THE DEVELOPMENTAL APPEARANCE OF PATERNAL FORMS OF LACTATE DEHYDROGENASE AND MALATE DEHYDROGENASE IN HYBRID HORSESHOE CRABS.

Differences in electrophoretic mobilities of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) existed between three Asian horseshoe crabs, Tachypleus tridentatus, Tachypleus gigas, and Carcinoscorpius rotundicauda, used for interspecific hybridization. After electrophoresis of extracts of hybrid horseshoe crab embryos on starch gels, the paternal, maternal, and hybrid forms of the LDH and MDH were detected with specific enzyme staining. In viable hybrids the paternal form of the LDH was detected at stage 17 (immediately before the 1st embryonic molt). Similarly, evidence of gene expression for mitochondrial MDH was seen at stage 14 (stage of appearance of rudimental appendages). Gene expression for supernatant MDH was seen at stage 17 (immediately before the 1st embryonic molt). Regarding the onset of genome control in embryogenesis, it was suggested that prior to the activation of the maternal gene of the LDH, the paternal gene of the LDH was activated in horseshoe crab hybrids. Furthermore, there was evidence that the maternal effects on early embryogenesis were due to enzymes present in the egg prior to fertilization, not to continued synthesis directed by stable messenger RNA.