Despite its use as a diagnostic taxonomic feature, the occurrence and distribution of plicidentine in the teeth of squamate reptiles is unclear. This appears to be due to several factors: the various kinds of folding, wrinkling, and striation that occur within different dental tissues; difficulty of interpreting conditions in poorly preserved extinct taxa; and incomplete knowledge of tooth development. We investigated tooth development and morphology in extant and fossil squamate reptiles using skeletal preparations, histological sections, and CT-scanning data. Among squamates, we found plicidentine only in the teeth of varanoid lizards and note that much more anatomical complexity exists than previously thought in the dental and attachment tissues of these groups. Degree of development of plicidentine is variable within varanoids, with the strongest development occurring in some species of Varanus. In contrast to some reports, we found no evidence for the occurrence of plicidentine in the teeth of mosasauroid lizards or snakes. Some mosasaurs exhibit raised ridges on the enamel surface that extend from the base to the tip of the tooth, as well as occasional striation of the tooth bases built from bone of attachment; neither of these features is considered homologous to plicidentine infolding. Some snakes exhibit weak wrinkling of the tooth base that corresponds closely to the pattern of wrinkling in the overlying bone of attachment. This condition occurs infrequently in snakes, and details of tooth development and attachment also do not support its homology with plicidentine. Our results indicate that plicidentine is best interpreted as a synapomorphy of Varanoidea.

We used the mitochondrial cytochrome-b gene and four microsatellite-DNA loci to assess levels of genetic introgression between two hybridizing poeciliid fishes in Texas, a locally endemic, endangered species, Gambusia heterochir, and a wide-ranging congener, G. affinis. Past morphological studies indicated a long history of hybridization and backcrossing. We detected ongoing, low-level hybridization, but no evidence of a long-term, evolutionary history of genetic introgression. Only one of 118 G. heterochir (0.9%) might have had an ancestor in G. affinis, but this was weakly supported. We detected one potential F₁ hybrid, but it was more likely a recent product of backcrossing between a hybrid and G. affinis. Two other fish were more distant products of such backcrossing. At present, there appears to be little cause for concern regarding the genetic integrity of G. heterochir. The widespread species, G. affinis, showed significant genetic structure over short geographic distances, including divergence between populations on two sides of a small dam with through-flowing water.

A new species of scorpionfish, Scorpaena gasta, is described on the basis of five specimens collected from the warm temperate central coast of Western Australia, eastern Indian Ocean, at depths of 3–7 m. Scorpaena gasta is most similar to a Western Australian species, S. sumptuosa. The two species are distinguished from other Indo-Pacific species of Scorpaena by the following combination of characters: lateral surface of maxilla with a distinct longitudinal ridge; relatively thick skin with numerous small sensory pores covering nearly the entire predorsal area to near the first pored lateral-line scale; anteroventral surface of lower jaw with one or two pairs of slender tentacles in ventral view. Scorpaena gasta and S. sumptuosa are separated by four meristic, several morphometric, and color features. Scorpaena gasta is a small species (smallest mature female 67.4 mm SL; largest known specimen 83.6 mm SL), whereas S. sumptuosa is a relatively large species, attaining at least 241 mm SL.

In the course of ongoing survey work in the lower Congo River, two collections of an undescribed species of the predatory cyprinid genus Raiamas have been made; one in the Congo main channel in the vicinity of Inga, and a second in the Inkisi River, a large south bank tributary of the Congo. Discovery of this new taxon has prompted a reexamination of potentially related taxa of adjacent regions and an attempt to provide generic diagnoses for the morphologically similar cyprinid genera Leptocypris, Raiamas, and Opsaridium. Based on a series of derived features of the neurocranium, pectoral girdle, jaws, and suspensorium, anatomical diagnoses for the three cyprinid genera are provided. We reassign Opsaridium christyi to Raiamas and Raiamas weeksii to Leptocypris. These two generic reassignments and the discovery of the new Raiamas bring the number of species of Raiamas confirmed from the lower Congo River to four: R. salmolucius, R. buchholzi, R. christyi, and the new species, R. kheeli, described herein. The reassignment of Opsaridium weeksii to Leptocypris raises the number of species of Leptocypris recorded from the region to four: L. modestus, L. lujae, L. weynsii, and L. weeksii.

Noturus stanauli and N. crypticus are two madtom catfish species of conservation concern with very restricted distributions in the Upper Tennessee River Drainage and Duck River. A recent phylogenetic analysis of Noturus using mtDNA sequences did not include these species. A new phylogenetic analysis of cytochrome b sequences including N. stanauli and N. crypticus is presented. Both maximum parsimony and Bayesian analyses indicate that N. stanauli and N. crypticus are closely related and nest within a genetically divergent clade comprising N. fasciatus, N. baileyi, N. elegans, and a paraphyletic N. hildebrandi. Limited intraspecific sampling of N. stanauli and N. crypticus revealed few genetic differences within these species. We discuss our results in the context of conservation status of these species and the use of phylogenetic trees and sequence data in the delimitation of cryptic species diversity in Noturus.

We describe two new species of Guianacara from the Guiana Shield of eastern Venezuela. Guianacara stergiosi, new species and G. cuyunii, new species belong in the subgenus Guianacara and thus are distinguished from G. oelemariensis (subgenus Oelemaria) by the possession of two (vs. one) supraneurals and produced lappets on the dorsal-fin spines. Guianacara stergiosi can be distinguished from all other species in the subgenus Guianacara by the possession of a round midlateral spot almost entirely below the upper lateral line, forming the darkest area in the midlateral bar. In other species with a midlateral spot, the spot is oval-shaped and located on and above the upper lateral line (G. sphenozona), or on and below the upper lateral line (G. owroewefi). In Guianacara stergiosi the midlateral bar progressively fades into a midlateral spot in all but small juvenile specimens, distinguishing the species from G. geayi, which generally has a complete midlateral bar; in G. geayi the midlateral bar can be reduced to a midlateral spot in large specimens, in which case the black coloration of the anterior dorsal-fin lappets is lost, whereas it is maintained in G. stergiosi at all sizes. Guianacara stergiosi is known from the Caroní and lower Aro River drainages, and from the upper Caura River basin upstream of the Para rapids. Guianacara cuyunii is distinguished from all other species in the subgenus by the possession of a thinner midlateral bar (about three scales wide vs. four scales wide) that is generally not replaced by a midlateral spot, except in very large specimens, by having a pectoral fin that does not reach the anal fin, and for being the only known species without a grayish branchiostegal membrane. Guianacara cuyunii is known from the upper Cuyuní River drainage in Venezuela, including its major tributaries. It is currently unknown whether the distribution of this species spans the lower reaches of the Cuyuní and Essequibo drainages.

Describimos dos especies nuevas de Guianacara del Escudo Guayanés en el este de Venezuela. Guianacara stergiosi sp. nov. y G. cuyunii sp. nov. pertenecen al subgénero Guianacara y por lo tanto se distinguen de G. oelemariensis (subgénero Oelemaria) por poseer dos (en lugar de uno) supraneurales y prolongaciones de las membranas de las espinas de la aleta dorsal. Guianacara stergiosi se distingue de las otras especies en el subgénero Guianacara por poseer una mancha medio-lateral redonda, localizada casi enteramente bajo la linea lateral superior formando el área más oscura de la banda medio-lateral. En otras especies con mancha medio-lateral, la mancha es de forma oval y está localizada sobre y arriba de la linea lateral superior (G. sphenozona), o sobre y abajo de la linea lateral superior (G. owroewefi). En Guianacara stergiosi la banda medio-lateral desaparece progresivamente hasta tornarse en una mancha medio-lateral en todos los especímenes excepto en pequeños juveniles, distinguién

We describe a new species of riparian gymnophthalmid from Guyana characterized by striated rostral and mental scales, three rows of scales of subequal size between the rostral and frontal scales, and the absence of a unpaired median postmental. The new taxon shares derived features with species in Echinosaura, Neusticurus, Potamites, and Teuchocercus, including heterogeneous and heavily keeled body squamation, an elongate snout, and gracile limbs.

The deep-sea ceratioid anglerfish genus Spiniphryne Bertelsen, 1951 (family Oneirodidae), diagnosed and described on the basis of new material recently collected from all three major oceans of the world, contains two species: the type species, Spiniphryne gladisfenae (Beebe, 1932), now represented by 21 specimens collected from the Western Pacific and Western Indian oceans, and from both sides of the Atlantic; and a new species, Spiniphryne duhameli, described here on the basis of two females from the Central and Eastern North Pacific. The new species differs from S. gladisfenae in having three pairs of long, slender, lateral escal filaments on each side and a greater number of teeth on the dentary (51–52 vs. 21–45). Diagnoses and descriptions are given for both taxa and a key to the species is provided.

The Neotropical auchenipterid catfish genus Entomocorus is reviewed and found to include four species widely distributed in lowland cis-Andean South America. Entomocorus benjamini is found in the Madeira River, E. gameroi occurs in the Orinoco River, E. melaphareus is from the lower Amazon River, and a previously undescribed species, E. radiosus, inhabits the upper Paraguay River. Entomocorus is diagnosed based on the shared presence of eight synapomorphies. Entomocorus radiosus is diagnosed by the unique combination of a long anal-fin base, 18–22 branched anal-fin rays, unpigmented pectoral and pelvic fins, and caudal fin hyaline, with distal half of dorsal and ventral lobes pigmented with black. All four species are diagnosed and illustrated, and a key to species is provided.

O gênero de Auchenipteridae Entomocorus é revisado e inclui quatro espécies amplamente distribuídas em terras baixas da porção cis-Andina da América do Sul. Entomocorus benjamini é encontrado no rio Madeira, E. gameroi ocorre no rio Orinoco, E. melaphareus é do rio Amazonas inferior, e uma espécie previamente não descrita, E. radiosus, habita o rio Paraguai superior. Entomocorus é diagnosticado com base na presença compartilhada de oito sinapomorfias. Entomocorus radiosus é diagnosticado pela combinação única de uma longa base da nadadeira anal, 18–22 raios ramificados na nadadeira anal, nadadeiras pélvicas e peitorais não pigmentadas, e nadadeira caudal hialina com a metade distal dos lobos superior e inferior pigmentados de preto. As quarto espécies são diagnosticadas e ilustradas e uma chave para as espécies é fornecida.

Notropis amplamala, the Longjaw Minnow, is described as a new species for the southern populations of N. buccatus. Notropis amplamala differs from its sister species, N. buccatus, by possessing longer gill rakers (length to width ratio average 2.2, 1.8–2.5 vs. average 1.0, 0.8–1.4), having no breast squamation (vs. breast with scales), and possessing five infraorbital ossicles (vs. four). The two species have a disjunct distribution with N. amplamala occurring in Gulf of Mexico and Atlantic Ocean tributaries from the Pearl River to the Altamaha River, and N. buccatus occurring in Mississippi River, Ohio River, and Atlantic coastal tributaries north of the Cumberland River from eastern Missouri to Virginia and Maryland.

Vertebral number is used frequently as a diagnostic species character in fishes, but it varies not only among but also within species. Much of the variation in vertebral number is associated with geographic gradients such as latitude, and it likely reflects both environmental and genetic influences on phenotype. Hence, comparison of intra- and interspecific geographic variation and its genetic basis in closely related species may contribute not only to taxonomy of the group concerned but also to understanding how such differences evolve. In this study, we examine intra- and interspecific latitudinal variation in vertebral number of two geographically contiguous, closely-related species: the Atlantic Silverside Menidia menidia (a northern species) and the Tidewater Silverside M. peninsulae (a southern species). In accordance with Jordan's rule, vertebral numbers of wild individuals increased with latitude within and among species. Mean vertebral number varied along a common linear trajectory both within and among species and could be predicted with very high accuracy from latitude alone (r = 0.98), indicating that vertebral number is not a diagnostic species character in Menidia. Common-garden experiments revealed that this latitudinal cline persists across all temperatures, demonstrating a strong genetic basis within and among species. The continuous variation throughout the entire geographic range across the species suggests that natural selection and adaptation is the most likely explanation, and that populations and species are free to evolve any vertebral number required in each environment.

The effects of temperature on prey capture kinematics were investigated in the Largemouth Bass, Micropterus salmoides. Five individuals were first acclimated to 22 C and then acutely exposed to temperatures of 15, 20, 25, and 30 C. At each temperature, feeding events were recorded using high-speed video at 500 frames s⁻¹. An analysis of variance on the five fastest feeding events from each individual at each temperature resulted in a significant trend for the fastest feeding events to occur at 25 C. This effect confirmed the expectation of thermal dependence of mouth opening movements, which was based on an inverse relationship between water viscosity and temperature and the assumption that temperatures outside optimum decrease muscular power and contraction rates. However, the Q₁₀ value between 15–25 C was only 1.28, well below the minimum expected value of 2.0. Thus, we suggest the possibility that Largemouth Bass partially compensate for the effects of acute temperature changes by recruiting additional motor units at lower temperatures. The capacity of Largemouth Bass to mitigate the impact of acute temperature change on muscle physiology and the physical properties of water may represent a physiological adaptation to a predatory lifestyle in a thermally variable environment.

A new species of scorpionfish, Maxillicosta meridianus, is described on the basis of 24 specimens collected from southeastern Australia at depths of 10–137 m. This species has previously been identified as M. whitleyi, but differs in having the following characters: central portion of inner ridge on ventral mandibular surface located on inner edge of dentary or closer to inner edge than to central ridge, no short ridge between posterior portions of inner and central ridges; 0–6 spinous points on anterior margin of nasal spine; 5–13 spinous points on surface of preocular spine; no spines or distinct ridges on lateral margin of occipital pit between tympanic spine and origin of parietal spine base; no ossified scale behind front edge of occipital pit between tympanic spines; dorsal surface of occipital pit smooth, without spines; two (rarely one or three) spinous points at tip of upper opercular spine; posterior margin of maxilla extending slightly beyond a vertical through posterior margin of pupil; and caudal fin usually without distinct markings in preserved specimens. Additionally, the two species significantly differ in eight meristic and six morphometric features. Morphological changes with growth and geographic variation are also discussed.

We examined the relative roles of contemporary (species interactions) and historical factors (phylogeny) in structuring a lizard assemblage (14 species) from one of the last remaining large expanses of undisturbed Cerrado in Brazil. Niche breadth for microhabitat was low for all species in the assemblage, and microhabitat niche overlaps varied from none to almost complete and appeared associated with phylogenetic similarity. Mean microhabitat and diet overlaps among lizard species did not differ statistically from random, based on a pseudocommunity analysis, indicating a negligible role of contemporary factors in assemblage structure. Prey overlaps were highest within Gymnophthalmidae and Teiidae. A cluster analysis of principal component scores of morphometric variables revealed groups corresponding to lizard families, suggesting a strong association between morphology and phylogeny. Similarities among closely related species in microhabitat use, diel activity, and diet breadth, based on cladogram inspection, suggested that phylogeny might affect assemblage structure. However, a Canonical Phylogenetic Ordination (CPO) analysis revealed no significant phylogenetic effects on lizard microhabitat use or diet composition. We suggest that under-representation of species in major clades (low taxon sampling) renders it difficult to detect potential historical and ecological effects on assemblage structure.

A new species of Cyprinodontidae, Orestias piacotensis new species, is described from Laguna Piacota in the southern high Andean region (18°11′49.8″S, 69°15′56.9″W). It is a small and slender-bodied fish with mottled blackish bands on its flanks, fading to white on the belly and should be classified in the “agassii complex.” Its head is moderately large with large eyes whose orbits do not reach the dorsal profile. This species is distinguished from the rest of the “agassii complex,” by possessing a wide protractile mouth with slightly upturned lower jaws, and pectoral, dorsal, and anal fins with elongate middle rays, pointed and with a reduced (12–16) and constant number of rays. It has a long and narrow caudal peduncle. Rounded, irregularly-sized, small scales cover the sides of the body, being absent from the dorsal and ventral parts of the body. The gill rakers are long, rounded, and closely spaced. Both sexes have 52 chromosomes.

Se describe una especie nueva de Cyprinodontidae, Orestias piacotensis nov. sp., en la Laguna Piacota ubicada en la región altoandina sur (18°11′49.8″S, 69°15′56.9″W). Es un pez pequeño y esbelto con bandas negras laterales, cambiando a color blanco en la zona ventral. Debería ser incluido en el “complejo agassii.” La cabeza es moderadamente grande con ojos grandes cuyas órbitas no alcanzan el perfil dorsal primario. Esta especie se distingue del resto de las especies del “complejo agassii” por poseer una boca protráctil ancha con mandíbulas levemente inclinadas hacia arriba, aletas dorsales, pectorales y anales con rayos centrales alargados por lo que se ven puntiagudas y tienen número de rayos reducido (12–16) y constante, con un pedúnculo caudal largo y angosto. Escamas pequeñas, redondeadas y de tamaño irregular cubren los costados del cuerpo y están ausentes en el dorso y vientre. Las branquioespinas son largas, redondeadas y cercanas entre sí. Ambos sexos tienen 52 cromosomas.

The ecological trade-off between foraging gains and predation risk shapes the ecology of many taxa, including larval amphibians and fishes. Is this ecological trade-off reflected at the population level as a negative genetic correlation between traits that contribute to growth and survival? We addressed this question for a single population of Green Frog tadpoles (Rana clamitans) by estimating heritabilities and correlations of traits that mediate the trade-off. Burst speed, growth rate, and size varied among sires and were significantly heritable, but swimming activity in the presence and absence of predator odors was not. Differences among traits in heritability generally accorded with differences in genetic coefficients of variation, with the exception of activity. Growth rate was not correlated with any measure of predator avoidance or escape ability. Likewise, predator escape ability (burst speed) was not correlated with predator avoidance ability (activity and its plasticity). Our results indicate that trait correlations observed among species may not be mirrored at the intraspecific level in the form of genetic correlations within a population.

Among the eight genera of Eleotridae known from the Neotropics, two, Microphilypnus and Leptophilypnus, are greatly reduced in size and, along with the Australian genus Philypnodon, form a separate phylogenetic radiation from the other six genera. Microeleotris was described with Leptophilypnus, but Hildebrand later placed the two in synonymy. The original descriptions for these taxa were brief and did not include illustrations. As a result, confusion exists, particularly with regard to the identity of the three described species of Microphilypnus: M. ternetzi, M. amazonicus, and M. macrostoma. Three valid species of Leptophilypnus are known: L. fluviatilis, L. panamensis, and a new species from the Gulf of Mexico drainages of Guatemala that is described herein. Microphilypnus is diagnosed and new information is offered on types of the three nominal species and the habitat characteristics of the genus.

The validity of the scorpionfish, Rhinopias eschmeyeri, known only from the holotype from Mauritius, is confirmed, and the species is redescribed in detail on the basis of ten specimens from the Indo-West Pacific Ocean (Mascarene Islands to Japan and Australia). Additionally, R. frondosa and R. aphanes are redescribed. These three species are characterized by having one or two small dense black spots in the soft dorsal fin; the opercle without scales between the tips of the upper and lower opercular spines and the opercular margin; and 16 (rarely 15 or 17) pectoral-fin rays. Rhinopias eschmeyeri differs from the latter two species in aspects of form, location, and number of tentacles on the head and body; form of dorsal-fin margins and caudal-fin ray tips; shape of penultimate dorsal-fin spine; degree of development in lacrimal and suborbital ridge; and coloration.

The taxonomy of the nominal species of giant trahiras Hoplias aimara (Valenciennes, 1846) and Hoplias macrophthalmus (Pellegrin, 1907), both described from Cayenne (French Guiana), was evaluated to determine whether they constitute distinct forms and to determine the geographic distribution of the recognized species. A total of 200 specimens were examined (30–624 mm standard length). Analysis of meristic and morphometric data resulted in the recognition of a single species. Study of the type-specimens revealed that both species names, H. aimara and H. macrophthalmus, refer to the same taxon. According to the Principle of Priority of the International Code of Zoological Nomenclature the name Hoplias aimara has precedence. This species is distinguished from congeners by the presence of a vertically-elongate dark spot on the median portion of the opercular membrane and by the absence of the accessory ectopterygoid. Hoplias aimara occurs in the drainages of Rio Tocantins, Rio Xingu, Rio Tapajós, Rio Jarí, and Rio Trombetas, in coastal drainages of the Guyanas, Suriname, and state of Amapá, Brazil. In the Río Orinoco basin, the species occurs only in the Río Caroní and rivers to the east of this drainage. Literature records of Hoplias aimara for the Rio Purus and upper Río Orinoco were based on misidentifications. This pattern of geographic distribution of Hoplias aimara in rivers of the Guyanas and Brazilian Shields also occurs in other Neotropical species of fishes.

We herein document intromittent organs in four Peruvian populations of inseminating fishes of the family Characidae, genus Monotocheirodon, which may comprise new species. All females histologically analyzed from these populations, as well as a female of Monotocheirodon pearsoni, had spermatozoa within the ovary, confirming insemination. Male M. pearsoni produced aquasperm with spherical nuclei (diameter 1.6 μm), with no intromittent organ. On the other hand, males from the Peruvian populations of Monotocheirodon produced spermatozoa with slightly ovoid to elongate nuclei (lengths 1.8–4.1 μm) and possessed distinct intromittent organs. Some populations with more elongate sperm nuclei had longer intromittent organs. Each intromittent organ consisted of an elongate extension of the body wall encompassing an extension of the common sperm duct and urinary duct, which joined with one another near the base of the organ and opened to the outside at the pointed tip of the organ. Skeletal muscle cells are present throughout the organ. At the base, the skeletal muscle is oriented around the organ (circular) possibly forming a sphincter. The skeletal muscle along the organ is mainly oriented longitudinally, although some circular bundles are present. These males are apparently able to manipulate the organs by means of this muscle. The wall of the sperm duct within the organ is folded and lined with a low cuboidal epithelium. The posterior portions of the testes of males with the longest intromittent organs lack spermatogenic tissue and serve as open storage regions for mature spermatozoa.

Hematocrit, the volume fraction of blood composed of erythrocytes, influences the oxygen transport capacity of blood by affecting both the oxygen content and viscosity of the blood. In lizards, variation in locomotor performance also depends on hematocrit. Here, I report that hematocrit, total plasma protein, and consequently blood viscosity increase allometrically with body size in the Western Fence Lizard, Sceloporus occidentalis. Blood viscosity varied exponentially with hematocrit and was substantially higher at 15 C than at 30 C. Hematocrit was lower in hatchling lizards (<five weeks old) than in juveniles and adults and increased significantly between four and five weeks after hatching. The size-dependent variation in these hematological parameters may contribute to size-dependent variation in aerobic performance or may be part of another adaptive ontogenetic change (e.g., in the osmoregulatory system).

Leiognathus longispinis (Valenciennes, in Cuvier and Valenciennes, 1835) is shown to be a senior synonym of Leiognathus smithursti (Ramsay and Ogilby, 1886). Many leiognathid species were described without a broad comparison to existing species, which has contributed to nomenclatural problems. Although the holotypes of both L. longispinis and L. smithursti were collected in New Guinea, the authors of the latter name were evidently unaware of the earlier named species, which is shown herein to be morphologically indistinct from L. smithursti.

The factors that influence spatial use and movement patterns in ectotherms may have important fitness consequences. To examine the effects of sex and condition on spatial use, we used radio telemetry to observe the movement of 18 adult Nerodia sipedon in a southwest Missouri lake. Snakes generally remained in close proximity (<5 m) to aquatic habitats throughout the summer. Home range size estimates differed according to calculation method. Monthly total home range sizes peaked in mid-summer, possibly in response to increased amounts of vegetative cover, although core area sizes were consistent across the season. Contrary to previous studies of snakes, mean movement rates and home range sizes of male and gravid female N. sipedon were statistically indistinguishable and highly variable. Body size and condition influenced spatial characteristics of females, but only appeared to influence movement frequency of males. When compared to other populations, we found that our population of N. sipedon tended to occupy similarly-sized shifting core areas associated with aquatic vegetation. Future studies should focus on the measurement of resource distribution to further understand the factors influencing variation in snake movements and spatial patterns.

This study described the behavior of the swamp-dwelling African cyprinid Barbus neumayeri in response to laboratory acclimation to normoxic and hypoxic conditions to detect costs associated with hypoxia exposure. Behavioral observations were conducted every two weeks over a four-week acclimation period in both normoxic and hypoxic conditions, and feeding trials were conducted after six weeks of acclimation. Gill ventilations were shallower in normoxia-acclimated fish than in hypoxia-acclimated individuals, and gill ventilation rate declined over the hypoxia acclimation. There was no effect of hypoxia acclimation on routine activity; however, individuals acclimated to hypoxia showed a depression in feeding rate relative to normoxia acclimation. This decline in feeding activity under hypoxia acclimation may account, at least in part, for the lower condition of the hypoxia-acclimated fish. These findings suggest that hypoxia exposure does not significantly impact routine activity levels of these swamp-adapted fishes, but seems to depress higher energy activities such as feeding rate.