Image Analysis of Faecal Material Grazed Upon by Three Species Of Copepods: Evidence For Coprorhexy, Coprophagy and Coprochaly

Abstract

Experiments involving three species of copepods(Acartia clausi Giesbrecht 1889, Pseudocalanus elongatus Boeck 1872 and Calanusfinmarchicus Gunnerus 1765) incubated with freshly produced copepod faecal material were conducted and analyzed using automatic image analysis. For two species (A. clausi and C. finmarchicus) the bulk of faecal material was not ingested but was fragmented. This process, coprorhexy, was accompanied by a shift toward smaller particles in the particle size-spectrum. Increases in total volume of the faecal particles after incubation with these copepods led us to propose a process which we refer to as 'coprochaly', derived from the Greek xot/Vaoio,(a loosening, as of bandages). Coprochaly was promoted by manipulation of the faecal material by the copepods. For the third species (P.elongatus) coprorhexy and coprochaly were coupled with coprophagy (ingestion of faecal material). Calculations indicated that the combined effect of coprorhexy and coprochaly reduced sinking velocities of the faecal particles by up to 50%. These processes increase pelagic residency time of particles, increase substrate area for aerobic microbes and presumably enhance remineralization of particulate organic matter.

Feeding by the euphausiid Euphausia pacifica and the copepod Calanus pacificus on marine snow

“…In addition, newly formed pellets could be easily distinguished from older pellets originally in aggregates because new pellets were compact and had intact membranes. Copepods are known to ingest their own or other species' fecal pellets (Noji et al 1991 Treatments experiments, they may have ingested some of them during the course of the experiment. However, coprophagy and coprorhexy were not evident, since pellets examined after experiments were not fragmented and were still intact in membranes.…”

“…Production of fecal pellets clearly demonstrates feedlng, and fecal pellets can be recovered and measured to quantify egestion, which can then be converted to ingest~on lf the assimilation efficiency is known. The disadvantage of this technique is that animals may ingest or break apart their own fecal pellets, resulting in an underestimation of feedin.g rate (Noji et al 1991). The majority of experiments reported here are fecal pellet production experiments.…”

Coprophagy and coprorhexy in the copepods Acartia tonsa and Temora longicornis: clearance rates and feeding behaviour

“…Fecal pellets were visibly opened, macerated and even cut in half during rejection. Eucalanus pileatus females have also been observed to inflict damage to fecal pellets during rejection (Paffenhöfer & Van Sant 1985) and Acartia clausi and Calanus finmarchicus were observed to fragment rather than ingest fecal pellet material (Noji et al 1991).…”

“…Both studies observed rejection of fecal pellets. Thus, coprorhexy rather than coprophagy may account for the role of some copepods in reducing the vertical flux of fecal pellets, by turning pellets into smaller, slower-sinking fragments, which are more prone to microbial degradation (Noji et al 1991). Evidence of coprorhexy has been found in the field where fecal pellets were observed to be converted into small, amorphous particles (Knappertsbusch & Brummer 1995, Suzuki et al 2003.…”

“…A reduced vertical flux is often attributed to recycling and repackaging of the fecal pellets by coprophagous (ingestion of pellets) copepods (Smetacek 1980, Bathmann et al 1987, González & Smetacek 1994, González et al 1994a, Lane et al 1994, Urban-Rich et al 1999. Also, coprorhexy (fragmentation of pellets) and coprochaly (loosening of pellets) may increase the residence time of fecal material in the water column (Lampitt et al 1990, Noji et al 1991) and make it subject to enhanced microbial degradation (Turner 2002), thus accelerating recycling of fecal pellet material in the water column.…”