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D M Neil

Publications and source records attributed to D M Neil.

21 records · Page 2Linked to original sources
PubMed1976

A quantitative analysis of exopodite beating in the larvae of the lobster Homarus gammarus (L.).

Raw data on exopodite beating in the first three developmental stages of the lobster Homarus gammarus were collected and analysed for key beating parameters. The analysis was computer assisted and the main procedures used are described. Beating patterns are the same in all three stages and are usually very regular although perturbations do occur (figures 1, 2). When beating stops the deceleration and subsequent re-acceleration is very rapid (figure 1) and limb movement sequences usually start posteriorly and move forwards (figures 1, 2d). Ipsilateral phase relations are generally maintained at 0.4-0.6 (figures, 3,4) and while the coupling between adjacent exopodites is usually stronger than for those further apart various deviations from this are occasionally seen (figure 5). No significant correlation between the ipsilateral phase relations of adjacent exopodites and base cycle duration was detected for any of the stages (figure 6). Contralateral phase relations undergo a constant progression (figures 7, 9) and this was found to be due to a heterodyne effect (figure 8) also described as gliding coordination. The powerstroke/returnstroke ratio for all stages was approximately 0.5 (figure 10) and no significant correlation was found with cycle duration (figure 11). The only substantial difference between the three larval stages which was noted was that of cycle duration, the cycles of stage III being shorter than those of the first two stages. The exopodite beating pattern was discussed in context with other metachronously cycling systems in arthropods and the implications of the present study discussed.

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PubMed1976

A comparison of beating parameters in larval and post-larval locomotor systems of the lobster Homarus gammarus (L.).

A study has been made of the interrelations between rhythmical exopodite beating in different larval stages and swimmeret beating in poast-larval stages of the lobster Homarus gammarus. Data on exopodite beat cycle durations have been used for statistical comparisons of exopodite performance within one larva, and also between different stages of larval development. Inter-exopodite comparisons reveal clear bilateral differences (table 1), although there is no consistently favoured relationship (tables 2 and 3). There are significant differences in cycle duration between the first three developmental stages, with a slight increase at the first moult, and a marked decrease at the second (table 4). However, within each stage the repeat frequency exhibits little change (table 5). Therefore it appears that changes in swimming behaviour occur discontinuously in development, and are associated with the larval moults. It is suggested that changes in beat frequency, and especially the faster beating in stage III, may represent responses to changed loading conditions (table 7). Measurements of swimmeret beating in post-larval lobsters have been analysed in terms of cycle durations, and inter- and intra-segmental phase relations. Swimmeret beating patterns are very regular (figure 1), but not restricted to a narrow range of frequencies (table 6a). Intersegmental phase lag remains constant around 0.2 (figure 3) independent of beat frequency (figure 4). Similarly the powerstroke/returnstroke ratio of approximately 0.5 (figure 5) shows no significant correlation with cycle duration (figure 6). Differences emerge in the performance of larval exopodites and post-larval swimmerets (table 6b), although the possibility cannot be excluded that the larval exopodite oscillator in some way influences the developing action of the post-larval swimmeret system.

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