Life history of Dulichiella appendiculata (Amphipoda, Senticaudata, Melitidae) in Maryland Coastal Bays, USA

Epibenthic samples collected from March to December 2012 (except September) in Maryland Coastal Bays (MCBs) were used to study the reproductive biology of Dulichiella appendiculata, an amphipod species common in estuaries of the Atlantic and Gulf coasts of the USA, whose life history is not well known. Mean densities (±SE) of D. appendiculata increased from May to July, and declined thereafter. The species reproduced continuously from April (spring) to October (fall). The proportions of ovigerous to non-ovigerous females increased with temperature, from ~70% (April), when mean water temperature was 14.7 ± 0.77°C, to ~94% (July), when water temperature was at its peak (26.4 ± 0.23°C), before decreasing to 0% (November) when the temperature was 9.6 ± 0.2°C. The maximum body lengths of non-ovigerous (9.75 mm) and ovigerous (9.85 mm) females, and males (11.1 mm) were larger than values previously reported in a D. appendiculata population in Beaufort, North Carolina, USA. Large ovigerous females from an overwintering cohort produced juveniles in April, and then disappeared from the population by June, leaving behind small, less fecund ovigerous females belonging to a new generation to produce juveniles. Thus, ovigerous females were smaller in size in June (mean ± SE: 4.8 ± 0.2 mm) than in April (7.3 ± 0.1 mm) and May (8.8 ± 0.5 mm). Males outnumbered females from May to October, but the reverse was the case in April (p < 0.05). The D. appendiculata population in MCBs has a semi-annual, iteroparous life history, with a longevity of about 6 mo (spring breeder) and 9 mo (fall breeder)