Individual growth histories of the shortfin squid Illex argentinus were reconstructed in 1512 individuals obtained during seven years of commercial exploitation in southern-south-eastern Brazil. Growth increments were directly measured on the gladius dorsal surface from the anterior part to posterior end in two-thirds of the entire length. Gladius growth increments were deposited at the same rate as statolith rings and the daily nature of the growth increments was supported. Because gladius length is strongly related to mantle length, growth increments closely approximated mantle length growth rates, allowing the reconstruction of both size- and age-dependent growth. Individual reconstruction was possible between 4 and 347 mm of gladius length, almost the entire life cycle of the species. The variability of the acceleration in gladius growth evidenced four life history transitions where the most noticeable occurred between paralarval/juvenile stages, delimiting male/female size differentiation. The changes in acceleration in growth throughout the size-range may be influenced by the thermal gradients experienced by individuals during life history events transitions in Brazilian waters.

Among invertebrates, cephalopods have one of the most well-organized nervous systems. However, with respect to the ontogeny of the nervous system, the post-embryonic development of the cephalopod brain has only been documented for a few species. Here, we investigated the development of the brain of captive oval squid Sepioteuthis lessoniana during the post-hatching phase. The central part of the brain of the oval squid is divided into four main regions, namely, the supraoesophageal, anterior suboesophageal, middle suboesophageal, and posterior suboesophageal masses, each consisting of several lobes. At various ages in juvenile squid, the total volume of the central part of the brain (except the optic lobe) is significantly correlated with its body size, indicated by mantle length and wet body weight. The vertical lobe, superior frontal lobe, and anterior subesophageal mass drastically increase in relative volume as the squid grows. In contrast, the middle suboesophageal mass and posterior suboesophageal mass do not increase in volume with increasing squid age and body size. The effects of these results have been discussed in relation to the onset of squid behaviours during post-hatching.

Growth rates of newly-metamorphosed urchins from a single spawning event (three males and three females) were highly variable, despite being held en masse under identical environmental and nutritional conditions. As individuals reached ~5 mm diameter (0.07–0.10 g wet weight), they were placed in growth trials (23 dietary treatments containing various nutrient profiles). Elapsed time from the first individual entering the growth trials to the last individual entering was 121 days (N = 170 individuals). During the five-week growth trials, urchins were held individually and proffered a limiting ration to evaluate growth rate and production efficiency. Growth rates among individuals within each dietary treatment remained highly variable. Across all dietary treatments, individuals with an initially high growth rate (entering the study first) continued to grow at a faster rate than those with an initially low growth rate (entering the study at a later date), regardless of feed intake. Wet weight gain (ranging from 0.13–3.19 g, P <0.0001, R2 = 0.5801) and dry matter production efficiency (ranging from 25.2–180.5%, P = 0.0003, R2 = 0.6162) were negatively correlated with stocking date, regardless of dietary treatment. Although canalization of growth rate during en masse early post-metamorphic growth is possible, we hypothesize that intrinsic differences in growth rates are, in part, the result of differences (possibly genetic) in production efficiencies of individual Lytechinus variegatus. That is, some sea urchins are more efficient in converting feed to biomass. We further hypothesize that this variation may have evolved as an adaptive response to selective pressure related to food availability.

The black goby Gobius niger (Linnaeus, 1758) (Gobiidae) is one of the most common gobies in southern Tunisian waters. This study provides the first detailed information on the reproductive biology of the G. niger in these areas. Samples of G. niger were collected by trawl from the Gulf of Gabès (Tunisia) between February 2009 and January 2010. A total of 1055 specimens were examined, ranging from 6.4 to 15.7 cm total length. The sex-ratio was in favour of males, especially in larger size-classes. The macroscopic analysis of the gonads and the progression of the monthly values of the gonadosomatic index (GSI) indicated that the reproductive season extended from March to June, with GSI peaking in May, and that spawning occurred from April to June. The utilization of lipid reserves, stored predominantly in the liver as well as in muscles, was important during the reproduction season. Monthly changes of the seminal vesicle somatic index showed that during the pre-spawning period they had a proliferation phase, followed by a regressive phase during the post-spawning period. Total fecundity of mature females ranged from 4280 to 14000 eggs per fish, showing a significant increase with size, with an average of 8522 ± 689 eggs per fish. The total length at 50% maturity was 10.13 ± 0.3 cm and 9.69 ± 0.18 cm for males and females, respectively.

The larval development of the Russell's snapper Lutjanus russellii is described and illustrated for the first time. Fertilized eggs, with a mean diameter of 0.80 ± 0.04 mm and a range from 0.71 to 0.84 mm, were spherical, transparent, buoyant and unpigmented. Embryonic development lasted 26 hours 50 minutes at 24.7°C. Newly hatched larvae were 1.86 ± 0.10 mm in total length (TL) with 24 (10 + 14) myomeres and had an oil globule in the ventroanterior area of the yolk sac. Two days after hatching (DAH, 2.61 mm TL), the mouth opened. Early larvae had melanophores scattered on the head, body and yolk surface. Thirteen DAH (2.74 mm TL), the buds of the second dorsal and pelvic-fin spines had appeared. At 5.81 mm TL, the notochord was slightly flexed, and the hypural bones and caudal-fin rays had begun to develop. The ratios of the second dorsal and pelvic-fin spine lengths to TL attained their maximum, 40% and 36%, respectively. At 14.02 mm TL, all fins had the adult complement of rays and spines. The characteristic of this species, with four black stripes on the sides and with a round black spot on the upper back, was completed in juvenile of 23.1 mm TL. The larval habitat shifted from the surface and middle layers to the tank bottom. A statistical model: Y equals 2.18e0.06X, where Y is mean TL (mm) and X represents DAH, explained 99.34% of variation in growth (P < 0.001, R2 = 0.9934).

The branching structure of the coral colonies from the genus Millepora provides substrate, shelter, and food resources for several reef organisms, such as fish and invertebrates. The present work analysed the association and behaviour of reef fish on the fire coral Millepora alcicornis and M. brasiliensis from September 2010 to February 2011, on the coastal reefs of Tamandaré, north-east Brazil. A total of 473 reef fish individuals of 27 species were sighted associated with the coral colonies, mainly composed of juveniles (65%). The most frequently observed behaviours were sheltered/stationary and swimming close to the coral; however, individuals were also observed foraging and breeding among Millepora spp. branching colonies. The agonistic behaviour performed by Stegastes fuscus individuals was highlighted in the present study, especially against Chaetodon striatus, Diodon holacanthus and Ophioblennius trinitatis individuals. Millepora spp. hydrocorals are ecologically important for juvenile and adult reef fish belonging to several trophic guilds. The complex structure of the coral colonies provides a wide variety of ecological functions on coral reefs (e.g. shelter, reproduction area, food and even territory). Nevertheless, the abundance of branching fire coral in Brazilian reefs have been declining over the past years; therefore, efforts must be made to protect this key habitat.