摘要:

Abstract.The structure of the epiphytic community (hydroids, bryozoans, and the most abundant macrophytes) ofPosidonia oceanicaleaves in a shallow meadow near Lacco Ameno, Ischia was studied. The structure of the community changed along an age gradient that extended from the inner to the outer leaves and from the basis to the apex of each leaf. This structure was also affected by microclimatic factors. The dynamics of community “maturation” is descri

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1987.tb00189.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.The role of prolactin (PRL) in the neuroendocrine control of schooling behaviour and activity in the demoiselleChromis viridisis analysed by administration of a prolactin‐releasing drug, metoclopramide (Paspertin®). In addition, the dependence of the activity state, schooling time, and colour changes on the administration of an epiphysial hormone, melatonin, is examined. Each substance tested affects schooling behaviour and activity by a different mechani

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1987.tb00190.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.The reproductive cycle of the comatulid crinoidNemaster rubiginosafrom Discovery Bay, Jamaica is described histologically. The cycle is annual and may be divided into (1) a “resting” phase (summer) in which most adults possess immature, unsexable gonads, (2) a recovery phase (early fall) marked by the re‐initiation of gametogenesis and rapid gonadal growth, (3) a breeding phase (late fall and winter) during which the gonads are mature and repeated spawning likely takes place, and (4) a post‐spawning phase (spring) during which relict gametes are removed from the shrinking gonads. Although unsexable individuals predominate during the “resting” phase, a small proportion of the adult population is unsexable at all times of the year. The reproductive condition of animals in the same month in two successive years was very similar, suggesting that the timing of reproduction is quite predictable from year to year. The re‐initiation of gametogenesis in the early fall is correlated with both rising sea temperature and shortening daylength, and the October to March breeding season corresponds to the period of short daylengths at the study site. The well‐defined and synchronized annual reproductive cycle ofNemaster rubiginosacontrasts with the more prolonged and variable reproductive cycles reported for other tropical crinoids and points to a diversity of breeding patterns among tr

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1987.tb00191.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.The diets of three syntopic Gulf of CaliforniaAcanthemblemaria (A. balanorum, A. crock‐eriandA. macrospilus)andA. castroifrom the Galapagos Island are nearly uniformly composed of harpacticoid copepods and other small benthic‐vagile or planktonic crustaceans. On occasion, large prey items such as crabs or other small fishes are taken. HORN'S index of niche overlap indicates that the three syntopicAcanthemblemariaare not separated along the food resource utilization axis. Slight variations in diets among the syntopic species seem to be related to differences in degree of microhabitat specializat

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1987.tb00192.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.The distribution of the thalassinidean shrimpUpogebia pusillawas studied at four sites in the North Adriatic Sea: 1) a tidal flat in the lagoon of Grado, 2) a tidal flat at Lido di Staranzano near the mouth of the Isonzo, 3) a mud flat seawards of a salt marsh in a protected bay north of Rovinj, and 4) a sublittoral station in 6m depth near Aurisina. Information on grain size distribution, organic content, amount of debris, redox profiles and pH of sediment as well as temperature and salinity is given. Density, as determined by hole counts and a hole: burrow relationship derived from resin casting, generally increased with increasing water depth in the intertidal. The upper limits ranged between +10cm (Rovinj) and ‐20cm (Grado); densities between mean water and low water level varied strongly due to microtopography and macrophyte cover. Maximum densities in the intertidal ranged from 189 (Grado) to 2420 (Rovinj, juveniles) animals m2. Shrimp density at the sublittoral station ranged between 80 and 230 m“2. The zonation of theUpogebiidaeandCallianassidaewith respect to environmental parameters is discus

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1987.tb00193.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.Ingestion rates and absorption efficiencies inGibbula umbilicarisandJujubinus striatusfeeding on green algal films, diatoms, macro‐epiphytes, and deadPosidoniaocean/'ca‐Ieaves have been investigated in laboratory experiments.For both gastropod species, ingestion rates were highest in diatoms and thin green algal films as food source.G. umbilicarisexhibited significant lower consumption rates when feeding on seagrass debris or macro‐epiphytes,J. striatusconsumed neitherPosidonia‐debrisnor macro‐epiphytes.Highest carbon absorption efficiencies were found in both gastropod species when feeding on diatoms and green algal films. Significantly lower efficiencies were found inG. umbilicariswhen consuming seagrass debris or macro‐epiphytes.Analyses of fecal material confirmed these findings. Highest organic carbon contents were measured in fecal pellets produced after consumption of seagrass debris or macro‐epiphytes reflecting the presence of structural carbohydrates. SEM examinations of feces revealed mainly diatom frustules, refractory parts of macroalgal and other plant material. Analyses of gut contents gave similar results suggesting a basically microphagous herbivory for both gastropod species.Since seagrass debris and macro‐epiphytes are not used very effectively, the high absorption efficiencies when animals feed on the microfloral component of the periphyton are discussed as possible adaptation to limited fo

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1987.tb00194.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY