Age, growth and mortality of the toadfish, Halobatrachus didactylus (Schneider, 1801) (Pisces: Batrachoididae), in the Bay of Cádiz (southwestern Spain)

Age, growth and mortality of the toadfish, Halobatrachus didactylus, were determined by examination of the whole sagittal otoliths of fish sampled in the Bay of Cádiz (southwestern Spain) from March 1999 to March 2000. A total of 844 specimens (425 males, 416 females, and 3 of indeterminate sex), ranging from 95 to 470 mm in total length were examined. Eighty-nine percent of the otoliths could be read allowing an age estimation. The opaque zone was formed between April and May coincident with the maximum reproductive peak, while the translucent zone formed mainly in summer-fall (June to December). Maximum ages for males and females were 12 and 10 years, respectively. The samples were dominated by 2- to 6-year-old specimens. Males matured at an age of approximately 2 years and females at 3 years. Fish total length and otolith radius were closely related. The von Bertalanffy growth curve was used to describe growth. The parameters were derived from back-calculated length-at-age. Significant differences in the growth parameters were found between sexes. Although the growth analysis revealed that this species is slow-growing, males reached larger sizes than females. Females appeared to experience higher natural mortality rates than males.

Egg surface structure of the freshwater toadfish Thalassophryne amazonica (Teleostei: Batrachoididae) with information on its distribution and natural habitat

The egg surface structure of Thalassophryne amazonica, a freshwater toadfish from the Amazon basin is described. Eggs of this species show a remarkable, highly unusual system of parallel ridges and intermittent grooves that originate at the equator of the egg and lead to the micropylar pit, at which they end in a spiralling pattern. A similar egg surface structure has so far been described only from a group of Asian anabantoid percomorphs, obviously not closely related to Thalassophryne. This egg surface pattern may enhance fertilization success by guiding sperm to the micropyle. We review museum records for T amazonica, present an updated map of its occurrence in the Amazon basin, and provide information on its habitat.

Feeding ecology and life-history strategy of nesting males in a fish with long parental care, Lusitanian toadfish (Halobatrachus didactylus, Batrachoididae)

The Lusitanian toadfish, Halobatrachus didactylus, like other batrachoidids, is a benthic fish species with nesting behaviour during the breeding season. During this prolonged period it engages in mating activities and remains in the nest providing parental care. It is not known whether males feed while providing parental care but it is likely that their limited mobility may restrict their diet and influence their fitness. As a consequence, egg cannibalism could occur as a life-history strategy. The aim of the present study is to ascertain the feeding behaviour of nesting males, in comparison to mature non-nesting males, and to identify potential life-history traits related to egg cannibalism. Nest-holders were sampled from artificial nests placed in an intertidal area of the Tagus estuary, only exposed during spring low tides. The diet of nest-holders was compared with that of non-nesting mature males from the same area, captured by otter trawl. The present study demonstrates that despite their constrained mobility nest-holders feed during the breeding season, although in a more opportunistic fashion than non-nesting males. Nest-holders showed a generalist feeding behaviour, with a more heterogeneous diet. Egg cannibalism was not related to male condition, paternity or brood size but showed a higher incidence early in the season when water temperatures were lower. The results suggest a possible seasonal trade-off strategy between care and energy recovery, triggered by environmental factors, where under unfavourable conditions to sustain viable eggs the male may recover energy by eating eggs, thus benefiting future reproductive success, later in the season.

Influência do comportamento vocal no sucesso reprodutor do xarroco lusitano Halobatracus didactylus (Bloch & Schneider, 1801)

Dissertação de mest., Biologia Marinha (Ecologia e Conservação Marinha), Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2011

Tolerância à amónia e grau de ureotelia no xarroco, Halobatrachus didactylus (Bloch & Schneider, 1801)

Tese mest., Biologia Marinha, Universidade do Algarve, Faculdade de Ciências do Mar e do Ambiente, 2008

The venomous toadfish Thalassophryne nattereri (niquim or miquim): report of 43 injuries provoked in fishermen of Salinópolis (Pará State) and Aracaju (Sergipe State), Brazil

Os peixes da família Batrachoididae causam um grande número de acidentes em pescadores das regiões Norte e Nordeste do Brasil. O gênero Thalassophryne apresenta várias espécies no Brasil e a espécie Thalassophryne nattereri é a mais comum, todas apresentando veneno. O veneno é inoculado por duas espículas ocas na nadadeira dorsal e duas nas regiões pré-operculares, ligadas a uma glândula de veneno na base. Os envenenamentos causaram dor intensa, edema e eritema iniciais em 43 pescadores observados em Salinópolis (Pará) e Aracaju (Sergipe). em todos os casos, não ocorreram fenômenos sistêmicos dignos de nota, mas ocorreu necrose local em oito pacientes e infecção bacteriana em dez. As circunstâncias dos acidentes são comentadas, assim como aspectos terapêuticos. Nossa conclusão foi que o envenenamento por Thalassophryne é importante e freqüente e deve ser considerado de média gravidade, em função de não haverem fenômenos sistêmicos, como observado nos acidentes por peixes-escorpião (Scorpaena) ou arraias marinhas e fluviais.

Clinical manifestations and experimental studies on the spine extract of the toadfish Porichthys porosissimus

Toadfish are fish from the family Batrachoididae that are found in marine and brackish environment around the world. Among the toadfish, Porichthys genus is very common, where Porichthys porosissimus, also called Atlantic Midshipman is found in Southwest Atlantic, from Rio de Janeiro, Brazil to eastern Argentina. There was no consensus about the classification of the genus Porichthys as venomous fish because so far there are no published Studies regarding human envenomations and/or toxic activities induced in animal models. Herein, we report two conclusive envenoming in human beings caused by P porosissimus spines, with clear signs and symptoms that were very important for the development of our experimental studies. We demonstrated that the P. porosissimus spine extract, now venom, can induce nociceptive and edematogenic responses in mice as well an induction of an inflammatory response elicited by intravital microscopy and leukocyte migration. Finally, we identified in the P. porosissimus spine extract, through analysis by mass spectrometry, the presence of proteins previously detected in the venoms of other fish species and other venomous animals. We believe that based on our studies we will dismiss the non-venomous nature of this fish and clarify this issue. (C) 2014 Elsevier Ltd. All rights reserved.

How effective are acoustic signals in territorial defence in the Lusitanian toadfish?

The function of fish sounds in territorial defence, in particular its influence on the intruder's behaviour during territorial invasions, is poorly known. Breeding Lusitanian toadfish males (Halobatrachus didactylus) use sounds (boatwhistles) to defend nests from intruders. Results from a previous study suggest that boatwhistles function as a 'keep-out signal' during territorial defence. To test this hypothesis we performed territorial intrusion experiments with muted Lusitanian toadfish. Males were muted by making a cut and deflating the swimbladder (the sound-producing apparatus) under anaesthesia. Toadfish nest-holder males reacted to intruders mainly by emitting sounds (sham-operated and control groups) and less frequently with escalated bouts of fighting. When the nest-holder produced a boatwhistle, the intruder fled more frequently than expected by chance alone. Muted males experienced a higher number of intrusions than the other groups, probably because of their inability to vocalise. Together, our results show that fish acoustic signals are effective deterrents in nest/territorial intrusions, similar to bird song.

Vocal differentiation parallels development of auditory saccular sensitivity in a highly soniferous fish

Vocal differentiation is widely documented in birds and mammals but has been poorly investigated in other vertebrates, including fish, which represent the oldest extant vertebrate group. Neural circuitry controlling vocal behaviour is thought to have evolved from conserved brain areas that originated in fish, making this taxon key to understanding the evolution and development of the vertebrate vocal-auditory systems. This study examines ontogenetic changes in the vocal repertoire and whether vocal differentiation parallels auditory development in the Lusitanian toadfish Halobatrachus didactylus (Batrachoididae). This species exhibits a complex acoustic repertoire and is vocally active during early development. Vocalisations were recorded during social interactions for four size groups (fry: <2 cm; small juveniles: 2-4 cm; large juveniles: 5-7 cm; adults >25 cm, standard length). Auditory sensitivity of juveniles and adults was determined based on evoked potentials recorded from the inner ear saccule in response to pure tones of 75-945 Hz. We show an ontogenetic increment in the vocal repertoire from simple broadband-pulsed 'grunts' that later differentiate into four distinct vocalisations, including low-frequency amplitude-modulated 'boatwhistles'. Whereas fry emitted mostly single grunts, large juveniles exhibited vocalisations similar to the adult vocal repertoire. Saccular sensitivity revealed a three-fold enhancement at most frequencies tested from small to large juveniles; however, large juveniles were similar in sensitivity to adults. We provide the first clear evidence of ontogenetic vocal differentiation in fish, as previously described for higher vertebrates. Our results suggest a parallel development between the vocal motor pathway and the peripheral auditory system for acoustic social communication in fish.

Feeding ecology and trophic relationships of fish species in the lower Guadiana River Estuary and Castro Marim e Vila Real de Santo Antonio Salt Marsh

In this study we analyze the feeding ecology and trophic relationships of some of the main fish species (Soleidae, Moronidae, Mullidae, Sparidae, Mugilidae, and Batrachoididae) of the lower Estuary of the Guadiana River and the Castro Marim e Vila Real de Santo Antonio Salt Marsh. We examined the stomachs of 1415 fish caught monthly between September 2000 and August 2001. Feeding indices and coefficients were determined and used along with the results of multivariate analysis to develop diagrams of trophic interactions (food webs). Results show that these species are largely opportunistic predators. The most important prey items are amphipods, gobies (Gobiidae), shrimps (Palaemon serratus and Crangon crangon), and polychaete worms. The lower Estuary and associated salt marshes are important nurseries and feeding grounds for the species studied. In this area, it is therefore important to monitor the effects of changes in river runoff, nutrient input, and temperature that result from construction of the Alqueva Dam upstream. (c) 2006 Elsevier Ltd. All rights reserved.