Taxonomy and review of the coccidian genus Cryptosporidium (protozoa, apicomplexa)

Reports of Cryptosporidium in various hosts and cross-transmission experiments are reviewed. Cryptosporidium has been found in mammals (Primates, Artiodactyla, Perissodactyla , Carnivora, Lagomorpha, and Rodentia), birds, reptiles, and fish. The only cross-transmission attempts that have been made have been from mammals to other mammals and to a few birds. Names have been given to 19 "species," but it is concluded that only four of these should be considered valid at present. These are: C. muris Tyzzer, 1907 in mammals, C. meleagridis Slavin , 1955 in birds, C. crotali Triffit , 1925 in reptiles, and C. nasorum Hoover , Hoerr , Carlton , Hinsman & Ferguson, 1981 in fish.     

A review on the impacts of feral cats (Felis silvestris catus) in the Canary Islands: implications for the conservation of its endangered fauna

Feral cats have been directly responsible for the extinction of numerous species on islands worldwide, including endemic species of mammals, birds and reptiles. The diet of feral cats in the main habitats of the Canary Islands, as generally occurred on oceanic islands, is mainly composed of introduced mammals, and native species of birds, reptiles and insects. The impact of feral cat upon the endangered species was assessed by evaluating their relative abundance in the cats’ diet and by considering their current conservation status. A total of 68 different preys were identified at species level in all studies carried out in the Canary Islands (5 mammals, 16 birds, 15 reptiles and 32 invertebrates). From all the species preyed by feral cats in the Canary Islands, only four of them are considered threatened by the IUCN Red List of Threatened Species: one endemic bird Saxicola dacotiae and three endemic giant lizards, Gallotia simonyi, Gallotia intermedia, and Gallotia gomerana. Although some efforts on management control have been carried out, it is necessary to enforce these conservation activities on those areas of Tenerife, La Gomera and El Hierro where giant lizards are still present. Furthermore some local areas where endangered bird species are highly predated should be protected. Nevertheless, it is important to take into account the presence of other introduced species such as rats, mice or rabbits in order to avoid problems derived from the hyperpredation process and mesopredator release effect.     

Prevalence and characterization of Chlamydia DNA in zoo animals in Japan

Because many people visit zoos, prevention of zoonoses is important from the standpoint of public health. This study examined the prevalence of Chlamydia among zoo animals in Japan by PCR and characterized these bacteria by performing phylogenetic analyses of the sequences of the variable domain (VD) 2 and VD4 regions of the ompA gene, which encodes the Chlamydia major outer membrane protein. Fecal samples were collected from 1150 zoo animals in five zoos and examined for Chlamydia DNA. Chlamydia psittaci DNA was found in 3.9% of mammals, 7.2% of birds and 8.1% of reptiles. The prevalence of Chlamydia pneumoniae DNA was significantly higher in reptiles (5.8%) than in mammals (0.3%) and birds (0.3%). Phylogenetic analysis of the ompA VD2 region from 18 samples showed that nine were in three different clusters containing C. psittaci strains, six were in a cluster containing C. pneumoniae strains and three each formed a distinct branch. Furthermore, phylogenetic analysis of the ompA VD4 region showed that C. pneumoniae DNAs from reptiles were close to those from human patients. The C. pneumoniae DNAs from the European glass lizard, Emerald tree boa, and Panther chameleon were classified in clusters that were distinct from other strains, suggesting that these reptiles had each been infected with a specific C. pneumoniae genotype. This study showed that diverse Chlamydia strains have been prevalent among a variety of zoo animals.     

Feeding habits of invasive American mink (Neovison vison) in northern Germany—potential implications for fishery and waterfowl

In order to collect ecological data of invasive American mink (Neovison vison) at a fishpond area in northeastern Germany, we conducted a telemetry study in which 14 mink were radio-tracked. During this project, 2,502 scats from radio-tracked individuals were collected in the period from October 2003 to October 2005. Investigated mink principally prey on fish, small mammals and birds (eggs inclusive), whereas amphibians, reptiles and invertebrates were caught infrequently. Analysing mink scats of different seasons, we found significant seasonal variations of diet composition. In spring, fish, mammals and birds were hunted in similar amounts. During summer, birds made up the main part of the diet followed by mammals. In autumn, the proportion of birds in the mink diet decreased, whereas fish gained in importance. This trend continued during the winter period, when mink preyed almost exclusively on fish. Amphibians, crustaceans, insects, molluscs and reptiles were found only occasionally in scat samples. Among birds, the mink preyed mainly on the Eurasian Coot (Fulica atra) followed by the Mallard (Anas platyrhynchos). Mammalian prey was clearly dominated by the water vole (Arvicola terrestris) and among fish, mink hunted especially perch (Perca fluviatilis), roach (Rutilus rutilus) and carp (Cyprinus carpio). Results clearly demonstrate that mink is an opportunistic predator, which hunts its prey according to availability and vulnerability, respectively. Despite the high portions of fish in their autumn and winter diet, the economic damage caused by mink seems to be negligible. However, high predation rates on birds during the breeding season indicate a potential negative impact of mink on waterfowl.     

Patterns in the geographical range sizes of ectotherms in North America

The distributions of homeothermic mammals and birds in continental North America show a distinct pattern in the configuration of their geographical ranges. Smaller ranges tend to be elongated north-south while larger ranges tend to be elongated east-west. To examine the generality of this pattern in ectotherms, we analyzed the distribution on continental North America of 139 species of mosquitoes, 164 amphibians, and 221 reptiles. Unlike birds and mammals, small ranges of ectotherms were not elongated north-south and the small ranges of snakes were elongated east-west. The distribution of ectotherms with small ranges does not appear to be affected by the major topographic features of North America which tend to run north-south. Like birds and mammals, large ranges of mosquitoes and reptiles but not amphibians are elongated east-west. The east-west orientation of mosquitoes with large ranges is not attributable to the three largest genera in North America taken singly, Aedes, Culex, or Anopheles, but appears only when all genera are pooled. The east-west orientation of reptiles with large ranges is attributable to turtles and snakes but not lizards. Climatic zones may thus affect the distribution of mosquitoes, turtles, and snakes with large ranges but are not the major determinants of range dimensions among ectotherms in general. Received: 1 September 1997 / Accepted: 8 February 1998     

REPTILIAN PHYSIOLOGY AND THE FLIGHT CAPACITY OF ARCHAEOPTERYX

Current scenarios frequently interpret the Late Jurassic bird Archaeopteryx as having had an avian-type physiology and as having been capable of flapping flight, but only from “the trees downward.” It putatively lacked capacity for takeoff and powered flight from the ground upward. Data from extant reptiles indicate that if Archaeopteryx were physiologically reptilian, it would have been capable of ground upward takeoff from a standstill, as well as “trees downward” powered flight. This conclusion is based largely on a previously unrecognized attribute of locomotory (skeletal) muscle in a variety of extant reptiles: During “burst-level” activity, major locomotory muscles of a number of active terrestrial taxa generate at least twice the power (watts kg^?1 muscle tissue) as those of birds and mammals. Reptilian physiological status also helps resolve the apparently uneven development of various flight support structures in Archaeopteryx (e.g., well-developed flight features but relatively unspecialized pectoral girdle, supracoracoideus muscles, etc.). Endothermy and capacity for longer-distance powered flight probably evolved only in Early Cretaceous birds, which were the first birds to have a keeled sternum, strap-like coracoid, and hypocleidium-bearing furcula.     

The diet of feral cats on islands: a review and a call for more studies

Cats are among the most successful and damaging invaders on islands and a significant driver of extinction and endangerment. Better understanding of their ecology can improve effective management actions such as eradication. We reviewed 72 studies of insular feral cat diet from 40 islands worldwide. Cats fed on a wide range of species from large birds and medium sized mammals to small insects with at least 248 species consumed (27 mammals, 113 birds, 34 reptiles, 3 amphibians, 2 fish and 69 invertebrates). Three mammals, 29 birds and 3 reptiles recorded in the diet of cats are listed as threatened by the IUCN. However, a few species of introduced mammals were the most frequent prey, and on almost all islands mammals and birds contributed most of the daily food intake. Latitude was positively correlated with the predation of rabbits and negatively with the predation of reptiles and invertebrates. Distance from landmass was positively correlated with predation on birds and negatively correlated with the predation of reptiles. The broad range of taxa consumed by feral cats on islands suggests that they have the potential to impact almost any native species, even the smallest ones under several grams, that lack behavioral, morphological or life history adaptations to mammalian predators. Insular feral cat??s reliance on introduced mammals, which evolved with cat predation, suggests that on many islands, populations of native species have already been reduced.     

The fastest contracting muscles of nonmammalian vertebrates express only one isoform of the ryanodine receptor.

The skeletal muscles of chickens, frogs, and fish have been reported to express two isoforms (alpha and beta) of the sarcoplasmic reticulum calcium release channel (ryanodine receptor or RYR), while mammals express only one. We have studied patterns of RYR isoform expression in skeletal muscles from a variety of fish, reptiles, and birds with immunological techniques. Immunoblot analysis with a monoclonal antibody that recognizes both nonmammalian RYR isoforms and a polyclonal antibody specific to the alpha isoform show two key results: (a) two reptilian orders share with mammals the pattern of expressing only the alpha (skeletal) RYR isoform in skeletal muscle; and (b) certain functionally specialized muscles of fish and birds express only the alpha RYR isoforms. While both isoforms are expressed in the body musculature of fish and birds, the alpha isoform is expressed alone in extraocular muscles and swimbladder muscles. The appearance of the alpha RYR isoform alone in the extraocular muscles and a fast-contracting sonic muscle in fish (toadfish swimbladder muscle) provides evidence that this isoform is selectively expressed when rapid contraction is required. The functional and phylogenetic implications of expression of the alpha isoform alone are discussed in the context of the mechanism and evolution of excitation-contraction coupling.     

An exploration of differences in the scaling of life history traits with body mass within reptiles and between amniotes

Allometric relationships linking species characteristics to body size or mass (scaling) are important in biology. However, studies on the scaling of life history traits in the reptiles (the nonavian Reptilia) are rather scarce, especially for the clades Crocodilia, Testudines, and Rhynchocephalia (single extant species, the tuatara). Previous studies on the scaling of reptilian life history traits indicated that they differ from those seen in the other amniotes (mammals and birds), but so far most comparative studies used small species samples and also not phylogenetically informed analyses. Here, we analyzed the scaling of nine life history traits with adult body mass for crocodiles (n = 22), squamates (n = 294), turtles (n = 52), and reptiles (n = 369). We used for the first time a phylogenetically informed approach for crocodiles, turtles, and the whole group of reptiles. We explored differences in scaling relationships between the reptilian clades Crocodilia, Squamata, and Testudines as well as differences between reptiles, mammals, and birds. Finally, we applied our scaling relationships, in order to gain new insights into the degree of the exceptionality of the tuatara's life history within reptiles. We observed for none of the life history traits studied any difference in their scaling with body mass between squamates, crocodiles, and turtles, except for clutch size and egg weight showing small differences between these groups. Compared to birds and mammals, scaling relationships of reptiles were similar for time‐related traits, but they differed for reproductive traits. The tuatara's life history is more similar to that of a similar‐sized turtle or crocodile than to a squamate.     

Peroxisomes in permanent and provisional kidneys

Peroxisomes in three forms of vertebrate kidney (pronephros, mesonephros, and metanephros), as permanent or provisional kidney, are summarized concerning their ultrastructure and developmental changes. Because the peroxisome is known to be diverse in mammalian metanephros, and species difference is its distinctive feature among cell organelles, information should be obtained on each kidney of each species. The ultrastructural and biochemical features of peroxisomes have at least been partly delineated in the metanephros and mesonephros, but nothing is known about the pronephros. Ultrastructural studies of the metanephric peroxisomes are present in mammals, birds, and reptiles, but information on their development is restricted to mammals and birds. As for the mesonephric peroxisomes, both ultrastructural and developmental data have been accumulating on mammals and amphibians, and ultrastructural information is present on fishes, but not on birds and reptiles. At present, studies on peroxisomes of provisional kidney have been restricted to mammalian mesonephros. The common features of renal peroxisomes previously examined are that they are spherical cell organelles with a single limiting membrane in ultrastructure, and are positive for catalase. Information on the ultrastructure and enzymes is not sufficient at present for comparing the ontogenesis of renal peroxisomes with their phylogenesis. Part of this study appeared as an original paper (11), and was presented as a poster at the International Symposium/CREST Research Conference, Peroxisome: Biogenesis, Function and Disease.     

Taxonomy and species delimitation in Cryptosporidium

Amphibians, reptiles, birds and mammals serve as hosts for 19 species of Cryptosporidium. All 19 species have been confirmed by morphological, biological, and molecular data. Fish serve as hosts for three additional species, all of which lack supporting molecular data. In addition to the named species, gene sequence data from more than 40 isolates from various vertebrate hosts are reported in the scientific literature or are listed in GenBank. These isolates lack taxonomic status and are referred to as genotypes based on the host of origin. Undoubtedly, some will eventually be recognized as species. For them to receive taxonomic status sufficient morphological, biological, and molecular data are required and names must comply with the rules of the International Code for Zoological Nomenclature (ICZN). Because the ICZN rules may be interpreted differently by persons proposing names, original names might be improperly assigned, original literature might be overlooked, or new scientific methods might be applicable to determining taxonomic status, the names of species and higher taxa are not immutable. The rapidly evolving taxonomic status of Cryptosporidium sp. reflects these considerations.     

The scaling and temperature dependence of vertebrate metabolism

Body size and temperature are primary determinants of metabolic rate, and the standard metabolic rate (SMR) of animals ranging in size from unicells to mammals has been thought to be proportional to body mass (M) raised to the power of three-quarters for over 40 years. However, recent evidence from rigorously selected datasets suggests that this is not the case for birds and mammals. To determine whether the influence of body mass on the metabolic rate of vertebrates is indeed universal, we compiled SMR measurements for 938 species spanning six orders of magnitude variation in mass. When normalized to a common temperature of 38 degrees C, the SMR scaling exponents of fish, amphibians, reptiles, birds and mammals are significantly heterogeneous. This suggests both that there is no universal metabolic allometry and that models that attempt to explain only quarter-power scaling of metabolic rate are unlikely to succeed.     

A phylogenetic survey of biliary lipids in vertebrates

Biliary lipids (bile salts, phospholipids, cholesterol, plant sterols) were determined in 89 vertebrate species (cartilaginous and bony fish, reptiles, birds, and mammals), and individual phospholipid classes were measured in 35 species. All samples contained conjugated bile salts (C(27) bile alcohol sulfates and/or N-acyl amidates of C(27) and/or C(24) bile acids). Phospholipids were generally absent in the bile of cartilaginous fish and reptiles and were present in low amounts relative to bile salts in bony fish and most birds. In mammals, the phospholipid-bile salt ratio varied widely. The bile from species with low biliary phospholipid-bile salt ratios often contained a high proportion of sphingomyelin, confirmed by HPLC-MS. In species with a high phospholipid-bile salt ratio, the predominant biliary phospholipid was phosphatidylcholine (PC). The phospholipid-bile salt ratio correlated weakly with the calculated weighted hydrophobic index value. Cholesterol was present in the bile of virtually all species, with plant sterols uniformly being present in only trace amounts. The cholesterol-bile salt ratio tended to be higher in mammals than in non-mammals, but bile of all species was unsaturated. Thus, most nonmammalian vertebrates have relatively low levels of biliary phospholipid and cholesterol, suggesting that cholesterol is eliminated predominantly as bile salts. Mammals have a higher phospholipid and cholesterol to bile salt ratio, with the dominant phospholipid being PC.     

Patterns of Vertebrate Isochore Evolution Revealed by Comparison of Expressed Mammalian,Avian, and Crocodilian Genes

Vertebrate genomes are mosaics of isochores, defined as long (>100 kb) regions with relatively homogeneous within-region base composition. Birds and mammals have more GC-rich isochores than amphibians and fish, and the GC-rich isochores of birds and mammals have been suggested to be an adaptation to homeothermy. If this hypothesis is correct, all poikilothermic (cold-blooded) vertebrates, including the nonavian reptiles, are expected to lack a GC-rich isochore structure. Previous studies using various methods to examine isochore structure in crocodilians, turtles, and squamates have led to different conclusions. We collected more than 6000 expressed sequence tags (ESTs) from the American alligator to overcome sample size limitations suggested to be the fundamental problem in the previous reptilian studies. The alligator ESTs were assembled and aligned with their human, mouse, chicken, and western clawed frog orthologs, resulting in 366 alignments. Analyses of third-codon-position GC content provided conclusive evidence that the poikilothermic alligator has GC-rich isochores, like homeothermic birds and mammals. We placed these results in a theoretical framework able to unify available models of isochore evolution. The data collected for this study allowed us to reject the models that explain the evolution of GC content using changes in body temperature associated with the transition from poikilothermy to homeothermy. Falsification of these models places fundamental constraints upon the plausible pathways for the evolution of isochores. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. Reviewing Editor: Dr. Nicolas Galtier     

Low incidence of atrial septal defects in nonmammalian vertebrates

The atrial septum enables efficient oxygen transport by separating the systemic and pulmonary venous blood returning to the heart. Only in placental mammals will the atrial septum form by the coming‐together of the septum primum and the septum secundum. In up to one of four placental mammals, this complex morphogenesis is incomplete and yields patent foramen ovale. The incidence of incomplete atrial septum is unknown for groups with the septum primum only, such as birds and reptiles. We found a low incidence of incomplete atrial septum in 11 species of bird (0% of specimens) and 13 species of reptiles (3% of specimens). In reptiles, there was a trabecular interface between the atrial septum and the atrial epicardium which was without a clear boundary between left and right atrial cavities. In developing reptiles (four squamates and one crocodylian), the septum primum initiated as a sheet that acquired perforations and the trabecular interface developed late. We conclude that atrial septation from the septum primum only results in a low incidence of incompleteness. In reptiles, the atrial septum and atrial wall develop a trabecular interface, but previous studies on atrial hemodynamics suggest this interface has a very limited capacity for shunting.     

Molecular phylogeny of the Cyathocotylidae (Digenea,Diplostomoidea) necessitates systematic changes and reveals a history of host and environment switches

The Cyathocotylidae is a globally distributed family of digeneans parasitic as adults in fish, reptiles, birds and mammals in both freshwater and marine environments. Molecular phylogenetic analysis of interrelationships among cyathocotylids is lacking with only a few species included in previous studies. We used sequences of the nuclear 28S rRNA gene to examine phylogenetic affinities of 11 newly sequenced taxa of cyathocotylids and the closely related family Brauninidae collected from fish, reptiles, birds and dolphins from Australia, Southeast Asia, Europe, North America and South America. This is the first study to provide sequence data from adult cyathocotylids parasitic in fish and reptiles. Our analyses demonstrated that the members of the genus Braunina (family Brauninidae) belong to the Cyathocotylidae, placing the Brauninidae into synonymy with the Cyathocotylidae. In addition, our DNA sequences supported the presence of a second species in the currently monotypic Braunina. Our phylogeny revealed that Cyathocotyle spp. from crocodilians belong to a separate genus (Suchocyathocotyle, previously proposed as a subgenus) and subfamily (Suchocyathocotylinae subfam. n.). Morphological study of Gogatea serpentum indicum supported its elevation to species as Gogatea mehri. The phylogeny did not support Holostephanoides within the subfamily Cyathocotylinae; instead, Holostephanoides formed a strongly supported clade with members of the subfamily Szidatiinae (Gogatea and Neogogatea). Therefore, we transfer Holostephanoides into the Szidatiinae. DNA sequence data revealed the potential presence of cryptic species reported under the name Mesostephanus microbursa. Our phylogeny indicated at least two major host switching events in the evolutionary history of the subfamily Szidatiinae which likely resulted in the transition of these parasites from birds to fish and snakes. Likewise, the transition to dolphins by Braunina represents another major host switching event among the Cyathocotylidae. In addition, our phylogeny revealed more than a single transition between freshwater and marine environments demonstrated in our dataset by Braunina and some Mesostephanus.     

Genome size, GC percentage and 5mC level in the Indonesian coelacanth Latimeria menadoensis

The living fossil Latimeria menadoensis is important to understand sarcopterygian evolution. To gain further insights into this fish species we studied its genome size, GC% and 5mC level. The genome size and the GC% of the Indonesian coelacanth seem to be very similar to those of the African coelacanth. Moreover the GC%, the CpG frequency and the 5mC level of L. menadoensis are more similar to those of fish and amphibians than to those of mammals, birds and reptiles and this is in line with the hypothesis that two different DNA methylation and CpG shortage equilibria arose during vertebrate evolution. Our results suggest that the genome of L. menadoensis has remained unchanged for several million years, maybe since the origin of the lineage which from lobe-finned fish led to tetrapods. These data fit a conservative evolutionary landscape and suggest that the genome of the extant crossopterygians may be a sort of evolutionarily frozen genome.     

Diversity of cortical bone morphology in anuran amphibians

The cortical bones of mammals, birds, and reptiles are composed of a complex of woven bone and lamellar bone (fibrolamellar bone) organized into a variety of different patterns; however, it remains unclear whether amphibians possess similar structures. Importantly, to understand the evolutionary process of limb bones in tetrapods, it is necessary to compare the bone structure of amphibians (aquatic to terrestrial) with that of amniotes (mostly terrestrial). Therefore, this study compared the cortical bones in the long bones of several frog species before and after metamorphosis. Using micro-computed tomography (CT), we found that the cortical bones in the fibrolamellar bone of Xenopus tropicalis (Pipoidea superfamily) and Lithobates catesbeianus (Ranoidea superfamily) froglets are dense, whereas those of Ceratophrys cranwelli (Hyloidea superfamily) are porous. To clarify whether these features are common to their superfamily or sister group, four other frog species were examined. Histochemical analyses revealed porous cortical bones in C. ornata and Lepidobatrachus laevis (belonging to the same family, Ceratophryidae, as C. cranwelli). However, the cortical bones of Dryophytes japonicus (Hylidae, a sister group of Ceratophryidae in the Hyloidea superfamily), Microhyla okinavensis (Microhylidae, independent of the Hyloidea superfamily), and Pleurodeles waltl, a newt as an outgroup of anurans, are dense with no observed cavities. Our findings demonstrate that at least three members of the Ceratophryidae family have porous cortical bones similar to those of reptiles, birds, and mammals, suggesting that the process of fibrolamellar bone formation arose evolutionarily in amphibians and is conserved in the common ancestor of amniotes.     

Global drivers of population density in terrestrial vertebrates

Aim

Although the effects of life history traits on population density have been investigated widely, how spatial environmental variation influences population density for a large range of organisms and at a broad spatial scale is poorly known. Filling this knowledge gap is crucial for global species management and conservation planning and to understand the potential impact of environmental changes on multiple species.

Location

Global.

Time period

Present.

Major taxa studied

Terrestrial amphibians, reptiles, birds and mammals.

Methods

We collected population density estimates for a range of terrestrial vertebrates, including 364 estimates for amphibians, 850 for reptiles, 5,667 for birds and 7,651 for mammals. We contrasted the importance of life history traits and environmental predictors using mixed models and tested different hypotheses to explain the variation in population density for the four groups. We assessed the predictive accuracy of models through cross‐validation and mapped the partial response of vertebrate population density to environmental variables globally.

Results

Amphibians were more abundant in wet areas with high productivity levels, whereas reptiles showed relatively higher densities in arid areas with low productivity and stable temperatures. The density of birds and mammals was typically high in temperate wet areas with intermediate levels of productivity. The models showed good predictive abilities, with pseudo‐R² ranging between 0.68 (birds) and 0.83 (reptiles).

Main conclusions

Traits determine most of the variation in population density across species, whereas environmental conditions explain the intraspecific variation across populations. Species traits, resource availability and climatic stability have a different influence on the population density of the four groups. These models can be used to predict the average species population density over large areas and be used to explore macroecological patterns and inform conservation analyses.     

Sociodemographics of Pet Ownership among Adolescents in Great Britain: Findings from the HBSC Study in England,Scotland, and Wales

The aim of this study was to assess the prevalence of pet ownership among adolescents in Great Britain and identify any sociodemographic differences between pet owners and non-pet owners. A total of 14,328 11-to 15-year-old adolescents from England, Scotland, and Wales were included in the analysis. Results revealed 15-year-old adolescents were significantly more likely than 11-year-old adolescents to own dogs (OR = 1.146, p < 0.001) but less likely to own fish, reptiles, or amphibians (OR = 0.629, p < 0.001), and small mammals (OR = 0.630, p < 0.001). Thirteen-year-olds were significantly more likely than 11-year-olds to own dogs (OR = 1.240, p = 0.021) and birds (OR = 1.299, p = 0.010), but significantly less likely to own fish, reptiles, or amphibians (OR = 0.795, p < 0.001). No gender differences were found. White adolescents were more likely than non-white adolescents to own all pet types. Those living in single-parent families were significantly more likely than those living with two parents to own dogs (OR = 1.186, p = 0.013) and cats (OR = 1.319, p < 0.001). Furthermore, those who reported living in stepfamilies were also more likely to own cats (OR = 1.428, p < 0.001). Adolescents with siblings were more likely to own cats (OR = 1.391, p = 0.001), fish, reptiles, or amphibians (OR = 1.220, p = 0.037) than adolescents without siblings. Adolescents with employed parents (both or one) were significantly more likely than those with unemployed parents to own dogs (OR = 1.414, p = 0.002) and birds (OR = 1.523, p = 0.018). Adolescents from high-affluence families were less likely than adolescents from low-affluence families to own dogs (OR = 0.888, p = 0.037), small mammals (OR = 0.832, p = 0.005), and birds (OR = 0.801, p = 0.046). Furthermore, family affluence differences were found in different pet types. Differences in all pet types and siblings were also found in a proxy measure of attachment to pets. This study provides evidence that pet ownership is related to several sociodemographic factors. These are relevant to take into account when performing HAI studies on adolescents.