Haemogregarina bigemina (Protozoa: Apicomplexa: Adeleorina) - past, present and future

Abstract

Abstract. This paper reviews past, current and likely future research on the fish haemogregarine, Haemogregarina bigemina Laveran et Mesnil, 1901. Recorded from 96 species of fishes, across 70 genera and 34 families, this broad distribution for H. bigemina is questioned. In its type hosts and other fishes, the parasite undergoes intraerythrocytic binary fission, finally forming mature paired gamonts. An intraleukocytic phase is also reported, but not from the type hosts. This paper asks whether stages from the white cell series are truly H. bigemina. A future aim should be to compare the molecular constitution of so-called H. bigemina from a number of locations to determine whether all represent the same species. The transmission of H. bigemina between fishes is also considered. Past studies show that young fish acquire the haemogregarine when close to metamorphosis, but vertical and faecal-oral transmission seem unlikely. Some fish haemogregarines are leech-transmitted, but where fish populations with H. bigemina have been studied, these annelids are largely absent. However, haematophagous larval gnathiid isopods occur on such fishes and may be readily eaten by them. Sequential squashes of gnathiids from fishes with H. bigemina have demonstrated development of the haemogregarine in these isopods. Examination of histological sections through gnathiids is now underway to determine the precise development sites of the haemogregarine, particularly whether merozoites finally invade the salivary glands. To assist in this procedure and to clarify the internal anatomy of gnathiids, 3D visualisation of stacked, serial histological sections is being undertaken. Biological transmission experiments should follow these processes.

Blood parasite biodiversity of reef-associated fishes of the eastern Caribbean

“…Scale bar = 10 µm to it. Balistes capriscus (Balistidae), H. flavolineatum, H. plumieri (Haemulidae), Halichoeres bivittatus (Labridae) and Epinephelus guttatus (Serranidae) ( Table S1 in the Supplement), were all found by Saunders (see Davies et al 2004) to host H. bigemina, and B. capriscus to also host a trypanosome (Saunders 1959b). However, only viral infections were found in these species during the present study.…”

“…Saunders (1954Saunders ( , 1955Saunders ( , 1958aSaunders ( ,b, 1959aSaunders ( ,b, 1966) only ever named 1 trypanosome and 3 haemogrega rines infecting the fishes of the Caribbean region. The fourth and most commonly reported hae mogregarine of Caribbean fishes by Saunders was H. bigemina, Saunders (1955Saunders ( , 1958aSaunders ( ,b, 1959aSaunders ( , 1966 reporting this parasite from 21 families of fishes from this region with 17 of these families being reef-associated (see Davies et al 2004). Eleven of the 17 families and 20 fish species sampled by Saunders were also sampled in our current study.…”

“…The combined observations of Saunders reported H. bigemina from a total of 28 families of fishes (see Davies et al 2004). However, Davies et al (2004) expressed their concern over such numerous sightings, particularly since Saunders never reported the complete development of H. bigemina during any of her studies, and furthermore did not report obser vation of the identifying paired mature gamonts characteristic of H. bigemina.…”

“…However, Davies et al (2004) expressed their concern over such numerous sightings, particularly since Saunders never reported the complete development of H. bigemina during any of her studies, and furthermore did not report obser vation of the identifying paired mature gamonts characteristic of H. bigemina. Most of Saunders' ob servations of this parasite were identified from intra leucocytic forms or immature stages in erythrocytes (see Saunders 1955, 1958a,b, 1964, 1966, Davies et al 2004) using inferior microscope equipment, and no photographs or voucher specimens were provided. The only other parasite, besides H. bigemina, ob served to undergo what appears to be binary fission in the present study was the Haemohormidium-like parasite found to be most prevalent in the Poma centridae (see Table S1).…”

“…Saunders (1960) also described H. rubrimarensis from the Red Sea samples of 1541 fishes from 104 species. Along with these descriptions, Saunders (1954Saunders ( , 1955Saunders ( , 1958aSaunders ( ,b, 1959aSaunders ( , 1960Saunders ( , 1964Saunders ( , 1966 reported H. bigemina from all collection localities -a haemogregarine now thought to be of questionable cosmo politan distribution (see Davies et al 2004). Similarly, from the GBR, Burreson (1989) reported 3 species of Haemogregarina in a survey including 69 fishes belonging to 28 species from Heron Island, and Smit et al (2006) documented 4 haemogregarines during a survey involving 497 fishes from 78 species from Lizard Island.…”