The gonadal health status of the chocolate clam Megapitaria squalida collected from the Santa Rosalía mining port and San Lucas beach (reference site), Gulf of California, Mexico, was assessed ...through histological analysis of the reproductive tissue, from which the histopathological alteration index (HAI) was determined. In addition, copper and iron accumulation in tissue was revealed using histochemical techniques. Our results showed a large presence of copper (30%) and iron (45%) only in the gonad tissue of clams from Santa Rosalía, in which histopathological alterations observed were inflammatory responses, degenerative–progressive processes, cell death, and response to infectious agents. The HAI was significantly higher in Santa Rosalía specimens (mean ± SE, 72.18 ± 6.12) than in San Lucas clams (4.60 ± 1.07). At San Lucas beach, a higher prevalence of histopathological alterations occurred in clams in the spent stage (43.2%) and in autumn (18.4%) and winter (17.8%) in concordance with the normal reproductive rest period, whereas at Santa Rosalía a higher prevalence occurred in clams at the ripe stage (76.9%) and in spring (83.7%). In conclusion, our results showed the deteriorated health condition of gonads in M. squalida from the Santa Rosalía mining port, which suggests there is a relationship with chronic exposure to local high levels of heavy metals. The high prevalence and intensity of histopathological alterations in the gonad suggest a strong adverse effect on gametogenesis, gamete quality, and, ultimately, in the reproductive potential of M. squalida at this site.
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•The first intermediate host of Elopicola bristowi is identified as an arcid bivalve.•Phylogenetic analyses demonstrate an elopomorph-infecting lineage of the family ...Aporocotylidae.•Two aporocotylid lineages are now known to use bivalve intermediate hosts.•Bivalve-infecting lineages differ in their cercarial furcae and sporocyst shape.•We infer at least three major first intermediate host switches for the Aporocotylidae.
The family Aporocotylidae is recognized as having the widest intermediate host usage in the Digenea. Currently, intermediate host groups are clearly correlated with definitive host groups; all known life cycles of marine teleost-infecting aporocotylids involve polychaetes, those of freshwater teleost-infecting aporocotylids involve gastropods, and those of chondrichthyan-infecting aporocotylids involve bivalves. Here we report the life cycle for a marine elopomorph-infecting species, Elopicola bristowi Orélis-Ribeiro & Bullard in Orélis-Ribeiro, Halanych, Dang, Bakenhaster, Arias & Bullard, 2017, as infecting a bivalve, Anadara trapezia (Deshayes) (Arcidae), as the intermediate host in Moreton Bay, Queensland, Australia. The cercaria of E. bristowi has a prominent finfold, distinct anterior and posterior widenings of the oesophagus, a tail with symmetrical furcae with finfolds, and develops in elongate to oval sporocysts. We also report molecular data for an unmatched aporocotylid cercaria from another bivalve, Megapitaria squalida (G. B. Sowerby I) (Veneridae), from the Gulf of California, Mexico, and six unmatched cercariae from a gastropod, Posticobia brazieri (E. A. Smith) (Tateidae), from freshwater systems of south-east Queensland, Australia. Phylogenetic analyses demonstrate the presence of six strongly-supported lineages within the Aporocotylidae, including one of elopomorph-infecting genera, Elopicola Bullard, 2014 and Paracardicoloides Martin, 1974, now shown to use both gastropods and bivalves as intermediate hosts. Of a likely 14 aporocotylid species reported from bivalves, six are now genetically characterised. The cercarial morphology of these six species demonstrates a clear distinction between those that infect chondrichthyans and those that infect elopomorphs; chondrichthyan-infecting aporocotylids have cercariae with asymmetrical furcae that lack finfolds and develop in spherical sporocysts whereas those of elopomorph-infecting aporocotylids have symmetrical furcae with finfolds and develop in elongate sporocysts. This morphological correlation allows predictions of the host-based lineage to which the unsequenced species belong. The Aporocotylidae is proving exceptional in is propensity for major switches in intermediate host use, with the most parsimonious interpretation of intermediate host distribution implying a minimum of three host switches within the family.
Different aspects of the reproductive biology of the Cortez angelfish Pomacanthus zonipectus were studied between July 1992, and June 1993 at Espiritu Santo Island, Baja California Sur, Mexico. The ...ovarian and testes development was analyzed using histological techniques. The reproductive cycle was determined and quantitatively analyzed. Five stages of gonadal development were established: resting, developing, ripe, spawning, and spent. P. zonipectus is a partial spawner that reproduces from June to November. The reproductive cycle of P. zonipectus shows a clear seasonally related with the water temperature, and gonadosomatic index. Gametogenesis started when water temperatures began to increase and continued during warmer months (26 degree C to 30 degree C). The interval of size at first sexual maturity was 210-220 mm total length.
High temperature increases energy demand in ectotherms, limiting their physiological capability to cope with hypoxic events. The present study aimed to assess the metabolic tolerance of juvenile ...Nodipecten subnodosus scallops to acute hyperthermia combined with moderate hypoxia. A previous study showed that juveniles exhibited a high upper temperature limit (32 °C), but the responses of juveniles to combined hyperthermia and low dissolved oxygen are unknown. Scallops were exposed to control conditions (treatment C: 22 °C, ∼7.1 mg O2 L−1 or PO2 156.9 mmHg), acute hyperthermia under normoxia (treatment T: 30 °C, ∼6.0 mg O2 L−1 or PO2 150.9 mmHg) or acute hyperthermia plus hypoxia (treatment TH: 30 °C, ∼2.5 mg O2 L−1 or PO2 62.5 mmHg) for 18 h. In T, juveniles exhibited an enhanced oxygen consumption, together with a decrease in adenylate energy charge (AEC) and arginine phosphate (ArgP), and with no changes in metabolic enzyme activity in the muscle. In TH, scallops maintained similar AEC and ArgP levels in muscle as those observed in T treatment. This response occurred along with the accumulation of inosine monophosphate and hypoxanthine. Besides, reduced citrate synthase and pyruvate kinase activities, enhanced hexokinase activity, and a higher octopine dehydrogenase/lactate dehydrogenase ratio in the mantle indicated the onset of anaerobiosis in TH. These responses indicate that juvenile scallops showed tissue-specific compensatory responses regarding their energy balance under moderate hypoxia at high temperatures. Our results give an insight into the tolerance limit of this species to combined hyperthermia and hypoxia in its northern limit of distribution.
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•Oxygen consumption increases at high temperatures, a response affected by hypoxia.•Adenylate energy charge decreases, buffered by phosphagen hydrolysis and adenylate kinase.•Tissue-specific responses of metabolic enzyme activity under hyperthermia and hypoxia.
We studied the effects of chronic exposure to metals on energy reserves and reproduction in the clam Megapitaria squalida in two nearby populations exposed to different levels of pollution from ...mining operations in the Gulf of California, Mexico. Female M. squalida from San Lucas beach had good reproductive health status, whereas Santa Rosalia specimens consistently showed low energy reserves, massive oocyte resorption throughout the year, high frequencies of undifferentiated individuals, low proportions of ripe and spawning organisms, smaller and fewer oocytes per follicle, and significantly lower follicular areas. Ovarian levels of Co, Cu, Pb, Mn, and Zn were consistently higher in clams from Santa Rosalia. The poor reproductive health of clams inhabiting this site may be attributed to their long-term exposure to high Co, Cu, and Pb concentrations, as these have been shown to cause toxicity and reproductive impairments in other marine organisms.
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•Female M. squalida from two nearby, metal-polluted sites showed contrasting reproductive health status.•Clams from San Lucas beach showed a good reproductive health status.•Clams from Santa Rosalia had lower energy reserves and impaired reproduction.•These negative effects may be attributed to long-term exposure to Co, Cu, and Pb.
The concentrations of 21 potentially toxic elements (PTEs) were determined in the tissues of Octopus hubbsorum from three locations along the Gulf of California coast: two near Santa Rosalia (SR), a ...site with historical metal contamination, and one in La Paz Bay, a reference site. Concentrations of Cd, Co, Cr, Mn, Ni, Pb, and Zn in octopus from the two SR sites were higher than those from the reference site, reflecting the higher sediment concentrations at the mining-impacted locations. The highest bioaccumulation and biomagnification of elements was found in digestive gland and branchial hearts, while the lowest was observed in the mantle, where the mean concentration of PTEs did not exceed international standards for human consumption of octopus. This study found elevated PTEs in octopus from sites with high metal contamination, and presents the first data on these elements in octopus from the Gulf of California.
•Octopuses from mining-impacted site showed the higher concentrations of elements.•The bioaccumulation of elements is higher in the digestive gland and branchial hearts.•Octopuses show high biomagnification of elements with respect to its clam preys.•Elemental composition of the mantle is in levels suitable for human consumption.•We present the first data on elements in octopus from the Gulf of California.
Latin American countries have a high diversity of sharks, rays, and chimaeras, yet many species are at high risk of extinction due to numerous threats. The conservation of chondrichthyans is key to ...achieving healthy and productive aquatic ecosystems, and countries in Latin America are increasingly recognizing the need for aligning conservation strategies across jurisdictions with similar ecological and socioeconomic challenges. Reflecting on the current state of knowledge and providing consensus expert opinion on research priorities are critical steps to ensure sound management and conservation strategies for chondrichthyans. The present study is a multinational collaboration by leading researchers in Latin America to identify the top-ten research priorities for the conservation of chondrichthyans within this region. Our results were highlighted from a total of 20 broader relevant topics including taxonomy and biology, ecological function, climate change and other stressors, contribution to local economies, and international collaboration. This constitutes the first comprehensive academic perspective on research priorities for chondrichthyans in Latin America which considers the varied perceptions and perspectives related to the management of sharks, rays, and chimaeras across the region and beyond. The main conservation implications highlighted by our study relate to the urgent need to implement, evaluate and/or improve management regulations based on scientific evidence and interdisciplinary research, especially in areas with little progress on the subject and/or where species threatened by extinction are distributed.
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•Chondrichthyans conservation in Latin America requires regulations based on research under an interdisciplinary approach.•We provide an academic perspective on chondrichthyan research top-ten priorities in the region.•Obtaining evidence is urgently needed to develop, apply, and improve successful sustainable management.•These priorities are related to previous and novel knowledge in taxonomy, biology, fisheries, and sociology.•Conservation can be compromised by mitigable factors such as pollution and climate change.
The main Spondylus limbatus population parameters were estimated based on the analysis of individual growth and reproductive aspects of specimens collected monthly (n = 30) from January to December ...2009 in the fishing area of Agua Verde, Gulf of California. The size structure determined from shell measurements was 82-167 mm and the direct reading of shell sections indicated ages of 1-14 years. The data were adjusted to the von Bertalanffy, Gompertz, logistic, Richards and Schnute (Type 1) growth models. The von Bertalanffy model provided the best fit to describe individual growth in this species (SH
∞
= 142.7 mm, k = 0.47, t
0
= −0.20 years). The spawning season was determined through gonadal histology, and the size and age at sexual maturity through a logistic model. Reproductive activity occurred from March to September, with spawning peaks in July and August. The size and age at sexual maturity were 10.8 mm and 2.7 years, respectively. This information provides the necessary knowledge to implement management measures in the area. We recommend independent studies to establish management measures for each fishing area.
Although various studies have reported the bioaccumulation of metals in bivalves of commercial interest from the Gulf of California (GC), the risk associated with their consumption remains poorly ...understood. In this study, our own and bibliographic concentrations of 14 elements in 16 species of bivalves from 23 locations were used to investigate (1) the species-specific and regional accumulation of metals and arsenic in bivalves, (2) the human health risks by age and sex, and (3) the maximum allowable consumption rates (CRlim). The assessments were done according to the US Environmental Protection Agency guidelines. The results indicate that the bioaccumulation of elements varies markedly between groups (oysters > mussels > clams) and localities (higher on Sinaloa due to intense anthropogenic activities). However, consuming bivalves from the GC remains safe for human health. To prevent health effects for residents or consumers on the GC, we recommend (1) following the CRlim proposed herein; (2) monitoring levels of Cd, Pb, and As (inorganic) in bivalves, as the elements of top concern, mainly when are consumed by children; (3) calculating CRlim for more species and locations, including at least: As, Al, Cd, Cu, Fe, Mn, Pb, and Zn; and (4) determine the regional consumption rates of bivalves.
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•Echinocephalus pseudouncinatus larvae in gonads of Atrina maura and Pinna rugosa.•Host specificity of a nematode parasitizing two coexisting species of bivalves.•First molecular ...sequences to identify larvae Echinocephalus pseudouncinatus.•Relationship of nematode infestation with host sex, size, and gonadal development.
The life cycle of Echinocephalus pseudouncinatus has not been described in detail to date, as is also the case of other species in the genus. This study contributes to the information available about the life history of the genus, particularly E. pseudouncinatus, by (1) using molecular techniques (small subunit rRNA gene SSU rRNA sequences) to identify larvae of this species; (2) describing the most conspicuous morphological characteristics that distinguish the species by scanning electron microscopy; (3) describing histological characteristics of the internal anatomy of larvae and the lesions caused by them in the gonads of hosts; (4) reporting new host and reporting evidence of host specificity of E. pseudouncinatus between two species of edible pen shells coexisting in the northern Pacific of Mexico; and (5) analyzing the frequency of infested gonads by host sex, size, and gonadal development stage. The molecular analysis confirmed the morphological and histological diagnosis of E. pseudouncinatus larvae infesting gonads of Atrina maura and Pinna rugosa in Ojo de Liebre and San Ignacio lagoons. The morphological characterization of larvae provides internal details of the cephalic bulb (including rows of hooks and ballonets), neural chord, and cell types of the body wall. Histopathological findings such as degenerated and atretic gametes and the displacement of gonadal tissue in hosts infested with E. pseudouncinatus larvae are discussed in terms of temperature anomalies caused by the “Godzilla El Niño”. The frequency of infestation increased with shell length and gonadal development in A. maura, with a higher infestation frequency in females versus males observed at both study sites. Our findings expand the list of hosts of E. pseudouncinatus, which was previously unknown as a parasite of P. rugosa. In P. rugosa, infestation frequencies are noticeably lower (<1 %) compared with those observed in A. maura (>30 %) at both study sites, suggesting host-specific requirements or preferences in E. pseudouncinatus larvae.
