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<p>Callianassid decapod shrimp are solitary deep-burrow dwellers in sandy seabeds. They notably eject sediments through surface burrow openings. Sediment-ejection rates have been measured in situ, with hydrodynamic-forced sediment inflows to burrows precluded. So, non-disturbing approaches are required. On an intertidal sandflat under clear water, southern Japan, videography was conducted at one sheltered site on four seasonal occasions for sediment-ejection (<i>se</i>)-bouts through 10−29 burrow openings of <i>Neotrypaea harmandi</i> with 20−24-mm average total lengths at 225−340-cm<sup>2</sup> plots during 8.6−10.9-h daytime submerged periods. Concurrently recorded were water temperature (<i>wt</i>), water level, current speed (<i>cs</i>) 10&#xa0;cm above the seabed, and sediment volume (<i>sv</i>) deposited in sediment traps per 10&#xa0;min. An exposed site was also sampled on one occasion with the highest-wave conditions. The ratios for sheltered site to exposed site were 0.50, 0.44, and 0.53 for each time-averaged value of <i>cs</i><sup>3</sup> (measure of currents’ power moving sediment), <i>sv</i>, and <i>se</i>-frequency in 10&#xa0;min per burrow opening, respectively. The average <i>se</i>-frequency was smaller when <i>wt</i> was 13°C than on the other occasions when <i>wt</i> ≥20°C. On one occasion during the shrimp’s reproductive season, observations continued during the nighttime submerged period, when <i>se</i>-bouts were limited to the initial 24%, likely reflecting shrimp nocturnal mating. The average sediment volume per individual shrimp’s <i>se</i>-bout in the laboratory was 0.09&#xa0;mL. With this value and the average <i>se</i>-frequency at the sheltered site on each occasion, it was estimated that 2.0−4.2-mL sediment was circulated between sandflat surface and a shrimp burrow with two openings over the submerged period.</p>

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Assessment of sediment-ejection activity of callianassid ghost shrimp on an intertidal sandflat in relation to seasonal hydrodynamic conditions, temperatures, and shrimp reproductive states

  • 期刊论文

  • 发表日期：

    2025年7月2日

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  • Shunsuke Sen-ju,
  • Sota Nakajo,
  • Akio Tamaki

摘要

Callianassid decapod shrimp are solitary deep-burrow dwellers in sandy seabeds. They notably eject sediments through surface burrow openings. Sediment-ejection rates have been measured in situ, with hydrodynamic-forced sediment inflows to burrows precluded. So, non-disturbing approaches are required. On an intertidal sandflat under clear water, southern Japan, videography was conducted at one sheltered site on four seasonal occasions for sediment-ejection (se)-bouts through 10−29 burrow openings of Neotrypaea harmandi with 20−24-mm average total lengths at 225−340-cm2 plots during 8.6−10.9-h daytime submerged periods. Concurrently recorded were water temperature (wt), water level, current speed (cs) 10 cm above the seabed, and sediment volume (sv) deposited in sediment traps per 10 min. An exposed site was also sampled on one occasion with the highest-wave conditions. The ratios for sheltered site to exposed site were 0.50, 0.44, and 0.53 for each time-averaged value of cs3 (measure of currents’ power moving sediment), sv, and se-frequency in 10 min per burrow opening, respectively. The average se-frequency was smaller when wt was 13°C than on the other occasions when wt ≥20°C. On one occasion during the shrimp’s reproductive season, observations continued during the nighttime submerged period, when se-bouts were limited to the initial 24%, likely reflecting shrimp nocturnal mating. The average sediment volume per individual shrimp’s se-bout in the laboratory was 0.09 mL. With this value and the average se-frequency at the sheltered site on each occasion, it was estimated that 2.0−4.2-mL sediment was circulated between sandflat surface and a shrimp burrow with two openings over the submerged period.