Underwater sampling needs to strike a balance between time-efficient and standardized data that allow comparison with different areas and times. The roving diver survey involves divers meandering and actively searching for species and has been useful for producing fish species lists but has seldom been implemented for benthic taxa. In this study, we used this non-destructive technique to register species associated with kelp forests at the sub-Antarctic Bécasses Island (Beagle Channel, Argentina), detecting numerous species while providing the first multi-taxa inventory for the area, including macroalgae, invertebrates, and fish, with supporting photographs of each observation hosted on the citizen science platform iNaturalist. This research established a timely and cost-effective methodology for surveys with scuba diving in cold waters, promoting the obtention of new records, data sharing, and transparency of the taxonomic curation. Overall, 160 taxa were found, including 41 not reported previously for this area and three records of southernmost distribution. Other studies in nearby areas with extensive sampling efforts arrived at similar richness estimations. Our findings reveal that the roving diver survey using photographs is a good approach for creating inventories of marine species, which will serve for a better understanding of underwater biodiversity and future long-term monitoring to assess the health of kelp environments.

Diplopteraster verrucosus is a sea star that incubates its offspring in nidamental chambers. The offspring rely exclusively on maternally provided nutrition. The retention of the embryonic stages allows the allocation of nutritional supplies from the female to the brooded juveniles during the brooding period. The main objectives of this study are, first, to quantify the reproductive investment of D. verrucosus and, second, to describe the morphology, energetics, and oxidative metabolism throughout early ontogenetic stages. A skewed sex ratio of 2:1 females:males was found, and 17 of 39 females were brooding. Both brooding and non-brooding females showed higher energy density and total antioxidant capacity in their gonads than males. We identified three cohorts of offspring being retained within the female body simultaneously. Energy density and reactive oxygen species increased significantly with the offspring’s volume throughout ontogeny. Moreover, we found evidence of at least two key events during ontogeny. First, the depletion of antioxidants, the increase of reactive oxygen species, and the development of a complete digestive system appear to trigger feeding on the mothers’s pyloric caeca. Second, another oxidative imbalance appears to be associated with the release of the brooded juveniles to the environment. Therefore, oxidative balance and energetic variances may be associated with development of autonomous feeding and juvenile release in D. verrucosus.

The brooding sea star Anasterias antarctica is distributed from the coast of Patagonia to the northern Peninsula of Antarctica. In the Beagle Channel, the females of A. antarctica brood their eggs for seven months and do not feed during this period. The endoparasite Dendrogaster argentinensis (Crustacea: Ascothoracica) causes castration in several species of Anasterias. We randomly collected four samplings of adults in May, August and October (brooding period) and January (non-brooding period). The gonad (GI) and pyloric caeca index (PCI) were calculated as organ wet weight (g) x 100/total wet weight (g). Each individual was sexed by microscopic examination of the gonads. Sex ratio, brooding females/non-brooding females and mature females/non-mature females ratios was 1:1. The male GI reached maximum values in January, when most individuals were sexually mature. The GI of non-brooding females reached its maximum during October when it was significantly higher than those from brooding females. The PCI was minimum in October, being lower in brooding females (August and October). During the non-brooding period, mature females had a significantly higher GI than non-mature females. The PCI did not vary neither between males, nor between mature and non mature females. By the end of the brooding period, non-brooding females showed a higher GI than the brooding females. This is explained by proliferation and increase of the oocytes size of non-brooding females. Mature females showed an incremented GI with presence of mature oocytes, while non-mature females exhibited more abundance of previtelogenic oocytes. Males showed synchronicity in reproductive condition. The females that have not brooded presented a process of active gametogenesis, reaching the summer with a high GI, therefore becoming mature females. Females that had brooded were probably lacking energy for new gonadal maturation. The pyloric caeca would be performing the role of a reserve organ in the brooding females, decreasing its size during the brooding period. Prevalence of D. argentinensis in A. antarctica was 11.06%. As this parasite was recorded in sea stars lacking gonads, these infected hosts could have been castrated. Rev. Biol. Trop. 65(Suppl. 1): S221-S232. Epub 2017 November 01.