American lobster (Homarus americanus) females characteristically extrude eggs in the summer of the year following a summer or autumn molt, but young females may extrude in the same year. Adult female lobsters were exposed to periods of 40, 80, or 120 d of short photophase (8 h light: 16 h dark) at different times during the molt cycle or as controls were kept under continuous long-day conditions (16 h light: 8 h dark). They were found to require 80 d of short photophase to complete primary vitellogenesis; they then completed secondary vitellogenesis and extruded following long day onset (LDO) only if the latter fell within ± 1400 dd6 (day-degrees above 6 °C) of the molt. The dependence of this latter relationship upon prior delayed extrusion and molting suggests that the decay in probability of LDO-elicited extrusion following the molt proceeds independently of the advance of the current molt cycle. The hypothesis is therefore rejected that the decay in extrusion potential following the molt is a result of increasing probability of interference from the oncoming premolt. Alternative hypotheses are discussed.
The timing of molts and of subsequent egg extrusion by female American lobsters (Homarus americanus) in the laboratory under near-ambient conditions at Bodega Bay suggested that final vitellogenesis was initiated only during the months between the vernal and autumnal equinoxes. In an experiment, the change from short-day (LD 8:16) to long-day (LD 16:8) photoperiod (long-day onset, LDO) began a 120-d period during which vitellogenesis could be initiated. Molting within this 120-d period was associated with a delay of as much as 80 d in the time of subsequent extrusion.
American lobster (Homarus americanus) females characteristically extrude eggs (E) in the summer of the year following a summer or autumn molt (M), but young females may extrude in the same year. The subsequent M is delayed until after hatching, resulting in the former case in a 2-yr reproductive molt cycle, measuring from M to M. Adult female lobsters were exposed to periods of short days (8 h light: 16 h dark) followed by long day onset (L) (16 h light: 8 h dark) at different times with respect to M, or as controls were kept under continuous long-day conditions. In this way were generated molt cycles with delayed or undelayed extrusions, as well as ones with incomplete vitellogeneses resulting from too-long delayed L, and molt cycles in which vitrellogenesis did not begin (control group). Delayed L results in delayed E and M, as measured either in days or in day-degrees above 6 °C. An incompleted vitellogenesis following a too-long delayed L changes neither the duration of the molt cycle nor its characteristic positive correlation with female size; the duration of molt cycles containing either delayed or undelayed E appears in contrast to become independent of size. Intermolt intervals following prior E are shorter than those following anovulatory cycles. Retention of the clutch to hatching is associated with an additional increment to the intermolt interval. The results suggest that following E, a "reproductive" program replaces the "somatic" program of control of molt cycle duration. Incompleted vitellogeneses are associated with significantly smaller molt increments and growth rates than in the evidently avitellogenic continuous long-day control group, even though intermolt duration and its relation to size remain the same. Growth rates of molt cycles containing incompleted vitellogeneses are significantly higher than ones containing E only if that is delayed. Differential dependence of molt cycle duration and growth rate measures upon size and temperature indicate that molting and growth are distinct and rather independently controlled processes in adult lobsters, however tightly linked they may be in juveniles. Implications for molting and reproduction in the natural environment are discussed.
Lobster aquaculture requires control of reproductive processes. We have previously described an electrical stimulation technique for collecting spermatophores from living lobsters (Homarus americanus). These spermatophores can potentially be used in a variety of ways including: 1) experimental manipulation of sperm, 2) artificial insemination of females, 3) sperm banking, and 4) evaluation of sperm production by the male. In this study, we evaluated spermatophore production and extrusion from: 1) laboratory reared H. americanus and H. gammarus, 2) stressed, wild‐caught H. americanus, and 3) laboratory bred and reared hybrid males from reciprocal interspecific crosses. Our results show that the extrusion technique can be used successfully on H. americanus, H. gammarus and hybrid males. Laboratory reared H. americanus and H. gammarus from both Aquaculture Enterprises and Bodega Marine Laboratory extruded spermatophores in 60–85% of all trials. The majority of these spermatophores were of high quality containing large sperm masses with morphologically normal sperm. Stressed H. americanus, obtained from a market in Sunset Beach, California, 24 hours after shipment from New England, extruded fewer spermatophores which were shorter in length and inferior in quality. Hybrid males extruded spermatophores possessing a morphologically normal wall, but lacking sperm. These results demonstrate that this electrical stimulation technique can be used to screen males for spermatophore production and identify certain types of infertility.
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