Candidatus Xenohaliotis californiensis (C Xc) is a Rickettsiales-like organism (RLO) that is considered the causal agent of withering syndrome (WS), a chronic and potentially fatal disease for several abalone species. C Xc can be infected by a bacteriophage (p C Xc), and both phage-infected and non-phage-infected C Xc can coexist with a presumable different species of RLO tentatively named stippled Rickettsiales-like organism (ST-RLO). Currently, the taxonomic affiliation of the ST-RLO is unknown, and no studies have been conducted to determine its presence in infected abalones in the Peninsula of Baja California, Mexico. To determine whether the ST-RLO is a histological variant of C Xc or a new species of RLO, we performed histology and species-specific in situ hybridization (ISH) for C Xc and p C Xc in red abalone, Haliotis rufescens , infected with C Xc and hyperparasitized by p C Xc, which also showed the presence of the ST-RLO. Additionally, a histological analysis of the presence of all of these RLOs from 2008 to 2019 from an aquaculture facility was performed. The results showed that all ST-RLOs were negative by ISH for C Xc and p C Xc, suggesting that the ST-RLO is a different species of bacterium and that it is not susceptible to infection by p C Xc. Histologically similar alterations to those produced by C Xc in the post esophagus were observed. The three RLOs regularly coexist in all the infected abalones, and there is a relatively constant proportion of each kind of RLO over time, suggesting that equilibrium is reached during coexistence; the largest percentage corresponded to C Xc non phage infected (81%), followed by C Xc infected by p C Xc (16%) and the ST-RLO (3%). In all cases, the ST-RLO infection remained at a subclinical level making it difficult to determine if it acts as pathogen or as a commensal. Therefore, the genetic characterization of the ST-RLO and pathogenicity studies are needed to further elucidate the role of this new RLO in the development of of WS in abalone species of North America. • Confirmation of the presence of an unidentified rickettsia in abalone. • This unidentified rickettsia produces similar damages to those attributed to Candidatus Xenohaliotis californiensis. • This rickettsia coexists with Candidatus Xenohaliotis californiensis non infected and infected by the bacteriophage pCXc. • The role of this rickettsia in the development of abalone Withering Syndrome is unknown. • This is the first study to perform ISH for pCXc and to confirm that the ST-RLO is not susceptible to infection by pCXc. [ABSTRACT FROM AUTHOR]