This study provides information concerning the feeding behaviour of Goniopsis cruentata (Latreille, 1803), through analysis of stomach contents according to demographic categories. Collections were carried out monthly from May 2005 through April 2006 in a subtropical estuary on the southeastern Brazilian coast (23 • 29 24 S 45 • 10 12 W). The crabs were collected by hand, with a 2-hour sampling effort by three people. In the laboratory, the crabs were sexed and measured for greatest carapace width, and grouped into demographic categories: adult males, juvenile males, adult females, juvenile females, and ovigerous females. For the fullness analysis, the stomachs were grouped into two categories: (1) E = Empty, with no food; and (2) F = Full, whether partially filled or totally. The frequency-of-occurrence method was used to characterize feeding behaviour, and the demographic categories recognired were compared. We obtained stomachs from 171 adult males, 69 juvenile males, 136 adult females, 72 juvenile females, and 41 ovigerous females, of which 85.6% were full. Of the eight food items recorded, sediment was the most frequent, and "unidentified material" was the least. Goniopsis cruentata can be characterized as a generalist feeder, exploiting most of the food items available in the mangrove swamps. In spite of this generalist behaviour, the dominant presence of sediment suggests that G. cruentata is primarily a detritivore that exploits particulate organic matter from microbial biodegradation, one of the most important mangrove functions. The trophic role of this crab in the ecosystem showed no significant differences among the demographic categories, and seems to be wider than those observed for sesarmid and ocypodid mangrove crabs. These ecosystem engineers may occupy different positions in the trophic chains of estuarine environments. RESUMOEste estudo providencia informações sobre a composição da dieta do caranguejo Goniopsis cruentata (Latreille, 1803) por meio de análise do conteúdo estomacal, caracterizando os hábitos alimentares nas diferentes categorias demográficas bem como a dinâmica temporal da alimentação desses animais. O estudo foi realizado em um estuário em Ubatuba, Estado de São Paulo, litoral sudeste do Brasil, no período de maio de 2005 a maio de 2006. Os estômagos foram retirados e conservados em álcool 70%. Foi utilizado o método de Freqüência de Ocorrência e as categorias demográficas foram comparadas. Foram analisados 489 estômagos, sendo 171 de machos adultos com tamanho médio de 33,14 ± 6,4 mm LC, 69 de machos jovens de tamanho médio 21,16 ± 4,9 mm LC, 136 de fêmeas adultas, com tamanho médio de 32,9 ± 5,1 mm LC, 72 de fêmeas jovens, com tamanho médio de 24,0 ± 3,3 mm LC e 41 estômagos de fêmeas ovígeras, com tamanho médio de 35,4 ± 4,4 mm LC. Foram identificados oito itens alimentares, sendo Sedimento o mais representativo. Não foi verificada diferença significativa entre as categorias alimentares entre as diferentes fases de desenvolvimento nem em relação aos sexos, com exceção do item...
ABSTRACT. The morphology of stomach ossicles of decapod crustaceans provides valuable information on their phylogeny and biology. We herein described ten new ossicles in the foreguts of two trichodactylid crabs, Sylviocarcinus pictus (H. Milne-Edwards, 1853) and Valdivia serrata White, 1847, in addition to previously described 38 ossicles, which are also recognized and listed. Five specimens each of S. pictus and V. serrata were selected for morphological analysis of gastric ossicles. The stomachs were obtained after removing the carapace, and they were fixed in 10% formalin for 24 hours. After this procedure, the stomachs were immersed in a solution of 10% Potassium Hydroxide (KOH) and heated to 100 °C during 60 minutes for tissue maceration. At this point, the clean skeletons were colored by adding 1% Alizarin Red to the KOH solution in order to facilitate visualization of the internal structures such as the setae and ossicles. The ten new ossicles are: dorsomedial cardiac plate; dorsolateral cardiac plate; suprapectineal lateral ossicle; inferior cardiac valve; lateral mesopyloric ossicle; ampullary roof-medium portion ossicle; process of the ampullary roof-upper portion; lateral-inferior post-ampullary plate; pleuro-pyloric valve's ossicle; and lateral pleuro-pyloric plate. Some ossicles are thin plates that together with the main ossicles assist in the structure and support of the stomach, which are similar in the two species studied herein. The current knowledge on gastric ossicles will be useful in establishing taxonomic characters, which can evaluate phylogenetic relationships among brachyuran crabs.
The gastric armature of decapod foregut is a feeding structure that sparks controversial debates about the role dietary and historical components have in shaping its morphological traits. Having previous information about the natural diet is an interesting way to gather evidence on this issue. For the present study, we analyzed the morphological traits of gastric ossicles involved directly in the maceration of food in nine species of freshwater crabs of the family Trichodactylidae (Brachyura: Decapoda) representing five genera, three tribes and two subfamilies. The analyzed gastric ossicles were quite consistent among closely related species, suggesting that the observed traits had a clear phylogenetic component. However, it was also noted that the morphological traits of the gastric teeth of trichodactylid crabs match well with the natural diet and presented likeness with general features of other species with a similar trophic habit. We discuss the influence of phylogeny and function on the design of morphological traits and propose to quantify the role of phylogeny and function in shaping morphological traits through the analysis of phylogenetic signals.
Crabs of the family Pseudothelphusidae are restricted to the Neotropical region and new species are described every year. They are threatened by habitat loss and knowledge of this family is almost limited to taxonomy and faunal surveys. Here, we investigate the presence of heterochely and laterality in Kingsleya castrensis, as a tool to infer ecological and behavioural aspects. Since most Pseudothelphusidae were described from a few individuals only, some aspects of morphological variation, sexual dimorphism, heterochely and laterality are confirmed herein for the first time for a species of Kingsleya. The sizes of dactylus and propodus of males, as well as the allometric growth of both sides of the chelipeds, were significantly larger and higher, respectively, when compared to females. The right side was significantly longer than the left and both sexes displayed right-handedness. These results are similar to those from other freshwater crab families, and provide a clue to a possible aggressive, display, and territorial behaviour in K. castrensis.
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