ECCRINALES, L.Leger & Duboscq, 1929

McDermott, John J., 2011, Parasites of shore crabs in the genus Hemigrapsus (Decapoda: Brachyura: Varunidae) and their status in crabs geographically displaced: a review, Journal of Natural History 45 (39 - 40), pp. 2419-2441 : 2425

Order ECCRINALES

Mesomycetozoans are obligate protistan symbionts living in the digestive tracts of millipedes, insects and crustaceans ( Moss 1979; Lichtwardt 1986; Misra 1998; Lichtwardt et al. 2001). Recent molecular research has shown that these organisms are not fungi (class Trichomycetes), but belong to the Mesomycetozoa ( Cafaro 2005) . Branched or unbranched thalli or filaments are attached by holdfasts to the chitinous lining of the digestive tract, and so, are shed when the host moults. Reproduction is primarily asexual but sexual reproduction also occurs, and may be synchronized with host moulting. Hosts provide nutrition, but the nature of the host–symbiont relationships among the numerous species is poorly documented. There is no clear evidence of parasitism except for pathogenicity in insect larvae and a wood-boring isopod ( Lichtwardt et al. 2001) so most relationships are considered commensal. The prevalence and intimacy of mesomycetozoan infections coupled with the lack of pertinent research suggest a need for future experimental studies to clarify relationships. This has been suggested recently for mesomycetozoan–hermit crab (Anomura) relationships ( Williams and McDermott 2004; McDermott et al. 2010).

The two known species of mesomycetozoans from Hemigrapsus species appear in Table 2. Johnson (1966) identified and described Taeniella carcini from the hindgut of H. nudus and H. oregonensis collected at Friday Harbor, Washington. In a later 2.5-year study, also at Friday Harbor, Hibbits (1978) described a new species, Taeniella grandis , from the hindgut of H. nudus and H. oregonensis . Prevalences in H. nudus and H. oregonensis were 100% and 50% in winter, respectively (no other data were given). Hibbits identified the same species in the thalassinideans Neotrypaea gigas Dana, 1852 , Neotrypaea californiensis (Dana, 1854) , Upogebia pugettensis (Dana, 1852) and the anomuran crab Oedignathus inermis (Stimpson 1860) . Lichtwardt (1986) dismissed Hibbits’ new species, indicating that it was the well-known Taeniella carcini , found also in Europe and Asia. He added an additional 15 brachyuran and anomuran hosts. Enteromyces callianassae , besides infecting the foregut of H. penicillatus , is symbiotic in the thalassinideans Neotrypaea uncinata H. Milne Edwards, 1837 , Notiax brachyophthalma A. Milne-Edwards, 1870 , Neotrypaea gigas , Neotrypaea californiensis , Upogebia affinis (Say, 1818) , Upogebia pugettensis , and the brachyuran Uca pugilator (Bosc, 1802) ( Lichtwardt 1986; Lichtwardt et al. 2001). This symbiont of crustaceans has been recorded in hosts from Chile, France, Japan and the east and west coasts of the USA.