Egg-number and ecology in commensal and parasitic copepods

Population dynamics and reproduction of Dissodactylus mellitae (Brachyura: Pinnotheridae) on its sand dollar host Mellita quinquiesperforata (Echinodermata)

“…Chemical detection of the host has been demonstrated for many pinnothends (Johnson, 1952;Davenport et al, 1960;Sastry and Menzel, 1962;Gray et al, 1968;Derby and Atema, 1980). Bivalves, tubicolous polychaetes and ascidians may be frequent hosts for symbionts because they produce a continuous exhalant current which could contain body scents (Gotto, 1962). Echinoids also give off chemicals which can be detected by their symbionts.…”

“…Gotto (1962) found that symbiotic copepods living on echinoderms had fewer eggs than those on other hosts, and postulated that because most echinoderms were large, abundant, moved slowly about the sediment surface and lived in sheltered subtidal waters, they could be invaded more easily. In addition, copepods with b u~~o w i n g echinoderm hosts had more eggs than those on more accessible surface-dwelling echinoderms.…”

“…Life history components should be particularly varied because a symbiont must contend with the constraints of the host in addition to those of the habitat in which the host lives. In marine waters, for instance, egg numbers of symbiotic copepods seemed to vary with the abundance, accessibility, mobility, and chemical cues of the host, as well as with the host habitat (Gotto, 1962). Although chemical cues followed by symbionts are discernible to investigators only by experimentation (e, g. Johnson, 1952;Davenport et al, 1960;Gray et al, 1968;Castro, 1978;Derby and Atema, 1980), host abundance, mobility, and habitat are relatively easily observed and could explain much of the variability in life histories of closely related synlbionts.…”

Dwarfs or giants? Sexual size dimorphism in Chondracanthidae (Copepoda, Poecilostomatoida)

“…The more difficult the host is to locate the more fecund the parasite (Gotto 1962). Further, it has been suggested that the challenge for fish parasites is greater than for invertebrate parasites, as fish may be more difficult to infect than invertebrates, the latter also tending to be less mobile or even sessile (Gotto 1962). Other things being equal, a high fecundity will be strongly favoured by selection, resulting in large females.…”

“…A common strategy to meet this challenge is to increase probability of encounters with potential hosts by increasing reproductive output. The more difficult the host is to locate the more fecund the parasite (Gotto 1962). Further, it has been suggested that the challenge for fish parasites is greater than for invertebrate parasites, as fish may be more difficult to infect than invertebrates, the latter also tending to be less mobile or even sessile (Gotto 1962).…”