Mesocyclops Leuckarti pehpeiensis Hu, 1943, Mesocyclops ruttneri Kiefer, 1981, and Mesocyclops sp. (leuckarti group)

Antennula are 17-segmented with groups or rows of spinules on segment 1, 4, 5 and 7–13 and segment 17 with one deep notch. Antennary basis with caudal spinule pattern of M. leuckarti, row of 6–7 spinules at level of medial setae and 2–4 spinules near distal margin. Maxillulary palp without spinules. Maxillar syncoxa shows frontally distinct rows of spinules. Medial distal margin of P1 basis without spine. Distal margin of connecting
plate of P4 with two large acute outgrowths, medial expansion of P4 basis naked. Pediger 5 without hairs laterally and dorsally. Seminal receptacle with two short lateral arms, slightly curved at their ends and transverse ducts from copulatory pore slightly Vshaped.  Caudal rami without hairs on medial margin and armed with spinules at bases of lateral and external terminal setae.  Legs 1-3 have the inner margin of the basiopod haired (first leg is not naked), leg 4 basiopod is naked (Ueda and Reid 2003).

Two CV copepodids (juveniles) were collected from ER60 (EPA monitoring station in western Lake Erie) on April 3, 2016.  An adult female was found at the same site  in August 2017 and a second adult female was found in a November 2017 sample collected nearshore in East Harbor, Lake Erie, Ohio. 

According to Reid (1993), this species is more of an epibenthic form dwelling in the littoral zones. M. pehpeiensis is considered thermophilic (Anufriieva and Shadrin 2016).

Phong et al. (2008) report a mean longevity of 50.9 days across 19 female M. pehpeiensis with a mean clutch size of 90.6 eggs (sample size=100) and mean interclutch period of 1.5 days (sample size=27).

Mesocyclops species in general are voracious predators, feeding on rotifers, cladocerans, and dipteran larvae (Williamson 1986; Gliwicz and Umana 1994; Brandl 1998a, 1998b; Rao and Kumar 2002; Chang and Hanazato 2003; Kumar and Rao 2003; Dieng et al 2003; Nagata and Hanazato 2006; Sarma et al 2013). M. pehpeiensis is a omnivorous tactile predator (Dieng et al 2003) and will feed on phytoplankton in addition to zooplankton (Sarma et al 2013). In mesocosm experiments (Chang 2005) M. pehpeiensis restructured the zooplankton community.  The population of a small cladoceran, Bosmina fatalis, was affected negatively, but B. longirostris was not similarly affected. On the other hand, small rotifers responded positively to M. pehpeiensis.  In laboratory experiments, Hwang et al (2009) found M. pehpeiensis to severely supress the population growth of all four cladoceran species tested -- including rare Great Lakes native species Scapholeberis kingii.  Mesocyclops edax populations in DC ponds disappeared shortly after the discovery of M. pehpeiensis in those systems (Reid 1996).

Two members of this genus -- Mesocyclops edax and Mesocyclops americanus -- are native to the Great Lakes.  Reid (1996) reported that in the ponds of Washington, D.C., M. pehpeiensis coexists with Mesocyclops edax and M. americanus; however, on later return the native species had disappeared. This would suggest that, despite the fact that these are omnivorous-carnivorous forms (Suárez-Morales et al. 2003), this introduced species is capable of successfully competing for part of the resources available in these systems.  

There is little or no evidence to support that Mesocyclops pehpeiensis has significant socio-economic impacts in the Great Lakes.

Current research on the beneficial effect of Mesocyclops pehpeiensis  in the Great Lakes is inadequate to support proper assessment.

M. pehpeiensis has been evaluated as a potential biocontrol of dengue fever (Aedes albopictus mosquito larvae) and was deemed to merit consideration (Dieng et al 2002).   

Note: Check federal, state, and local regulations for the most up-to-date information.

Control

Biological

There is a variety of pelagic planktivorous fish in the Great Lakes that likely feed on M. pehpeiensis.  

Physical

Mesocyclops pehpeiensis is a thermophile. The thermal regime of the Great Lakes may confine this species’ range to warmer, nearshore waters.

Chemical

The Great Lakes and Mississippi River Interbasin Study (USACE 2012) suggests that alteration of water quality using carbon dioxide, ozone, nitrogen, and/or sodium thiosulfate could be effective in preventing upstream and downstream movement of copepods. It should be noted that the effectiveness of these methods is likely significantly diminished against copepod ephippia.