Journal Articles - UP - MSI
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- Natural diet, feeding periodicity and functional response to food density of the abalone,Haliotis asininaL., (Gastropoda)Tahil, A. S.; Juinio‐Menez, M. A. (Hindawi Limited, 1999-02)The natural food spectrums of the different size groups of abalone, Haliotis asinina L., from Tawi-Tawi, southern Philippines, were determined by analysis of gut contents. Laboratory experiments were conducted to determine the feeding and defecation patterns and functional response of the abalone to varying food density under ambient water conditions. Like other tropical haliotids, H. asinina prefers red algae to brown algal species. Eighteen algal species, 72.2% of which are red algae (Rhodophyta), were observed in the gut contents of all size groups of abalone; Laurencia, Hypnea, Amphiroa and Coelothrix are the most frequent food species. Hypnea and Laurencia are also the most abundant food items of H. asinina. A chi-square test indicated that frequency of occurrence (%) of most algal food species in the gut samples is independent of the size of the animal. About 84% of all algal species were observed in the gut contents of small abalone. Haliotis asinina (mean shell length ± SD = 3.48 ± 0.05 cm) showed a distinct nocturnal feeding periodicity and remained cryptic during daylight hours. Feeding activity was intense from 1800 to 0200 h, but it slowed down a few hours before sunrise, resulting in about 11 h of feeding time within a 24-h cycle. Defecation occurred during the feeding period in proportion to the amount of food consumed and faecal production during the night was significantly higher than during the daylight hours. The total daily faecal output was 1.26 mg dry weight abalone–1. The experiments showed that H. asinina (mean shell length ± SD = 3.55 ± 0.02 cm) consumed more food when food density increased in linear proportion to food abundance. However, food consumption levelled off at a food density equivalent to 35% of body weight.
- Ontogenetic variability in the diel activity pattern of the marine gastropod Cassis cornuta(Mollusca: Cassidae)Calle, Lala Grace; Cabaitan, Patrick C; Sayco, Sherry Lyn G; Tan, Shau Hwai; Conaco, Cecilia (Oxford University Press, 2024-01-25)Examining activity patterns is essential in understanding gastropod feeding and movement ecology. However, the diel activity patterns of large-bodied gastropods, such as Cassis cornuta, remain poorly studied. Here, we conducted outdoor hatchery-based experiments to examine the diel activity patterns of C. cornuta adults and juveniles under natural sunlight and photoperiod. Activities of C. cornuta, such as crawling, hunting, feeding, burrowing and resting on the substratum, were examined every hour for 3 days. Although most individuals were inactive for a greater part of the observation period, active behaviours were recorded for some individuals during both daytime and nighttime, suggesting that C. cornuta is cathemeral, as supported by a nonsignificant result from a Rayleigh's test of uniformity. A higher proportion of adult and juvenile C. cornuta were inactive, either burrowed or resting on the substratum, during the 24-h period. Peak activity time for juveniles started at 20:00, with up to 50% of individuals active, while peak activity time for adults started at 21:00, with up to 20% of active individuals. Adults spent more time resting aboveground, whereas juveniles spent more time burrowed under the sand when not feeding. Juveniles hunted more frequently and spent more time feeding compared to adults. Additionally, juveniles crawled faster and were more successful in capturing sea urchins than adults. The information on variability in the diel activity patterns and movement rates between adult and juvenile C. cornuta would allow further demographic studies, and provide insights into possible conservation strategies for this species.
- Feeding and diel vertical migration cycles of Metridia gerlachei (Giesbrecht) in coastal waters of the Antarctic PeninsulaLopez, M. D. G.; Huntley, M. E. (Springer, 1995-01)Diel vertical migration and feeding cycles of adult female Metridia gerlachei in the upper 290 m of a 335-m water column were measured during a total of 65 h in two periods of early summer (Dec 20–21 and Dec 25–26, 1991). Samples collected in eight depth strata by 35 MOCNESS tows (333-μm mesh) were analyzed for abundance and mean individual gut pigment content. Most of the copepod population was concentrated in a 50-m depth interval at all times. Feeding began simultaneously with nocturnal ascent from a depth of 200–250 m at ≈ 18:00 h (local time), when the relative change in ambient light intensity was greatest. Ingestion rate increased exponentially (ki = 0.988 h−1) at double the gut evacuation rate (ke = 0.488 h−1) as the population moved upward at 22.3–26.5 m h−1 through increasing concentrations of particulate chlorophyll-a. Although the bulk of the population did not move to depths shallower than 50 m, and began its downward migration at a rate of 20.8–31.7 mh−1 in complete darkness, individual females continued to make brief excursions into chlorophyll-rich surface waters (4–8 μg l−1) during the first few hours of population descent. Ingestion rate diminished abruptly by one order of magnitude (ki = 0.068 h−1) at dawn (≈ 03∶30 h). Within four more hours, the population had reached its daytime depth and gut pigment content remained constant at a minimum value until the next migration cycle. No feeding appeared to take place at depth during the day. Ingestion by M. gerlachei females removed < 4% of daily primary production, with only ≈ 20% of this amount being removed from surface waters by active vertical transport.