Vetufebrus ovatus n. gen., n. sp. (Haemospororida: Plasmodiidae) vectored by a streblid bat fly (Diptera: Streblidae) in Dominican amber

Background Both sexes of bat flies in the families Nycteribiidae and Streblidae (Diptera: Hippoboscoidea) reside in the hair or on the wing membranes of bats and feed on blood. Members of the Nycteribiidae transmit bat malaria globally however extant streblids have never been implemented as vectors of bat malaria. The present study shows that during the Tertiary, streblids also were vectors of bat malaria. Results A new haemospororidan, Vetufebrus ovatus, n. gen., n. sp., (Haemospororida: Plasmodiidae) is described from two oocysts attached to the midgut wall and sporozoites in salivary glands and ducts of a fossil bat fly (Diptera: Streblidae) in Dominican amber. The new genus is characterized by ovoid oocysts, short, stubby sporozoites with rounded ends and its occurrence in a fossil streblid. This is the first haemosporidian reported from a streblid bat fly and shows that representatives of the Hippoboscoidea were vectoring bat malaria in the New World by the mid-Tertiary. Conclusions This report is the first evidence of an extant or extinct streblid bat fly transmitting malaria. Discovering a mid-tertiary malarial parasite in a fossil streblid that closely resembles members of a malarial genus found in nycteribiid bat flies today shows how little we know about the vector associations of streblids. While no malaria parasites have been found in extant streblids, they probably occur and it is possible that streblids were the earliest lineage of flies that transmitted bat malaria to Chiroptera.


Background
Amber is known for its ability to preserve vertebrate microbial pathogens. Thus far, there are records of malaria, leishmaniasis and trypanosomiasis associated with insect vectors in amber deposits ranging from 20 to 100 million years of age [1]. Sporogonic stages of the bird malaria, Plasmodium dominicana, occurred in Culex malariager in Dominican amber [2] and developmental stages of Paleohaemoproteus burmacis (Haemospororida: Plasmodiidae) were reported from an Early Cretaceous Burmese amber biting midge (Diptera: Ceratopogonidae) [3]. The present study describes the sporogonic stages of a new genus of bat malaria in a Dominican amber fossil streblid [4]. Extant streblids have never been implicated as vectors of bat malaria, however members of the closely related family Nycteribiidae transmit bat malaria globally [5,6] (Table 1). Since both sexes of streblid bat flies (Diptera: Hippoboscoidea: Streblidae) feed on the blood of bats and reside in the hair or on the wing membranes [7][8][9], they would be excellent vectors of bat malaria.

Specimen
The fossil streblid is in a piece of amber 5 mm long by 4 mm wide by 4 mm deep ( Figure 1). Observations, drawings, and photographs were made with a Nikon SMZ-10 R stereoscopic microscope and Nikon Optiphot compound microscope with magnifications up to 600×.
Since it was not possible to photograph the malarial organisms without polishing away portions of the fly, photographs had to be taken through the thickness of the amber matrix as well as the width of the body wall of the vector. Adobe Photoshop was used to enlarge the photos and obtain the clearest images.

Locality
The amber with the bat fly came from La Búcara mine in the Cordillera Septentrional of the Dominican Republic. Dating of Dominican amber is still controversial with the latest purposed age of 20-15 mya based on foraminifera [10] and the earliest as 45-30 mya based on coccoliths [11]. In addition, Dominican amber is secondarily deposited in sedimentary rocks, which makes a definite age determination difficult [12]. A range of ages for Dominican amber is possible since the amber is associated with turbiditic sandstones of the Upper Eocene to Lower Miocene Mamey Group [13]. Dominican amber was produced by the leguminous tree, Hymenaea protera Poinar [14] and a re-construction of the Dominican amber forest based on amber fossils indicated that the environment was similar to that of a present day tropical moist forest [15].

Description of malarial pathogen
Phylum Apicomplexa Levine, 1970 Class Aconoidasida Mehlhorn, Peters & Haberkorn, 1980 Order Haemospororida Danilewsky, 1885 The description is based on two oocysts and sporozoites in the oocysts and salivary glands/secretions of a fossil streblid bat fly [4].
Polychromophilus sp. bats [13]  Etymology: The generic name is from the Latin "vetus" for old and the Latin "febris" for fever. The specific epithet is from the Latin "ovatus" for ovate, referring to the shape of the oocysts.

Conclusions
The present study represents the first description of a haemosporidian reported from a streblid bat fly and shows that representatives of the Hippoboscoidea were vectoring bat malaria in the mid-Tertiary. The presence of sporozoites in salivary glands and ducts indicates that the streblid was a successful vector of Vetufebrus.
Bats are infected with four genera of malaria: Plasmodium, Hepatocystis, Nycteria and Polychromophilus [5,6]. Species of the former three genera infect Old World bats while Polychromophilus occurs globally and is the only bat malaria reported from the New World [16]. All known strains of Polychromophilus are vectored by nycteriibid flies of the genera Nycteribia, Penicillidia and Basilia ( Table 2).
The sporogonic stages of Polychromophilus are characterized by round, slow growing oocysts attached to   the midgut of the vector and short, stubby sporozoites with rounded ends [5]. The mature round oocysts of Polychromophilus spp. contrast with the small oval oocysts of Vetufebrus (Table 2) (Figures 2, 4A, B). However, Adam and Landau [17] noted a small (31 × 10 μm), oval Polychromophilus oocyst in the nycteribiid fly, Penicillidia fulvida Bigot, 1889. It is likely that this oval oocyst in the nycteribiid was still developing, which could be the case with the two oocysts of Vetufebrus. While the sporozoites noted in the two oocysts of Vetufebrus are similar in size and shape to those in the salivary glands, it is possible that some of the salivary gland sporozoites originated from an earlier infection.
Short and stubby sporozoites with rounded ends as reported here for Vetufebrus (Figures 3, 4C) are characteristic of Polychromophilus infections [17][18][19] (Table 2) and the dimensions of Vetufebrus sporozoites fall within the range of some Polychromophilus spp. (Table 2). While Vetufebrus could represent an early lineage of Polychromophilus, this is unclear due to the small size of the oocysts. Also bat malaria has not been found in extant streblids even though species of the closely related Nycteribiidae carry bat malaria (  All measurements in microns.