Ecological and Behavioural Studies on Harpacticoid Copepoda in the Intertidal Zone at Ardmore Point, Clyde Estuary, with Some Observations on the Anatomy of Tachidius discipes

Saleh, Ibrahim Mohammed Saad (1990) Ecological and Behavioural Studies on Harpacticoid Copepoda in the Intertidal Zone at Ardmore Point, Clyde Estuary, with Some Observations on the Anatomy of Tachidius discipes. PhD thesis, University of Glasgow.

Abstract

The present work was carried out between 1985 and 1990, mainly on harpacticoid copepods collected from Ardmore Bay, Clyde Estuary, Scotland. The purpose of this work was to determine the annual cycle of population density of sediment dwelling harpacticoids in the intertidal zone in Ardmore Bay, to compare in detail the summer and winter population densities of harpacticoid and nematode populations in the intertidal zone and to relate these to particle size parameters, and to conduct behavioural studies on sedimentary harpacticoid copepods collected from the intertidal zone at Ardmore. Some preliminary taxonomic work is also described on the external anatomy of Calanus finmarchicus. a taxonomic description is given of the intertidal sand- dwelling harpacticoid, Tachidius discipes. and the anatomy of the two species is compared. Scanning electron microscopy showed differences between the two species Calanus finmarchicus and Tachidius discipes. The body of Calanus finmarchicus is smooth, the abdomen is much narrower than the thorax, the first antenna is as long as the body length, and few hairs are present on the external side of the exopodites and endopodites of the legs. The body of Tachidius discipes is broadly elongated, having 9 segments. The abdomen is thinner than the thorax, and long setae are carried by the caudal rami. The thoracic segments have hairs along their posterior margins which may keep the joints between the segments clean and also aid in movement through the sediment. The five pairs of legs have spines and setae which are likely to be important in moving between sediment grains. The setae at the distal end of the legs are also likely to be important in swimming when the adults emerge from sediments. In contrast, Calanus finmarchicus. which is entirely pelagic, is smoother and has no spines but many setae on its legs, which are clearly an adaptation for swimming. The annual survey of harpacticoids at Ardmore Bay showed that at low and mid tide population densities were low in winter and high in summer. At high tide there was a peak in autumn (October) and spring (February). Copepodites were abundant throughout the year at low tide, but at mid tide peaked in winter (December, January). Virtually no copepoditcs were found at high tide. The high tide population may therefore be replenished from the low and mid tide regions. During the survey, adults and copepodites were found to be most abundant in the top 2 cm of sediment. Detailed comparisons of harpacticoids, nematodes and particle size in summer and winter were conducted at five stations on a transect from high tide to low tide at Ardmore Bay and showed that the summer population of harpacticoids and nematodes was much higher than winter population at all five stations. Nematodes were more abundant at deeper depths in the sediment in winter than summer, suggesting a downward migration to avoid cold winter temperatures. In contrast to harpacticoids, nematodes although more abundant near the sediment surface occurred to a depth of at least 14 cm. The high tide stations tended to have finer sediments with larger standard deviations (less well sorted), and lower kurtoses (less peaked). There were fewer differences in particle size parameters vertically into the sediment, and more between summer (July) and winter (January). Harpacticoids were restricted to sediments having a narrower range of mean particle size than were nematodes. Harpacticoids and nematodes were most abundant in sediments having intermediate standard deviations and a high negative skewness. The behaviour experiments showed that harpacticoid copepods migrate out of sediments into the overlying water in the dark. This is considered to be an important dispersal mechanism. Vertical migration out of the sediments is inhibited by light, by high and low temperatures (20

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Zoology, Biological oceanography
• Date of Award: 1990
• Depositing User: Enlighten Team
• Unique ID: glathesis:1990-78108
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 15:40
• Last Modified: 30 Jan 2020 15:40
• URI: https://theses.gla.ac.uk/id/eprint/78108