshwater zooplankter having a structural defenseeffective against young fish. Present address: Department of Biological Sciences, Lake SuperiorEcosystems Research Center, Michigan Technological University,Houghton, Ml 49931, USA     

Blood sampling techniques and storage duration: effects on the presence and magnitude of the red blood cell beta-adrenergic response in rainbow trout (Oncorhynchus mykiss)

Many teleostean fish, including rainbow trout, regulate red blood cell (RBC) pH (pH(i)) in the presence of a stress-induced acidosis such as hypoxia, hypercapnia, or exhaustive exercise. This is accomplished through activation of RBC Na+/H+ exchange (beta-NHE), ultimately minimizing impairment to oxygen transport. Presence and characterization of the RBC beta-NHE in fish is best tested in blood from cannulated, resting animals; however, several studies have used blood from stressed animals drawn from the caudal vein and stored prior to use. The effects of sampling procedures and storage on the beta-NHE response is not known and is the focus of this study. Whole blood drawn from cannulated, resting rainbow trout was compared with RBCs obtained from the caudal vein rinsed and stored at 4 degrees C for 0, 6, 24, 48, 96 or 144 h. Isoproterenol (10(-5) M), a beta-adrenergic agonist, was added to hypoxia/hypercapnia incubated RBCs in vitro. In all treatments, isoproterenol induced a large beta-NHE response, and storage duration (< or =96 h) had a minimal affect, indicating that rinsing and storing is an easy and viable means by which to obtain RBCs and investigate function. Storage for 144 h still resulted in a significant RBC beta-NHE response; however, viability of RBCs may be compromised.     

中国鲤形目鱼类的中轴骨骼数及其生态适应性

为探讨中国鲤形目鱼类中轴骨骼数及其与系统发育和生态习性的相关性,采用X光透视照相法对157种鲤科(Cyprinidae)、鳅科(Cobitidae)、平鳍鳅科(Balitoridae)鱼类的脊椎骨数、肋骨数、尾椎数进行了比较分析。结果显示,中国鲤形目鱼类的脊椎骨数在30-52枚之间,均值39.45?4.44;肋骨数在8-28对之间,均值15.27?3.08;尾椎数在14-34枚之间,均值21.08?2.89。依据脊椎骨数、肋骨数、尾椎数对鲤科各亚科进行聚类,显示鲤科12个亚科分为2大类：雅罗鱼类,包括雅罗鱼亚科、鲌亚科、鲴亚科、裂腹鱼亚科等4亚科;鲃类,包括鲢亚科、鮈亚科、鱼丹亚科、鲃亚科、野鲮亚科、鳅鮀亚科、鲤亚科、鱊亚科等8亚科。单因素方差分析显示,鲤科肉食性鱼类的肋骨数与脊椎骨数的比值显著少于植食性鱼类(P＜0.05),而脊椎骨数、尾椎数则显著多于植食性鱼类(P＜0.05)。中上层鱼类的脊椎骨数、尾椎数显著多于下层鱼类(P＜0.05)。极小型鱼类的脊椎骨数、肋骨数,以及肋骨数与脊椎骨数之比显著少于大型鱼类(P＜0.05)。表明鲤科鱼类的中轴骨骼数与其系统发育和生态习性及体型具有明显的相关性。     

Strain-specific white-spotting patterns in laboratory mice

White spotting is the absence of melanocytes (pigment cells) from part or all of the locations in the body where they are normally found. At least in the case of the W (kit) locus, white spotting has been attributed to apoptosis. In addition to the death of melanoblasts, white spotting might result from their failure to migrate to their normal locations. These developmental failures are known to be melanocyte-specific in some instances and environment-specific in others. The environment is defined as the tissues surrounding the melanoblast. Patterns of white spotting were examined on mice mutant at the piebald (s), patch (Ph), dominant spotting (W(J2)) rumpwhite (Rw) or belted (bt) loci. The dominant spotting locus has been cloned and found to encode KIT; it has been suggested that Patch encodes the linked alpha-PDGF receptor. Piebald encodes the endothelin beta receptor. In each case, the phenotypes expressed when the allele was backcrossed onto one inbred strain C57BL/6 (B6), were compared with phenotypes expressed when the allele was backcrossed onto a different inbred strain, JU/CtLm (JU). The literature documents genetic loci that influence the extent of the white spotted area; we herein demonstrate that genetic loci also influence the location where the white spot (absence of melanocytes) will occur over the body of the mouse. Spotting occurs in a more anterior direction on JU mice that are piebald, patch or dominant-spotted compared with similar B6 mice. The relationship is reversed in rumpwhite mice, where white spotting is more anterior in the C57BL/6 mice than in the JU mice. The spotting pattern of belted mice was not modified by the background genome. Thus, the Mendelian observations indicate that several loci, which differ in JU compared with B6 mice, influence the size and the location of white spots on the mouse.     

Mapping QTL for an Adaptive Trait: The Length of Caudal Fin in <Emphasis Type="Italic">Lates calcarifer</Emphasis>

The caudal fin represents a fundamental design feature of fishes and plays an important role in locomotor dynamics in fishes. The shape of caudal is an important parameter in traditional systematics. However, little is known about genes involved in the development of different forms of caudal fins. This study was conducted to identify and map quantitative trait loci (QTL) affecting the length of caudal fin and the ratio between tail length and standard body length in Asian seabass (Lates calcarifer). One F1 family containing 380 offspring was generated by crossing two unrelated individuals. One hundred and seventeen microsatellites almost evenly distributed along the whole genome were genotyped. Length of caudal fin at 90 days post-hatch was measured. QTL analysis detected six significant (genome-wide significant) and two suggestive (linkage-group-wide significant) QTL on seven linkage groups. The six significant QTL explained 5.5–16.6% of the phenotypic variance, suggesting these traits were controlled by multiple genes. Comparative genomics analysis identified several potential candidate genes for the length of caudal fin. The QTL for the length of caudal fin detected for the first time in marine fish may provide a starting point for the future identification of genes involved in the development of different forms of caudal fins in fishes.     

On the Caudal Heart of Myxine (Myxinoidea:Cyclostomata)

The anatomy of the caudal heart of Myxine glutinosa is reviewed and a hypothesis of its mode of action is outlined. It is a double-action force pump in which each stroke produces two results, the filling of one chamber and the emptying of the other. This hypothesis is supported by records of blood pressures (a) in the caudal vein, which show elevations of pressure as the left and right chambers are alternately emptied, and (b) in the subcutaneous sinuses, which show alternating reductions of pressure corresponding to the aspiration phases of the left and right sides. The caudal heart shows a diminishing sequence of bursts of activity following each bout of swimming; blood continues to flow slowly through the resting caudal heart. The conclusion is drawn that it is an auxillary venous pump, and it is compared with the lymph heart in the tail of teleost fish.     

A new anthiine fish (Perciformes: Serranidae),Holanthias kingyo, from the Ryukyu Islands

A new anthiine fish,Holanthias kingyo sp, nov., is described on the basis of two specimens (male and female) from the Ryukyu Is., Japan. The new species is most similar toH. natalensis (Fowler, 1925), known only from South Africa, in having the following characters: dorsal fin soft rays 16 or 17, anal fin soft rays 9, pored lateral line scales 46 or 47, scale rows above lateral line to origin of dorsal fin 9 1/2 or 10 1/2, and gill rakers 10 or 11 +24 or 25=34–36. It differs from the latter in having more scales below the lateral line to the origin of the anal fin (27 1/2 vs. 18–24), a U-shaped caudal fin with paddle-like lobes (vs. deeply forked caudal fin with each lobe ending in a long slender filament), the outer margin of the soft anal fin vertical (vs. gently convex) and brown spots on the body in female (vs. spots absent in females).