. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. &• «•» is '*»*>. Tt tr tr rt rt Cr Tg g1 gt tg Tt Tt 17 14 15 14 15 18 19 19 20 (6) 19 20 FIGURE 4. Electrophoretic patterns of the MDH from the 28th-day (A) and 32nd-day (B) embryos of 3 Asian horseshoe crabs and their hybrids. Electrophoretic patterns of the MDH in embryos obtained from different sets of 3 pairs (3 species) of horseshoe crabs are shown separately in A and B. Horizontal starch gel electrophoresis was carried out at 4°C with 11 % gel using the same buffer system as in Figure 3. Numbers indicate the de
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. &• «•» is '*»*>. Tt tr tr rt rt Cr Tg g1 gt tg Tt Tt 17 14 15 14 15 18 19 19 20 (6) 19 20 FIGURE 4. Electrophoretic patterns of the MDH from the 28th-day (A) and 32nd-day (B) embryos of 3 Asian horseshoe crabs and their hybrids. Electrophoretic patterns of the MDH in embryos obtained from different sets of 3 pairs (3 species) of horseshoe crabs are shown separately in A and B. Horizontal starch gel electrophoresis was carried out at 4°C with 11 % gel using the same buffer system as in Figure 3. Numbers indicate the developmental stage of Sekiguchi's normal plate (Sekiguchi, 1973). The number 6 in parentheses means that the hybrid embryo was able to live on until the 32nd day after insemination, although the development had stopped at stage 6 (blastula stage). All symbols are explained in Figures 1, 2, and 3. 3, and C. rotundicauda 9 X T. gigas 6 embryos did not express the paternal forms of the MDH-1 and MDH-2. DISCUSSION The LDH of horseshoe crabs is D-lactate specific and has a molecular weight of approximately 70,000 (Long and Kaplan, 1968, 1973). This D-LDH occurs in 3 dimeric forms, not in 5 tetrameric forms as does the L-LDH of vertebrates with a molecular weight of 140,000 (Selander and Yang, 1970; see columns Tt and Cr in Fig. 1 A). Although each LDH from the larvae of 3 Asian horseshoe crabs shows only one dimeric form with different electrophoretic mobility from one another, the LDH from the first-instar larvae of hybrid horseshoe crabs is composed of 3 mo- lecular forms: a maternal homodimer, a paternal homodimer, and a hybrid heter- odimer (Fig. 1 B). This hybrid LDH heterodimer was detected with maternal and paternal homodimers in T. gigas 9 X T. tridentatus 6 embryo at stage 20 (Fig. 2B). However, the paternal LDH homodimer from this cross-fertilized embryo was first observed without the hybrid heterodimer at stage 18 (results not shown). Similarly, in T. tridentatus 9
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