Functional morphology of cephalopod gills

There is a wealth of literature dealing with fish gills (Review, see Hoar & Randall, 1984), yet hardly anything is known about the gills of cephalopods. This is rather surprising considering the commercial importance of the cephalopods. In view of the paucity of information available it was necessary to start by establishing the morphology of the gills. This is covered in the first section of this thesis. Of all the cephalopods, Octopus vulgaris was singled out for more detailed investigation (see chapters 2 & 3) as its physiology is comparatively well understood (Wells, 1978). The gills of cephalopods are the major sites for respiratory gaseous exchange. It follows that their dimensions might be expected to govern their potential for absorbing oxygen. Section two deals with the morphometries of cephalopod gills, and predicted values are compared with physiological measurements of oxygen uptake for four representative The final section describes the physiological experiments I performed on octopuses. These experiments were designed to find out whether the animals could regulate the gills' potential to take up oxygen through changes to the gills themselves.

Distribution, relative abundance and developmental morphology of paralarval cephalopods in the Western North Atlantic Ocean

Paralarval and juvenile cephalopods collected in plankton samples on 21 western North Atlantic cruises were identified and enumerated. The 3731 specimens were assigned to 44 generic and specific taxa. This paper describes their spatial and temporal distributions and their developmental morphology. The smallest paralarvae recognized for a number of species are identified and illustrated. The two most abundant and most frequently collected taxa were identifiable to species based on known systematic characters of young, as well as on distribution of the adults. These were the neritic squids Loligo pealeii and Illex illecebrosus collected north of Cape Hatteras, both valuable fishery resources. Other abundant taxa included two morphotypes of ommastrephids, at least five species of enoploteuthids, two species of onychoteuthids, and unidentified octopods. Most taxa were distributed widely both in time and in space, although some seasonal and mesoscale-spatial patterns were indicated. The taxa that appeared to have distinct seasonal distribution included most of the neritic species and, surprisingly, the young of the bathypelagic cranchiids. In eight seasonal cruises over the continental shelf of the middle U.S. Atlantic states, neritic taxa demonstrated approximately the same seasonal patterns during two consecutive years. Interannual differences in the oceanic taxa collected on the shelf were extreme. The highest abundance and diversity of planktonic cephalopods in the oceanic samples were consistently found in the vicinity of the Gulf Stream. Only eight of the oceanic taxa appeared to have limited areal distributions, compared with twelve taxa that were found throughout the western North Atlantic regions sampled in this study. Many taxa, however, were not collected frequently enough to describe seasonal or spatial patterns. Comparisons with published accounts of other cephalopod surveys indicate both strengths and weaknesses in various sampling techniques for capturing the young of oceanic cephalopods. Enoploteuthids were abundant both in our study and in other studies using midwater trawls in several areas of the North Atlantic. Thus, this family probably is adequately sampled over its developmental range. In contrast, octopoteuthids and chtenopterygiids are rare in collections made by small to medium-sized midwater trawls but are comparatively common in plankton samples. For families that are relatively common in plankton samples, paralarval abundance, derived similarly to the familiar ichthyoplankton surveys of fisheries science, may be the most reliable method of gathering data on distribution and abundance. (PDF file contains 58 pages.)

Effects of a flash-flood on channel morphology and some insects of a small stony stream in the Peak District, Derbyshire

In this paper, some observations are made following a flash-flood that occurred in Stake Clough, a small tributary of the River Goyt, during the evening of 6 August 1996. The site was visited eight times between 8 August - 30 October 1996 to take samples and make observations on the stream. The flood scoured the bed of Stake Clough but more significantly, caused it to change course along the middle part of the floodplain. Initially after the flood, the numbers of insects in all stretches of the stream channel were low (100-200 m super(2)), but then gradually rose to population densities approaching ten times this figure. The benthos was dominated by the Chironomidae and also leuctrid stoneflies (Leuctra nigra, L. hippopus and L. inermis). On 8th August 1996, 12 mesh bags, each containing oak leaves, were placed in the stream and collected after 24 hours. These were also dominated by chironomids, and contained relatively high numbers of the caddis, Potamophylax cingulatus.

Observations on the physiological development of trout eggs [Translation from: Roux. Arch. f. Entwicklungsmechanik der Organismen, 114. 771, 1929]

The osmotic pressure of the perivitelline fluid and the yolk of trout (Salmo trutta) eggs were measured separately by the Drucker-Schrein method. The permeability of the egg membrane and the variations in the osmotic pressure of the eggs when placed in salt solutions were also investigated.

Sphaerotilus natans: description of the morphology, growth and systematics of [Translation from: Schr. Ver. Zellstoff u. Pap.-Chem. u. -Ing., 26, 20-37, 1956]

The morphology, increase and systematica of Sphaerotilus natans is studied and culture methods examined.

The use of otolith morphology to indicate the stock structure of common coral trout (Plectropomus leopardus) on the Great Barrier Reef, Australia

We investigated the use of otolith morphology to indicate the stock structure of an exploited serranid coral reef fish, Plectropomus leopardus, on the Great Barrier Reef (GBR), Australia. Otoliths were measured by traditional one-and two-dimensional measures (otolith length, width, area, perimeter, circularity, and rectangularity), as well as by Fourier analysis to capture the finer details of otolith shape. Variables were compared among four regions of the GBR separated by hundreds of kilometers, as well as among three reefs within each region, hundreds of meters to tens of kilometers apart. The temporal stability in otolith structure was examined by comparing two cohorts of fully recruited four-year-old P. leopardus collected two years before and two years after a signif icant disturbance in the southern parts of the GBR caused by a large tropical cyclone in March 1997. Results indicated the presence of at least two stocks of P. leopardus, although the structure of each stock varied depending on the cohort considered. The results highlight the importance of incorporating data from several years in studies using otolith morphology to discriminate temporary and possibly misleading signals from those that indicate persistent spatial structure in stocks. We conclude that otolith morphology can be used as an initial step to direct further research on groups of P. leopardus that have lived at least a part of their life in different environments.