Positive Allometry Research Articles

Allometric Growth of the Enigmatic Deep-Sea Megamouth Shark Megachasma pelagios Taylor, Compagno, and Struhsaker, 1983 (Lamniformes, Megachasmidae)

Megamouth sharks Megachasma pelagios Taylor, Compagno, and Struhsaker, 1983, are a large-bodied, planktivorous, deep-sea species with peculiar morphology. Since their initial description in the late 20th century, many individuals of different sizes have been reported, but few studies examined ontogenetic changes in body shapes. Here, we assess the growth changes in their heads and fins based on length measurements from nine different-sized individuals (177–544 cm in total length). Bivariate analyses showed that the head becomes larger relative to body length with increasing body size (i.e., positive allometry), whereas the relative size of the caudal fin remains constant (i.e., isometric growth). This trend differs from basking sharks and apparently resembles whale sharks and some baleen whales, although they are all large-bodied filter feeders. Given that relative mouth size is linked to feeding modes, our results suggest that megamouth sharks have different feeding modes from ram-feeding basking sharks and may have some similarity with suction-feeding whale sharks and engulfment-feeding baleen whales.

Growth, allometry, and characteristics of a sexually selected structure in wolverine (Gulo gulo (Linnaeus, 1758)), northern river otter (Lontra canadensis (Linnaeus, 1758)), and sea otter (Enhydra lutris (Linnaeus, 1758))

Allometric analyses of sexually selected structures have revealed many patterns of evolutionary and behavioural significance, for example, in weapons, ornaments, and genitalia. We investigated allometry of the baculum (penis bone) relative to body size in post-growth adults of three large mustelids: wolverine ( Gulo gulo (Linnaeus, 1758)), northern river otter ( Lontra canadensis (Linnaeus, 1758)), and sea otter ( Enhydra lutris (Linnaeus, 1758)). The baculum grew over a longer period than did body size. Correlations among bacular variables were positive in post-growth adults. No regression slopes expressed positive allometry (i.e., slope > 1 for linear variables). These trends point to the possibility that bacular size is adapted to the average size of the reproductive tract of sexually mature female northern river otters and possibly sea otters, and that pre-ejaculatory (“pre-copulatory”) selection is highest in those species. Bacular size varied more than skull or limb-bone size, and bacular shape also varied greatly. Species differed in size and complexity of the urethral groove and bacular apex, suggesting functional differences in intromission. Substantial variation in bacular shape resulted from healed fractures, especially in sea otter. Knowledge of copulatory behaviour, age of breeding, female reproductive anatomy, and genitalic interactions during intromission is needed for comprehensive understanding of bacular anatomy, allometry, and variation for these species.

The More the Merrier or the Fewer the Better Fare? Effects of Stand Density on Tree Growth and Climatic Response in a Scots Pine Plantation

In forests, the growth and productivity of individual trees and stands as a whole are regulated by stand density among other factors, because access to vital resources is limited by competition between trees. On 18 experimental plots of Scots pine (Pinus sylvestris L.) planted with a density of 500–128,000 trees/ha in the south taiga (Middle Siberia), interactions between stand density, tree- and stand-scale productivity, and tree-ring parameters were investigated. Tree-scale productivity variables, tree-ring width, and latewood width had stable negative allometric relationships with stand density (R2 > 0.75), except for tree height (insignificant for inventory surveys at ages of 20 and 25 years; R2 > 0.4 at the age of 35 years), while positive allometry was registered for stand productivity variables (R2 > 0.7) and the all-time average latewood ratio (R2 = 0.5 with planting density). Tree-ring parameters aside from the age trends correlate (p < 0.05) between the plots and demonstrate common responses to moderate moisture deficit. Although, its seasonality apparently depends on the resource base and intensity changes with stand density. February–June precipitation is more important for pine growth in dense stands, July–August conditions affect the latewood ratio stronger in sparse stands, and medium-density stands are more resistant to winter frosts.

Using a fisherman’s harvest in Acapulco, México, to characterize population structure, allometry, and body condition in the edible intertidal mollusc Chiton articulatus (Chitonida: Chitonidae)

The large benthic mollusc Chiton articulatus, known locally as “sea cockroach”, is commercialized among tourists and locals at Acapulco Bay for its muscular foot (i.e., the edible meat), so it is harvested intensely. However, it has not been declared a fishing resource. Acapulco Bay is the main harvesting and consumption site for this species; thus, it is a proxy fishing area compared to other sites, where it is harvested sporadically. The population size structure, allometry (through length–weight relationship), and body condition of C. articulatus were characterized based on monthly harvest data obtained over course of one year in Acapulco Bay. The harvest was carried out by an exclusive chiton fisherman known as the “cucarachero” or “sea cockroach harvester”. The total harvest was 16,211 specimens/fisherman/year, with an estimate of 88–121 kg/fisherman/year of chiton. 97% of the total catch was concentrated between 30–60 mm in total length, i.e., the juvenile to adult stages. The length–weight relationship showed positive allometry during the sub-juvenile to juvenile stages (b = 3.16) but negative allometry during the subadult (b = 2.51) and adult stages (b = 2.84). The entire size range showed negative allometry (b = 2.78), which is consistent with an indeterminate length growth. The body condition “K” ranged on average between 16.3 and 20, showing significant differences between class intervals; however, over time, three condition periods were generated that related to the reproductive season and feeding of the species. While the size structure of C. articulatus in Acapulco appears to be stable over time, the size classes at sexual maturity are strongly harvested, which could lead to a depleted population structure. Currently, 15 fishermen collect chitons in Acapulco, collectively representing approximately 1.5 ± 0.3 tons/year. This information could be useful for making future management decisions related to the harvest of the species and establishing catch quotas.

The relative contributions of multiarticular snake muscles to movement in different planes.

Muscles spanning multiple joints play important functional roles in a wide range of systems across tetrapods; however, their fundamental mechanics are poorly understood, particularly the consequences of anatomical position on mechanical advantage. Snakes provide an excellent study system for advancing this topic. They rely on the axial muscles for many activities, including striking, constriction, defensive displays, and locomotion. Moreover, those muscles span from one or a few vertebrae to over 30, and anatomy varies among muscles and among species. We characterized the anatomy of major epaxial muscles in a size series of corn snakes (Pantherophis guttatus) using diceCT scans, and then took several approaches to calculating contributions of each muscle to force and motion generated during body bending, starting from a highly simplistic model and moving to increasingly complex and realistic models. Only the most realistic model yielded equations that included the consequence of muscle span on torque-displacement trade-offs, as well as resolving ambiguities that arose from simpler models. We also tested whether muscle cross-sectional areas or lever arms (total magnitude or pitch/yaw/roll components) were related to snake mass, longitudinal body region (anterior, middle, posterior), and/or muscle group (semispinalis-spinalis, multifidus, longissimus dorsi, iliocostalis, and levator costae). Muscle cross-sectional areas generally scaled with positive allometry, and most lever arms did not depart significantly from geometric similarity (isometry). The levator costae had lower cross-sectional area than the four epaxial muscles, which did not differ significantly from each other in cross-sectional area. Lever arm total magnitudes and components differed among muscles. We found some evidence for regional variation, indicating that functional regionalization merits further investigation. Our results contribute to knowledge of snake muscles specifically and multiarticular muscle systems generally, providing a foundation for future comparisons across species and bioinspired multiarticular systems.

Growth and competitions of the Australian red-claw crayfish, Cherax quadricarinatus (von Martens, 1868) in Thailand: the experimental approaches

The Australian red-claw crayfish (RCC) Cherax quadricarinatus (von Martens 1868) (Crustacea: Decapoda: Parastacidae) has been introduced and promoted for freshwater aquaculture in many countries including Thailand. This study i) evaluates the growth performance of RCC in near-natural conditions relative to captive conditions and ii) investigates how successfully RCC can compete with a trophically and functionally analogous native species. Growth of RCC was compared among two aquaculture systems (concrete tank and earthen pond) and a treatment with simulated natural conditions. After 12 months of rearing, total length and weight were greatest in the earthen pond and poorest in the near-natural treatment, with significant differences in total length between the near-natural treatment and the two culture systems. Length-weight relationships showed that the RCC had positive allometry in the culture systems but negative allometry in the near-natural treatment. Competition was evaluated by means of a biotic resistance test and an additive–substitutive experiment between RCC and the native freshwater crab Esanthelphusa dugasti (Rathbun, 1902) (Crustacea: Decapoda: Gecarcinucidae). Specific growth rates after 90 days of the experiments suggest that the crab inhibited growth of RCC. This implies that the invasion of RCC in Thai waters could be limited by competition from resident freshwater crabs.

Growth and microanatomy of the paranasal sinuses in two species of New World monkeys

Paranasal sinuses of living apes and humans grow with positive allometry, suggesting a novel mechanism for bone enlargement. Here, we examine the paranasal sinuses of the owl monkey (Aotus spp.) and a tamarin (Saguinus midas) across postnatal development. The prediction that paranasal sinuses grow disproportionately faster than the main nasal chamber is tested. We used diffusible iodine-based contrast-enhanced computed tomography and histology to study sinuses in eight Aotus and three tamarins ranging from newborn to adult ages. Sinuses were segmented at the mucosa-air cavity interface and measured in volume. All sinuses were lined by a ciliated respiratory epithelium, except for the ethmoid air cells in Aotus, which are lined in part by olfactory epithelium. An age comparison indicates that only the maxillary sinus and ethmoid air cells are present in newborns, and two additional sinuses (invading the orbitosphenoid and the frontal bone), do not appear until late infancy or later. Comparing newborns and adults, the main nasal airway is 10 times larger in the adult Aotus and ~ 6.5 times larger in adult Saguinus. In contrast, the maxillary sinus far exceeds this magnitude of difference: 24 times larger in the adult Aotus and 46 times larger in adult Saguinus. The frontal sinuses add significantly to total paranasal space volume in both species, but this growth is likely delayed until juvenile age. Results suggest ethmoid air cells expand the least. These results support our prediction that most paranasal sinuses have a distinctly higher growth rate compared to the main nasal chamber.

Ontogeny of cranial musculoskeletal anatomy and its relationship to allometric increase in bite force in an insectivorous bat (Eptesicus fuscus).

Bite force is a performance metric commonly used to link cranial morphology with dietary ecology, as the strength of forces produced by the feeding apparatus largely constrains the foods an individual can consume. At a macroevolutionary scale, there is evidence that evolutionary changes in the anatomical elements involved in producing bite force have contributed to dietary diversification in mammals. Much less is known about how these elements change over postnatal ontogeny. Mammalian diets drastically shift over ontogeny-from drinking mother's milk to feeding on adult foods-presumably with equally drastic changes in the morphology of the feeding apparatus and bite performance. Here, we investigate ontogenetic morphological changes in the insectivorous big brown bat (Eptesicus fuscus), which has an extreme, positive allometric increase in bite force during development. Using contrast-enhanced micro-computed tomography scans of a developmental series from birth to adult morphology, we quantified skull shape and measured skeletal and muscular parameters directly related to bite force production. We found pronounced changes in the skull over ontogeny, including a large increase in the volume of the temporalis and masseter muscles, and an expansion of the skull dome and sagittal crest that would serve to increase the temporalis attachment area. These changes indicate that development of the jaw adductors play an important role in the development of biting performance of these bats. Notably, static bite force increases with positive allometry with respect to all anatomical measures examined, suggesting that modifications in biting dynamics and/or improved motor coordination also contribute to increases in biting performance.

Direct quantification of skeletal pneumaticity illuminates ecological drivers of a key avian trait.

Skeletal pneumaticity is a key feature of extant avian structure and biology, which first evolved among the non-flying archosaurian ancestors of birds. The widespread presence of air-filled bones across the postcranial skeleton is unique to birds among living vertebrates, but the true extent of skeletal pneumaticity has never been quantitatively investigated-hindering fundamental insights into the evolution of this key avian feature. Here, we use microCT scans of fresh, frozen birds to directly quantify the fraction of humerus volume occupied by air across a phylogenetically diverse taxon sample to test longstanding hypotheses regarding the evolution and function of avian skeletal pneumatization. Among other insights, we document weak positive allometry of internal air volume with humeral size among pneumatized humeri and provide strong support that humeral size, body mass, aquatic diving, and the presence or absence of pneumaticity all have independent effects on cortical bone thickness. Our quantitative evaluation of humeral pneumaticity across extant avian phylogeny sheds new light on the evolution and ontogenetic progression of an important aspect of avian skeletal architecture, and suggests that the last common ancestor of crown birds possessed a highly pneumatized humerus.

Growth allometry and dental topography in Upper Triassic conodonts support trophic differentiation and molar-like element function

AbstractConodont elements have high rates of morphological evolution, but the drivers of this disparity are debated. Positive allometric relationships between dimensions of food-processing surfaces and entire P1 elements have been used to argue that these elements performed mechanical digestion. If involved in food processing, the surface of the element should grow at a rate proportional to the increase in energy requirements of the animal. This inference of function relies on the assumption that the energy requirements of the animal grew faster (≅ mass0.75) than the tooth area (≅ mass0.67). We reevaluate this assumption based on metabolic rates across animals and calculate the allometry in platform-bearing P1 elements of Late Triassic co-occurring taxa, Metapolygnathus communisti and Epigondolella rigoi, using 3D models of ontogenetic series. Positive allometry is found in platform and element dimensions in both species, supporting a grasping-tooth hypothesis, based on the assumption that metabolic rate in conodonts scaled with body mass similarly to that in fish and ectotherms. We also calculate the curvature of the P1 platform surface using the Dirichlet normal energy (DNE) as a proxy for diet. DNE values increase with body mass, supporting the assumption that conodont metabolic rates increased faster than mass0.67. We finally find that adults in both taxa differ in their food bases, which supports trophic diversification as an important driver of the remarkable disparity of conodont elements.

Sizing up spotted lanternfly nymphs for instar determination and growth allometry.

A major ongoing research effort seeks to understand the behavior, ecology and control of the spotted lanternfly (SLF) (Lycorma delicatula), a highly invasive pest in the U.S. and South Korea. These insects undergo four nymphal stages (instars) before reaching adulthood, and appear to shift host plant preferences, feeding, dispersal and survival patterns, anti-predator behaviors, and response to traps and chemical controls with each stage. However, categorizing SLF life stage is challenging for the first three instars, which have the same coloration and shape. Here we present a dataset of body mass and length for SLF nymphs throughout two growing seasons and compare our results with previously-published ranges of instar body lengths. An analysis using two clustering methods revealed that 1st-3rd instar body mass and length fell into distinct clusters consistently between years, supporting using these metrics to stage nymphs during a single growing season. The length ranges for 2nd-4th instars agreed between years in our study, but differed from those reported by earlier studies for diverse locations, indicating that it is important to obtain these metrics relevant to a study's region for most accurate staging. We also used these data to explore the scaling of SLF instar bodies during growth. SLF nymph body mass scaled with body length varied between isometry (constant shape) and growing somewhat faster than predicted by isometry in the two years studied. Using previously published data, we also found that SLF nymph adhesive footpad area varies in direct proportion to weight, suggesting that footpad adhesion is independent of nymphal stage, while their tarsal claws display positive allometry and hence disproportionately increasing grasp (mechanical adhesion). By contrast, mouthpart dimensions are weakly correlated with body length, consistent with predictions that these features should reflect preferred host plant characteristics rather than body size. We recommend future studies use the body mass vs length growth curve as a fitness benchmark to study how SLF instar development depends on factors such as hatch date, host plant, temperature, and geographic location, to further understanding of life history patterns that help prevent further spread of this invasive insect.

Ontogenetic allometry reveals the imprint of myrmecophagy in the skull of the numbat, Myrmecobius fasciatus Waterhouse, 1836 (Marsupialia: Myrmecobiidae)

Ontogenetic allometry, the covariation of shape with size over the course of development, represents a fundamental component of morphological diversification that can vary across species and in association with ecological factors. Ontogenetic allometry patterns for the skull have been described for species from several marsupial lineages, associated with common dietary niches, e.g., carnivory. We here conduct a novel detailed examination of cranial ontogeny in the numbat (Myrmecobius fasciatus), unique among marsupials in being myrmecophagous and adopting a strictly diurnal habit. We investigated ontogenetic allometry using multivariate analyses in a postnatal series (n = 28) of complete numbat skulls to estimate the rate of growth of its major constituent elements, described by 15 measurements. We find positive allometry for length of the nasals and palate, which relates directly to the remarkable rostral elongation in the species relative to other marsupials, in addition to several other ontogenetic changes. These comprise negative allometry of palate breadth, elongation of upper and lower toothrows that produces diastemata between weakly developed teeth, and decreasing muzzle height, all of which contribute to the development of a long, tapering, narrow rostrum, with limited mastication ability, as seen in the small temporal space and poor development of crests and processes associated with jaw musculature. Our specific allometric results and comparisons, together with qualitative observations, reveal a distinct imprint of myrmecophagy on skull ontogeny in the numbat and help explain the development and evolution of specialized feeding function of this species.Norberto P. Giannini [ngiannini@amnh.org], CONICET Fundacion Miguel Lillo, Unidad Ejecutora Lillo, UEL, Tucumán, Argentina, Facultad de Ciencias Naturales, Instituto Miguel Lillo, Universidad Nacional de Tucumán, Tucumán, Argentina, Department of Mammalogy, American Museum of Natural History, New York, NY, USA;Fernando Abdala [nestor.abdala@wits.ac.za], CONICET Fundacion Miguel Lillo, Unidad Ejecutora Lillo, UEL, Tucumán, Argentina, Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa;David A. Flores [dflores@macn.gov.ar], CONICET Fundacion Miguel Lillo, Unidad Ejecutora Lillo, UEL, Tucumán, Argentina, Instituto de Vertebrados, Fundación Miguel Lillo, Tucumán, Argentina;Laura A. B. Wilson [laura.wilson@anu.edu.au], School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia, School of Archaeology and Anthropology, The Australian National University, Canberra, ACT 2601, Australia.

Clavicle length and shoulder breadth in hominoid evolution.

For a given body mass, hominoids have longer clavicles than typical monkeys, reflecting the lateral reorientation of the hominoid glenoid. Relative length of the clavicle varies among hominoids, with orangutans having longer clavicles than expected for body mass and gorillas and chimpanzees having shorter clavicles than expected. Modern humans conform to the general hominoid distribution, but Neandertals and Upper Paleolithic Homo sapiens have longer clavicles than expected for their size and exhibit marked positive allometry in clavicle length. Relative to clavicle length, adult and newborn humans have broader shoulders (biacromial breadths) than comparable apes, because the reduced elevation of the human shoulder swings the acromion laterally downward away from the head. Since broadened shoulders yield an increased risk of maternal and neonatal injury and/or death from shoulder dystocia during birth, we might expect hominins to manifest trends toward reduction in shoulder breadth and clavicle length. They do not, presumably because of countering selection pressures favoring a long clavicle in the adults. The marked sexual dimorphism seen in patterns of clavicular growth and static adult allometry in humans suggests that those selection pressures have disproportionately affected the males.

New occurrences of the endangered Notholebias minimus (Cyprinodontiformes: Rivulidae) in coastal plains of the State of Rio de Janeiro, Brazil: populations features and conservation

Abstract Notholebias minimus is an endangered annual killifish endemic to the coastal plains of the State of Rio de Janeiro, Brazil. This study aimed to present new occurrences in the Atlantic Forest biome, provide unprecedented population features (body and egg size, fecundity, sexual ratio, and length-weight relationship – LWR), and compare changes in land use and coverage between 1985 and 2021 in biotopes located inside and outside protected areas. Three new occurrence localities were found in shallow temporary wetlands with acidic pH (6.4 ± 0.2) and low concentrations of dissolved oxygen (2.0 ± 0.9 mg/L). Males and females total length ranged from 11.1 to 31 mm and 11 to 26 mm, respectively. Batch fecundity ranged from 18 to 40 oocytes (24.8 ± 8.8), corresponding to oocytes with sizes between 800–1,006 µm (905 ± 56). Males were significantly larger than females (W = 2193.5, p = 0.0067), but both sexes occurred in similar proportions (p = 0.472). LWR showed positive allometry (b = 3.18). Biotopes located within protected areas exhibited higher conservation. Our discoveries expand the knowledge about habitat and population features of N. minimus and reinforce the importance of establishing protected areas for the conservation of annual fish biotopes.

Males armed with big weapons win fights at limited cost in ant-mimicking jumping spiders.

A core assumption of sexual selection theory is that sexually selected weapons, specialized morphological structures used directly in male contests, can improve an individual's reproductive success but only if the bearer can overcome associated costs, the negative effects on the bearer's fitness components. However, recent studies have shown that producing and wielding exaggerated weapons may not necessarily be costly. Rather, some traits can be selected for supporting, or compensating for, the expense of producing and wielding such exaggerated weapons. In the ant-mimicking jumping spider Myrmarachne gisti, exaggerated chelicerae are borne only by adult males and not females, showing sexual dimorphism and steep positive allometry with body size. Here, we determine the potential benefits of bearing exaggerated chelicerae during male contests and explore the potential for costs in terms of prey-capture efficiency and compensation between chelicera size and neighboring trait size. While males with longer chelicerae won most of their male-male contests, we found no significant differences in prey-capture efficiency between males and females regardless of whether prey was winged or flightless. Males' elongated chelicerae thus do not impede their efficiency at capturing prey. Furthermore, we found that the sizes of all neighboring traits are positively correlated with chelicera size, suggesting that these traits may be under correlational selection. Taken together, our findings suggest that M. gisti males armed with the exaggerated chelicerae that function as weapons win more fights at limited cost for performance in prey capture and compensate for neighboring structures.

Length–weight relations of 16 mesopelagic fishes (Actinopterygii: Myctophiformes and Stomiiformes) from the eastern Mediterranean Sea

For many mesopelagic fishes, even basic knowledge regarding their biology is missing, greatly impeding their effective management. Here we present length–weight relations for 16 mesopelagic fishes sampled during research surveys in the Greek seas (eastern Mediterranean). The following species were studied: Benthosema glaciale (Reinhardt, 1837); Ceratoscopelus maderensis (Lowe, 1839); Diaphus holti Tåning, 1918; Diaphus metopoclampus (Cocco, 1829); Diaphus rafinesquii (Cocco, 1838); Hygophum benoiti (Cocco, 1838); Hygophum hygomii (Lütken, 1892); Lampanyctus crocodilus (Risso, 1810); Lobianchia dofleini (Zugmayer, 1911); Myctophum punctatum Rafinesque, 1810; Notoscopelus elongatus (Costa, 1844); Symbolophorus veranyi (Moreau, 1888) [Myctophidae]; Argyropelecus hemigymnus Cocco, 1829; Maurolicus muelleri (Gmelin, 1789) [Sternoptychidae]; Stomias boa (Risso, 1810); Chauliodus sloani Bloch et Schneider, 1801 [Stomiidae].With the exception of Diaphus holti and Symbolophorus veranyi, parameter b diverged significantly from isometry. Only two species (Benthosema glaciale and Chauliodus sloani) displayed negative allometry, while for the remaining 12 species a positive allometry was found, with the highest parameter b values estimated for Stomias boa and Diaphus rafinesquii. The median value of parameter b for all species was 3.236 and 50% of its values ranged from 3.173 to 3.323. Some variations of the parameter b were observed between our findings and other studies from the Atlantic and the western Mediterranean.

Length-weight relationship and condition factor revealed possibility of mix strains in Clarias gariepinus population of Oueme Valley, Benin Republic (West Africa)

Growth behaviour (Length-Weight Relationship-LWR), condition factor (K) and phylogenetic linkage of sourced Clarias gariepinus from Oueme valley (main catfish brooder source in Benin) was investigated to understand possible sources of diversity in growth pattern in spawned C. gariepinus . 30 random C. gariepinus ‘labelled’ brooders from sellers in each of Adjohoun(wild-habitat); Dangbo(culture-habitat) and Porto-Novo(culture-habitat) were characterized for differences(p<0.05) in Mean Length-ML (cm), Mean Weight-MW (kg), condition factor (K) and growth behavior (LWR intercept-a; slope-b) in sexes and unsexed populations. 16S barcode gene sequences of 10 random tissue subsamples from each group (n=30) were analyzed for genetic linkages using Maximum Likelihood Method. ML was similar across populations; MW and K similar across Dangbo and Porto-novo; MW similar across sexes of populations; ML and K similar across sexes in Adjohoun, but differ across sexes in Dangbo and Porto-Novo. In unsexed populations, Iintercept-a ranged 0.46(Porto-novo)-0.82(Dangbo), Slope-b -1.37(Porto-novo), 2.14(Dangbo), 2.60(Adjohoun); intercepts were 0.94; 0.63, 0.87; 0.78, and 0.36; 0.61 in respective male and female Adjohoun, Dangbo and Porto-novo; Slope ‘b’ 2.97; 2.05(Adjohoun); 2.87; 2.34(Dangbo), -1.23;-1.78(Porto-novo). Irrespective of sexes, growth was negative allometry in Adjohoun and Dangbo; positive allometry in Porto-novo. 80%Porto-novo were closest to Clarias batrachus ; 20% closest to C. gariepinus x C. batrachus- crossbred; 70%Dangbo closest to C. gariepinus x C. batrachus- crossbred , 10% closest to Clarias batrachus . 20% closest to C. gariepinus. 90%Adjohoun was closest to C. gariepinus x C. batrachus -crossbred, 10% closest to C. gariepinus . Growth behaviour and condition factor diverged irrespective of sexes in populations. Each populations contained mixed strains of Catfish species mistaken as C. gariepinus whose growth pattern could be influenced by growth behaviour of the dominant strain . Dominance of C. batrachus x C. gariepinus- crossbreds’ in culture-Dangbo and Wild-Adjohoun signals possible introgression of the invasive C. batrachus gene, indicating dire need for stricter management and conservation of local catfish gene pool for posterity.

Allometric inter-relationships between jaw musculature mass, skull size and body mass in Psittaciformes

Abstract Functional characteristics of the jaw apparatus, for example bite force, in vertebrates is a combination of the skeleton and the musculature. In birds, bite force has been measured directly or calculated using various methods including summation of forces generated by the different elements of the jaw musculature. However, there have been no reports of the relationships between body size with the mass of the different muscle groups in a closely related group of birds. This study explored allometry in the different jaw muscle masses from parrot (Psittaciformes) species differing in body mass by 40-fold. It was hypothesised that the different muscle masses would exhibit isometry with body mass and skull size. Parrot heads were dissected and the masses of the individual muscle complexes were recorded. Data were subjected to phylogenetically-controlled regression analysis to document scaling effects with body mass and skull size. Most, but not all muscles, exhibited positive allometry with body mass but most were isometric with skull size. Consequently, as parrots get bigger, their skulls get proportionally longer, but that the muscles within the head isometrically scaled relative to the size of these proportionally larger skulls. The large muscles imply greater bite forces in parrots than have been reported to date, which seems to be associated with an increase in skull size to accommodate more muscles. It is unknown whether this pattern is applicable to other birds within specific orders or even across birds as a whole. There needs to be further investigation into the allometry of the morphological and functional properties of the avian jaw musculature.

Quasi-equilibrium channel metamorphosis in planform of a subtropical river in India in post-dam period

A basic fluvio-dynamics process in the sediment-energy fluxes is channel meandering and braiding. The construction of dams and barrages has primarily altered the meandering and braiding patterns of the world's large rivers. To this end, the present study aims to analyze post-dam planform characteristics of the Damodar River, a subtropical river in India, based on the analysis of meander geometry, Mueller’s sinuosity index, braiding index, channel count index, and channel length index during the last 50 years (1970–2020) using topographical maps and satellite images. The study also intends to forecast channel meandering and braiding characteristics for 2030 and 2050 using an Artificial Neural Network (ANN) model. The study results show that between 1970 and 2020, the standard sinuosity index (SSI) showed a larger tendency to meander in the middle of the river than the upper and lower courses owing to hydraulic control, while the lower and upper courses were controlled by topographic factors. Similarly, channel braiding indices (BI*, BI, and Pt) exhibit swelling in the upper and middle courses followed by a gradual fall in the lower stretch. The building of dams, the presence of lineaments, faults, and other anthropogenic controls primarily regulate the physical planform characteristics of the river. Regarding allometry, the river's upper segments exhibit both positive and negative allometry in certain combinations, whereas the lower segments primarily exhibit negative allometry. The study demonstrates that over the past 50 years, overall channel meandering has slightly decreased while braiding has slightly increased over time, indicating a quasi-equilibrium channel metamorphosis. However, the prediction with higher accuracy (80–95 %) shows that the river meandering and braiding (BI* and BI) will increase in the short run (2030), and decrease in the long (2050). The study findings may be helpful for the various planners and stakeholders involved in the development of the river basin.

Sediment yield in a basin in Brazilian Semiarid Regions: A discussion on positive allometry

Sedimentological analyses are essential to understand the system that dictates the sediment yield processes of a basin. Basins have their own characteristics according to climatic, geological, geomorphological, pedological, and phytogeographic influences, on the sediment yield at different scales. This study evaluated the hydrosedimentological aspects of the Rio Seridó hydrographic basin to understand the sediment yield behaviour in the drainage area at different scales. Primary and secondary data, such as imagery (remote sensing), geostatistical methods, hydrosedimentological modelling, and calculations, were used to produce thematic maps, to implement theoretical–methodological revisions of the objects, and determine the specific sediment yield. The sediment delivery ratio was utilized to model the sediment yield at the basin scale, which was calculated using Maner’s Equation and the Universal Soil Loss Equation from 1992 to 2015. The measured data comprised sediment collection, a bathymetric survey of reservoirs, and erosion pins in the drainage basin on a timescaleof up to 82 years. The modelled sediment yield of the basin (2.5 t ha−1 y−1) was comparable to the measurements performed in the semiarid regions for basins of the same scale. The average sediment yield in the reservoirs (2.15 t ha−1 y−1) was very close to the modelled value. Positive allometry was identified for areas of up to 400 km2 in the upper, middle, and lower reaches. Positive allometry was observed with an increase in sediment yield in the drainage area. Globally, this pattern is rare in regions that have not experienced glaciation and this identification is tan important contribution of this research.