Seven Asiatic Lion cubs die in suspected disease outbreak.

Seven Asiatic Lion cubs have died in the Gir Forest National Park in the last week of May 2026, with a number of extra deaths thought to have occurred in areas of the forest outside the park. Seventeen adult Lions from the same population have been taken into quarantine by park officials.

A female Asiatic Lion with a cub in the Gir Forest National Park. Priyank Dhami/Wikimedia Commons.

The initial cause of the deaths was thought likely to be Canine Distemper Virus, a single-stranded RNA Virus of the Family Paramyxoviridae (the family of Viruses that includes the agents which cause Measles and Mumps in Humans), which can spread from domestic Dogs to wild Mammals, with Big Cats being particularly vulnerable. An outbreak of Canine Distemper in the Gir Forest killed 11 Lions in less than a month in 2018, and an outbreak in the Kanha National Park in Madhya Pradesh has killed four Tigers in April and May 2026.

However, it is now thought more likely that the Lions have been infected with Babesiosis, which is caused by Babesia spp., a type of Apicomplexan (single-celled parasitic Eukaryote) related to the Malaria parasite, Plasmodium. The Babesia is common in Deer, which make up a significant part of the diet of Asiatic Lions, although it can be spread to other species via biting Ticks. Like the Plasmodium parasite which causes Malaria, Babesia attacks the red blood cells, causing a similar illness to Malaria, with symptoms including anaemia and failure of the liver and kidneys. This can occasionally infect Humans, but is more commonly a problem for Cattle who can become infected if grazing in areas where Deer graze. In Lions, Babesiosis is particularly dangerous to cubs, with healthy adults usually able to shake off the infection.

Asiatic Lions are a sub-population of the Northern Lion, Panthera leo leo, which was once found across West, Central, and North Africa, southern Europe, the Middle East, and the North Indian Plain. The Lions of Southern and East Africa are a separate subspecies, Panthera leo melanochaita. All surviving Asiatic Lions are found within a single population, the Gir Forest of southern Gujarat State, India. This population has been growing in recent years, with 350 Lions recorded in 2008 and 891 in 2025. However, like all Lions, Asiatic Lions are territorial, and with each pride needing a fairly large home range. Thus the recovery of the species means that they have spread beyond the Gir Forest National Park into the neighbouring Amreli and Bhavnagar districts, areas where they come into conflict with Human herders and farmers, presenting additional challenges for their conservation. Asiatic Lions are considered to be Endangered under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species.

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Human Sleeping Sickness eliminated in Kenya.

The World Health Organization has officially confirmed that Kenya can be declared free of Human Sleeping Sickness (otherwise known as Human African Trypanosomiasis) in a press release issued on 8 August 2025. This is the second Neglected Tropical Disease to have been eliminated in Kenya, following the country being declared free of Guinea Worm, Dracunculus medinensis, in 2018, and makes Kenya the tenth country to be declared free of Human Sleeping Sickness. To date, 57 countries have been confirmed as having eliminated at least one of the seventeen recognised Neglected Tropical Diseases.

Human Sleeping Sickness is caused by a Protozoan, Trypanosoma brucei, which is an extracellular parasite infecting the blood plasma and other bodily fluids of its victims (unlike other parasitic Protozoans, such as the Malaria parasite Plasmodium spp., which infect the victim's cells). Trypanosoma brucei is a zoonotic infection, which is to say infection that affects Animals as well as Humans, and is typically carried by an Animal vector. This can create a reservoir of potential infectious agents in an Animal population, making such diseases difficult to eliminate. 

There are two subspecies of Trypanosoma brucei which infect humans, Trypanosoma brucei gambiense, which is found in West Africa, and Trypanosoma brucei rhodesiense, which is found in East and Southern Africa (and which was the form formerly found in Kenya). A third form, Trypanosoma brucei brucei, does not infect Humans, but can infect domestic Animals. All three known forms of Trypanosoma brucei infect a variety of Mammals (it is possible that other subspecies exist, but infect neither Humans nor domestic Animals, leading to their being overlooked), and are transferred from one host to another by the bite of the Tsetse Fly, Glossina spp.. Because of this, Humans involved in professions where they work closely with Animals, such as Animal husbandry or hunting, are particularly at risk of infection.

A smear of blood from a patient with Human Sleeping Sickness, stained with Giemsa (a histological stain which binds to areas of DNA with high levels of adenine-thymine bonding, making it useful for identifying parasitic organisms in blood), revealing two Trypanosoma brucei ssp. parasites. Centers for Disease Control and Prevention.

Because Trypanosoma brucei infections are not restricted to cells, the parasite is able to cross the blood-brain barrier with greater ease than most parasitic infections. The parasite breeds by binary fission, enabling its population within a host to increase exponentially. Once the population within the bloodstream become to high, the parasites begin to migrate within the body, frequently entering the cerebrospinal fluid and then the brain, where it caused Human Sleeping Sickness. As an Eukaryotic infection, Trypanosoma brucei is not vulnerable to antibiotics, and is typically treated with a form of chemotherapy which is also hazardous for the patient. As such, prevention of the disease is greatly preferable to treatment.

Human Sleeping Sickness was first recorded in Kenya in the early twentieth century, and has been the subject of strenuous control efforts ever since. A declaration of elimination for a disease is made at least ten years after the least recorded transmission of that disease within a country. In Kenya, the last reported case where the patient is believed to have contracted the disease within the country occurred in 2009, while the most recent reports of patients who are believed to have acquired the infection while out of the country (two patients) occurred in 2012. Despite this apparent success, Kenya has recently strengthened monitoring for Human Sleeping Sickness in counties where the disease was formerly endemic.

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Malaria in Ethiopia.

Between 1 January and 20 October 2024 more than 7.4 million cases of Malaria were reported in Ethiopia, with 1157 deaths recorded, a case fatality rate of 0.02%, according to a press release issued by the World Health Organization on 31 October 2024. On these infections, 95% were causes by Plasmodium falciparum. This is the highest number of cases reported in Ethiopia in seven years, and part of an ongoing rising trend of Plasmodium falciparum infections; in 2023, 4.21 million Malaria infections, with 527 deaths, with 70% caused by Plasmodium falciparum.

The overwhelming majority of cases occurred in the west of the country, with four regions accounting for 81% of all recorded infections and 89% of known deaths, with 44% of cases and 667 deaths in Oromo, 18% of cases and 56 deaths in Amhara, 12% of cases and 250 deaths in Southwest Ethiopia, and 7% of cases and 45 deaths in South Ethiopia. 

Geographical distribution of Malaria cases as of 20 October 2024. World Health Organization.

Of Ethiopia's 523 worodas (districts), 222 have been identified as having a high Malaria burden, together accounting for 75% of recorded Malaria cases in 2023. Fifty of these high-burden worodas are considered to be hard-to-access due to ongoing conflicts.

A slight majority of cases are males, who accounted for 56% of cases treated as outpatients and 52% of inpatient admissions. Children accounted for 16% of outpatients and 25% of inpatient admissions. This age and sex distribution is thought to be due to patterns of seasonal migration, with large numbers of adult male migrant workers seeking work in high-risk areas during the peak of the Malaria season. 

From 2000-onwards, Ethiopia had a steady reduction in the number of Malaria cases each year, driven by improved surveillance, roll-out of malaria interventions, and community health extension program. The number of cases fell to an all-time low in 2019, when only 900 000 cases were recorded, and there was no wide-ranging major epidemic, only sporadic local outbreaks. However, the country began to suffer a resurgence of the disease from 2021 onwards, with 1.3 million cases in 2021, 3.3 million cases in 2022, and 4.1 million cases in 2023. This return appears to have been driven by the Plasmodium falciparum strain of the disease, which caused 70% of the infections in 2023, and which appears to have become endemic in areas where it was not previously known.

Weekly trend of malaria cases in Ethiopia, 01 January 2021 to 13 October 2024. World Health Organization.

Malaria is caused by parasitic unicellular Eukaryotes of the genus Plasmodium, and affects a wide range of terrestrial Vertebrates. Five different species of Plasmodium can cause Malaria in Humans, with most infections caused by either Plasmodium falciparum or Plasmodium vivax, both of which are endemic to Ethiopia. The parasites are primarily spread via the bite of the female Anopheles Mosquitoes (males do not bite), but can also be spread through blood transfusions, organ transplants, or practices such as needle-sharing.

Photomicrograph of a blood smear containing a macro- and microgametocyte of the Plasmodium falciparum parasite. Both macro- and microgametocytes are products of the erythrocytic life cycle. Within a few minutes after the Anopheles sp. vector ingests the gametocytes, microgametocytes develop into microgametes, which are able to fertilize gametes. Centers for Disease Control and Prevention/Wikipedia Commons.

Malaria manifests with approximately 10-15 days after infection, as a fever, headache, and chills. Mild cases often pass soon, and can be difficult to identify as Malaria, however, more severe cases can be fatal in as little as 24 hours after the onset of symptoms. 

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Sleeping Sickness no longer considered a public health threat in Côte d'Ivoire.

Côte d'Ivoire has successfully eliminated Human African Trypanosomiasis, also known as 'Sleeping Sickness', as a public health problem, becoming the second African country after Togo to be validated by the World Health Organization, according to a press release isssued on 25 March 2021.

'I dedicate this milestone to decades of hard work and the individual contribution of every single health worker who braved some of the toughest challenges in reaching populations, often in remote rural areas,' said Eugène Aka Aouele, Minister of Health and Public Hygiene of Côte d'Ivoire. 'Our challenge now is to maintain the required level of surveillance and, with the help of everyone, to achieve interruption of transmission by 2030.' 

In the 1990s, Côte d'Ivoire reported hundreds of cases of Sleeping Sickness every year. Cases have progressively declined over the last 2 decades, and in the past few years, the country has reported fewer than 10 cases per year. At this low level, Côte d'Ivoire qualifies as having eliminated the disease as a public health problem. 

This achievement is attributed to robust control and surveillance measures, active (and passive) screening of people at risk, and targeted vector control, which helped to strongly decrease the number of cases in areas of transmission. Hospitals and health centres checked patients using specific diagnostic tests, while laboratory mobile units screened people in villages. 

 

A Human African Trypanosomiasis mobile unit in Côte d’Ivoire. CT Brink/World Health Organization.

'Côte d’Ivoire’s achievement marks an important step that brings Africa closer to eliminating Sleeping Sickness,' said Matshidiso Moeti, the World Health Organization's Regional Director for Africa. 'Sustained control measures over the past two decades have brought a significant decline in cases, a positive sign that many countries will soon be crossing this landmark.'

Treatment of infected people meant that the vector, the Tsetse Fly, Glossina sp., could no longer transmit the disease to others. This had to be maintained over years in order to progressively eliminate the disease.  

 

A Tsetse Fly, Glossina sp. International Atomic Energy Agency/Wikimedia Commons.

'The result which Côte d'Ivoire has achieved after several decades of fighting against Human African Trypanosomiasis, reflects the excellent leadership of the Ministry of Health and Public Hygiene through the Directorate of the Human African Trypanosomiasis Elimination Programme” said Jean Marie Vianny Yameogo, the World Health Organization's Representative in Côte d'Ivoire.” It is also the expression of the commitment and determination of the regional and departmental health directorates, health professionals, the communities' participation in control strategies and the vitality of the partnership.'

Two other countries, Benin and Equatorial Guinea, have submitted their dossiers to the World Health Organization, requesting validation for elimination of Sleeping Sickness as a public health problem. To achieve validation for the elimination of a public health problem, a complete dossier must be submitted to present detailed information on the past and present disease incidence throughout the territory. The country must show evidence of effective, ongoing surveillance to prove that the capacity of detecting the disease is strong. The figures must be below the specific thresholds required by the World Health Organization, which means one case per 10 000 inhabitants in all districts, during a five-year period.

Under the World Health Organization’s leadership, national control programmes, bilateral cooperation agencies and nongovernmental organizations have substantially reduced cases of the disease to unprecedented low numbers, specifically less than 1000 globally, before 2020.  

Sleeping sickness is a potentially fatal disease spread by the bite of an infected Tsetse Fly, which are native to the African continent. More than 60 million people living mainly in rural parts of 36 countries across East, Central and West Africa are at risk of contracting the disease.

The World Health Organization and partners are targeting the interruption of transmission of the Trypanosoma brucei gambiense form of the disease in all endemic countries by 2030. 

 

A blood sample showing infection with Trypanosoma brucei gambiense, the causative agent for African Sleeping Sickness. Public Health Image Library/Centers for Disease Control and Prevention/Wikimedia Commons.

The main approaches to controlling Sleeping Sickness include reducing the reservoirs of infection and reducing the presence of the Tsetse Fly.

Screening of people at risk helps identify patients during the early stage of the disease. If diagnosis is made early, it is possible to avoid complicated and risky treatment procedures during the advanced stage.

Human African Trypanosomiasis is a vector-borne parasitic disease caused by infection with Protozoan parasites belonging to the genus Trypanosoma. The causative parasite is transmitted to Humans through the bite of a Tsetse Fly which has acquired the infection from Humans or Animals harbouring the Human pathogenic parasites.  

 

The life cycle of the Trypanosoma parasite, the causative agent for African Sleeping Sickness. Centers for Disease Control and Prevention.

There are two forms of the disease: one due to Trypanosoma brucei gambiense, which is found in 24 countries in West and Central Africa and accounts for more than 98% of cases; and another due to Trypanosoma brucei rhodesiense, which is found in 13 countries in East and Southern Africa and accounts for the remaining cases.

When bitten by an infected Tsetse Fly, a red sore may erupt within a few weeks. The person may experience fever, swollen lymph nodes, aching muscles and joints, headaches and irritability.  

People who become infected feel lethargic and sleepy during the day, then awake but exhausted at night. This is followed by neuropsychiatric and sensory disorders, and then a coma. Death may occur within months or even years. 

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Haemosporidian parasites in Bats in Bangladesh.

Bats, Chiroptera, have long been postulated to play an important role in Arthropod suppression, seed dispersal, and pollination. The rich diversity in bat dietary habits assists in maintaining ecosystem health. In Bangladesh, 31 Bat species are found, three of which are fruit-eating. Of all frugivorous Bats, Pteropus medius and Rousettus leschenaultii are common and widely distributed in the country. The False Vampire Bat, Megaderma lyra, largest of the insectivorous Bats, is also quite common and widespread in Bangladesh. Bats are associated with zoonotic transmission of Viruses including Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), and Middle East Respiratory Syndrome Coronavirus (MERS-CoV), as well as the Ebola, Nipah, and Hendra Viruses, as well as disease-causing Protozoa like Plasmodium sp., Hepatocystis sp., Nycteria sp., and Polychromophilus sp. Among nine Hemosporidian genera, are Hepatocystis, which infects a wide range of hosts including Primates, Bats, Ungulates, and Rodents, in addition to Plasmodium, the causitive agent of Malaria in a wide range of Mammals. Parasites of seven other Haemosporidian genera, however, have been found exclusively in Bats, emphasising that they might harbor the most diverse set of Haemosporidian parasites within the Mammalian clade. The prevalence of Haemosporidian parasites among fruit and insectivorous Bats has been detected previously to be 40% among Bats from West Africa. Hepatocystis sp. was identified from a species of Flying Fox, Pteropus hypomelanus, in Southeast Asia, displaying an unusually high diversity and is also prevalent in Epauletted Fruit Bats, Epomophorus wahlbergi, in West Africa.

In light of these findings, Bats have been identified as possible reservoirs of Haemoprotozoa. They are included in epidemiological surveys, and particularly for the detection of Bat-specific blood Protozoa. Due to the gross destruction of habitat with rapid urbanisation, contact between Human and Bats is showing an increasing trend. Frugivorous Bats usually suck the juice of fruits instead of eating the whole fruits. They may play an important role in the transmission of infectious agents to rural communities, particularly small children, who collect those Bat-wasted fruits. In addition, ectoparasites which feed on Haemoprotozoa-infected Bats, could serve as a route of transmission to Humans. The potential public health threats posed by Bats thus suggests the importance of studying Haemoprotozoa towards its proper control and better management of Human diseases related to Bats. Maximum research has led on emerging Viruses in Bats; however, Bacterial and parasitic agents in Bats have been least studied and most neglected. 

In a paper published in the Journal of Threatened Taxa on 26 July 2020, Shariful Islam of the Institute of Epidemiology, Disease Control and Research, and the EcoHealth Alliance, Rakib Uddin Ahmed of the Faculty of Veterinary Medicine at the Chattogram Veterinary and Animal Sciences University, Mohammed Kaisar Rahman and Jinnat Ferdous, also of the Institute of Epidemiology, Disease Control and Research, and the EcoHealth Alliance, Mohammed Helal Uddin, Sazeda Akter, Abdullah Al Faruq, and Mohammad Mahmudul Hassan, also of the Faculty of Veterinary Medicine at the Chattogram Veterinary and Animal Sciences University, Ausraful Islam of the International Centre for Diarrhoeal Disease Research, and Ariful Islam, once again of EcoHealth Alliance, present the results of a study which aimed to aimed to gain a better understanding of parasitic pathogens in Bats, by conducting a study to identify the Haemoparasites of Bats in Bangladesh.

As part of a larger study through the United States Agency for International Development Emerging Pandemic Threats PREDICT project and associated Ecology of Nipah Virus survey, Islam et al. captured Bats in seven districts within or near Human settlements across Bangladesh. A total of 533 Bats (377 Pteropus medius, 111 Rousettus leschenaultii, and 45 Megaderma lyra) blood samples were collected randomly from Bats during 2010 and 2013. The methods of Bat were identified by species, age, weight, sex, physiological, and reproductive status. The Bats were released immediately after sample collection.

 

Bat sampling sites in Bangladesh 2010–2013. Islam et al. (2020).

Nine percent of the total sample was found to be positive for Haemoprotozoa. The overall prevalence of Haemoprotozoa was 5%, 13%, and 29%, respectively in Pteropus medius, Rousettus leschenaultii, and Megaderma lyra. 

In Pteropus medius, Babesia sp. was found at the same percentage in both sexes (3%), Hepatocystis sp. was found higher in females (3%). The prevalence of Babesia sp. was higher in adults (4%) while Hepatocystis sp. prevalence was higher in neonates (6%). Both Babesia sp. (4%) and Hepatocystis sp. (3%) prevalence were higher in peri-urban area compared to rural settings. In Megaderma lyra, male were more infected (25%) by Babesia sp. than females (16%) whereas Hepatocystis sp. infection was higher in females (12%) than in males (5%). On the other hand, Babesia sp. infection is more prevalent in adult Megaderma lyra (20%) and bats of rural areas (20%) than Hepatocystis sp. (9%). In case of Rousettus leschenaultii, Babesia sp. infection was higher in males (13%) than in females (6%) but Hepatocystis sp. was found to be at higher percentage in females (4%) than males (2%). Juveniles were more prone to Babesia sp. (13%) than adult Bats (8%). No Hepatocystis sp. infection was found in juveniles. In rural areas, Babesia sp. infection was more frequent (10%) than Hepatocystis sp. (2.7%). No associations, however, were found to be statistically significant.

To Islam et al.'s knowledge, this is the first study to report the prevalence of Haemoprotozoa in the Bats of Bangladesh. The study identified Babesia sp. and Hepatocystis sp. in three different Bat species. The identified Haemoparasites in Bats are similar to other reports from Bats globally. Bats have harbored a diverse set of Haemosporidian species for centuries and Hepatocystis was found to be at a high endemic level in Pteropodidae. Although the identified parasite species have not been associated with public health implications, there is evidence of co-infection of Primates and crossing of the Primate barrier by Hepatocystis sp. Furthermore, some of the Haemosporidian species from Bats resemble Rodent Mammalian parasites. The potential for Bat-Human, Bat-Rodent-Human, and Bat-Arthropod-Human cross-species transmission of Haemoprotozoa is not known but warrants further investigation, particularly as the Bat species included in the study are native to Bangladesh and share habitat as well as food and water sources with Humans, suggesting potential plausible routes of accidental transmission.

 

(A) Babesia sp., (B) Hepatocystis sp. found in microscopic examination of Pteropus medius blood from Bangladesh. Rakib Uddin Ahmed, Abdullah Al Faruq & Sazeda Akter in Islam et al. (2020).

The overall prevalence of blood Protozoa (9%) was lower than that of earlier reports from various countries. Haemoparasites in Bats can be found as a result of feeding habits (e.g. feeding on Insect vectors from which they may acquire the Haemoprotozoa). The prevalence of Babesia canis in Bats was reported as 2.7% in a 2015 study of Bats in Hungary and the Netherlands, which is much lower than Islam et al.'s study. Other studies reported 50% and 23% prevalence of Babesia sp. in bats from Britain. Most of the previous studies identified Babesia vesperuginis in  Bat species throughout the world. The role of Bats in the ecology of Babesia sp. and the vectors involved in transmission of Babesia sp. among them warrants further investigation. In Islam et al.'s study, the Protozoa were identified up to the level of genus. Hepatocystis sp. prevalence was lower in this study than in a previous study in Malaysia. These findings, however, may vary due to the study area, duration of the study, resistance of Bats and lack of Bat Fly vectors in Bangladesh.

Infection with Babesia sp. was higher in males (Megaderma lyra and Rousettus leschenaultii) whereas in case of Hepatocystis sp. the prevalence was higher for females. These differences can be attributed to variation in behavior, feed composition, and body mass between sexes. Besides, the sex hormone, testosterone increases the susceptibility to parasitism. Moreover, parasite development and transmission is favoured by the colonial habits of females. Adult Pteropus medius had higher Babesia percentage than juvenile, may be due to increased growing host age. Young animals are less susceptible to Babesia due to inverse age resistance. But the same Haemoparasite was higher in juvenile Rousettus leschenaultii which can be attributable to the ability of the parasite’s vertical transmission. Hepatocystis was higher in juvenile Pteropus medius, because they have low body mass, naive immune system, and nearly no anti-parasite behavior. The pattern of parasitism in Bats, however, should be explored in-depth in future studies.

Islam et al. report a survey of Haemoparasites in Bats undertaken over three consecutive years at habitat fragmented landscape in Human settlements areas in Bangladesh, where the prevalence and diversity of Bat-infecting Haemosporidian parasites have not been studied before. Molecular screening should be undertaken in future to overlay data in the microscopy with those from molecular biology. Molecular characterisation is the only way to definitively confirm the species of a Haemoparasite. The findings, however, remain of great interest. Further studies are needed to determine the species of parasites harbored in Bats of Bangladesh.

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Neobolus wulongqingensis: A Cambrian Brachiopod with encrusting kleptoparasites.

Parasitism is an enduring symbiotic relationship in which the parasite is nutritionally dependent upon the host for at least part of its life cycle, increasing its own fitness in the process and directly impinging upon the biological fitness of the host. Parasite–host interactions form a significant proportion of the biotic interactions in extant global ecosystems, influencing many characteristics of species networks including behavior, population structure, and ecological function. The antagonistic relationship between parasites and hosts has also been proposed as the primary mechanism leading to the evolution and maintenance of sexual reproduction, due to the negative frequency-dependent selection associated with parasitism. Despite its obvious importance, the origins and early evolution of Metazoan parasitism remains enigmatic. Molecular phylogenies predict the emergence of parasitic clades in the Cambrian and putative instances of shell damage, shell scarring and occasional bioclaustration from the early Cambrian represent circumstantial evidence that hint at possible parasitism, but the rarity of well-preserved specimens precludes decisive identification of parasite–host interactions in the earliest Phanerozoic. Possible examples of epibiontism, commensal infestation, and hitchhiking are also known from the early Cambrian, but none of these constitute definitive instances of parasitism with a clear negative biological effect on the host. This absence of clear evidence for parasitism in the earliest animal communities may, in part, be due to a lack of cross-sectional quantitative analyses on Cambrian material of the type that have been demonstrated as necessary to identify and discriminate instances of animal parasitism in deep time.

In a paper published in the journal Nature Communications on 2 June 2020, Zhifei Zhang and Luke Strotz of the State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology at Northwest University, Timothy Topper, also of the State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology at Northwest University, and of the Department of Palaeobiology at the Swedish Museum of Natural History, Feiyang Chen, again of the State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology at Northwest University, and of the Department of Biological Sciences at Macquarie University, Yanlong Chen and Yue Liang, again of the State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology at Northwest University, Zhiliang Zhang, also of the State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology at Northwest University, of the Department of Biological Sciences at Macquarie University, Christian Skovsted, also of the State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology at Northwest University, and Department of Palaeobiology at the Swedish Museum of Natural History, and Glenn Brock, once again of the State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology at Northwest University, of the Department of Biological Sciences at Macquarie University, describe a new species of Lingulid Brachiopod from the early Cambrian Guanshan Konservat-Lagerstätte, and the encrusting kleptoparasites which cover many specimens of this species.

The early Cambrian (Stage 4) Guanshan Konservat-Lagerstätte occurs mostly in the lower 40m of the Wulongqing Formation, which crops out over a geographically wide area in eastern Yunnan, located in southern China. The Guanshan Biota is unusual in being proportionately dominated by Brachiopods, and so, is strongly differentiated from other Cambrian Konservat-Lagertätten such as the Chengjiang, Sirius Passet, Emu Bay Shale and the Burgess Shale, which are Euarthropod-dominated assemblages. 

 

Locality map and stratigraphic position of the Guanshan Konservat-Lagerstätte in Yunnan Province. (a) Locality map for the Guanshan Konservat-Lagerstätte in Yunnan Province. All specimens of Neobolus wulongqingensis included in Zhang et al.'s study were sampled from the Gaoloufang section (Locality 3). (b) Cambrian stratigraphic scheme, both international and for China, showing the relative position of the Wulongqing Formation. Zhang et al. (2020).

The new species is placed in the genus Neobolus, and given the specific name wulongqingensis, meaning 'from Wulongqing', in reference to the Wulongqing Formation, from which the fossils were extracted. It is an Organophosphatic Linguliform Brachiopod with an adult shell subcircular, no visible pits or pustules on surface, peripherally ornamented with distinct growth lines; metamorphic shell, average of 2396 μm in width and 1907 μm in length (based upon 13 measured specimens); ventral pseudointerarea orthocline to apsacline with wide and triangular pedicle groove; ventral propareas vestigial or indistinguishable; dorsal pseudointerarea forming narrow, crescent-shaped rim; ventral visceral field short, slightly thickened and not extending beyond midvalve; dorsal interior with long median septum extending to or beyond ⅓ valve length. Short spirolophe lophophore present.

 

The Brachiopod Neobolus wulongqingensis, with associated obligate, encrusting kleptoparasitic tubes. (a) ELI GB-N-0301, densely aggregated valves of Neobolus wulongqingensis forming distinctive shell beds with their associated kleptoparasites. Scale bar 4 mm. (b), (c) Specimens of Neobolus wulongqingensis with varying numbers of encrusting kleptoparastic tubes; (b) ELI GB-N-0650, (c) ELI GB-N-0648-5. (d) ELI GB-N-0008, Neobolus wulongqingensis with baculate mantle canals preserved. (e) ELI GB-N-0261-18, Neobolus wulongqingensis with encrusting kleptoparastic tubes. (f) ELI GB-N-0255-6, internal view of a pair of conjoined valves with kleptoparasitic tubes encrusted to both valves. (g) ELI GB-N-0869-2-1. Neobolus wulongqingensis with encrusting kleptoparasitic tubes and Trilobite cranidium (exuviae) lacking attached tubes. Scale bars 2 mm, unless otherwise stated. Zhang et al. (2020).

Neobolus wulongqingensis is the most numerically abundant taxon in the Wulongqing Formation, with many thousands of specimens forming dense concentrations of monotypic, mostly conjoined shells, clustered closely on bedding plane surfaces. Remarkably, many of the Brachiopod shells are encrusted with elongate, tapering biomineralised tubes. Symbiotic relationships such as this are seldom directly observed in the fossil record because taphonomic biases generally impede the preservation of direct interaction between organisms. The high-fidelity preservation and great abundance of specimens in the Wulongqing Formation provides a rare opportunity to investigate this unique interaction between a Brachiopod host and their associated encrusting tube-dwelling organisms.

 

Additional examples of Neobolus wulongqingensis from the Guanshan Biota encrusted with varying numbers of obligate, kleptoparasitic tube-dwelling organisms. (a) ELI GB-N- 263A5-1. (b) ELI GB-N-254-1-1, Neobolus wulongqingensis with visceral region preserved (c) ELI GB-N-253-19- 1-D2, Neobolus wulongqingensis with tube outlines visible from the interior of the Brachiopod shell (d) ELI GB-N-290-8-1. (e) ELI GB-N-263A-2-3, Neobolus wulongqingensis with the outline of the kleptoparasitic tubes visible from the interior of the Brachiopod shell (f) ELI GB-N-0263B-3. (g) ELI GB-N-0253. (h) 284-3-1. i, ELI GB-N-0255-8. Zhang et al. (2020).

Zhang et al. assess differences in biomass between Brachiopod individuals of the species Neobolus wulongqingensis encrusted with tubes and those individuals lacking tubes, with biomass representing a proxy for the biological fitness of an individual. This analyses suggests that the tube-dwelling organisms reduced the biological fitness of the host and, when considered in combination with observations of the preferred growth orientation of the encrusting tubes, these results suggest the interaction between the tube-dwelling organisms and their host Brachiopod represents kleptoparasitism. This instance in a Cambrian epibenthic marine community likely represents the oldest known parasite–host relationship in the fossil record and reveals that parasite–host interactions emerged in conjunction with the rise of the earliest Animal communities during the Cambrian radiation.

 

Exceptionally preserved examples of Neobolus wulongqingensis from the Guanshan biota with chaetae preserved together with morphological details of encrusting biomineralised tubes. (a), (b) exceptionally preserved specimens of Neobolus wulongqingensis with chaetae preserved: (a) ELI GB-N 632-1. (b) 648-6-1-GLF. (c) ELI GB-N 561-2-1, close up of kleptoparsitic tube extending into the chaetal fringe of a Neobolus wulongqingensis individual. (d), (e) ELI GB-N 258-1-1. d, twisted dorsal and ventral valves with encrusting kleptoparasitic tubes. (e) enlarged view of boxed area in (d). (f) 258 -1-2 –GLF, Close up of biomineralised tubes showing clear surface annulations. (g), (h) 250 -1 -1-2- GLF. Detail and micro X-ray fluorescence elemental mapping of biomineralised tubes detached from Brachiopod valve. (g) Light photo. (h) Micro X-ray fluorescence elemental mapping of potassium. (i) Micro X-ray fluorescence elemental mapping of silicon. (j) Micro X-ray fluorescence elemental mapping of iron. (k) Close up of the three biomineralised tubes. (l) Close up of kleptoparasitic tubes still attached to Neobolus wulongqingensis. Zhang et al. (2020).

The preservation of marginal chaetae, mantle canals, visceral areas, and, rarely, the lophophore in the Brachiopods indicates rapid burial and minimal transport by episodic obrution deposits. Despite this, the soft body of the tube-dwelling Animal is not well-preserved, and its biological affinities are not self-evident. The greyish-white tubes, normally flattened by post depositional compaction, are immediately apparent. The tubes, some with preserved accretionary growth increments, encrust the exterior of both dorsal and ventral valves of Neobolus wulongqingensis with the open apertures exclusively oriented toward the anterior commissure of host Brachiopods, indicating an intimate, life-long, in-vivo association. The tubes exclusively encrust the exterior of the host shell, which occasionally shows signs of minor damage or disruption of shell growth lines, but there is no evidence of boring into the interior of the brachiopod by the tube-dwelling organism. The tubes are not found attached to any other hosts or substrates, such as the Trilobite or Palaeoscolecid exuviae that occasionally occur in the shell beds. Consequently, Zhang et al. interpret this interaction as representing an obligate relationship, as there is no evidence to suggest that the tube-dwelling organisms can adopt a free-living lifestyle in the absence of their Brachiopod host.

 

The basibiont Neobolid (Lingulata) Brachiopod Neobolus wulongqingensis from the Guanshan biota (Cambrian Stage 4) of eastern Yunnan. (a) Holotype, ELI GB-N-0377-1, a composite mould with dorsal and ventral valves strongly compressed. Note the fringe of chaetae and proximal pedicle. (b) ELI GB-N-0297-4, a 3- dimensional ventral valve with a preserved elongated pedicle attached to an exoskeleton of a Trilobite. (c) ELI GB-N-0625, compressed dorsal and ventral valves, showing the dorsal and ventral chaetae cross to form a fine sieve or mesh. (d), (e) ELI GB-N-0385: (d) View of dense anterior marginal chaetae; (e) Magnified view of boxed area in Fig. (d). (f), (h) ELI GB-N-SJJ-1308, shell interior, showing paired spiral lophophore: (f) light photograph; (g) enlarged view of boxed area in (f); (h) Micro X-ray fluorescence elemental mapping of aluminium, slilicon and iron shows paired spiral lophophore in high contrast. Zhang et al. (2020).

Bayesian estimation analysis (a widely used technique for estimating the probability density function of random variables with unknown parameters) demonstrates that a credible difference in biomass exists between Brachiopods with encrusting tubes (205 specimens) compared to those without (224 specimens). There is no overlap in the 95% highest density interval of the posterior distribution for the means of the two groups and the highest density interval for effect size does not overlap with zero. Mean biomass for individuals with encrusting tubes is thus credibly lower than for those without tubes. A null hypothesis significance testing approach also identified a significant difference between encrusted and non-encrusted individuals with a small effect size. Zhang et al. therefore contend that individual Brachiopods encrusted with tubes have reduced fitness when compared with their non-encrusted counterparts. On the basis of the difference in the values for mean biomass between the two groupings, encrustation results in a 26.08% reduction in overall fitness across the entire measured cohort.

 

Results of analyses demonstrating encrusted tubes were parasitic. (a) Posterior distribution of mean biomass derived from Bayesian estimation for Brachiopods without attached tubes (μ1; left) versus those brachiopods with encrusted tubes (μ2; right). Highest density interval denotes highest density interval and represents credible values for mean biomass for each grouping. (b) Posterior distribution of effect size for μ1 versus μ2 derived from Bayesian estimation. Highest density interval exceeds 0, indicating that a credible difference exists between the mean values for Brachiopods with encrusted tubes versus those Brachiopods without tubes. (c) Plot of Attachment Distance versus Biomass. Attachment distance from the posterior margin of Neobolus wulongqingensis represents a proxy for the duration of the symbiotic relationship between an individual Brachiopod and its associated encrusted tubes. Correlation between these two variables therefore indicates that those Brachiopods with enduring symbiotic relationships are reduced in biomass in comparison to those where time of attachment has been short. Zhang et al. (2020).

Although Zhang et al.'s analyses indicate that Brachiopods with encrusting tubes are reduced in biomass compared to those without, there is no clear relationship between the biomass of host individuals and increasing numbers of encrusted tubes per individual. In some symbiotic relationships, the impact on the host is amplified depending on the number of parasites present, but this relationship can be highly variable. For Zhang et al.'s dataset, the biomass of the Brachiopod host decreases when a single tube is encrusted to the shell surface, but no further decline is associated with an increasing number of tubes. Both proxies for increasing total parasite load also show no correlation with biomass. This suggests the tube-dwelling organism did not directly inhibit the feeding capability of the host, as larger numbers of parasites do not result in decreased fitness. However, a significant relationship exists between the attachment point of the encrusting tubes and the biomass of the brachiopod host, indicating encrustation earlier in ontogeny results in greater reduced biomass relative to hosts that have been infected at later ontogenetic stages, regardless of the number of symbionts present. In living Brachiopods, smaller individuals generally display an increased growth rate compared to larger individuals. It would therefore be expected that the impact on fitness would be greater for host individuals that are settled by parasites during earlier ontogenetic stages. The increase in median attachment distance for larger numbers of symbionts and the larger size of specimens with greater than four tubes establishes that higher infection rates can only occur when Brachiopod hosts have already managed to grow to larger adult sizes and there is sufficient Brachiopod shell surface area to accommodate a larger number of encrusting tubes.This also indicates that the tube-dwelling organisms do not preferentially encrust smaller Brachiopod individuals, as Brachiopods are clearly encrusted in large numbers later in their ontogeny, when they have reached larger sizes.

 

Supplementary plots exploring relationship between Brachiopod biomass and characteristics of attached tubes. (a) Box and whisker plot of number of attached tubes versus Brachiopod biomass. Whilst 1-3 attached tubes results in lower median biomass compared to individuals without tubes, individuals with 4+ tubes are indistinguishable from those with no attached tubes. (b) Plot of total tube width versus biomass. Total tube width for each individual is calculated as the sum total width of all tubes present on the relevant individual. (c) Plot of total tube area versus biomass. Total tube area for each individual is calculated as the sum total area of the shell surface covered by the attached tubes for the relevant individual. (d) Box and whisker plot of number of attached tubes versus attachment distance. Increasing the number of tubes per individual results in an increase in attachment distance. With attachment distance representing a proxy for time of attachment, this result suggests that large numbers of parasites are present for shorter durations and are only possible on larger, older shells. Number of biologically independent specimens used for each plot: (a) 429; (b) 408; (c) 383; (d) 167. Zhang et al. (2020).

Zhang et al.'s analyses demonstrate that the tube-dwelling organism directly impinges upon the biological fitness of the host, supporting the assertion that the encrusting tube-dwelling organisms are parasitic, rather than being either mutualistic or commensal with the Brachiopod host. A reduction in host biomass or growth rate has been directly attributed to the presence of a parasite in a variety of extant symbiotic relationships. Parasites typically increase the energetic requirements of infected organisms, as the host must generate sufficient energy to not only maintain its own requirements but also the needs of the parasite. This commonly leads to hosts with decreased biomass when compared with uninfected individuals. This result represents the first definitive and statistically supported instance of parasitism from the Cambrian and indicates that parasite–host systems were well established by Cambrian Stage 4, suggesting this type of interaction probably emerged even earlier during the main pulse of the Cambrian radiation.

Variations in biomass between individuals and assemblages of the same species have also been previously attributed to regional variation in environmental stressors. All specimens of Neobolus wulongqingensis included in this analysis occur in dense aggregations (estimated 60 000 individuals per m²) from the same geographic locality and stratigraphic package with similar sedimentological features subject to similar environmental and depositional conditions. Consequently, the reduced biomass of tube-encrusted Neobolus wulongqingensis individuals cannot be attributed to environmental factors and a parasitic affect is the most strongly supported probable cause.

 

Aggregations of Neobolus wulongqingensis with associated attached obligate kletoparasitic tube-dwelling organisms, showing the density of individuals per unit area. Each square equals 1 cm² and each black dot equals one individual Brachiopod. (a) ELI GB-N-N-0300. (b) ELI GB-N-N-0301. Zhang et al. (2020).

In all instances, the apertures of tubes are orientated toward the Brachiopod commissure, spanning an arc (plan view) of about 150°. No tubes have been observed orientated toward the hinge line of the Brachiopod. Tubes consistently grow beyond the commissural margin of Neobolus wulongqingensis into, and slightly above but rarely beyond, the Brachiopod chaetal fringe. Critically, the dominant growth direction of the tubes aligns tightly along a vector between 40° and 70° either side of the median plane of symmetry of the Brachiopod; this alignment is most pronounced in shells with a single encrusting tube but the same orientation pattern occurs in shells with all numbers of tubes, strongly supporting a preferential growth direction in the tubes toward the antero-lateral margin of the Brachiopod shell.

 

Evidence demonstrating the associated encrusted tube-dwelling organisms were kleptoparasitic. (a) Shell interior of specimen ELI GB-N-0595A of Neobolus wulongqingensis from Wuding showing the presence of a paired spirolophe lophophore (as indicated by white arrows). Scale bar is 1 mm. (b) Micro X-ray fluorescence elemental mapping of iron for ELI GB-N-SJJ-0595A provides a high contrast image of the spirolophe lophophore (as indicated by white arrows). (c), (d) Rose diagrams of attached tube orientation for: (c) All measured individuals of Neobolus wulongqingensis (146 specimens) and; (d) Neobolus wulongqingensis individuals with only one attached tube (31 specimens). Each division represents a 10° interval. Intervals coloured in orange are those that correspond to the inhalant laminar currents generated by Neobolus wulongqingensis. For all numbers of attached tubes, orientations that align with inhalant laminar currents are preferred but for individuals with only one attached tube, where the symbiont has all available orientations still available, orientations that align with the inhalant laminar currents are strongly preferred. Zhang et al. (2020).

Five specimens of Neobolus wulongqingensis from Wuding Quarry preserve a partial spirolophe lophophore. A spirolophe lophophore produces two separate inhalant laminar feeding currents at the antero-lateral edge of the shell margin that match the preferred orientation and growth position of the encrusting tubes on shells of Neobolus wulongqingensis. The preferred orientation of growth demonstrates that the tube-dwelling organisms were not purely utilising the Brachiopod as a hard substrate on which to construct their tubes. This data when combined with the demonstrated empirical cost to the host in the form of reduced biomass, strongly supports kleptoparasitic behavior. Kleptoparasitism is a form of competition, where food that is either already in the possession of the host or which the host has expended energy on obtaining and capture is imminent, is stolen by the parasite. In Zhang et al.'s scenario, this involves the tube-dwelling organisms acting as intercept feeders, stealing a portion of the Brachiopod feeding stream before it reached the chaetal fringe. Erika Iyengar recognised six distinct morphological, behavioral and physiological criteria that characterise living sedentary/sessile kleptoparasitic interactions in a 2002 study of such relationships. At least five of these criteria can be directly applied to the relationship between the encrusting tube-dwelling organism and Neobolus wulongqingensis further reinforcing a kleptoparasitic relationship.

 

Additional rose diagrams of attached tube orientation for all values of attached tubes. Each division represents a 10º interval. Intervals coloured in orange are those that correspond to the inhalant laminar currents generated by Neobolus wulongqingensis. The radii of each sector is equal to the square root of the relative frequencies of observations for each group. (a) Individuals with 2 attached tubes. (b) Individuals with 3 attached tubes. (c) Individuals with 4 attached tubes. (d) Individuals with 5 attached tubes. (e) Individuals with 6 attached tubes. (f) Individuals with 7+ attached tubes. Zhang et al. (2020).

Kleptoparasitism is rarely identified in the fossil record, and no instances of kleptoparasitism, as far as Zhang et al. are aware, have been proposed for Cambrian communities. Detailed empirical investigations of the energetic and nutritional cost of kleptoparasitism to the host, even for extant systems, are few. For this reason, it is currently difficult to assess if the reduction in host fitness (about 26%) Zhang et al. detect for Neobolus wulongqingensis is typical of sessile kleptoparasitic relationships. Brachiopods are particularly vulnerable to exploitation by kleptoparasites, since active filter feeding represents the greatest energy expenditure in the life of Brachiopods, and the time lag between collection and ingestion of nutritionally beneficial particles also provides potential for other organisms to exploit this resource. Combined with the fact that the biotic interaction  Zhang et al. document is interpreted as obligate for the parasite, this suggests that the effect observed is likely greater than would be the case in facultative kleptoparasitic associations. Intriguingly, obligate kleptoparasitism is exceedingly rare in modern marine systems, which might suggest that this novel ecological relationship is always rare in benthic communities or has been secondarily lost some time during the Phanerozoic.

 

Artist’s reconstruction of the Wulongqing Formation benthic community, showing the dense aggregations of monotypic Neobolus wulongqingensis forming benthic ‘meadows’ on the soft sediment with their associated obligate encrusting kleptoparasitic tube-dwelling organisms. Rebecca Gelernter/Near Bird Studios in Zhang et al. (2020).

Verification of this kleptoparasitic relationship reveals that the heritage of parasite–host interactions can be traced back more than half a billion years to the rise of Bilaterian Animal communities during the Cambrian and further establishes the importance of the early Cambrian as a primary source of ecological novelty. Antagonistic biotic interactions have also been proposed as the drivers of widespread evolutionary phenomena such as the maintenance of sexual reproduction and genetic polymorphism at disease loci. Both of these phenomena are known drivers of biodiversity increase, suggesting that the already established presence of parasitic relationships in Cambrian communities potentially had a fundamental role in the upsurge in evolutionary innovation associated with the Cambrian Radiation.

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