Experimental infection of the echinoid Strongylocentrotus droebachiensis with Paramoeba invadens: quantitative changes in the coelomic fluid

Abstract

Paramoebiasis, due to Paramoeba invadens, was transmitted from diseased to healthy echinoids Strongylocentrotus droebachiensis in the waterborne infection apparatus of Scheibl~ng & Stephenson (1984). Control echinoids were exposed to healthy S. droebachiensis in a parallel apparatus. Groups of 8 individuals from the infected treatment were sacrificed in the pre-symptomatic period and at 24 and 72 h after development of symptoms of the disease, as evidenced by loss of attachment (LOA) to aquanum surfaces. Groups of 8 individuals from the control treatment were removed and sampled at the same time. Coelom~c fluid (CF) was drawn into EGTA as an anticoagulant, and the concentration of coelomocytes determined dlrectly and after density-gradient fractionation into 3 different cell bands. The concentration of total coelomocytes was significantly lower in infected echinoids than in controls, due to smaller numbers of cells in the band containing white spherule and vibratile cells and that containing red spherule cells. The concentration of phagocytes did not differ significantly between the infected and control groups. Protein concentration in cell-free CF of infected echinoids at 72 h post-LOA (mean +SE = 446.25 k 51.69 L L g ml-l) was about twice that of control individuals (238.56 +- 16.60 pg ml-l). Terminally sick echinoids yielded CF with large numbers of bacterial contaminants. However, in vltro bactericidal activity of the fluid towards a reference marine pseudomonad did not change significantly during progression of paramoebiasis. Membrane-filtered coelomic fluid with elevated protein values from moribund, infected individuals was injected into healthy echinoids for toxin detection, but no disease symptoms appeared. Subsequent exposure of these individuals to waterborne P. invadens resulted in the usual course of dsease. While pathogenesis of pararnoebiasis remains obscure, possible mechanisms include activation of autolysis in the echinoid or production of degradative enzymes by the amoeba.

Phylogeny of Neoparamoeba strains isolated from marine fish and invertebrates as inferred from SSU rDNA sequences

“…Based on our experience with AGD, we consider this sampling procedure reasonable. Jellet et al (1988) also proved experimentally that trophozoites of P. invadens are present in the radial nerves of echinoids well before the onset of visible symptoms of the disease. This shows that even sampling that is not related to outbreaks of amoebic diseases can help us accumulate new data in the field.…”

“…The lack of strains isolated from invertebrates that are stored in culture collections is surprising considering the fact that Paramobea invadens, for example, was isolated from radial nerves and water vessels of the green sea urchin Strongylocentrotus droebachiensis, then readily cultured on agar plates and used for experimental infections (Jellet et al 1988). It is possible that some tissue-invading amoebae are more difficult to maintain in agar plate cultures or liquid media than those isolated directly from water.…”

Establishing a Diagnostic Technique for Coelomocentesis in the Long‐Spined Sea Urchin Diadema antillarum

“…Coelomic fluid analysis is vital to comprehensive health assessments in echinoderms and may be collected for direct microscopic cytological examination, microbial culture, immune function testings, and protein or amoebocyte quantification (Bang and Lemma ; Jellett et al. ; Harms ). Previous studies of mass mortality events in sea urchins have struggled to conclusively identify etiologic agents.…”

“…General techniques for clinical sample collection in sea urchins (class Echinoidea) have been documented and are utilized for both scientific research (Wardlaw and Unkles ; Jellett et al. ; Clemente et al. ) and in clinical settings such as public aquariums (Harms ).…”

“…Coelomic fluid analysis is an important diagnostic tool in echinoderms and has been employed to identify bacteremia, quantify total protein concentration, and conduct amoebocyte counts (Bang and Lemma ; Jellett et al. ; Harms ). In healthy echinoderms that are properly maintained, coelomic fluid is typically sterile and free of microorganisms due to effective pathogen defense mechanisms and immune responses, such as coelomocytes, antimicrobial substances, hemolysins, and hemagglutinins (Bang and Lemma ; Unkles ; Jangoux ).…”