Temperature effect on the African pea crab Afropinnotheres monodi: Embryonic and larval developments, fecundity and adult survival

Abstract

Effects of temperature on the survival of the pea crab Afropinnotheres monodi, and on its realized fecundity (number of eggs) and actual fecundity (number of zoeas) were experimentally estimated on individuals from the Gulf of Cadiz (Huelva and Cadiz) at Southwestern Spain. The adult crabs of different demographic categories (soft females, hard females, and males) were cultured in seawater (salinity of 36) at six different temperatures: 5, 10, 15, 20, 25, 30 °C. After 42 days of culture, the three demographic categories survive at a wide range of temperatures (10 to 30 °C), although survival was high (88.5% to 98.8%, on average) for adults cultured at temperatures between 15 and 30 °C and moderate (69.4%, on average) for those cultured at 10 °C. When ovigerous females collected in winter (field temperature: 15 °C) were cultured at the four temperatures at which survival rates were high (15, 20, 25 and 30 °C), the actual fecundity average of the first brood decreased from 95.9% for females maintained at 15 °C to 3.2% for those maintained at 30 °C; whereas when females were collected in summer (field temperature: 23 °C) this actual fecundity average only displayed a moderate decrease from of 98.3% at 30 °C to 88.3% at 15 °C. Irrespective of the temperature, the number of eggs of the second brood of each female was on average smaller than that of the first brood. The duration of embryonic development was temperature dependent, becoming shorter as the temperatures increased between 15 °C and 30 °C. The embryonic plus larval development times in the Bay of Cadiz, estimated with a temperature dependent model, lasts from 105 days in winter to 43 days in summer. Besides, the effect of temperature on fecundity in the natural environment was estimated on ovigerous females seasonally collected from Cadiz and Huelva. The realized fecundity of A. monodi is higher than in most brachyurans and increases potentially with the size of the female; within females of the same size, there were no significant differences between seasons or locations, except in Huelva in autumn, when a decrease in fecundity was observed. Adult survivals and development time, expected for this species at the current seawater temperatures in the north of the Iberian Peninsula, suggest that northward expansion of A. monodi constitutes a potential risk to the mussel cultures and bivalve shellfishery catch in that area.