Abstract. Plasmodium dominicana n. sp. is described from Tertiary Dominican Republic amber. The description is based on ooÂ¨cysts, sporozoites and possible ...
Systematic Parasitology (2005) 61: 47–52 DOI 10.1007/s11230-004-6354-6
Plasmodium dominicana n. sp. (Plasmodiidae: Haemospororida) from Tertiary Dominican amber George Poinar, Jr Department of Zoology, Oregon State University, Corvallis, Oregon 97331, USA Accepted for publication 24th September, 2004
Abstract Plasmodium dominicana n. sp. is described from Tertiary Dominican Republic amber. The description is based on oo¨cysts, sporozoites and possible microgametes and an ookinete in the body-cavity of a female Culex mosquito (Diptera: Culicidae: Culicinae). The large pedunculated oo¨cysts, together with the culicine vector, align the fossil with the extant avain malaria species, P. juxtanucleare Versiani & Gomes, 1941. Based on the host range of P. juxtanucleare, a possible primary host would have been a member of the order Galliformes. This discovery establishes a minimum age for the genus Plasmodium Marchiafava & Celli, 1885 and places avian malaria in the Americas by the mid-Tertiary. It also supports earlier theories that some species of primate malaria could have evolved in the Americas.
Introduction During an investigation of fossil haematophagous insects, a female Culex mosquito in Dominican amber (Poinar, 2005) was discovered to harbour stages of a malaria parasite in its body-cavity. Fossil evidence of vector-borne diseases is quite rare and consists of a single report of a leishmanial parasite associated with an Early Cretaceous phlebotomine sand ﬂy (Poinar & Poinar, 2004). This is the ﬁrst report of a fossil member of the Plasmodiidae Mesnil, 1903. The present study describes this fossil based on sporogonic stages observed in the body-cavity of the mosquito, discusses its possible vertebrate hosts and suggests implications regarding the origin of primate malaria in the Americas.
Materials and methods The piece of amber containing the fossil was collected in April, 1993 from La Toca mine, located between the cities of Puerto Plata and Santiago surrounding the Cordillera Septentrional mountain range in the northern portion of the Domin-
ican Republic. The piece originally contained three haematophagous arthropods which were separately removed with a diamond saw. One was the allotype of Ornithodorus antiquus (Poinar, 1995) (deposited in the Poinar amber collection [accession no. A-10-74]). The second was a triatomine bug deposited in the Poinar amber collection (accession no. He-4-73). The third was a female Culex mosquito infected with the sporogonic stages of a species of Plasmodium Marchiafava & Celli, 1885, which is the subject of the present paper. The amber piece containing the mosquito with the Plasmodium is trapezoidal in outline, the sides measuring 14 17 · 25 · 15 mm, the thickness 3 mm and the weight 2 g. The Plasmodium stages were observed and photographed with a Nikon Optiphot microscope at magniﬁcations up to · 1050. The dating of Dominican amber is still controversial, with the latest proposed age of 20– 15 mya based on foraminifera (Iturralde-Vincent & MacPhee, 1996) and the earliest as 45–30 mya based on coccoliths (Ceˆpek in Schlee, 1990). What makes dating of the amber diﬃcult is that it is secondarily deposited in turbiditic sandstones of
48 the Upper Eocene to the Lower Miocene Mamey Group (Draper et al., 1994).
Results While only the sporogonic stages of the fossil species are known, these contain diagnostic characters that place the malarial organism in Plasmodium. Decomposing blood cells were present in the thoracic and anterior abdominal mid-guts of the mosquito, indicating that it had taken a blood meal shortly before it perished. Phylum Apicomplexa Levine, 1970 Class Aconoidasida Mehlhorn, Peters & Haberkorn, 1980 Order Haemospororida Danilewsky, 1885 Family Plasmodiidae Mesnil, 1903 Genus Plasmodium Marchiafava & Celli, 1885
Plasmodium dominicana n. sp. Holotype: Oo¨cyst in the body-cavity of a female Culex mosquito deposited in the Poinar amber collection (accession no. D-7-6B) maintained at Oregon State University. Type-host: An extinct species of mosquito in the genus Culex L. (Culicinae: Culicidae: Diptera) (Poinar, 2005). Type-locality: La Toca amber mine in the northern portion of the Dominican Republic, between the cities of Puerto Plata and Santiago. Description (Figures 1–12) Oo¨cysts. (Figures 1, 3, 8). Four heavily pigmented oo¨cysts were present in the fossil mosquito; two had just ruptured, releasing numerous sporozoites, while the other two were entire but appear mature. All of the oo¨cysts were large, spherical to oval in outline and ranged from 75 to 105 lm in diameter. The point of attachment of only two oo¨cysts could be seen clearly and both were pedunculate. The peduncles were 18 and 32 lm in length and 14 and 18 lm in width. Sporozoites (Figures 4, 5, 6, 10). Masses of sporozoites, appearing light in reﬂected light but dark
in transmitted light, were adjacent to two ruptured oo¨cysts. Individual sporozoites were elongate, nucleated and ranged from 10 to 14 lm in length and 1–2 lm in width. Sporozoites also occurred in groups in the salivary glands and in parallel rows in the ducts of the salivary glands of the fossil mosquito. Possible oo¨kinete (Figures 7, 11). A possible oo¨kinete was observed with a constricted anterior end that appeared to be wedged between two host cells. It contained dense areas, was elongate, 20 lm in length and 5 lm in greatest width. A prominent, round, dense nucleus was located near one end and adjacent to it was a clear, circular vacuole. In the posterior truncated portion of the body was a prominent longitudinal, cytoplasmic stria. Possible microgametes (Figures 2, 12). Microgametogenesis may have been in progress when the mosquito entered the resin, since what appears to be microgametes were emerging from a possible microgametocyte. The possible microgametocyte was 6 lm in diameter and contained a dark central nucleus. The possible microgametes were elongate and some had adhered with one another. Those, which could be delineated, were 20, 20, 24 and 29 lm in length. Remarks There are several genera of the Plasmodiidae vectored by insects (Perkins et al., 2000). Members of Hepatocystis Levaditi & Schoen, 1932 occur in mammals and are vectored by Culicoides biting midges. Species of Haemoproteus Krause, 1890 infect birds, reptiles and amphibians and are vectored by hippoboscid ﬂies, Culicoides biting midges and Chrysops deerﬂies. Species of Leucocytozoon Sambon, 1908, which has small (