Effect of crowding on nauplii production during mating time inTisbe clodiensis andT. holothuriae (Copepoda, Harpacticoida)

Abstract

Tisbe clodiensis and T. holothuriae females and males were maintained at different densities, from sexual maturity to the extrusion of the first egg sac, in order to study the effect of crowding on the number of nauplii produced by the first egg sac. They were tested in pure cultures at densities of 1, 2, 4, 6 and 8 couples per 20 ml of sea water, and in mixed cultures (half of the individuals belonging to each of the two species) with 2, 4, 6 and 8 couples per 20 ml, without food limitation. At the highest crowding level, and for T. holothuriae only, the effect of daily renewal of the culture water was examined. The mean number of nauplii per female decreases with increased density. A significant linear regression of number of nauplii on number of couples was found. The regression slopes appear to be the same for both species, regardless of whether they are cultured singly or together. The daily renewal of water diminishes the effect of crowding. The possibility that a complex chemical compound, produced by the animals, which enables the latter to perceive and to react to crowding, is discussed.

Life History Adaptation to Demographic Regime in Laboratory-Cultured tisbe furcata (Copepoda, Harpacticoida)

“…Probable instances of direct phenotypic responses have been described in Tisbe (Hoppenheit, 1976;Lopez, 1982). In contrast with these studies and with previous research on physiological density effects in harpacticoid copepods (Braioni and Parise, 1971;Fava and Crotti, 1979;Walker, 1979), the individuals whose life cycle I observed never experienced the particular demographic regime which they represent. Indeed, observations were made on the F1 of 'wild' or 'culture' females rather than on these females themselves.…”

Effect of density on larval development and female productivity ofTisbe holothuriae (Copepoda, Harpacticoida) under laboratory conditions

“…Female fecundity is affected not only by the density of females during their breeding phase, but also by the density of larvae during the larval stages. Fava & Crotti (1979) found the crowding of females during mating time caused a decreasing number of nauplii hatched from the first egg-sac. This is in close agreement with our results.…”

“…He proposed some factors called "imprinting" to explain the mechanism that enables animals to perceive and respond to different crowding levels. Fava & Crotti (1979) suggested a complex chemical compound might be produced by the animals as a reaction to crowding. However, the crowding effects are still obvious and verifiable when cultures of different densities are reared in the running-water system, where all of them are exposed to identical conditions even within the same culture medium.…”

Developing the harpacticoid copepod Tisbe biminiensis culture: testing for salinity tolerance, ration levels, presence of sediment and density dependent analyses

“…Most studies, however, presented the life‐table approach, which could estimate the maximum reproductive potential of some species without any kind of density‐dependent mechanisms. These mechanisms of density‐dependent population regulation were described for at least four harpacticoid species: T. clodiensis (Fava & Crotti 1979), T. holothuriae (Fava & Crotti 1979; Zhang & Uhlig 1993), Amphiascoides sp. (Walker 1979) and Tigriopus japonicus (Kahan, Berman & Bar‐El 1988).…”