Settlement and recruitment of the crab Halicarcinus planatus (Crustacea: Decapoda: Hymenosomatidae) in Golfo San Jorge, Argentina

Abstract

The settlement and recruitment of the small brachyuran crab Halicarcinus planatus from the central area of Golfo San Jorge, south-western Atlantic Ocean, was studied. Three different artificial collectors were evaluated: smooth-surface panels, panels covered with synthetic lawn and ballasted plastic boxes filled with remains of fishing nets. In addition, plankton samples were taken monthly and water salinity and temperature were recorded. Between July 2006 and June 2007, the collectors were deployed monthly in the subtidal zone of two nearby localities and collected two months later. The recovered crabs were classified into four stages: settlers, recruits, advanced juveniles and mature crabs. There were differences in the presence of stages among collector types and seasons but not between localities. Settlers and recruits were abundant on the panels with synthetic lawn, while late juvenile and mature females were more frequent in the boxes. Larval stages occur between July and February, and only zoeas I and II were found. The males, which were only represented by early juveniles, were exclusively found on the panels with synthetic lawn, from where they would subsequently migrate to cryptic habitats such as the holdfast of Macrocystis pyrifera. Settlement occurs between September and April. Settlers showed a peak in abundance during November–December, while the recruits showed two peaks, one in December and the other in February–March. For late juveniles, the maximum abundance was recorded in April–May. Ovigerous females were found between May and September, when the experiment ended. Settlement and recruitment of H. planatus in Golfo San Jorge occur over a prolonged period. Individuals may undergo shifts in microhabitat use during this period, probably related to the search for food and shelter, and avoidance of predation and cannibalism.

Growth and maturity of the spider crab Halicarcinus planatus (Brachyura: Hymenosomatidae) females in the southwestern Atlantic Ocean. Can these parameters be influenced by the population sex ratio?

“…Samplings for these experiments were carried out in autumn (April and May) of 2013, 2014 and 2015, because this time has higher moult activity and is close to the beginning of the reproductive period (Vinuesa & Ferrari 2008a;Vinuesa et al 2011).…”

“…The causes of these variations are unknown. However, an early male dispersal to subtidal cryptic microhabitats has been proposed to explain the deviation in sex ratio (Vinuesa et al 2011;Diez & Lovrich 2013).…”

“…Different traits related to the growth of H. planatus have been studied in the Kerguelen Islands (Richer de Forges 1977), Puerto Deseado (Vinuesa & Ferrari 2008a), Comodoro Rivadavia (Vinuesa et al 2011) and the Beagle Channel (Diez & Lovrich 2013). Different stages in females according to the abdomen morphology have been identified (Vinuesa & Ferrari 2008a): immature (IMM), adolescent (ADO), which refers to the last instar before terminal moult, and mature (MAT).…”

“…A common feature in Halicarcinus spp. populations is the significant size overlapping between ADO and MAT females (Vinuesa & Ferrari 2008a;Vinuesa et al 2011). According to , size overlapping in H. cookii Filhol, 1885 females is related to variable moult increments in immature crabs and precocious maturity in the female fraction.…”

Growth and reproduction investment of the young of the year of the squat lobster <em>Munida gregaria</em> (Crustacea: Anomura) in the Patagonian coast

“…In coastal areas, the minimum surface temperature is 7.6°C and the maximum is 17.3°C. Salinity ranges between 33.1 and 34.2 (Vinuesa et al 2011).…”