Ontogenetic Changes Research Articles

The effect of ontogenetic diet shifts on sagittal otolith shape of European perch, Perca fluviatilis (Actinopterygii: Percidae) from Lake Ladik, Turkey

European perch undergoes several ontogenetic dietary shifts during its lifetime. The present study focused on the variability in otolith shape caused by ontogenetic dietary changes in this species. A total of 172 specimens (7.5 to 27.5 cm TL) were caught by local fishermen in Lake Ladik from April to November 2019. Shape indices (SIs) and elliptic Fourier coefficients (EFCs) were calculated for each otolith. To detect ontogenetic changes in otolith shape, SIs and EFCs were compared among the three defined size classes (I, II, and III). Size-related groups were distinguished by both SIs and EFCs. Otolith shape analysis was more effective than morphometric analysis in distinguishing ontogenetic groups. Simultaneous use of both methods improved the classification success of each method alone. This study demonstrated that otolith shape of European perch is influenced by ontogenetic changes in diet. However, sexual maturity of the fish is also responsible for these variations in otolith shape.

Exceptionally Rapid Tooth Development and Ontogenetic Changes in the Feeding Apparatus of the Komodo Dragon

Exceptionally Rapid Tooth Development and Ontogenetic Changes in the Feeding Apparatus of the Komodo Dragon

Larval development of Characidium orientale (Actinopterygii: Crenuchidae) a small Neotropical fish

ABSTRACT The Characidium orientale Buckup & Reis, 1997 larvae development is described using specimens collected in the natural environment of Antas River, in the Taquari-Antas river basin, Rio Grande do Sul, Brazil. Were considerate ontogenetic changes in morphology, pigmentation, fin morphology, and meristic characters. Thirty-six larvae (33 in the preflexion stage, two in flexion, and one in the postflexion stage), with a standard length between 4.24 and 11.26 mm were analyzed. The larvae of C. orientale are altricial and present fusiform body, subterminal mouth, long intestine with anal opening posterior to the vertical line over the median region of the body. Two chromatophores are evident in the interorbital region, as well pigments concentrated on the side of the body, forming a longitudinal stripe, and between the rays of the caudal fin, which intensify during the development. Also, a conspicuous remnant of the embryonic membrane (finfold) in front of the dorsal fin appears to be characteristic of species of the genus during larval development. The total number of myomeres varies from 32 to 35 (18-23 pre; 11-16 postanal). The main changes in morphometry occur during the preflexion stage and suggest physiological and behavioral changes.

Diagnosis and ontogenetic changes in morphological characters and coloration in young stages of four Japanese species of Kyphosus (Perciformes: Kyphosidae)

Diagnosis and ontogenetic changes in morphological characters and coloration in young stages of four Japanese species of <i>Kyphosus</i> (Perciformes: Kyphosidae)

Ontogenetic Changes in Phenolic Contents and Essential Oil Composition of Hypericum Androsaemum and Hypericum Xylosteifolium

Ontogenetic Changes in Phenolic Contents and Essential Oil Composition of Hypericum Androsaemum and Hypericum Xylosteifolium

Integrative Taxonomy, Distribution and Ontogenetic Colouration Change in Neotropical Mountain Catfishes of the Trichomycterus nigroauratus Group (Siluriformes: Trichomycteridae).

Catfishes of the genus Trichomycterus comprise the most diverse fish group in mountain river basins crossing the Atlantic Forest of south-eastern Brazil, with a great concentration of species in the Rio Paraíba do Sul basin. The present study is directed to the T. nigroauratus group, endemic to the Rio Paraíba do Sul basin, comprising species commonly found associated with bottom leaf litter. Field studies revealed two sympatric, distinct colour morphs, one comprising small specimens with a black longitudinal stripe over a pale brown ground colour on the flank and another comprising a single larger specimen with small dark browns spots scattered over a pale-yellow ground colour. These specimens were found in the upper Rio Paraitinga drainage, an area disjunct from the area inhabited by the other species of the group. We performed coalescent single-locus analyses for species delimitation using a cytochrome b fragment (1088 bp) for specimens from eight localities, including sequences taken from specimens exhibiting different colouration morphs and topotypes of all the three nominal species of the T. nigroauratus group. The analyses supported the two colouration morphs as belonging to a single species that is herein described. It is distinguished from other congeners by its unique colour pattern, dorsal and anal fins fin more posteriorly placed, and by the morphology of the opercle, metapterygoid and pelvic bone. The Maximum Likelihood analysis indicated the new species as sister to a clade containing all other congeners of the group, which is corroborated by osteological data. The occurrence of different lineages in neighbouring areas of the upper Rio Paraíba do Sul basin is interpreted as a possible vestige of a past complex paleogeographical scenario during the Cenozoic. The present record of striking ontogenetic colouration change, revealed only after checking DNA sequences of individuals exhibiting different colouration phenotypes, again highlights the importance of combining morphological and molecular data in taxonomical studies.

Phoretic sharksuckers Echeneis naucrates associated with an elasmobranch host occupy higher relative trophic positions

The relationship between phoretic diskfishes and their hosts is a classic example of marine symbiosis, yet surprisingly few studies have quantified this trophic relationship. We investigated the hypothesis that by consuming host parasites and prey scraps phoretic diskfishes (Echeneidae) feed at a higher relative trophic position than free-living individuals through expanded foraging opportunities. We used carbon and nitrogen stable isotope analysis of muscle tissue from both free-living and commensal sharksuckers Echeneis naucrates and their hosts, supplemented with gut-content analysis, to investigate this hypothesis. Our analysis revealed that commensal sharksuckers likely occupy higher relative trophic positions than free-living sharksuckers. The importance of scavenging host prey decreased ontogenetically as sharksuckers shifted from symbiotic phoresis to free-swimming behavior, leading to an ontogenetic change in which obligately commensal juveniles occupy higher trophic positions than free-living adults which are only facultatively commensal. Relative differences in δ13C and δ15N among individual host-commensal pairs varied among host species, suggesting potential differences in foraging opportunities among host taxa.

A new species of the genus Colopalpus Pritchard and Baker (Trombidiformes: Tenuipalpidae) from China, with ontogenetic patterns in chaetotaxy.

A new species, Colopalpus hibiscus sp. nov. (Acari: Tenuipalpidae) is described from Hibiscus in Hainan province, China. The ontogenetic changes in the idiosoma and leg chaetotaxy on adults (female and male) and immature stages of this new species are presented. A key to species of Colopalpus is also provided.

Retrospective stable isotopes of vertebrae reveal sexual ontogenetic patterns and trophic ecology in oceanic whitetip shark, Carcharhinus longimanus.

There is a common phenomenon in nature whereby some animals have differences in their ontogenetic changes in dietary preferences between sexes, especially apex predators. These reflect changes in the needs of development during their lifetimes. Apex predators potentially have diverse dietary niches and a large impact on the trophic dynamics within ecosystems. However, the difference in life history between males and females often leads to increased difficulty in management and conservation. In this study, 25 oceanic whitetip sharks, Carcharhinus longimanus, were collected from the central and eastern tropical Pacific. Retrospective stable isotope analysis of vertebrae was used to evaluate the potential ontogenetic differences in feeding habits and niche width between sexes. Results showed that C. longimanus had a wide range of δ13C values (−18.1 to −12.3‰) and δ15N values (8.9–14.8‰). However, males and females had similar trophic positions with large niche overlap at similar growth stages. Both sexes had increasing δ13C values but relatively constant δ15N values along the vertebrae. These results indicated that male and female C. longimanus may share similar feeding strategies and movement patterns. The results presented in this study enhance our understanding of sexual ontogenetic patterns and ecological role of C. longimanus and highlighted the applicability of vertebrae for characterizing shark life‐history traits.

Stepwise changes in morphology during the settlement process in a merobenthic octopus, Octopus sinensis, raised in the laboratory

AbstractCephalopoda have no true larval stage because they lack any abrupt morphological changes during growth. However, in shallow‐water merobenthic octopuses, changes occur in the relative proportions of their body parts during the planktonic paralarval phase and the transitional phase from plankton to benthos. How this lifestyle transition is achieved is unclear because the morphological changes during their early life have yet to be fully elucidated. To address this issue, using laboratory‐raised East Asian common octopus, Octopus sinensis, aged 0–100 days after hatching, measurements were taken of total length (TL), mantle length (ML), arm length (AL), the number of suckers on an arm (ASC), and body dry weight (DW). These values were used to explore break points (BPs) in the log‐transformed allometric growth equation: lny = lna + blnx, where x is TL (a reference body dimension) and y is one of the other measurements. In all measurements, a three‐segmented allometric growth model with two BPs was statistically evident, and each segment had a different relative growth coefficient b along with growth, indicating that there are distinct stages of ontogenetic morphological change. Taking into account the times of behavioral changes reported so far, four stepwise phases were detected in the progress of O. sinensis towards settlement: (1) a true planktonic paralarval phase with rapid increase of ASC; (2) a transitional phase between plankton and benthos, characterized by rapid AL increase; (3) a provisional initial benthic juvenile phase, attaining longer AL than ML and approaching adult‐like proportion; and (4) a true benthic juvenile phase, reaching almost completion of the change in body proportion. The stepwise morphological changes seem to be a compromise measure to achieve changes in functional morphology and behavior necessary to lifestyle transition from plankton to benthos for an organism that goes through morphological change without metamorphosis.

Taxonomy, allometry, sexual dimorphism, and conservation of the trans-Andean watersnakeHelicops danieliAmaral, 1937 (Serpentes: Dipsadidae: Hydropsini)

The extensive lack of knowledge on the morphological aspects of South American watersnakes includes a poor understanding of phenotypic parameters, intraspecific variation, and conservation of the trans-Andean Helicops species, Daniel’s Keelback (Helicops danieli Amaral, 1937). For the first time, we provide a multidisciplinary view using key features (e.g., morphology and niche modeling) to improve the taxonomic recognition of this species, as well as describing ontogenetic color changes, allometry, sexual dimorphism, and the conservation status of this poorly studied snake. First, we emended the morphological diagnosis of H. danieli with 23 characters and detected that juvenile tail length is positively related to allometric growth, and that juveniles differ from adults through the presence of the white nuchal collar. Females are larger than males for snout–vent length, whereas males showed proportionally longer tails and smaller head length growth. Suitable areas for H. danieli are restricted to the trans-Andean regions from the Magdalena drainage to the Caribbean coast, which also showed high values of anthropic impacts. Our multidisciplinary approach provided new insights into this South American watersnake’s morphology, intraspecific variation, and distribution.

Age‐related breeding success in little penguins: a result of selection and ontogenetic changes in foraging and phenology

AbstractReproductive performance typically improves with age, reaching a plateau at middle age and subsequently declining in older age classes (senescing individuals). Three potential non‐exclusive mechanisms can explain the improvement in reproductive performance with age: (1) selection (poor quality individuals are removed from the population with increasing age), (2) constraint (individual efficiency increases through experience), and (3) restraint (reproductive investment increases with age as the residual reproductive value decreases). While all three mechanisms received strong empirical support, few studies have aimed at teasing apart those hypotheses and understanding their underlying functioning. In little penguins (Eudyptula minor), we used a 19‐yr longitudinal dataset on breeding and foraging of more than 450 individuals to investigate the effect of age on breeding success. We separated within‐individual from among‐individual age effects using state‐of‐the‐art statistical methods (within‐subject centering and population change decomposition). We then assessed whether within‐individual changes in breeding resulted from ontogenetic changes in foraging performances, breeding phenology or access to mates and nest sites. Fidelity and assortative pairing explained the high correlation in male and female ages within a pair. Breeding performances followed a typical bell‐shaped curve with performance increasing up to 8 yr old, before reaching a plateau and subsequently declining after age 16. Both selection and within‐individual processes occurred, although within‐individual changes dominated differences in age‐dependent breeding success. The selective appearance had almost no effect (apart from ages 2–3), and selective disappearance mostly affected changes at old ages (above 16), although they were also responsible for the slight increase in reproductive performances from ages 5–8. Focusing on within‐individual changes, birds exhibited higher performances at middle ages, with birds foraging better, laying earlier and changing partner and nest less often. Their reproductive investment did not vary with age for females and slightly decreased for males. This supports the constraint hypothesis but not the restraint one. Finally, the increase in breeding performances at young ages was explained by the age‐related increase in foraging performances during chick‐rearing and advancement of laying. In contrast, reproductive senescence was defined by a general decrease in bird performances.

Widespread azendohsaurids (Archosauromorpha, Allokotosauria) from the Late Triassic of western USA and India

AbstractArchosauromorph reptiles underwent rapid lineage diversification, increases in morphological and body size disparity, and expansion into new adaptive landscapes. Several of the primary early archosauromorph clades (e.g. rhynchosaurs) are easy to differentiate from others because of their characteristic body types, whereas the more lizard‐like and carnivorous forms with long necks (e.g. tanystropheids) were historically all relegated to the groups Protorosauria or Prolacertiformes. However, it is now clear that these groups are polyphyletic and that a lizard‐like, carnivorous form is plesiomorphic for Archosauromorpha, and multiple subclades started with that body plan. Among these early forms is Malerisaurus from the Upper Triassic of India (M. robinsonae) and the Upper Triassic of south‐western USA (M. langstoni). In this paper, we critically re‐evaluate the genus. We find both species of Malerisaurus as valid, and identify Malerisaurus as an early diverging, but late‐surviving, carnivorous member of Azendohsauridae within Allokotosauria. Our histological analysis and assessment of ontogenetic changes of limb bones of small and large individuals demonstrate that the skeletons of the small forms grew slowly and became more robust through ontogeny, and that the larger recovered bones are at or near the maximum size of the taxon. Malerisaurus and Malerisaurus‐like taxa were common members of the Otischalkian–Adamanian (late Carnian to mid‐Norian) faunal assemblages from Upper Triassic strata of the south western USA, but they are absent from the younger Revueltian holochronozone. Specimens from western North America show that Allokotosauria had a near‐Pangaean distribution for much of the Middle Triassic to Late Triassic.

Ontogenetic changes in limb posture, kinematics, forces and joint moments in American alligators (Alligator mississippiensis).

As animals increase in size, common patterns of morphological and physiological scaling may require them to perform behaviors such as locomotion while experiencing a reduced capacity to generate muscle force and an increased risk of tissue failure. Large mammals are known to manage increased mechanical demands by using more upright limb posture. However, the presence of such size-dependent changes in limb posture has rarely been tested in animals that use non-parasagittal limb kinematics. Here, we used juvenile to subadult American alligators (total length 0.46-1.27 m, body mass 0.3-5.6 kg) and examined their limb kinematics, forces, joint moments and center of mass (CoM) to test for ontogenetic shifts in posture and limb mechanics. Larger alligators typically walked with a more adducted humerus and femur and a more extended knee. Normalized peak joint moments reflected these postural patterns, with shoulder and hip moments imposed by the ground reaction force showing relatively greater magnitudes in the smallest individuals. Thus, as larger alligators use more upright posture, they incur relatively smaller joint moments than smaller alligators, which could reduce the forces that the shoulder and hip adductors of larger alligators must generate. The CoM shifted nonlinearly from juveniles through subadults. The more anteriorly positioned CoM in small alligators, together with their compliant hindlimbs, contributes to their higher forelimb and lower hindlimb normalized peak vertical forces in comparison to larger alligators. Future studies of alligators that approach maximal adult sizes could give further insight into how animals with non-parasagittal limb posture modulate locomotor patterns as they increase in mass and experience changes in the CoM.

Size-related, seasonal and interdecadal changes in the diet of the Patagonian longfin squid Doryteuthis gahi in the South-western Atlantic

AbstractThe Patagonian longfin squid Doryteuthis gahi has an annual life cycle with two seasonal cohorts (autumn and spring spawners). Earlier studies on the Patagonian shelf found a predominance of Euphausiacea in the D. gahi diet, but no studies to date have investigated differences between feeding spectra of the two cohorts or decadal diet shifts. The present study investigated differences in diet of D. gahi on the Patagonian shelf sampled two decades apart, and differences between seasonal cohorts. Classical stomach content analysis and generalized additive models were used to investigate and model the influence of mantle length, sampling period and spawning cohort on the diet. Results revealed an ontogenetic diet change from ~70% Frequency of Occurrence of Euphausiacea in small squid to more than 60% FO of fish and Cephalopoda at larger sizes. Cannibalism was also frequently observed. Euphausiacea were ingested more frequently and in higher amounts during the austral summer and therefore were consumed more by the autumn spawning cohort, whereas fish was more frequently fed upon during austral winter and also by the spring spawning cohort. Cannibalism was also recorded more in austral winter months but, contrary to feeding on fish, was more prevalent in the autumn spawning cohort. Increased predation of Munida gregaria was observed in 2020 compared with 2001. This study is an important step towards improving the knowledge of D. gahi's two seasonal cohorts, providing data that can be used for future ecosystem modelling.

Ontogenetic variation in the crocodylian vestibular system.

Crocodylians today live in tropical to subtropical environments, occupying mostly shallow waters. Their body size changes drastically during ontogeny, as do their skull dimensions and bite forces, which are associated with changes in prey preferences. Endocranial neurosensory structures have also shown to change ontogenetically, but less is known about the vestibular system of the inner ear. Here we use 30high-resolution computed tomography (CT) scans and three-dimensional geometric morphometrics to investigate the size and shape changes of crocodylian endosseous labyrinths throughout ontogeny, across four stages (hatchling, juvenile, subadult and adult). We find two major patterns of ontogenetic change. First, the labyrinth increases in size during ontogeny, with negative allometry in relation to skull size. Second, labyrinth shape changes significantly, with hatchlings having shorter semicircular canal radii, with thicker diameters and an overall dorsoventrally shorter labyrinth than those of more mature individuals. We argue that the modification of the labyrinth during crocodylian ontogeny is related to constraints imposed by skull growth, due to fundamental changes in the crocodylian braincase during ontogeny (e.g. verticalisation of the basicranium), rather than changes in locomotion, diet, or other biological functions or behaviours.

Metabolomics reveals changes in metabolite profiles due to growth and metamorphosis during the ontogeny of the northern damselfly

Many insects have complex life cycles where a drastic ontogenetic change happens between the larval stages and the adult stage, i.e. metamorphosis. Damselflies (order Odonata, suborder Zygoptera) are widely distributed and ecologically important semi-aquatic insects with a complex life cycle. Phenotypic changes over damselfly ontogeny have been documented, however, if and how metabolite profiles are also changing is currently unknown. Here we used a metabolomics methodology to gain insights into the metabolic changes during the life cycle of the Northern damselfly (Coenagrion hastulatum). Hatchlings of wild-caught damselflies were reared in the laboratory and metabolomics analyses using liquid chromatography and gas chromatography coupled to mass spectrometry were carried out at three larval stages and on adult damselflies. Additionally, a subset of larvae was exposed to wastewater effluent to assess how metabolite profiles responded to an environmental stressor. A total of 212 compounds belonging to several classes (e.g. amino acids, fatty acids, sugars) were annotated. Across metamorphosis, we found that damselflies shifted from protein catabolism to lipid catabolism. Wastewater effluent exposure resulted in ontogenetic stage-dependent changes of individual metabolites, but not to a marked extent. Overall, our study is one of the first to describe changes of metabolite profiles during ontogeny of an insect, and it provides a first step towards a greater understanding of the physiological changes occurring during general insect—but especially damselfly—ontogeny.

Visual and brain lateralization during the posthatching phase in squid under solitary and group conditions

Lateralization appears as a left–right asymmetry of morphology and behaviour in many animal species including both vertebrates and invertebrates and provides functional advantages for survival. Lateralization is expressed at individual and population levels (most individuals in a group are lateralized in the same direction) and switches during ontogeny. Lateralization has been observed in coleoid cephalopods (squid, cuttlefish and octopus) which possess sophisticated lens eyes and a large brain, the largest among invertebrates. In this study, we investigated ontogenetic changes in the lateralization of oval squid, Sepioteuthis lessoniana , by observing their behaviour and the brain region, that is, the optic lobes, that process visual information. Behavioural lateralization was tested by observing which eye solitary and group individuals used to detect prey, predators and conspecifics. Optic lobe lateralization was examined by estimating the left and right optic lobe volumes using microcomputed tomography. We found that eye use and optic lobe lateralization in oval squid changed with the development of schooling behaviour. The right eye was used at a population level for detecting specific targets during the preschooling period, while no trend was detected in both the solitary and group conditions during the schooling period. In the period before school formation, the right eye was used for detecting conspecifics in the solitary condition, while in the group condition, the right eye was used for detecting predators and conspecifics. The strength of eye use, regardless of the direction, appeared at the population level in both the solitary and the group conditions during all life stages. The volume of the right optic lobe gradually became larger than the left lobe during the schooling period, although this was not correlated with behavioural lateralization. The potential role of lateralization in oval squid is discussed. • Ontogeny of visual and brain lateralization were examined for oval squid. • One eye use side is specifically directed towards prey or conspecifics. • The eye use side that is specifically directed changes as schooling develops. • Optic lobe volume is biased to a rightward direction during the schooling period. • Asymmetry of optic lobe volume and a specific side of eye use are not correlated.

Uses for Incomplete Ammonite Sutures: Lateral Lobe and Second Saddle as Markers of Sutural Complexity

Ammonoid sutures are geometric patterns formed by the intersection of the septa and the shell wall, and have long been a diagnostic tool for ammonite researchers for such applications as species identification, taxonomic relationships, ontogenetic change, functional and evolutionary morphology, determination of ecological niche, and other aspects of ammonoid paleobiology. Researchers interested in a variety of paleobiological questions related to ammonoids have almost always required access to the entire hemisuture. Without access to specimens in museum or institutional collections, researchers must rely on previously published illustrations and photographs of ammonoid sutures. However, due to the perspective in photographs, distortion of the marginal elements of suture geometry occurs due to shell curvature near the venter and umbilicus when photographed in profile. The revised approach described here, which we refer to as the Lateral Lobe Saddle, or LLS approach, makes use of only the lateral lobe and second saddle S2 (lateral lobe-second saddle pairs, or LLS) which lie in the central, mid-whorl undistorted sector of a suture line as viewed in lateral, profile shell photos and illustrations. The factors by which fractal dimension of LLS data convert to fractal dimension of the standard hemisuture measurements are largely consistent within genera. The LLS method’s non-requirement of a full hemisuture also facilitates comparisons among sutures within an ontogenetic sequence, or sutures from multiple ammonite taxa where ventral and umbilical sutural elements are hidden by whorl overlap or poor preservation.

Does dietary β-carotene influence ontogenetic colour change in the southern corroboree frog?

Ontogenetic colour change occurs in a diversity of vertebrate taxa and may be closely linked to dietary changes throughout development. In various species, red, orange and yellow colouration can be enhanced by the consumption of carotenoids. However, a paucity of long-term dietary manipulation studies means that little is known of the role of individual carotenoid compounds in ontogenetic colour change. We know even less about the influence of individual compounds at different doses (dose effects). The present study aimed to use a large dietary manipulation experiment to investigate the effect of dietary β-carotene supplementation on colouration in southern corroboree frogs (Pseudophryne corroboree) during early post-metamorphic development. Frogs were reared on four dietary treatments with four β-carotene concentrations (0, 1, 2 and 3mgg-1), with frog colour measured every 8 weeks for 32 weeks. β-Carotene was not found to influence colouration at any dose. However, colouration was found to become more conspicuous over time, including in the control treatment. Moreover, all frogs expressed colour maximally at a similar point in development. These results imply that, for our study species, (1) β-carotene may contribute little or nothing to colouration, (2) frogs can manufacture their own colour, (3) colour development is a continual process and (4) there may have been selection for synchronised development of colour expression. We discuss the potential adaptive benefit of ontogenetic colour change in P. corroboree. More broadly, we draw attention to the potential for adaptive developmental synchrony in the expression of colouration in aposematic species.