ABSTRACT A population of Mastomys natalensis was studied by the catch-mark-release method from Ap... more ABSTRACT A population of Mastomys natalensis was studied by the catch-mark-release method from April 1983 to June 1984 in Morogoro, Tanzania. The observed cessation of reproduction during the dry season was accompanied by a reduction in growth. Average growth rates decreased during the dry season to the extent that the larger individuals suffered a considerable weight loss. The relationship between individual weight and reduction in growth suggests that resource limitation is sufficient to explain the break in reproduction. On a étudié une population de Mastomys natalensis par la méthode de capture-marquage-recapture, d'avril 1983 à juin 1984, à Morogoro, en Tanzanie. L'arrêt de la reproduction observé pendant la saison sèche s'accompagnait d'une baisse de croissance. Les taux moyens de croissance baissaient pendant la saison sèche au point que les plus gros animaux subissaient une perte de poids considérable. La relation entre le poids individuel et la baisse de croissance suggère que la limitation des ressources est suffisante pour expliquer l'arrêt de la reproduction.
INTRO. It has long been recognized, that relationships exist between habitat and parameters like ... more INTRO. It has long been recognized, that relationships exist between habitat and parameters like weight, shell thickness, length of shells and radulas. Small limpets, Patella granularis L., are restricted to the lower shore and their size increases gradually higher on the shore to a maximum in the balanoid zone (Branch, 1975). In Patella vulgata L., Brian & Owen (1952), Ebling et al. (1962) and Choquet (1966) observed the opposite trend. In dog-whelks, Nucella lapillus, variation in shell shape and thickness could be related to exposure (Crothers, 1974 a,b). Many examples of variation in bivalves are also published. Galucci & Hylleberg (1976) found variation in bentnose clams, Macoma nasuta, in relation to exposure and Kristensen (1957) called it a curious phenomenon that cockles, Cardium edule, from two localities displayed different characteristics. In other words, it is well documented that for individual species many types of variation can be correlated with environmental factors in specific areas. Unfortunately it is often cryptic, how genetical factors affect visible variation (Berry & Crothers, 1974). The purpose of the present study is to show that allometric variation of periwinkles, Littorina littorea, is consonant with the range of variation of the environmental factor exposure. The consonance is studied in terms of phenotypical fitness. The environment of the periwinkles studied is not uniform nor constant thus the optimal phenotype will be the one that is on the average the best fit in the local environment. The variation associated with the optimal phenotype is expressed as standard deviations from the average with respect to the parameter measured. [1977. J. Hylleberg & J. Tang Christensen]
Mangroves of the Indo-Pacific region harbour a varied and usually abundant fauna of littorinids o... more Mangroves of the Indo-Pacific region harbour a varied and usually abundant fauna of littorinids of the genusLittoraria, the taxonomy, geographical distribution and anatomy of which have been described by Reid (1986, 1989). Mangrove-dwelling species of the genus spend all of their adult lives on stems, proproots and leaves of the trees, but very little is known of their diets. As an initial study of the food of Indo-Pacific Littoraria, gut contents of the closely related L. pallescens(Philippi, 1846),L. intermedia(Philippi, 1846) andL. scabra(L., 1758) living onRhizophora apiculata were analysed.L. pallescenslives on the leaves ofRhizophorawhile L. intermediaspends most of its time on stems and prop-roots. L. scabrais also found on stems, and is usually found lower than L. intermedia. L. pallescensfeeds on the leaf surface apparently without damaging the leaf, though Ohgaki (1990) reported radular marks on leaves of R. stylosa. Snails were collected from mangrove trees on Phuket, Thailand, and killed by dropping into 70% alcohol. Stomach contents and faeces were removed under a dissecting microscope, smeared on to microscope slides and imbedded in glycerol gelatin. Some smears were heat-fixed, flushed with aniline blue, rinsed with water and imbedded in glycerol gelatin before microscopic examination. For Scanning Electron Microscopy of Rhizophora leaf surfaces, leaves were picked from trees and immediately fixed in alcohol (70% v/v) or formalin (4% v/v in seawater). For identification of mucous trails, leaves were dipped in a solution of toluidine blue and stained sections cut out and fixed. Output of faecal material was determined by placing snails individually in small vials which contained seawater for one hour. Faecal pellets were counted and their size (volume) determined as the mean of ten pellets. The height of the shell was also measured. Additional microscopic preparations were made from the faeces collected in this manner. Stomachs ofL. pallescenscontained much fungal hyphae, hyphal fragments and a variety of fungal spores. Spores from 9 genera were found in addition to mycelium and spores of Cladosporium cladosporioides(Figure 1) (identification by K. D. Hyde, Hong Kong University). Fragments of leaf epidermis were also found. Spores were present in the faeces, but hyphae were only found as small fragments here. Hyphae stained blue with aniline blue. In L. intermedia large amounts of plant material, mainly cork cells, were found in stomachs in addition to fungal hyphae and spores. Some of the cork cells contained fungal mycelium. Faeces also contained large amounts of cork cells, but faecal material was more fragmented. Stomach contents of L. scabrawere similar to that of L. intermedia, but fragments were larger. Diatoms were occasionally found. Scanning electron microscopy of leaf surfaces revealed fungi as the most conspicuous biotic element (Figure 2), and in mucous trails diatoms and foraminiferans could also be found. The size of the faecal pellets was correlated with the size of the snail ([log(pellet vol.) = 0.05 (shell height) – 2.07]; r = 0.76, p<0.0001) but was independent of species. Within species the number of pellets produced was independent of snail size. Thus, the number of pellets produced can be used as a relative measure of faecal output in interspecies comparisons. There was a highly significant difference between species with L. intermediahaving a higher output thanL. pallescens(Mann-WhitneyU = 582.5, p<0.001). A similar difference in faecal output was found betweenL. scabraandL. pallescenscollected onAvicennia on Bunaken Island, Indonesia (U = 102.5, p<0.001; data supplied by F. Boneka) (Figure 3).
Information on levels of polycyclic aromatic compounds (PACs) in the marine environment from pris... more Information on levels of polycyclic aromatic compounds (PACs) in the marine environment from pristine areas of the world are still sparse. In this study, PACs were analyzed in sediments and various organisms from the area of Qeqertarsuaq/Disko in the western part ...
The rodent genus Beamys is known from only a few localities in Africa. Two species have been desc... more The rodent genus Beamys is known from only a few localities in Africa. Two species have been described, Beamys hindei (Thomas, 1909), recorded from Kenya and Tanzania (Dieterlen, 1979; Hubbard, 1970), and Beamys major (Dollman, 1914), recorded from Malawi and Zambia (Ansell, 1960; Ansell and Ansell, 1973; Hanney, 1965). Their disjunct distribution and rarity suggest that they are relict forms. Egoscue (1972), Hanney and Morris (1962), and Hubbard (1970) have reported on the biology. In Tanzania Beamys has been recorded in the northeastern part of the country, in the Kilimanjaro, Pare, and Usambara areas, and Kingdon (1974) also reported it from the southwest, although he gave no specific localities. While surveying agricultural rodent problems in southeastern Tanzania I trapped four specimens of this rare rodent. The specimens were collected on the Rondo Plateau (10*10'S, 39*10'E) in Lindi District. The southern part of Tanzania is still not very well studied zoologically, and the Rondo Plateau is especially interesting, since stands of native forest still are present on the slopes. The animals were taken near the village of Mnara in snaptraps, baited with pieces of coconut. The habitat is best described as bush fallow, the most recent crop having been cassava. All four specimens were damaged by ants, rendering some measurements unobtainable. Three subadult males taken on 22 March 1983 ranged in weight from 26 g to 50 g. The largest individual had a head and body length of 125 mm and a tail length of 120 mm. A subadult female, weighing only 22 g was caught on the following day. The material is deposited in Zoologisk Museum, Copenhagen, under numbers CN14962, CN14963, CN14964, and CN14965. The state of the material does not validate classification with one of the two forms, and, as pointed out by Hubbard (1970) and Ansell and Ansell (1973), hindei and major are probably to be regarded as conspecific. Kingdon (1974) listed the two forms as subspecies of Beamys hindei, classifying specimens from southwestern Tanzania as B. h. major. Trapping was carried out during the rains in March 1983. Attempts to trap more specimens in September 1983 and in August 1984 were unsuccessful. Other rodent species trapped in the area were Praomys natalensis, Mus minutoides, Rattus rattus, Acomys spinosissimus, Lemniscomys griselda, Grammomys dolichurus and Tatera robusta. The shrew, Crocidura hirta, was also caught.
The morphology of the inner ear in rheas was examined by light and electron microscopy. The shape... more The morphology of the inner ear in rheas was examined by light and electron microscopy. The shape is typically bird-like with very long semicircular canals. The anterior and posterior cristae have small septa cruciata. The vestibular sensory epithelia contain two main types of hair cell innervation; bouton-innervated hair cells and calyceal hair cells characterized by a surrounding nerve calyx. The utricular macula has a single zone of calyceal hair cells, while all other previously examined birds, except the mute swan, have 2 zones. The height of the tallest sensory hairs of the cristae is 20-30 microns. In the utricular and lagenar macula, the hairs are 5-7 microns in the striola and 10-20 microns in the main parts of the sense organs. Along the edges of the maculae the longest hairs may reach 20-30 microns. The number of stereovilli on mature vestibular hair cells is 40-60. The sensory hairs of the hearing organ, the basilar papilla, are generally shorter but more numerous than the vestibular sensory hairs. In the proximal end, the tallest of the 175-200 stereovilli are 2.8-3.7 microns; in the distal end of the papilla, the number of stereovilli decrease to 65-100, and their height increases gradually to 7.3-8.7 microns. The neural sensory hairs are generally taller than those of the abneural side.
Summary Rodent populations in cultivated and fallow fields in Tanzania were sampled by trapping. ... more Summary Rodent populations in cultivated and fallow fields in Tanzania were sampled by trapping. Mastomys natalensis (Smith) was by far the most abundant rodent in these habitats (62% or more of samples). Estimates of densities of this rodent were obtained by removal trapping at scattered localities in Tanzania (range 23–236 ha-1) and from a catch-mark-release (CMR) study through a seasonal cycle (range 40–384 ha-1). Home ranges were analysed using CMR data. Seasonal variation in home-range size was not found, but reproductive males “had larger ranges than females and subadults. Resume On a preleve au moyen de pieges des echantillons des populations de rongeurs dans des champs cultives et dans d'autres en jachere. Mastomys natalensis (Smith) etait de loin le rongeur le plus abondant dans ces habitats (62% ou plus des echantillons). On a obtenu des estimations de la densite de ce rongeur au moyen de pieges disperses dans differentes localites en Tanzanie, les animaux n'etant pas relâches (distribution 23–236/ha), et par une etude de capture-marquage-recapture (CMR) pendant un cycle saisonnier (distribution 40–384/ha). On a analyse les espaces vitaux en se servant des donnees de CMR. On n'a pas trouve de variation saisonniere de la taille de l'espace vital mais les mâles reproducteurs ont des territoires plus vastes que les femelles et les subadultes.
Microscopic analysis of gut contents performed on three Littoraria species from mangrove forests ... more Microscopic analysis of gut contents performed on three Littoraria species from mangrove forests in Thailand revealed differences in diet among species. Analysis of carbon and nitrogen stable isotopes was used as an alternative way of tracing food sources. Rhizophora leaves, scrapings from both leaf and prop-root surfaces, and local particulate organic matter (POM) were well separated on the basis of their δ13C and δ15N values. In contrast, the three Littoraria species exhibit considerable overlap and scatter in both carbon and nitrogen isotope ratio values, suggesting that the snails are opportunistic feeders sharing similar food resources. The wide range of δ13C values of Littoraria (-17.2% to -26.3%) is consistent with carbon assimilation from multiple sources (epiphytes from leaves and prop roots, suspended POM, and Rhizophora detritus). Littoraria intermedia and L. pallescens, the smallest species, had similar δ13C values, whereas L. scabra was significantly more 13C depleted. ...
INTRO. It has long been recognized, that relationships exist between habitat and parameters like ... more INTRO. It has long been recognized, that relationships exist between habitat and parameters like weight, shell thickness, length of shells and radulas. Small limpets, Patella granularis L., are restricted to the lower shore and their size increases gradually higher on the shore to a maximum in the balanoid zone (Branch, 1975). In Patella vulgata L., Brian & Owen (1952), Ebling et al. (1962) and Choquet (1966) observed the opposite trend. In dog-whelks, Nucella lapillus, variation in shell shape and thickness could be related to exposure (Crothers, 1974 a,b). Many examples of variation in bivalves are also published. Galucci & Hylleberg (1976) found variation in bentnose clams, Macoma nasuta, in relation to exposure and Kristensen (1957) called it a curious phenomenon that cockles, Cardium edule, from two localities displayed different characteristics. In other words, it is well documented that for individual species many types of variation can be correlated with environmental factor...
Invasive Aquatic Species of Europe. Distribution, Impacts and Management., 2002
218 S. Gollasch et al. tentially deleterious effects on native species, the receiving habitats an... more 218 S. Gollasch et al. tentially deleterious effects on native species, the receiving habitats and their economies (Hedgpeth 1993). Whilst some species are introduced deliberately to new areas for aquaculture purposes, shipping is often regarded as one of the main vectors for the ...
... However, both Yaragina &amp; Marshall (2000) and Rose &amp; O&#x27;Driscoll (2002... more ... However, both Yaragina &amp; Marshall (2000) and Rose &amp; O&#x27;Driscoll (2002) found the lipid condi-tion index values, an indicator of ... exchange in spring leads to relatively large losses of phytoplankton from the shelf, retarding development of intensive spring blooms (Eliasen et al. ...
ABSTRACT A population of Mastomys natalensis was studied by the catch-mark-release method from Ap... more ABSTRACT A population of Mastomys natalensis was studied by the catch-mark-release method from April 1983 to June 1984 in Morogoro, Tanzania. The observed cessation of reproduction during the dry season was accompanied by a reduction in growth. Average growth rates decreased during the dry season to the extent that the larger individuals suffered a considerable weight loss. The relationship between individual weight and reduction in growth suggests that resource limitation is sufficient to explain the break in reproduction. On a étudié une population de Mastomys natalensis par la méthode de capture-marquage-recapture, d&#39;avril 1983 à juin 1984, à Morogoro, en Tanzanie. L&#39;arrêt de la reproduction observé pendant la saison sèche s&#39;accompagnait d&#39;une baisse de croissance. Les taux moyens de croissance baissaient pendant la saison sèche au point que les plus gros animaux subissaient une perte de poids considérable. La relation entre le poids individuel et la baisse de croissance suggère que la limitation des ressources est suffisante pour expliquer l&#39;arrêt de la reproduction.
INTRO. It has long been recognized, that relationships exist between habitat and parameters like ... more INTRO. It has long been recognized, that relationships exist between habitat and parameters like weight, shell thickness, length of shells and radulas. Small limpets, Patella granularis L., are restricted to the lower shore and their size increases gradually higher on the shore to a maximum in the balanoid zone (Branch, 1975). In Patella vulgata L., Brian & Owen (1952), Ebling et al. (1962) and Choquet (1966) observed the opposite trend. In dog-whelks, Nucella lapillus, variation in shell shape and thickness could be related to exposure (Crothers, 1974 a,b). Many examples of variation in bivalves are also published. Galucci & Hylleberg (1976) found variation in bentnose clams, Macoma nasuta, in relation to exposure and Kristensen (1957) called it a curious phenomenon that cockles, Cardium edule, from two localities displayed different characteristics. In other words, it is well documented that for individual species many types of variation can be correlated with environmental factors in specific areas. Unfortunately it is often cryptic, how genetical factors affect visible variation (Berry & Crothers, 1974). The purpose of the present study is to show that allometric variation of periwinkles, Littorina littorea, is consonant with the range of variation of the environmental factor exposure. The consonance is studied in terms of phenotypical fitness. The environment of the periwinkles studied is not uniform nor constant thus the optimal phenotype will be the one that is on the average the best fit in the local environment. The variation associated with the optimal phenotype is expressed as standard deviations from the average with respect to the parameter measured. [1977. J. Hylleberg & J. Tang Christensen]
Mangroves of the Indo-Pacific region harbour a varied and usually abundant fauna of littorinids o... more Mangroves of the Indo-Pacific region harbour a varied and usually abundant fauna of littorinids of the genusLittoraria, the taxonomy, geographical distribution and anatomy of which have been described by Reid (1986, 1989). Mangrove-dwelling species of the genus spend all of their adult lives on stems, proproots and leaves of the trees, but very little is known of their diets. As an initial study of the food of Indo-Pacific Littoraria, gut contents of the closely related L. pallescens(Philippi, 1846),L. intermedia(Philippi, 1846) andL. scabra(L., 1758) living onRhizophora apiculata were analysed.L. pallescenslives on the leaves ofRhizophorawhile L. intermediaspends most of its time on stems and prop-roots. L. scabrais also found on stems, and is usually found lower than L. intermedia. L. pallescensfeeds on the leaf surface apparently without damaging the leaf, though Ohgaki (1990) reported radular marks on leaves of R. stylosa. Snails were collected from mangrove trees on Phuket, Thailand, and killed by dropping into 70% alcohol. Stomach contents and faeces were removed under a dissecting microscope, smeared on to microscope slides and imbedded in glycerol gelatin. Some smears were heat-fixed, flushed with aniline blue, rinsed with water and imbedded in glycerol gelatin before microscopic examination. For Scanning Electron Microscopy of Rhizophora leaf surfaces, leaves were picked from trees and immediately fixed in alcohol (70% v/v) or formalin (4% v/v in seawater). For identification of mucous trails, leaves were dipped in a solution of toluidine blue and stained sections cut out and fixed. Output of faecal material was determined by placing snails individually in small vials which contained seawater for one hour. Faecal pellets were counted and their size (volume) determined as the mean of ten pellets. The height of the shell was also measured. Additional microscopic preparations were made from the faeces collected in this manner. Stomachs ofL. pallescenscontained much fungal hyphae, hyphal fragments and a variety of fungal spores. Spores from 9 genera were found in addition to mycelium and spores of Cladosporium cladosporioides(Figure 1) (identification by K. D. Hyde, Hong Kong University). Fragments of leaf epidermis were also found. Spores were present in the faeces, but hyphae were only found as small fragments here. Hyphae stained blue with aniline blue. In L. intermedia large amounts of plant material, mainly cork cells, were found in stomachs in addition to fungal hyphae and spores. Some of the cork cells contained fungal mycelium. Faeces also contained large amounts of cork cells, but faecal material was more fragmented. Stomach contents of L. scabrawere similar to that of L. intermedia, but fragments were larger. Diatoms were occasionally found. Scanning electron microscopy of leaf surfaces revealed fungi as the most conspicuous biotic element (Figure 2), and in mucous trails diatoms and foraminiferans could also be found. The size of the faecal pellets was correlated with the size of the snail ([log(pellet vol.) = 0.05 (shell height) – 2.07]; r = 0.76, p<0.0001) but was independent of species. Within species the number of pellets produced was independent of snail size. Thus, the number of pellets produced can be used as a relative measure of faecal output in interspecies comparisons. There was a highly significant difference between species with L. intermediahaving a higher output thanL. pallescens(Mann-WhitneyU = 582.5, p<0.001). A similar difference in faecal output was found betweenL. scabraandL. pallescenscollected onAvicennia on Bunaken Island, Indonesia (U = 102.5, p<0.001; data supplied by F. Boneka) (Figure 3).
Information on levels of polycyclic aromatic compounds (PACs) in the marine environment from pris... more Information on levels of polycyclic aromatic compounds (PACs) in the marine environment from pristine areas of the world are still sparse. In this study, PACs were analyzed in sediments and various organisms from the area of Qeqertarsuaq/Disko in the western part ...
The rodent genus Beamys is known from only a few localities in Africa. Two species have been desc... more The rodent genus Beamys is known from only a few localities in Africa. Two species have been described, Beamys hindei (Thomas, 1909), recorded from Kenya and Tanzania (Dieterlen, 1979; Hubbard, 1970), and Beamys major (Dollman, 1914), recorded from Malawi and Zambia (Ansell, 1960; Ansell and Ansell, 1973; Hanney, 1965). Their disjunct distribution and rarity suggest that they are relict forms. Egoscue (1972), Hanney and Morris (1962), and Hubbard (1970) have reported on the biology. In Tanzania Beamys has been recorded in the northeastern part of the country, in the Kilimanjaro, Pare, and Usambara areas, and Kingdon (1974) also reported it from the southwest, although he gave no specific localities. While surveying agricultural rodent problems in southeastern Tanzania I trapped four specimens of this rare rodent. The specimens were collected on the Rondo Plateau (10*10'S, 39*10'E) in Lindi District. The southern part of Tanzania is still not very well studied zoologically, and the Rondo Plateau is especially interesting, since stands of native forest still are present on the slopes. The animals were taken near the village of Mnara in snaptraps, baited with pieces of coconut. The habitat is best described as bush fallow, the most recent crop having been cassava. All four specimens were damaged by ants, rendering some measurements unobtainable. Three subadult males taken on 22 March 1983 ranged in weight from 26 g to 50 g. The largest individual had a head and body length of 125 mm and a tail length of 120 mm. A subadult female, weighing only 22 g was caught on the following day. The material is deposited in Zoologisk Museum, Copenhagen, under numbers CN14962, CN14963, CN14964, and CN14965. The state of the material does not validate classification with one of the two forms, and, as pointed out by Hubbard (1970) and Ansell and Ansell (1973), hindei and major are probably to be regarded as conspecific. Kingdon (1974) listed the two forms as subspecies of Beamys hindei, classifying specimens from southwestern Tanzania as B. h. major. Trapping was carried out during the rains in March 1983. Attempts to trap more specimens in September 1983 and in August 1984 were unsuccessful. Other rodent species trapped in the area were Praomys natalensis, Mus minutoides, Rattus rattus, Acomys spinosissimus, Lemniscomys griselda, Grammomys dolichurus and Tatera robusta. The shrew, Crocidura hirta, was also caught.
The morphology of the inner ear in rheas was examined by light and electron microscopy. The shape... more The morphology of the inner ear in rheas was examined by light and electron microscopy. The shape is typically bird-like with very long semicircular canals. The anterior and posterior cristae have small septa cruciata. The vestibular sensory epithelia contain two main types of hair cell innervation; bouton-innervated hair cells and calyceal hair cells characterized by a surrounding nerve calyx. The utricular macula has a single zone of calyceal hair cells, while all other previously examined birds, except the mute swan, have 2 zones. The height of the tallest sensory hairs of the cristae is 20-30 microns. In the utricular and lagenar macula, the hairs are 5-7 microns in the striola and 10-20 microns in the main parts of the sense organs. Along the edges of the maculae the longest hairs may reach 20-30 microns. The number of stereovilli on mature vestibular hair cells is 40-60. The sensory hairs of the hearing organ, the basilar papilla, are generally shorter but more numerous than the vestibular sensory hairs. In the proximal end, the tallest of the 175-200 stereovilli are 2.8-3.7 microns; in the distal end of the papilla, the number of stereovilli decrease to 65-100, and their height increases gradually to 7.3-8.7 microns. The neural sensory hairs are generally taller than those of the abneural side.
Summary Rodent populations in cultivated and fallow fields in Tanzania were sampled by trapping. ... more Summary Rodent populations in cultivated and fallow fields in Tanzania were sampled by trapping. Mastomys natalensis (Smith) was by far the most abundant rodent in these habitats (62% or more of samples). Estimates of densities of this rodent were obtained by removal trapping at scattered localities in Tanzania (range 23–236 ha-1) and from a catch-mark-release (CMR) study through a seasonal cycle (range 40–384 ha-1). Home ranges were analysed using CMR data. Seasonal variation in home-range size was not found, but reproductive males “had larger ranges than females and subadults. Resume On a preleve au moyen de pieges des echantillons des populations de rongeurs dans des champs cultives et dans d'autres en jachere. Mastomys natalensis (Smith) etait de loin le rongeur le plus abondant dans ces habitats (62% ou plus des echantillons). On a obtenu des estimations de la densite de ce rongeur au moyen de pieges disperses dans differentes localites en Tanzanie, les animaux n'etant pas relâches (distribution 23–236/ha), et par une etude de capture-marquage-recapture (CMR) pendant un cycle saisonnier (distribution 40–384/ha). On a analyse les espaces vitaux en se servant des donnees de CMR. On n'a pas trouve de variation saisonniere de la taille de l'espace vital mais les mâles reproducteurs ont des territoires plus vastes que les femelles et les subadultes.
Microscopic analysis of gut contents performed on three Littoraria species from mangrove forests ... more Microscopic analysis of gut contents performed on three Littoraria species from mangrove forests in Thailand revealed differences in diet among species. Analysis of carbon and nitrogen stable isotopes was used as an alternative way of tracing food sources. Rhizophora leaves, scrapings from both leaf and prop-root surfaces, and local particulate organic matter (POM) were well separated on the basis of their δ13C and δ15N values. In contrast, the three Littoraria species exhibit considerable overlap and scatter in both carbon and nitrogen isotope ratio values, suggesting that the snails are opportunistic feeders sharing similar food resources. The wide range of δ13C values of Littoraria (-17.2% to -26.3%) is consistent with carbon assimilation from multiple sources (epiphytes from leaves and prop roots, suspended POM, and Rhizophora detritus). Littoraria intermedia and L. pallescens, the smallest species, had similar δ13C values, whereas L. scabra was significantly more 13C depleted. ...
INTRO. It has long been recognized, that relationships exist between habitat and parameters like ... more INTRO. It has long been recognized, that relationships exist between habitat and parameters like weight, shell thickness, length of shells and radulas. Small limpets, Patella granularis L., are restricted to the lower shore and their size increases gradually higher on the shore to a maximum in the balanoid zone (Branch, 1975). In Patella vulgata L., Brian & Owen (1952), Ebling et al. (1962) and Choquet (1966) observed the opposite trend. In dog-whelks, Nucella lapillus, variation in shell shape and thickness could be related to exposure (Crothers, 1974 a,b). Many examples of variation in bivalves are also published. Galucci & Hylleberg (1976) found variation in bentnose clams, Macoma nasuta, in relation to exposure and Kristensen (1957) called it a curious phenomenon that cockles, Cardium edule, from two localities displayed different characteristics. In other words, it is well documented that for individual species many types of variation can be correlated with environmental factor...
Invasive Aquatic Species of Europe. Distribution, Impacts and Management., 2002
218 S. Gollasch et al. tentially deleterious effects on native species, the receiving habitats an... more 218 S. Gollasch et al. tentially deleterious effects on native species, the receiving habitats and their economies (Hedgpeth 1993). Whilst some species are introduced deliberately to new areas for aquaculture purposes, shipping is often regarded as one of the main vectors for the ...
... However, both Yaragina &amp; Marshall (2000) and Rose &amp; O&#x27;Driscoll (2002... more ... However, both Yaragina &amp; Marshall (2000) and Rose &amp; O&#x27;Driscoll (2002) found the lipid condi-tion index values, an indicator of ... exchange in spring leads to relatively large losses of phytoplankton from the shelf, retarding development of intensive spring blooms (Eliasen et al. ...
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