Induction of reproductive failure in the planktonic copepod Calanus pacificus by diatoms

Abstract

The inhibitory effect of diatoms upon egg viability was investigated by feeding the planktonic copepod Calanus pacificus (collected in coastal waters off Oregon. USA) 3 diatom species (Chaetoceros difficilis, Ditylurn brightweh, isolated from Oregon coastal waters, and Thalassiosira weissflogii, from culture collections at Oregon State University) ad libitum (2.6 to 3.9 mg C I-'). These diatoms induced the production of abnormal eggs which failed to hatch or hatched into deformed nauplii. In contrast, a dinoflagellate diet (Prorocentrum mlnirnurn, from the culture collections) resulted in the production of normal eggs, 96 6 , of which hatched into healthy nauplii. D~atom inhibitory effect disappeared quickly ( c 2 to 3 d ) when females were transferred from diatom suspensions to dinoflagellate suspension. The inhibitory effect was also apparent when newly spawned eggs were exposed to dense diatom cell extracts, indicating that blocking of the embryonic development is chemically mediated. The production of unidentified anti-mitotic chemical compounds by diatoms may be ubiquitous.

An assessment of the effects of diatoms on planktonic copepods

“…This study provided the initial information on the probable negative effects of diatoms on calanoid reproduction. Similar negative effects on the egg viability of Calanus pacificus were found with 3 different diatom species (Uye 1996). A concerted effort by 23 investigators (Ban et al 1997), studying 16 copepod species with 17 species of diatoms, revealed 4 different types of effect of diatoms on copepods: (1) diatoms reduced fecundity and hatching; (2) diatoms reduced fecundity but not hatching; (3) diatoms did not reduce fecundity but affected hatching; (4) diatoms did not reduce either of the two.…”

Role of diatoms in copepod production:good, harmless or toxic?

“…These experiments suggest a toxic or deleterious effects of diatom extracts on embryonic development and hatching (Poulet et al 1994, Ianora et al 1995, Uye 1996. However, this effect is evident only at concentrations that exceed those encountered in nature by many orders of magnitude.…”

First evidence of some dinoflagellates reducing male copepod fertilization capacity

“…These authors have demonstrated that diatom diets induced the production of abnormal eggs that either failed to develop to hatching or hatched into deformed nauplii. This effect was diatom density dependent (Chaudron et al 1996) and was reversible when females were transferred from a diatom to dinoflagellate diet Uye 1996). Inhibition of mitosis has also recently been demonstrated during embryonic development of echinoderms exposed to cell extracts of the diatom Thalassiosira rotula (Buttino et al 1998) and in human bronchopulmonary tumoral cell lines exposed to diatom Skeletonema costatum extracts (Bergé et al 1997).…”

“…However, Jónasdóttir (1994), Pond et al (1996) found no significant correlation between egg size and hatching success in Acartia tonsa and C. helgolandicus. Differences in egg viability were related to the concentration of specific polyunsaturated fatty acids in the diet, in particular to the content of 20 : 53 and 22 : 63 (Kleppel and Burkhart 1995; Jónasdóttir and Kiørboe 1996), and were negatively correlated with the carbon and nitrogen content of the eggs (Pond et al 1996).It has been suggested that low hatching success is related to the presence of antimitotic compounds in diatoms blocking egg development (Poulet et al 1994Ianora et al 1995Ianora et al , 1996Miralto et al 1995;Uye 1996;Ban et al 1997). These authors have demonstrated that diatom diets induced the production of abnormal eggs that either failed to develop to hatching or hatched into deformed nauplii.…”