Research Article |
Corresponding author: Renata C. Lima-Gomes ( renatacslima@yahoo.com.br ) Academic editor: Carolina Arruda Freire
© 2017 Renata C. Lima-Gomes, Jô de Farias Lima, Célio Magalhães.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Lima-Gomes RC, de Farias Lima J, Magalhães C (2017) Description of ten additional ossicles in the foregut of the freshwater crabs Sylviocarcinus pictus and Valdivia serrata (Decapoda: Trichodactylidae). Zoologia 34: 1-7. https://doi.org/10.3897/zoologia.34.e13731
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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.
Amazon, anatomy, foregut, morphology, Neotropical, stomach, Valdiviini
The stomach of decapod crustaceans is composed of a muscular and nervous complex called gastric mill (
Studies on the gastric skeleton of Amazonian decapods are very recent, and only a few have been developed for brackish and freshwater decapods.
Uncatalogued specimens of S. pictus and V. serrata were obtained from the crustacean collection of the Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil. The stomachs of five specimens of each species were analyzed: four males and a female of S. pictus, and two males and three females of V. serrata. The stomachs of crabs do not differ in regard to gender and so did not matter the number of each gender. The stomachs were obtained after carapace removal and fixed in 10% formalin for 24 hours. For tissue maceration, the stomachs were cooked for 60 minutes in 10% Potassium Hydroxide (KOH) solution and heated to 100 °C (
The nomenclature and abbreviations used in the morphological description of the gastric skeleton followed
All the 38 ossicles previously described by
The stomach ossicles are grouped according to the following regions of the gastric skeleton: 10 ossicles of the gastric mill; 11 ossicles of the lateral supporting cardiac region; 4 ossicles of the cardio-pyloric valve; 6 ossicles supporting the dorsal pyloric stomach; 9 ossicles supporting the ventral pylorus and bulb; 3 ossicles supporting the supra-ampullary region; and 5 ossicles supporting the lateral pylorus region (Table
The ten new ossicles are described below and illustrated in Figs
Ossicles of the gastric mill: Dorsomedial cardiac plate (VIIa) (Figs
Dorsolateral cardiac plate (VIIb) (Figs
Lateral supporting cardiac ossicles: Suprapectineal lateral ossicle (VIIIa) (Figs
Supporting ossicles of the dorsal pyloric chamber: Lateral mesopyloric ossicle (XIXa) (Figs
Supporting ossicles of the ventral pylorus and ampullae: Ampullary roof-mediun portion ossicle (XXVa) (Figs
Lateral-inferior post-ampullary plate (XXVIIa) (Figs
Supporting ossicles of the lateral pylorus: Pleuro-pyloric valve’s ossicle (XXXIa) (Figs
The ten additional ossicles of the foregut of Sylviocarcinus pictus and Valdivia serrata, found in the present study and not previously recognized by
Nomenclatures and abbreviations used in morphological descriptions ossicles of the stomachs of Sylviocarcinus pictus and Valdivia serrata, and the comparison between the study of
Name of the ossicles | Number assigned to the ossicles |
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Present paper |
---|---|---|---|
Ossicles of the gastric mill | |||
Mesocardiac ossicle | (I) | X | X |
Pterocardiac ossicle | (II) | X | X |
Post-pterocardiac ossicle | (IIb) | X | X |
Pyloric ossicle | (III) | X | X |
Exopyloric ossicle | (IV) | X | X |
Zygocardiac ossicle | (V) | X | X |
Propyloric ossicle | (VI) | X | X |
Urocardiac ossicle | (VII) | X | X |
Pectineal ossicle | (VIII) | X | X |
Dorsomedian cardiac plate | (VIIa) | – | X |
Dorsolateral cardiac plate | (VIIb) | – | X |
Lateral supporting cardiac ossicles | |||
Suprapectineal lateral ossicle | (VIIIa) | – | X |
Prepectineal ossicle | (IX) | X | X |
Postpectineal ossicle | (X) | X | X |
Quill of the postpectineal ossicle | (Xa) | – | X |
Anterior lateral cardiac plate | (XI) | X | X |
Posterior lateral cardiac plate | (XII) | X | X |
Inferior cardiac valve | (XIIa) | – | X |
Inferior lateral cardiac | (XIII) | X | X |
Subdentate | (XIV) | X | X |
Lateral cardiac-pyloric ossicle | (XV) | X | X |
Ossicles of the cardio-pyloric valve | |||
Anterior ossicle of the cardio-pyloric valve | (XVI) | X | X |
Posterior lateral cardiac plate | (XVII) | X | X |
Lateral ossicle of the cardio-pyloric valve | (XVIII) | X | X |
Supporting ossicles of the dorsal pyloric chamber | |||
Anterior mesopyloric ossicle | (XIX) | X | X |
Lateral mesopyloric ossicle | (XIXa) | – | X |
Posterior mesopyloric ossicle | (XX) | X | X |
Uropyloric ossicle | (XXI) | X | X |
Infra-uropyloric fragment | (XXIa) | X | X |
Posterior uropyloric ossicle | (XXIb) | X | X |
Supporting ossicles of the ventral pylorus and ampullae | |||
Preampullary ossicle | (XXII) | X | X |
Anterior inferior pyloric ossicle | (XXIII) | X | X |
Inferior ampullary ossicle | (XXIV) | X | X |
Ampullary roof ossicle, lower portion | (XXV) | X | X |
Ampullary roof-mediun portion ossicle | (XXVa) | – | X |
Ampullary roof ossicle, upper portion | (XXVI) | X | X |
Process of the ampullary roof-upper portion | (XXVIa) | – | X |
Posterior inferior pyloric ossicle | (XXVII) | X | X |
Lateral-inferior post-ampullary plate | (XXVIIa) | – | X |
Supporting ossicles of the supra-ampullary | |||
Anterior supra-ampullary ossicle | (XXVIII) | X | X |
Middle supra-ampullary ossicle | (XXIX) | X | X |
Posterior supra-ampullary ossicle | (XXX) | X | X |
Supporting ossicles of the lateral pylorus | |||
Anterior pleuropyloric ossicle | (XXXI) | X | X |
Pleuro-pyloric valve’s ossicle | (XXXIa) | – | X |
Middle pleuropyloric ossicle | (XXXII) | X | X |
Lateral pleuro-pyloric plate | (XXXIIa) | – | X |
Posterior pleuropyloric ossicle | (XXXIII) | X | X |
Cardiac-pyloric valve (v.c.p.) | (v.c.p.) | X | X |
We recognized 48 ossicles in the gastric skeletons of S. pictus and V. serrata whereas
The ‘dorsomedial cardiac plate’ and the ‘dorsolateral cardiac plate’, the ‘lateral inferior post-ampullary plate’ and the ‘lateral pleuro-pyloric plate’ ossicles were not mentioned by
The ‘lateral mesopyloric ossicle’ was first recognized by
The ‘inferior cardiac valve’ looks like a very small ossicle from an external perspective coming from the outer side of the stomach, but it is quite distinct and easily recognizable from a point of view coming from the inner surface of the stomach. However, if a disruption of the heart sac occurs during dissection of the stomach, this structure can be lost.
The ‘ossicles of the ampullary roof-mediun portion ossicle’, the ‘ampullary roof-upper portion ossicle’, and the ‘pleuro-pyloric valve’s ossicle’, may have been overlooked because they are fused to each other, appearing to be a single piece. The ‘ampullary roof-mediun portion ossicle’ may have been confused or even not noticed because they are very small and are situated between the ‘ampullary roof-upper portion ossicle’ and ‘ampullary roof-lower portion ossicle’.
A careful recognition of these stomach ossicles and enhanced understanding of the gastric mill complex can provide useful information to establish relevant characters which in turn will be helpful for tracing affinities and evaluating phylogenetic relationships not only in trichodactylid crabs but also among other taxa of Eubrachyura.
The authors are grateful to Michael Türkay (in memoriam) for his constructive comments to an early version of the manuscript; and to Felipe B. R. Gomes for his comments and preliminary English revision, and to Colleen L, Flannagan for the final English revision; and to Leandro M. Sousa for the figures edition. RCLG thanks the team of the Laboratory of Limnology of the Instituto Nacional de Pesquisas da Amazônia, particularly Josedec Faria Monteiro, for their help in laboratory procedures, and the Conselho Nacional de Desenvolvimento Científico e Tecnológico − CNPq for a Master’s Degree scholarship (process 134785/2011-8). CM also thanks CNPq for an ongoing research grant (process 304736/2015-5).