Distribución y estructura poblacional del cangrejo Halicarcinus planatus (Brachyura, Hymenosomatidae) en el Canal Beagle, Tierra del Fuego

Abstract

Distribución y estructura poblacional del cangrejoHalicarcinus planatus (Brachyura, Hymenosomatidae) en el Canal Beagle, Tierra del Fuego America and has a sub-Antarctic distribution, including the peri-Antarctic islands and New Zealand. In this paper, we report the abundance and population structure of H. planatus for a year in the intertidal zone of Bahía Brown, Beagle Channel, Tierra del Fuego. Moreover, we show variations in the population structure in other beaches and environments of the channel. In contrast with males, female density showed monthly variations and was higher during austral summer months. High densities of H. planatus could be related with low mortality during the larval stage and oceanographic features of Bahía Brown, probably enhanced by the presence of both culture and mussel beds, substrates where settlement would occur. The populational sex ratio was biased towards females only in summer, while the operational sex ratio was biased towards males during all periods studied, suggesting strong competition among males for mating. In turn, males were present only in the intertidal zone of Bahía Brown and Macrocystis pyrifera but were absent in the other studied intertidal areas.This is perhaps related to the lack of shelter in the subtidal zone of Bahía Brown. Recruitment occurs in two different periods, summer (JanuaryFebruary) and autumn-winter (May-June), which corresponds with the two larval cohorts of H. planatus in the Beagle Channel.Key words: Abundance, sex ratio, sexual maturity, recruitment, sub-AntarcticResumen.-El cangrejo Halicarcinus planatus es el único himenosomátido que habita el extremo austral de Sudamérica, con una distribución subantártica, incluyendo las islas periantárticas y Nueva Zelanda. En este trabajo, se presenta información sobre la abundancia y estructura poblacional de H. planatus en el intermareal de Bahía Brown, Canal Beagle, Tierra del Fuego durante un año. Además, se muestran las variaciones en la estructura poblacional en otras playas y ambientes del canal. A diferencia de los machos, la densidad de hembras mostró fluctuaciones mensuales en el intermareal de Bahía Brown y fue mayor durante los meses de verano. Las altas densidades de H. planatus podrían relacionarse con la baja mortalidad de estadios larvales y las características oceanográficas de la bahía, probablemente aumentado por la presencia de bancos y cuerdas de cultivo de mejillones, sustratos donde ocurriría el asentamiento de H. planatus. La proporción de sexos poblacional estuvo sesgada hacia las hembras solo en verano, mientras que la proporción sexual operativa se sesgó hacia los machos durante casi todo el período estudiado, sugiriendo una fuerte competencia entre machos por el apareamiento. A su vez, los machos solo estuvieron presentes en el intermareal de Bahía Brown y en los grampones de Macrocystis pyrifera pero no se encontraron en el resto de los intermareales estudiados, probablemente relacionado con la ausencia de refugio en el submareal de Bahía Brown. El reclutamiento existiría ...

Seasonal variations in size, biomass, and elemental composition (CHN) of Halicarcinus planatus (Brachyura: Hymenosomatidae) larvae from the Beagle Channel, southern South America

“…It ranges along the southwestern Atlantic coasts from Mar del Plata (36°S) to the archipelago of Tierra del Fuego (55°S) (Boschi et al, 1992;Spivak, 1997;Vinuesa and Ferrari, 2008), where it inhabits rocky substrates and kelp holdfasts in the intertidal and shallow sublittoral zones (Arntz et al, 1999;Pérez-Barros et al, 2004;Diez et al, 2011). The planktonic larval development of H. planatus comprises three zoeal stages (Boschi et al, 1969), which are not followed by a megalopa stage.…”

“…Like other Hymenosomatidae, H. planatus has an extended reproductive season with multiple spawning, but the duration of this period decreases towards the southern range limits (Dellatorre, 2009;Vinuesa and Ferrari, 2008;Diez and Lovrich, 2010). In the Beagle Channel (Tierra del Fuego), there are two main periods of reproduction, which correspond with two larval cohorts in the zooplankton, September and January (Lovrich, 1999) and with seasonal changes in reproductive traits of this species, including higher fecundity and smaller eggs in winter than in spring (Diez and Lovrich, 2010).…”

“…Using data of chemical composition as indicators of larval condition, this information may indicate possible intraspecific variation in the larval dependence on planktonic food sources. Furthermore, variations in larval condition may indicate variations in the survival potential of larval H. planatus in different environments, including the potential of this species to invade Antarctic waters with highly seasonal and temporarily low planktonic food production (Diez and Lovrich, 2010).…”

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?

“…The short time between terminal moult and egg extrusion provides additional support for this observation. Also, this fact has previously been observed in H. planatus populations of Puerto Deseado (Vinuesa & Ferrari 2008a, 2008b and Brown Bay (Diez & Lovrich 2011), and recorded in other hymenosomatid species (Lucas 1980;). However, the relationship between physiological maturity and impregnation showed differences between Camarones and Rada Tilly populations, which could be attributed to differences in sex ratio.…”

“…Vinuesa et al (2011) suggested that mature males have cryptic habits in subtidal environments, which makes them difficult to find. According to Diez & Lovrich (2011), the presence of Macrocystis pyrifera (Linnaeus) C. Agardh forests in subtidal environments can explain the absence of males in intertidal environments, because males prefer the complex habitat provided by holdfasts. However, males of H. planatus have been recorded in intertidal areas with subtidal kelp forests (e.g.…”