https://vital.seals.ac.za/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://vital.seals.ac.za/vital/access/manager/Repository/vital:4380 Wed 12 May 2021 23:59:48 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:8075 Wed 12 May 2021 23:35:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30877 Wed 12 May 2021 23:29:14 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30217 Wed 12 May 2021 23:13:37 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:20055 Wed 12 May 2021 22:19:37 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:39063 Wed 12 May 2021 20:51:53 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:3419 Wed 12 May 2021 20:37:15 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1775 Wed 12 May 2021 20:32:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4348 Wed 12 May 2021 20:29:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1765 Wed 12 May 2021 19:42:06 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30875 Wed 12 May 2021 19:38:00 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:8074 Wed 12 May 2021 19:23:12 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4855 Wed 12 May 2021 19:17:37 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:6381 Wed 12 May 2021 19:07:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2349 Wed 12 May 2021 18:50:25 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4017 Wed 12 May 2021 18:40:54 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5485 Wed 12 May 2021 18:37:47 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:35782 Wed 12 May 2021 18:18:34 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1012 Wed 12 May 2021 18:18:15 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:7013 Wed 12 May 2021 17:51:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4857 Wed 12 May 2021 17:49:51 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:6829 Wed 12 May 2021 17:48:26 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4938 Wed 12 May 2021 17:39:17 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30878 Wed 12 May 2021 17:22:11 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1776 Wed 12 May 2021 17:21:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1742 Wed 12 May 2021 16:37:34 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4215 Wed 12 May 2021 16:35:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5776 22 mm were generally female. Helcion pectunculus grows allometrically, increasing in height faster than length, which is expected of a high shore gastropod mollusc attempting to reduce evaporative water loss. Growth rates were similar on both east and west coasts regardless of the differing oceanographic conditions. The theoretical values of Lmax were also similar being 30.86 mm and 30.71 mm respectively. Micro-growth bands are laid down within its' shell which have the same periodicity as the tidal cycle and these enabled age estimates to be made. Younger individuals were male whilst older animals were female, suggesting that H pectunculus is a protandrous hermaphrodite. Histological examination proved, unequivocally, that this limpet undergoes a protandric sex change, changing from male to female when they are about 2 years old. Both east and west coast popUlations had a marked reproductive cycle, exhibiting two spawning periods a year, one in April and another in November. The possibility that the reproductive pattern exhibited is now phylogeneticallyconstrained is discussed. It is suggested that H pectunculus has evolved a reproductive cycle which will allow its planktonic larvae to utilise the valuable phytoplankton bloom food source whilst using onshore winds to ensure that larvae are not transported out to sea and lost. The number of foraging excursions carried out by individuals of H pectunculus was found to have a significant effect on Gonad Index and hence potential reproductive output. The activity pattern of H pectunculus varied depending upon micro-habitat; animals inhabiting both east and west facing rock surfaces are active during nocturnal low tides whilst animals on west facing rock surfaces are also active during daytime low tides whilst in the shade. Limpets travel further during foraging excursions in winter (X = 85.53 cm) than in either spring (x = 55.7 cm) or summer (X = 48.8 cm) and also during spring low tides (x = 89.8 cm) compared with neaps (x = 40.9 cm). This limpet exhibits rigid homing to a fixed scar within a-crevice and feeding excursions were found to cons.is.t. of three distinct phases, a rapid outward phase, a slower foraging phase and a rapid homeward phase. Foraging was always highly directional, with a mean vector which took limpets onto an area of the rockface with the highest microalgal biomass and also the smoothest rock surface. Helcion pectunculus exhibits a free-running endogenous rhythm of locomotor activity with both circadian and circatidal components and it is suggested that this rhythm plays a role in allowing the limpet to avoid unfavourable environmental conditions. The exogenous entrainment factor of this endogenous rhythm was the time of exposure to air in the field. There was found to be an organized distribution of limpets within crevices with smaller, younger limpets being towards the back of the crevice and larger, older limpets towards the crevice mouth. It is hypothesized that juvenile limpets of this species actively select and settle at the backs of crevices responding to chemical cues of adult conspecifics. The crevice refuge supplies the limpets with a stable and buffered environment with higher relative humidities (X = 72.3%) and lower rock surface temperatures (X = 19.7°C) than adjacent exposed rock surfaces (X = 64.5%; x = 22.9°C). Limpet body temperatures were significantly lower in crevic~refuges compared to limpets on exposed rock surfaces. Body temperatures never exceeded the rock surface temperatures. It is suggested that this is the result of morphological adaptations such as shell ornamentation and allometric growth. Light levels above 1000 J.1E.m-2.s-1 inhibited foraging activity in H. pectunculuswhilst limpets subjected to 30-50% shade foraged even during daytime lowtides. This limpet is one of the least tenacious (2.75 ± 0.13 kg.cm-2 ) of all South African limpets and the possibility that wave activity governs both the activity patterns and homing behaviour of this limpet is discussed. Limpets deprived of a crevice refuge experienced extremely high mortalities, with 45% of the limpets being lost during the first high tide period. A hypothetical model of the hierarchy of exogenous factors controlling limpet foraging activity is introduced and discussed in relation to the results of this study. Finally, it is suggested that in addition to the "migratory" and "non-migratory" groups of limpets present on southern African shores a third group of limpets seem to be present which may be classed as "specialized non-migratory" species. These are species that do not migrate, garden or aggressively fight off like conspecifics. They have overcome the competition for space and food on intertidal rocky shores by adapting to a particular habitat which is exclusive to them alone. From the combined results of these studies, it can be stated that H. pectunculus has adapted physiologically, morphologically and behaviourally to successfully survive the extreme conditions in the upper Balanoid zone.]]> Wed 12 May 2021 16:34:32 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2797 Wed 12 May 2021 16:29:58 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2095 Wed 12 May 2021 16:17:51 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:40569 Wed 12 May 2021 14:39:58 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:41871 Wed 12 May 2021 14:25:25 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:40752 Wed 12 May 2021 13:55:27 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:6286 Wed 10 Aug 2022 05:25:17 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2096 Wed 07 Jul 2021 13:13:52 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63026 Tue 28 Mar 2023 13:13:52 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63020 Tue 28 Mar 2023 13:07:12 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63022 Tue 28 Mar 2023 13:06:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63016 Tue 28 Mar 2023 13:00:22 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63014 Tue 28 Mar 2023 12:53:04 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63012 Tue 28 Mar 2023 12:38:58 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63011 Tue 28 Mar 2023 12:38:56 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62972 Tue 28 Mar 2023 09:58:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62969 Tue 28 Mar 2023 09:51:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62971 Tue 28 Mar 2023 09:51:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62967 Tue 28 Mar 2023 09:44:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62965 Tue 28 Mar 2023 09:16:03 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62966 Tue 28 Mar 2023 09:09:13 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62964 Tue 28 Mar 2023 09:08:59 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62961 Tue 28 Mar 2023 09:08:51 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62960 Tue 28 Mar 2023 09:02:12 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62962 Tue 28 Mar 2023 09:01:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62963 Tue 28 Mar 2023 09:01:51 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:38876 Tue 18 Jul 2023 22:48:00 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63342 Tue 11 Apr 2023 10:12:07 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63339 Tue 11 Apr 2023 10:04:55 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63338 Tue 11 Apr 2023 09:58:08 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63336 Tue 11 Apr 2023 09:58:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63333 Tue 11 Apr 2023 09:51:41 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63335 Tue 11 Apr 2023 09:51:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63331 Tue 11 Apr 2023 09:43:55 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:38858 Tue 10 Aug 2021 12:45:36 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:6129 Tue 01 Feb 2022 14:44:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57084 Thu 29 Sep 2022 22:30:33 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57077 Thu 29 Sep 2022 19:56:24 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57076 Mn(II)Pc > Fe(II)Pc > Ni(II)Pc > Cu(II)Pc > H2Pc > Zn(II)Pc > GCE. When [Co(II)TSPc]4− (TSPc=tetrasulfo Pc) was added to aqueous solutions containing the cresols and phenols, an enhancement of the oxidation currents was also observed.]]> Thu 29 Sep 2022 19:52:36 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57074 5 μg ml−1) are determined by adsorptive cathodic stripping voltammetry (AdCSV) on a mercury film glassy carbon electrode, using catechol, 4-methylcatechol, 4-t-butylcatechol and resorcinol as complexing ligands. Complexes of lead, copper and bismuth with resorcinol showed the largest increase in current with increase in metal concentration, whereas complexes of these metals with 4-t-butylcatechol showed the lowest current response. Cadmium showed a different behaviour from the other three metals in that the highest current response was observed with 4-methylcatechol. The four metals could be determined simultaneously in the presence of resorcinol, although considerable interference was observed between bismuth and copper.]]> Thu 29 Sep 2022 19:47:43 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:7135 Thu 15 Jul 2021 21:37:35 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:7134 Thu 15 Jul 2021 21:37:34 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5736 Thu 13 May 2021 08:19:42 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4844 Thu 13 May 2021 08:12:15 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:6382 Thu 13 May 2021 07:14:28 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2817 Thu 13 May 2021 07:08:20 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4345 Thu 13 May 2021 05:56:24 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:3051 Thu 13 May 2021 05:38:53 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:3018 Thu 13 May 2021 05:29:36 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30879 Thu 13 May 2021 05:11:24 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30876 Thu 13 May 2021 04:39:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:38857 Thu 13 May 2021 04:37:51 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:35823 Thu 13 May 2021 04:00:31 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4016 Thu 13 May 2021 03:57:00 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4814 Thu 13 May 2021 03:40:42 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2340 Thu 13 May 2021 03:36:27 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1690 Thu 13 May 2021 02:48:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:8131 Thu 13 May 2021 02:27:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:39038 Thu 13 May 2021 02:13:28 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:3049 Thu 13 May 2021 01:49:03 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2228 Thu 13 May 2021 01:48:03 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4848 Thu 13 May 2021 01:19:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2224 Thu 13 May 2021 01:12:42 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30880 Thu 13 May 2021 01:04:34 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5240 Thu 13 May 2021 00:22:42 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5165 Thu 13 May 2021 00:21:45 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:6504 Thu 11 Aug 2022 07:09:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2760 Thu 01 Feb 2024 09:52:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62957 Mon 27 Mar 2023 16:23:19 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62935 Mon 27 Mar 2023 12:18:21 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:68492 Mon 02 Oct 2023 14:23:56 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57087 Fri 30 Sep 2022 06:09:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57341 Fri 28 Oct 2022 12:31:52 SAST ]]>