The larva of Oculotrema hippopotami (Monogenea: Polystomatidae)

Oculotrema hippopotami Stunkard parasitizes the eye of the hippopotamus and is the only monogenean known from a mammalian host. Eggs from the uterus of O. hippopotami hatch in water in about 30 days at 24 to 26°C. The ciliated larva resembles the larvae of other polystomatid monogeneans, apart from the absence of hamuli and the unequal lengths of the two intestinal caeca.
Up to 62 eggs are stored within the uterus of the mature worm. They are not expelled when the worm is transferred from the eye of the hippopotamus to a tube of water. Development starts when the eggs are placed in fresh-water. There is no development in saline, and no evidence to suggest that larvae develop in situ around the eye, although very small worms have been collected from this site.     

A Malaria Parasite of the Hippopotamus

SYNOPSIS. A new species of Hepatocystis (H. hippopotami) is described from the blood and liver of a Rhodesian hippopotamus ( Hippopotamus amphibius ). Its relationship with other members of the genus is briefly discussed.     

Surgical castration of the male common hippopotamus (Hippopotamus amphibius)

In a prospective, clinical, surgery study we report here for the first time, in detail, on the surgical castration of 10 captive adult male common hippopotami (Hippopotamus amphibius). The successful procedures, a species-specific modification of standard equine castration techniques, provide valuable insight into the spatially dynamic nature of the common hippopotamus testis. The use of ultrasonography to locate the testis before and during the procedures and species-specific positioning during surgery greatly facilitated this distinctive procedure. Additionally, this surgical method provides an important additional tool for captive management of the common hippopotamus. Castration of individual males not only facilitates population control but can potentially also be employed to limit intermale aggression.     

The Mitochondrial Genome of the Sperm Whale and a New Molecular Reference for Estimating Eutherian Divergence Dates

Extant cetaceans are systematically divided into two suborders: Mysticeti (baleen whales) and Odontoceti (toothed whales). In this study, we have sequenced the complete mitochondrial (mt) genome of an odontocete, the sperm whale (Physeter macrocephalus), and included it in phylogenetic analyses together with the previously sequenced complete mtDNAs of two mysticetes (the fin and blue whales) and a number of other mammals, including five artiodactyls (the hippopotamus, cow, sheep, alpaca, and pig). The most strongly supported cetartiodactyl relationship was: outgroup,((pig, alpaca),((cow, sheep),(hippopotamus,(sperm whale,(baleen whales))))). As in previous analyses of complete mtDNAs, the sister-group relationship between the hippopotamus and the whales received strong support, making both Artiodactyla and Suiformes (pigs, peccaries, and hippopotamuses) paraphyletic. In addition, the analyses identified a sister-group relationship between Suina (the pig) and Tylopoda (the alpaca), although this relationship was not strongly supported. The paleontological records of both mysticetes and odontocetes extend into the Oligocene, suggesting that the mysticete and odontocete lineages diverged 32–34 million years before present (MYBP). Use of this divergence date and the complete mtDNAs of the sperm whale and the two baleen whales allowed the establishment of a new molecular reference, O/M-33, for dating other eutherian divergences. There was a general consistency between O/M-33 and the two previously established eutherian references, A/C-60 and E/R-50. Cetacean (whale) origin, i.e., the divergence between the hippopotamus and the cetaceans, was dated to ≈55 MYBP, while basal artiodactyl divergences were dated to ≥65 MYBP. Molecular estimates of Tertiary eutherian divergences were consistent with the fossil record. Received: 12 July 1999 / Accepted: 28 February 2000     

Origins of Hippopotamidae (Mammalia, Cetartiodactyla): towards resolution

The old debate on hippopotamid origins is still unresolved, balancing between two main phylogenetic hypotheses: origins within the Anthracotheriidae vs. origins within the Tayassuidae. The characters used in the literature to support one, the other, or both hypotheses were re-examined in light of a better known primitive hippopotamid morphology. A cladistic analysis was performed on the basis of these characters. On the one hand, although many features similar in hippopotamuses and anthracotheres appear to have evolved in parallel, the family Anthracotheriidae remains the best putative hippopotamus stem group on the basis of the reviewed characters. However, the precise identification of a stem group within this family is still uncertain. On the other hand, the lineage proposed in the tayassuid hypothesis should not be retained, being mostly based on some incorrect observations and without taking into account the derived or primitive nature of the features. The anatomic similarities seen between modern peccaries and Hippopotamus amphibius are the results of convergences between advanced species of both families.     

Structure of ivory

Profiles with all orientations have been used to visualize the 3D structure of ivory from tusks of elephant, mammoth, walrus, hippopotamus, pig (bush, boar, and warthog), sperm whale, killer whale, and narwhal. Polished, forming, fractured, aged, and stained surfaces were prepared for microscopy using epi-illumination. Tusks have a minor peripheral component, the cementum, a soft derivative of the enamel layer, and a main core of dentine=ivory. The dentine is composed of a matrix of particles 5-20 microm in diameter in a ground substance containing dentinal tubules about 5 microm in diameter with a center to center spacing of 10-20 microm. Dentinal tubules may be straight (most) or curly (pigs). The main findings relate to the way that dentinal tubules align in sheets to form microlaminae in the length of the tusk. Microlaminae are sheets of laterally aligned dentinal tubules. They are axial but may be radial (most), angled to the forming face (pigs and hippopotamus canines), or radial but helical (narwhals). Within the microlaminae the dentinal tubules may be radial, angled to the axis (whales, walrus, and pigs), or may change their orientation from one microlamina to the next in helicoids (canines of hippopotamuses, incisors of proboscidea). In the nonbanded, featureless ivories from the hippopotamus incisors, the dentinal tubules form radial microlamina from which the arrangements in other ivories can be derived. In the canines of hippopotamuses and incisors of proboscidea, the dentinal tubule orientation changes incrementally from one microlamina to the next in a helicoid, a stack of dentinal tubules that change their orientation by 180 degrees anticlockwise. Dentinal tubules having different orientations are laid down concurrently, not layer by layer as in most examples of helicoidal architecture (e.g., insect cuticle). In proboscidean ivory, the microlaminae are radial, normal to the banding of growth layers marking the plane of deposition. They form radial segments with each 180 degrees turn in the orientation of their constituent dentinal tubules. Below the cementum they are almost complete 180 degrees helicoids, but nearer to the core they become narrower with the loss of radially oriented dentinal tubules. These truncated helicoidal patterns appear in longitudinal profile as VVVV feather patterns rather than intersection intersection intersection intersection, each V or intersection being the side view of a partial or complete helicoid. The Schreger pattern in proboscidean ivory consists of these helicoids divided tangentially into columns in the length of the tusk. Narwhals have the most abundant matrix particles with their radial/helical dentinal tubules having a twist opposite to that in the cementum.     

Different Sex Allocations in Two Related Species: The Case of the Extant Hippopotamus

Social and reproductive systems remain among the main predictors affecting mammalian birth sex ratio. The two extant hippopotamus species differ in their social and reproductive systems. While common hippopotamus (Hippopotamus amphibius) form herds and tend to be polygynous, solitary living pygmy hippopotamus (Choeropsis liberiensis) are promiscuous. Although it is one of the most studied topics, only few empirical studies using large sample sizes have reported distorted birth sex ratio. We examined the birth sex ratio in both hippopotamus species using international studbooks including large data sets exceeding a thousand individuals (1138 for common hippopotamus and 1161 for pygmy ones). In both species, the birth sex ratio differed from 1:1. Whereas more males than females were recorded in common hippopotamus (53.9% males), the opposite was found in pygmy hippopotamus (41.5% males). We also found that the birth sex ratio was affected by individual dams in common hippopotamus, and by individual sires in pygmy hippopotamus. The most plausible explanation for differentially skewed birth sex ratios in both species may be related to differences in social and reproductive systems. Whereas the polygynous, sexually dimorphic common hippopotamus biased the birth sex ratio towards males, the promiscuous and sexually monomorphic pygmy hippopotamus skewed the sex ratio in favour of females. Our results are in line with recent studies showing that not only manipulation by the mother (in common hippopotamus), but also by the father (in pygmy hippopotamus), may be responsible for the birth sex ratio in different species.     

A newly-identified lineage of Schistosoma

Because of their role in causing schistosomiasis, flukes of the genus Schistosoma are the best known of all digeneans. The genus has traditionally been divided into four familiar species groups. Here we report on three poorly known species of Schistosoma, one of which, Schistosoma hippopotami, is known from the hippopotamus, one of which is provisionally identified as Schistosoma edwardiense, another hippo parasite, and a third that has not previously been described. All were collected from freshwater snails obtained from Lake Edward, western Uganda, the type locality for both known hippo schistosomes. The three different kinds of schistosome cercariae differ from one another in size, and all are readily differentiated by their long tail stems from the cercariae of human-infecting species. Furthermore, each was recovered from a different genus of snail host, Biomphalaria sudanica, Bulinus truncatus or Ceratophallus natalensis. Molecular analysis, based on 8350 bases of combined nuclear and mitochondrial DNA, groups these three long tail-stem cercariae into a well supported clade that does not associate with any of the recognised species groups. The placement of this clade, basal to all African species plus several Asian species, suggests that there has been an ancient association between Schistosoma and hippos. This new African Schistosoma clade advocates the need for further modification of the traditional species group-based classification. Two of the four species groups are paraphyletic. It also suggests that Schistosoma has been remarkably plastic with respect to adapting to snail hosts-three distantly related genera of planorbid snails have been exploited by worms within a single clade. Finally, it adds a new layer of complexity to deciphering the origins of Schistosoma, often considered to be African but recently challenged as being Asian. In the late Cenozoic the distribution of hippo species straddled both Africa and Asia and they may have provided a means for the introduction of blood flukes to Africa.     

If hippopotamuses cannot swim,how did they colonize islands?

Owing to their aquatic lifestyle, hippopotamuses are normally believed to have reached islands by swimming. Yet, some studies suggest they cannot swim due to their relatively high density. If so, this raises the question of how hippopotamuses would have reached some islands. Their immigration into the British Isles, Sicily, Malta, Zanzibar and Mafia can be accounted for, because these islands sit on continental shelves and were often linked to the mainland during the Pleistocene glacio‐eustatic sea‐level falls. In contrast, their occurrence in Crete, Cyprus and Madagascar would be more difficult to explain. Available geological evidence does not seem to rule out that the latter islands might have been connected with the nearest mainland areas in very recent times. This study intends to consider possibilities about how hippopotamuses reached islands and to show that more effective collaboration is required among specialists involved with the study of insular evolution, colonization and speciation.     

Influence of river geomorphologic features on hippopotamus density distribution along the Luangwa River,Zambia

River geomorphologic features along a 165‐km stretch of the Luangwa River in eastern Zambia were assessed in 2008 to determine their influence on hippopotamus pattern of density distribution. A fixed high wing Cessna 206 aircraft fitted with geographical positioning system (GPS) was flown over the stretch taking coordinates for each geomorphologic feature, followed by taking length in metres of each geomorphologic feature on the ground. A total hippopotamus count was later carried out along the same stretch. Sixty‐four geomorphologic features were recorded along the stretch of the river. Of the total geomorphologic features recorded, 34 (53%) were river bends, 13 (20%) lagoons and 17 (27%) were confluences. Hippo density was highest in river bends (75.48%), confluences (9.18%), lagoons 6.03% and all the other features put together had only 9.38%. It was concluded that geomorphologic features influenced hippopotamus pattern of density distribution in the Luangwa River.     

Establishment and characterization of fibroblast cultures derived from a female common hippopotamus (Hippopotamus amphibius) skin biopsy

The population decline of the common hippopotamus (Hippopotamus amphibius) has necessitated the preservation of their genetic resources for species conservation and research. Of all actions, cryopreservation of fibroblast cell cultures derived from an animal biopsy is considered a simple but efficient means. Nevertheless, preserving viable cell cultures of the common hippopotamus has not been achieved to our knowledge. To this end, we established and characterized fibroblast cell cultures from the skin sample of a newborn common hippopotamus in this study. By combining the tissue explant direct culture and enzymatic digestion methods, we isolated a great number of cells with typical fibroblastic morphology and high viability. Neither bacteria/fungi nor mycoplasma was detectable in the cell cultures throughout the study. The population doubling time was 34 h according to the growth curve. Karyotyping based on Giemsa staining showed that the cultured cells were diploid with 36 chromosomes in all, one pair of which was sex chromosomes. The amplified mitochondrial cytochrome C oxidase subunit I gene sequence of the cultured cells was 99.26% identical with that of the registered H. amphibius complete mitochondrial DNA, confirming the species of origin of the cells. Flow cytometry and immunofluorescence staining results revealed that the detected cells were positive for fibroblast markers, S100A4, and vimentin. In conclusion, we generated the fibroblast cell cultures from a common hippopotamus and identified their characteristics using multiple techniques. We believe the cryopreserved cells could be useful genetic materials for future research.     

Evolution of ontogeny in the hippopotamus skull: using allometry to dissect developmental change

Allometry describes the effect of size change on aspects of an organism's form and can be used to summarize the developmental history of growing parts of an animal. By comparing how allometric growth differs between species, it is possible to reveal differences in their pathways of development. The ability to compare and categorize developmental change between species is demonstrated here using morphometric methods. This involves the interspecific statistical comparison of a large number of bivariate relationships that summarize ontogenetic trajectories. These linear ontogenetic trajectories can be modified as they evolve in any of three ways: ontogenetic scaling indicative of change in the duration of growth, lateral shifts indicative of changes in prenatal development, and directional change indicative of novel modes of postnatal growth. I apply this analysis to skulls of the common hippopotamus ( Hippopotamus amphibius ) and the pygmy hippopotamus ( Hexaprotodon liberiensis ). The number of allometric changes falling into each category was statistically determined and Jolicoeur's multivariate generalization of simple allometry was used to provide an overview of cranial variation. For these skulls, directional change was not found to be statistically significant, but ontogenetic scaling and lateral shifts were both common. This indicates that conserved patterns of growth covariance (ontogenetic scaling) can be separated from novel or derived patterns (directional change and/or lateral shifts). This study demonstrates that He. liberiensis is not simply an ontogenetically scaled version of its larger relative. The evolutionary implications of allometric growth variation are discussed in the light of these findings and those of other studies.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 625–638.     

Gastrointestinal parasites of critically endangered primates endemic to Tana River, Kenya: Tana River red colobus (Procolobus rufomitratus) and crested mangabey (Cercocebus galeritus)

We conducted fecal egg counts of gastrointestinal parasites of 2 critically endangered primates endemic to the forest of Tana River, Kenya. We aimed to use the fecal egg counts as proxies to quantify the prevalence of gastrointestinal parasites between the 2 primates. The Tana River red colobus (Procolobus rufomitratus) and crested mangabey (Cercocebus galeritus) are of similar body size, but their behavioral ecology is very different. We predicted that mangabeys would have a higher prevalence of parasites because they are mostly terrestrial omnivores, live in larger social groups, and therefore range widely. We detected 10 nematodes and 3 protozoans in mangabeys and 7 nematodes and 2 protozoans in colobus. We detected a higher number of different parasite species in individual mangabeys, and 4 of the 5 nematodes requiring intermediate hosts were found in mangabeys. The overall prevalence of parasites was higher for mangabeys, but this difference was not statistically significant. For colobus, we found a trend whereby the number of different parasite species in individual monkeys was higher in males and in lactating females. However, there was no difference in the prevalence of parasites between the sexes or between lactating and nonlactating females.     

A SINE species from hippopotamus and its distribution among animal species

Thirty sequences of a short interspersed repetitive element (SINE) were isolated from genomic DNA of Hippopotamus amphibius (hippopotamus). RNA polymerase III split promoter sequence was observed in all of the 30 sequences; and poly(A)-like structure at 3′-end, as well as direct repeat flanking to the repetitive sequence in many of the 30 sequences. A comparison of the consensus sequence of the 30 sequences with sequences in a DNA database (DDBJ/GENBANK/EMBL) revealed 93% homology to the consensus sequence of a whale SINE, CHR-2, and 73% homology to mouse glutamic acid tRNA. Phylogenetic analysis of tRNA-related regions of the sequences with all of the mouse tRNAs revealed that glutamic acid tRNA was genetically closest to the hippopotamus SINE. In addition, the tRNA-related region of the consensus sequence was folded into a cloverleaf structure as with mouse glutamic acid tRNA. These findings led us to conclude that the SINE of hippopotamus was genetically related to a whale SINE, CHR-2 [the hippopotamus SINE was named CHR-2(hippo)] and was a retroposon derived from glutamic acid tRNA. Hipo53 and hipo95, which were the genetically most separated CHR-2(hippo) sequences in the present study, were used as a probe for dot-blot hybridization to examine the distribution of their homologous sequences among animal species. Although the distribution spectra of hipo53 and hipo95 homologous sequences in animal species differed to some extent, large amounts of both sequences were found in Hippopotamus amphibius and Globicephala macrorhynchus (whale); and small amounts in most of the animal species in Artiodactyla examined. These findings indicated that the hippopotamus and whale had more recently branched off from the clade that includes chevrotain and pecorans than the other animal species in the clade. The 30 CHR-2(hippo) sequences were aligned, and the substitution rates among the sequences were calculated with a different substitution rate model for transition and for transversion. The calculation combined with the mutation rate of the pseudogenes (r = 4.6 × 10⁹) indicated that CHR-2(hippo) sequences diversified at least 132 million years ago (Myr). Received: 1 December 1997 / Accepted: 4 March 1998     

Female nile hippopotamus (Hippopotamus amphibius) space use in a naturalistic exhibit

Zoological institutions provide naturalistic exhibits for their animals in order to offer a more appealing look for visitors and give the animal the opportunity to engage in more natural behaviors. Examining space use of the animals in the naturalistic exhibit may aid in the management of these animals and inform future naturalistic exhibit design. The hippopotamus is an amphibious ungulate that spends much of its days in the wild in the water but may be found along the banks of the rivers basking in the sun. Our objective was to determine how captive female hippos utilize their exhibit by examining whether hippos selected for certain areas of a naturalistic exhibit. Scan sample data were collected on a group of nine captive female hippos housed at Disney's Animal Kingdom®. Using ArcView, the data were analyzed to determine distribution of hippos in the exhibit and their utilization of depth categories while in the water. Hippos were found to aggregate in preferred areas of the exhibit, mostly water, and selected most for water depths of 0.6–1.0 m. These results will aid in the understanding of hippopotamus space use and may aid zoological institutions in the design of naturalistic exhibits for hippos. Zoo Biol 31: 129–136, 2012. © 2010 Wiley Periodicals, Inc.     

Subordinal artiodactyl relationships in the light of phylogenetic analysis of 12 mitochondrial protein-coding genes

Ursing, B. M., Slack, K. E. & Arnason, U. (2000) Subordinal artiodactyl relationships in the light of phylogenetic analysis of 12 mitochondrial protein-coding genes. — Zoologica Scripta , 29 , 83–88.
Extant artiodactyls (even-toed hoofed mammals) are traditionally divided into three main lineages: Suiformes (pigs, peccaries and hippopotamuses), Tylopoda (camels and llamas) and Ruminantia (bovids, deer, tragulids and giraffes). Recent molecular studies have not supported a close relationship between pigs and hippopotamuses, however, instead grouping hippopotamuses with Cetacea (whales, dolphins and porpoises). In this study we have sequenced the complete mitochondrial genome of a tylopod — the alpaca (Lama pacos), the only artiodactyl suborder not previously represented by a complete mitochondrial sequence. This sequence was included in phylogenetic analyses together with the complete mitochondrial protein-coding sequences of other artiodactyls plus two cetaceans. Despite the length of the data set, the relationship between Suina (Suiformes sine Hippopotamidae), Tylopoda and Ruminantia/Hippopotamidae/Cetacea could not be fully resolved, however, a basal position of the alpaca (Tylopoda) relative to the other artiodactyls/cetaceans was unsupported.     

Inclusion of Cetaceans Within the Order Artiodactyla Based on Phylogenetic Analysis of Pancreatic Ribonuclease Genes

Mammalian secretory ribonucleases (RNases 1) form a family of extensively studied homologous proteins that were already used for phylogenetic analyses at the protein sequence level previously. In this paper we report the determination of six ribonuclease gene sequences of Artiodactyla and two of Cetacea. These sequences have been used with ruminant homologues in phylogenetic analyses that supported a group including hippopotamus and toothed whales, a group of ruminant pancreatic and brain-type ribonucleases, and a group of tylopod sequences containing the Arabian camel pancreatic ribonuclease gene and Arabian and Bactrian camel and alpaca RNase 1 genes of unknown function. In all analyses the pig was the first diverging artiodactyl. This DNA-based tree is compatible to published trees derived from a number of other genes. The differences to those trees obtained with ribonuclease protein sequences can be explained by the influence of convergence of pancreatic RNases from hippopotamus, camel, and ruminants and by taking into account the information from third codon positions in the DNA-based analyses. The evolution of sequence features of ribonucleases such as the distribution of positively charged amino acids and of potential glycosylation sites is described with regard to increased double-stranded RNA cleavage that is observed in several cetacean and artiodactyl RNases which may have no role in ruminant or ruminant-like digestion. Received: 2 June 1998 / Accepted: 31 August 1998     

Determinants of distribution and prevalence of avian malaria in blue tit populations across Europe: separating host and parasite effects

Although avian malarial parasites are globally distributed, the factors that affect the geographical distribution and local prevalence of different parasite lineages across host populations or species are still poorly understood. Based on the intense screening of avian malarial parasites in nine European blue tit populations, we studied whether distribution ranges as well as local adaptation, host specialization and phylogenetic relationships can determine the observed prevalences within populations. We found that prevalence differed consistently between parasite lineages and host populations, indicating that the transmission success of parasites is lineage specific but is partly shaped by locality-specific effects. We also found that the lineage-specific estimate of prevalence was related to the distribution range of parasites: lineages found in more host populations were generally more prevalent within these populations. Additionally, parasites with high prevalence that were also widely distributed among blue tit populations were also found to infect more host species. These findings suggest that parasites reaching high local prevalence can also realize wide distribution at a global scale that can have further consequences for host specialization. Although phylogenetic relationships among parasites did not predict prevalence, we detected a close match between a tree based on the geographic distance of the host populations and the parasite phylogenetic tree, implying that neighbouring host populations shared a related parasite fauna.     

Structure of populations and ecological nishes of ectoparasites in the parasite communities of small forest mammals

The paper reports the results of eight-year investigations on the ectoparasites of rodents and insectivores carried out in southern taiga of the Ilmen-Volkhov lowland (Novgorod Region) and Kurgolovsky reserve (Leningrad Region). Twelve species of small mammals were captured including three dominate species--bank vole Clethrionomys glareolus (2722 specimens), common shrew Sorex araneus (1658 specimens), and wood mouse Apodemus uralensis (367 specimens). Parasite community of the bank vole comprises 34 species of mites, ticks, and insects, the community of common shrew comprises 25 species, and the community of A. uralensis includes 28 species. Taxonomic diversity of the ectoparasite communities was shown to be based on the diversity of types of parasitism and ecological nishes of the host body. Permanent ectoparasites are found to be represented by 2 species of lie and 14 species of acariform mites. The group of temporary parasites includes 13 species of fleas, 10 species of gamasid mites. 3 ixodid species and 1 Trombiculidae. There is a common pool of temporary parasites of small mammals in the ecological system of taiga. Significance of different shrew and rodent species as hosts were found to be dependent on the population density in possible hosts and many other factors. Species diversity in the parasite communities of different small mammal species is dependent on the number of possible ecological nishes in the host body. Actual infill of these nishes by ectoparasites is usually lesser than potential one. Species composition of temporary parasites, their occurrence and abundance changes according to season. Interspecific competition in the temporary parasite species can decrease because of the seasonal disjunction of their population peaks. Diversification of the ecological niches of ectoparasites allow simultaneous feeding of more parasite individuals on one host, than in the case of parasitising of single species or several species with similar ecological nishes. The distribution of parasites on their hosts was also studied. The aggregative distribution has been found in ixodid larvae only, and the distribution of fleas was close to the Poisson distribution. Deviations from the aggregative distribution can be an effect of several independent factors, including limited ability of small mammals for providing numerous parasites with food. On the most part of hosts simultaneous parasitizing of no more than 1-3 individuals of each tick, mite, and flea species was registered. Excessive infestation by ectoparasites may probably be limited by effective reactions of self-purification in the mammal hosts.     

THE COPPER CONTENT OF THE LIVER OF SOME GAME ANIMALS IN KENYA

The liver copper levels of a number of game animals in Kenya were determined. It was found that the results fell naturally into two fairly distinct groups; for those with simple and those with complex stomachs respectively. The latter, generally speaking, had a higher mean content and a much greater range, with more individual variation. An exception to this was the hippopotamus which appeared to have a much higher content of liver copper than others in the simple stomach group.