Patterns of coccidial prevalence in lizards of Mauritius

This paper reports prevalence of coccidial oocysts in fecal samples from 6 endemic and 2 introduced lizard species on Mauritius, an island nation in the Indian Ocean. Total coccidian prevalence was 54% (n = 341) for the endemic 'ornate day gecko,' Phelsuma ornata; 48% (n = 159) for the endemic 'Durrell's night gecko,' Nactus durrelli; 53% (n = 15) for the endemic 'Serpent Island night gecko,' N. serpensinsula; and 78% (n = 248) for the introduced gecko, Hemidactylus frenatus. These high prevalences may reflect lack of long-lasting immune response to coccidial infection. There were few significant differences in prevalence among age, island, sex, or body condition within species, suggesting that these coccidia are relatively nonpathogenic and have little effect on host fitness. Prevalence was higher in the dry season than the wet season. These data suggest other factors, such as low host immune response to reinfection, affect overall prevalence more significantly than the effect of humidity on oocyst survival on Mauritius. No coccidia were found in samples from the endemic 'Gunner's Quoin night gecko,' N. coindemirensis (n = 155), probably reflecting parasite extinction due to a host population bottleneck following historical introduction of rats. There was no evidence of competitive or facilitative interactions between Eimeria sp. and Isospora sp., but evidence of competition between 2 Eimeria species in the 'ornate day gecko,' Phelsuma ornata. No evidence was found of cross-species infection, suggesting that reptile coccidia have high host specificity and are, therefore, poor subjects for studies of parasite-mediated competition and the evolution of sex.     

The founding of Mauritian endemic coffee trees by a synchronous long‐distance dispersal event

The stochastic process of long‐distance dispersal is the exclusive means by which plants colonize oceanic islands. Baker's rule posits that self‐incompatible plant lineages are unlikely to successfully colonize oceanic islands because they must achieve a coordinated long‐distance dispersal of sufficiently numerous individuals to establish an outcrossing founder population. Here, we show for the first time that Mauritian Coffea species are self‐incompatible and thus represent an exception to Baker's rule. The genus Coffea (Rubiaceae) is composed of approximately 124 species with a paleotropical distribution. Phylogenetic evidence strongly supports a single colonization of the oceanic island of Mauritius from either Madagascar or Africa. We employ Bayesian divergence time analyses to show that the colonization of Mauritius was not a recent event. We genotype S‐RNase alleles from Mauritian endemic Coffea, and using S‐allele gene genealogies, we show that the Mauritian allelic diversity is confined to just seven deeply divergent Coffea S‐RNase allelic lineages. Based on these data, we developed an individual‐based model and performed a simulation study to estimate the most likely number of founding individuals involved in the colonization of Mauritius. Our simulations show that to explain the observed S‐RNase allelic diversity, the founding population was likely composed of fewer than 31 seeds that were likely synchronously dispersed from an ancestral mainland species.     

Using ancient and recent DNA to explore relationships of extinct and endangered Leiolopisma skinks (Reptilia: Scincidae) in the Mascarene islands

Phylogenetic analysis, using 1455 bp of recent mtDNA (cytochrome b 714 bp, 12S rRNA 376 bp) and nuclear (c-mos 365 bp) sequence from 42 species and 33 genera of Scincidae, confirms Leiolopisma telfairii, now confined to Round island off Mauritius, is a member of the mainly Australasian Eugongylus group of the Lygosominae. Ancient mtDNA (cytochrome b 307 bp, 12S rRNA 376 bp) was also extracted from subfossils of two other Mascarene taxa that are now extinct: the giant L. mauritiana from Mauritius and Leiolopisma sp., known only from fragmentary remains from Réunion. Sequence divergences of 4.2-5.7% show that all three forms were distinct and form a clade. There is restricted evidence that L. mauritiana and L. sp. from Réunion were sister species. Monophyly and relationships suggest Leiolopisma arose from a single transmarine invasion of the oceanic Mascarene islands from Australasia, 5600-7000 km away. This origin is similar to that of Cryptoblepharus skinks and Nactus geckos in the archipelago but contrasts with Phelsuma day geckos, which appear to have arrived from Madagascar where Mascarene Cylindraspis tortoises may also have originated. Diversification of the known species of Leiolopisma occurred from about 2.3-3.4 Mya, probably beginning on Mauritius with later invasion of Réunion. The initial coloniser may have had a relatively large body-size, but L. mauritiana is likely to have become gigantic within the Mascarenes. Other relationships supported by this investigation include the following. Scincines: Pamelaescincus+Janetaescincus, and Androngo (Amphiglossus, Paracontias). Lygosomines: Sphenomorphus group--(Sphenomorphus, Lipinia (Ctenotus, Anomalopus (Eulamprus and Gnypetoscincus))): Egernia group--Egernia (Cyclodomorphus, Tiliqua); Eugongylus group--(Oligosoma, Bassiana. (Lampropholis (Niveoscincus, Carlia))).     

The Mauritian Piracy Act: A Comment on the Director of Public Prosecutions v Ali Abeoulkader Mohamed Decision

In 2011 Mauritius adopted the Piracy and Maritime Violence Act (the Act). The Act does not expressly state that Mauritian Courts have jurisdiction over offenses committed outside of Mauritius. In Director of Public Prosecutions v Ali Abeoulkader Mohamed & Ors, the Mauritian Supreme Court dealt with the issue of whether the Act applied to non-Mauritius citizens where the alleged piracy acts had been committed outside of Mauritius on the high seas. This article assesses the Supreme Court's decision and suggest ways that the Act can be strengthened.     

Feeding response of the Aldabra giant tortoise (Geochelone gigantea) to island plants showing heterophylly

Aim Heterophylly is present in many plant species on oceanic islands. Almost all of these plants are island endemics, and heterophylly may have evolved as a response to feeding from large insular browsers such as giant tortoises and flightless birds. We tested this anti‐browser hypothesis by feeding Aldabra giant tortoises (Geochelone gigantea) with leaves of native Mauritian plants to see if they distinguished between juvenile and adult leaves and between heteophyllous and homophyllous species. Location Mauritius. Methods In a choice experiment we recorded feeding response of four captive Aldabra giant tortoises to 10 species of Mauritian plants, of which seven were heterophyllous and three homophyllous. Results In general, juvenile leaves of heterophyllous species showed convergence in shape and midrib coloration. Homophyllous foliage was preferred to heterophyllous, and among heterophyllous species adult foliage was preferred to juvenile. Main conclusions Several Mascarene heterophyllous plants show convergence in morphology of juvenile leaves and these are avoided by giant tortoises. This indicates a strong selection history from large browsers such as the giant tortoises. The Mascarene example is in accordance with several other comparable cases of plant‐large browser interactions from other archipelagos.     

Mutation analysis of a Mauritian hereditary breast cancer family reveals the BRCA2 6503deITT mutation previously found to recur in different ethnic populations

Mauritius, a small island some 855 km off the east coast of Madagascar, has a multiethnic population of about 1.2 million with a high population density of about 611 per km(2). The recent industrialization of the island seems to have been accompanied, in less than 10 years, by an increase of at least 30% in breast cancer incidence. We have detected the BRCA2 6503delTT mutation in two sisters of the same family of Indian origin but living in Mauritius for at least five generations. This mutation has been found to recur in geographically diverse populations and haplotype analysis has shown a common ancestry. The haplotype of the mutation found in the Mauritian family differs from that found in other populations harbouring the same mutation, suggesting that the BRCA2 6503delTT mutation most likely arose independently.     

NOTES ON THE BIOLOGY OF THE MAURITIUS BLACK BULBUL HYPSIPETES OLIVACEUS

Safford, R.J. 1996. Notes on the biology of the Mauritius Black Bulbul Hypsipetes olivaceus. Ostrich 67: 151–154.

The Mauritius Black Bulbul Hypsipetes olivaceus is a threatened passerine endemic to Mauritius. Direct observations of food items indicate that it is an arboreal omnivore. Animal prey consists mostly of insects and native day-geckoes (Phelsuma spp.). A wide variety of native and exotic fruits is also taken. The species is apparently monogamous, with an egg-laying season extending from at least November to February, usual clutch and brood sizes of two to three, ability rapidly to lay repeat clutches in a new nest, and post-breeding complete moult. In these respects, its annual cycle resembles that of the other native Mauritian passerines. It occurs at very low population density compared to its Indian Ocean congeners; possible reasons for this are given.     

Mitochondrial DNA of the Mauritian macaques (Macaca fascicularis): An example of the founder effect

Macaque monkeys (Macaca fascicularis) were introduced to the island of Mauritius approximately 400 years ago. This study compares the mitochondrial DNA of macaques on Mauritius with those from Indonesia and the Philippines. The goal is to measure the amount of evolutionary change that has occurred in this isolated population over 400 years, and to address questions regarding the origin of the Mauritian founders. Amplification of the control region of the mitochondrial genome via the polymerase chain reaction yielded an 1800 base pair DNA fragment which was surveyed for variation using restriction endonucleases. Fifty-two macaques were separated into 17 haplotypes by mapping the restriction sites. No haplotypes were shared among the three populations, and only two closely related haplotypes appeared in the Mauritian sample. Nucleotide variation in the mitochondrial DNA in the Mauritian sample was 10-fold less than the Indonesian and Filipino samples. In contrast, allozyme data estimates of genetic diversity on Mauritius are similar to populations from the ancestral range. The evidence of the more severe bottleneck as measured by mitochondrial data may be explained in part by almost exclusive male dispersal in this species, and may support models of founder events in which rapid population growth prevents substantial loss of nuclear variation. The mitochondrial evidence supports the morphologically and historically based hypothesis that the original founders came from Indonesia. © 1995 Wiley-Liss, Inc.     

Electrocardiographic abnormalities and associated factors in Chinese living in Beijing and in Mauritius. The Mauritius Non-Communicable Disease Study Group.

OBJECTIVE--To compare the prevalence of electrocardiographic abnormalities and to evaluate the association between these abnormalities and the levels of coronary heart disease among Chinese living in different environments. DESIGN--Cross sectional surveys. SETTING--Beijing, China, and the island of Mauritius. SUBJECTS--Random samples of people aged 35-64 years in Beijing (621 men, 642 women) in 1984 and in Mauritius among Chinese (137 men, 130 women) and non-Chinese (1265 men, 1432 women) in 1987. MAIN OUTCOME MEASURES--Prevalence of electrocardiographic abnormalities suggesting coronary heart disease and of associated risk factors. RESULTS--Prevalence of electrocardiographic abnormalities suggesting coronary heart disease was significantly lower in Beijing (4.0%) than in Mauritian Chinese (24.3%) and Mauritian non-Chinese (24.5%). Mean serum concentrations of total and non-high density lipoprotein cholesterol were lower in Beijing Chinese than in Mauritian Chinese, but smoking and hypertension were slightly more prevalent. Overall, men with electrocardiographic abnormalities had higher risk factor levels than those with a normal electrocardiogram regardless of ethnic origin. CONCLUSIONS--The prevalence of coronary heart disease and associated risk factors was different among Chinese living in two different environments: in Beijing in the People''s Republic of China and in Mauritius. Chinese, who traditionally have a very low frequency of coronary heart disease, are by no means protected against coronary heart disease and other non-communicable diseases. Therefore, primary prevention of coronary heart disease is a major challenge for preventive medicine in China, as well as in many other developing countries.     

Unusually high frequency MHC class I alleles in Mauritian origin cynomolgus macaques

Acute shortages of Indian origin Rhesus macaques significantly hinder HIV/AIDS research. Cellular immune responses are particularly difficult to study because only a subset of animals possess MHC class I (MHC I) alleles with defined peptide-binding specificities. To expand the pool of nonhuman primates suitable for studies of cellular immunity, we defined 66 MHC I alleles in Cynomolgus macaques (Macaca fascicularis) of Chinese, Vietnamese, and Mauritian origin. Most MHC I alleles were found only in animals from a single geographic origin, suggesting that Cynomolgus macaques from different origins are not interchangeable in studies of cellular immunity. Animals from Mauritius may be particularly valuable because >50% of these Cynomolgus macaques share the MHC class I allele combination Mafa-B*430101, Mafa-B*440101, and Mafa-B*460101. The increased MHC I allele sharing of Mauritian origin Cynomolgus macaques may dramatically reduce the overall number of animals needed to study cellular immune responses in nonhuman primates while simultaneously reducing the confounding effects of genetic heterogeneity in HIV/AIDS research.     

Seed dispersal and establishment of endangered plants on Oceanic Islands: the Janzen-Connell model, and the use of ecological analogues

Background

The Janzen-Connell model states that plant-specific natural enemies may have a disproportionately large negative effect on progeny close to maternal trees. The majority of experimental and theoretical studies addressing the Janzen-Connell model have explored how it can explain existing patterns of species diversity in tropical mainland areas. Very few studies have investigated how the model''s predictions apply to isolated oceanic islands, or to the conservation management of endangered plants. Here, we provide the first experimental investigation of the predictions of the Janzen-Connell model on an oceanic island, in a conservation context. In addition, we experimentally evaluate the use of ecological analogue animals to resurrect the functional component of extinct frugivores that could have dispersed seeds away from maternal trees.

Methodology/Principal Findings

In Mauritius, we investigated seed germination and seedling survival patterns of the critically endangered endemic plant Syzygium mamillatum (Myrtaceae) in relation to proximity to maternal trees. We found strong negative effects of proximity to maternal trees on growth and survival of seedlings. We successfully used giant Aldabran tortoises as ecological analogues for extinct Mauritian frugivores. Effects of gut-passage were negative at the seed germination stage, but seedlings from gut-passed seeds grew taller, had more leaves, and suffered less damage from natural enemies than any of the other seedlings.

Conclusions/Significance

We provide the first experimental evidence of a distance-dependent Janzen-Connell effect on an oceanic island. Our results potentially have serious implications for the conservation management of rare plant species on oceanic islands, which harbour a disproportionately large fraction of the world''s endemic and endangered plants. Furthermore, in contrast to recent controversy about the use of non-indigenous extant megafauna for re-wilding projects in North America and elsewhere, we argue that Mauritius and other oceanic islands are ideal study systems in which to empirically explore the use of ecological analogue species in restoration ecology.     

Biogeography and diversification of hermit spiders on Indian Ocean islands (Nephilidae: Nephilengys)

The origin of the terrestrial biota of Madagascar and, especially, the smaller island chains of the western Indian Ocean is relatively poorly understood. Madagascar represents a mixture of Gondwanan vicariant lineages and more recent colonizers arriving via Cenozoic dispersal, mostly from Africa. Dispersal must explain the biota of the smaller islands such as the Comoros and the chain of Mascarene islands, but relatively few studies have pinpointed the source of colonizers, which may include mainland Africa, Asia, Australasia, and Madagascar. The pantropical hermit spiders (genus Nephilengys) seem to have colonized the Indian Ocean island arc stretching from Comoros through Madagascar and onto Mascarenes, and thus offer one opportunity to reveal biogeographical patterns in the Indian Ocean. We test alternative hypotheses on the colonization route of Nephilengys spiders in the Indian Ocean and simultaneously test the current taxonomical hypothesis using genetic and morphological data. We used mitochondrial (COI) and nuclear (ITS2) markers to examine Nephilengys phylogenetic structure with samples from Africa, southeast Asia, and the Indian Ocean islands of Madagascar, Mayotte, Réunion and Mauritius. We used Bayesian and parsimony methods to reconstruct phylogenies and haplotype networks, and calculated genetic distances and fixation indices. Our results suggest an African origin of Madagascar Nephilengys via Cenozoic dispersal, and subsequent colonization of the Mascarene islands from Madagascar. We find strong evidence of gene flow across Madagascar and through the neighboring islands north of it, while phylogenetic trees, haplotype networks, and fixation indices all reveal genetically isolated and divergent lineages on Mauritius and Réunion, consistent with female color morphs. These results, and the discovery of the first males from Réunion and Mauritius, in turn falsify the existing taxonomic hypothesis of a single widespread species, Nephilengys borbonica, throughout the archipelago. Instead, we diagnose three Nephilengys species: Nephilengys livida (Vinson, 1863) from Madagascar and Comoros, N. borbonica (Vinson, 1863) from Réunion, and Nephilengys dodo new species from Mauritius. Nephilengys followed a colonization route to Madagascar from Africa, and on through to the Mascarenes, where it speciated on isolated islands. The related golden orb-weaving spiders, genus Nephila, have followed the same colonization route, but Nephila shows shallower divergencies, implying recent colonization, or a moderate level of gene flow across the archipelago preventing speciation. Unlike their synanthropic congeners, N. borbonica and N. dodo are confined to pristine island forests and their discovery calls for evaluation of their conservation status.     

PARTHENOGENESIS IN THE TROPICAL GEKKONID LIZARD,NACTUS ARNOUXII (SAURIA: GEKKONIDAE)

As currently diagnosed, Nactus arnouxii includes unisexual and bisexual populations. The geographic distribution of each type was estimated by sex-ratio analysis of samples from southwestern Pacific islands. Males were absent from southern Vanuatu (excluding Aneityum), New Caledonia, and all islands to the east that have been sampled. Both types of populations appear to be present on Aneityum. Chromosome and protein analyses showed that the bisexual populations are highly polytypic and probably consist of more than one biological species. The unisexual N. arnouxii were diploid, highly heterozygous, and showed no genetic segregation. The absence of segregation suggests clonal reproduction, substantiating parthenogenesis. The high heterozygosity of the unisexuals indicates their origin through hybridization. One parent was genetically similar to the extant bisexual population from northern Vanuatu. The other parent has not been identified, but its genetic characteristics are predicted by phylogenetic analysis.     

The politics of diaspora and the morality of secularism: Muslim identities and Islamic authority in Mauritius

Previous work on inter-ethnic coexistence in Mauritius has portrayed secularism as the only possible site of the national, which is at the same time described as clearly separated from religious traditions. In contrast, focusing on understandings of secularism among Mauritian Muslims in the context of a politics of diasporic 'ancestral cultures', this article analyses secularism as a field of morality which is inseparable from questions of religious reform and authenticity. The discussion of ethnographic material from Mauritius suggests that the opposition between secularity and religiosity should be treated as a productive tension rather than a liberal antinomy.     

Ancient mitochondrial DNA and morphology elucidate an extinct island radiation of Indian Ocean giant tortoises (Cylindraspis).

Ancient mitochondrial DNA sequences were used for investigating the evolution of an entire clade of extinct vertebrates, the endemic tortoises (Cylindraspis) of the Mascarene Islands in the Indian Ocean. Mitochondrial DNA corroborates morphological evidence that there were five species of tortoise with the following relationships: Cylindraspis triserrata ((Cylindraspis vosmaeri and Cylindraspis peltastes) (Cylindraspis inepta and Cylindraspis indica)). Phylogeny indicates that the ancestor of the group first colonized Mauritius where speciation produced C. triserrata and the ancestor of the other species including a second sympatric Mauritian form, C. inepta. A propagule derived from this lineage colonized Rodrigues 590 km to the east, where a second within-island speciation took place producing the sympatric C. vosmaeri and C. peltastes. A recent colonization of Réunion 150 km to the southwest produced C. indica. In the virtual absence of predators, the defensive features of the shells of Mascarene tortoises were largely dismantled, apparently in two stages. 'Saddlebacked' shells with high fronts evolved independently on all three islands. This and other features, such as a derived jaw structure and small body size, may be associated with niche differentiation in sympatric species and may represent a striking example of parallel differentiation in a large terrestrial vertebrate. The history of Mascarene tortoises contrasts with that of the Galápagos, where only a single species is present and surviving populations are genetically much more similar. However, they too show some reduction in anti-predator mechanisms and multiple development of populations with saddlebacked shells.     

Genetic substructure in cynomolgus macaques (Macaca fascicularis) on the island of Mauritius

Background

Nonhuman primates are commonly used in biomedical research as animal models of human disease and behavior. Compared to common rodent models, nonhuman primates are genetically, physiologically, behaviorally and neurologically more similar to humans owing to more recent shared ancestry and therefore provide the advantage of greater translational validity in preclinical studies. The cynomolgus macaque (Macaca fascicularis) is one of the most commonly used nonhuman primates in academic and industry settings, yet population genetic research has revealed significant substructure throughout the species distribution that may confound studies. Cynomolgus monkeys introduced to Mauritius specifically have previously been thought to maintain the least genetic heterogeneity of all cynomolgus monkeys, although recent work, including work from our lab, suggests macaques from Mauritius too may harbor cryptic substructure.

Results

To evaluate putative substructure in Mauritian cynomolgus macaques, we designed a panel of 96 single nucleotide polymorphisms based on preliminary findings from previous work to screen 246 of cynomolgus monkeys from two primary suppliers. Results from this study support substructure in Mauritian macaques and suggest a minimum of two populations and maybe three on Mauritius, with moderate admixture.

Conclusion

These findings inform the natural history of these monkeys suggesting either a previously unrecognized physical or ecological barrier to gene flow on Mauritius and/or the breakdown of historic substructure resulting from the history of macaque introduction to the island. These findings are relevant to ongoing research using these models in part because of increased appreciation of segregating common variation with functional effects and may be used to better inform animal selection in preclinical research.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-748) contains supplementary material, which is available to authorized users.     

Eel community structure,fluvial recruitment of <Emphasis Type="Italic">Anguilla marmorata</Emphasis> and indication for a weak local production of spawners from rivers of Réunion and Mauritius islands

Anguillid eels were sampled from permanent rivers in the Réunion and Mauritius islands, western Indian Ocean, with a standardized electrofishing method. A. marmorata was very dominant, corresponding to 91.7 and 90.7% of all the eels collected in Réunion and Mauritius, respectively. Three other species (A. mossambica, A. bicolor bicolor and A. nebulosa labiata) were also present in both islands. A. marmorata showed a strong altitudinal gradient of densities from the lower to upper zones, especially in the younger stages (TL <250 mm), while A. mossambica was only found in the upper zones and A. bicolor bicolor occurred only in the lower zones (A. nebulosa labiata was rare). The eel species composition in freshwaters of both islands is very similar because these two adjoining islands are located in the same trail of drifting marine larvae. Mean estimated eel biomasses were noticeably low (11.1 and 22.2 kg ha⁻¹ in Réunion and Mauritius islands, respectively), especially when compared to those of other tropical insular systems without any eel fishery (Comoros or Polynesia, more than 100 kg ha⁻¹). Nevertheless, the fluvial recruitment of A. marmorata seemed to be regular during the surveyed period, staggering from October to April. The obvious lack of large eels in Mauritius but more significantly in Réunion suggests a high pressure from traditional fishery, and the local reproductive turnover is uncertain. Because sexual maturation seems to occur at a large body size for A. marmorata, as for temperate species, the Réunion and Mauritius rivers may only have a weak contribution to the regional production of spawners. However, the giant mottled eel population in the western Indian Ocean is believed to be panmictic at the regional scale, and may not rely exclusively on these islands’ contribution. A comparison is made with those of freshwater systems in other tropical islands.     

Captive birds on Dutch Mauritius: bad-tempered parrots,warty pigeons and notes on other native animals

During the occupation of Mauritius by the Dutch in the seventeenth century, live dodos and other animals were transported to the east and west as curiosities and gifts by the Dutch East India Company. How these animals managed to survive these journeys, when human casualties on-board ship were so high, has remained a mystery. Here, we present for the first time a translation of the recently discovered report of Johannes Pretorius, who stayed on Mauritius from 1666 to 1669. Pretorius kept a number of now extinct birds in captivity, which was probably an experiment to ascertain their captive requirements prior to transportation. He also provides the first ecological details of some of the now-extinct birds and Mauritian giant tortoises, the impact of introduced animals, and highlights how little of the interior of Mauritius had actually been explored during this time.     

Mauritius type black rats with peculiar karyotypes derived from robertsonian fission of small metacentrics

All seventeen black rats collected from Mauritius Island were characterized by having many extra small acrocentric autosomes. Their basic karyotype was of Oceanian type, because of the presence of the large metacentric M₁ and M₂ pairs, but chromosome numbers in 13 specimens among them were 42, those of 3 specimens 43, and those of the remaining one specimen 44. Although the Oceanian type rat had 2 small acrocentric autosomes (pair no. 13), 16 Mauritius rats had 10 small acrocentrics, and the remaining one had 8 small acrocentrics. Comparative karyotype analysis between Oceanian and Mauritius type rats showed that the extra small acrocentrics found in Mauritius rats were due to Robertsonian fission of small metacentric pairs no. 14 and 18 of the original Oceanian type rat. Only one rat with 8 small acrocentrics showed the heteromorphic pair no. 18 consisting of one metacentric and two acrocentrics. The large metacentric M₁ chromosome in 13 of 17 rats examined showed homologous pair, but two of them were heteromorphic by involving one metacentric M₁ and two acrocentrics. In the remaining two rats M₁ chromosome was not observed, but acrocentric pairs no. 4 and 7 were included. These acrocentrics were also suggested to be originated from Robertsonian fission of the large metacentric M₁ chromosome. Robertsonian fission seemed to be one of the important mechanism found in karyotype evolution.