Foregut morphology and ontogeny of the spider crab Maja brachydactyla (Brachyura, Majoidea, Majidae)

Abstract

We describe the morphology of the foregut of the spider crab Maja brachydactyla Balss, 1922, from first larval stage to adult, with detailed stage-specific documentation using light and scanning electron microscopy. A total of 40 ossicles have been identified in the foregut of adults of M. brachydactyla using Alizarin-Red staining. The morphological pattern of the ossicles and gastric mill is very similar to other Majoidea species with only a few variations. The foregut of the zoeae stages appeared as a small and simple cavity, with a cardio-pyloric valve that separates the stomach into cardiac and pyloric regions. The pyloric filter is present from the first zoea, in contrast to the brachyuran species which have an extended larval development. Calcified structures have been identified in the cardio-pyloric valve and pyloric region of the zoeal stages. The most significant changes in foregut morphology take place after the metamorphosis from ZII to megalopa, including the occurrence of the gastric mill. In the megalopa stage, the foregut ossicles are recognizable by their organization and general morphology, but are different from the adult phase in shape and number. Moreover, the gastric teeth show important differences: the cusps of the lateral teeth are sharp (no molariform); the dorsal tooth have a small, dentate cusp (not a well-developed quadrangular cusp); and the accessory teeth are composed of one sharp peak (instead of four sharp peaks). The gastric mill ontogeny from megalopa to adult reveals intermediate morphologies during the earlier juvenile stages. The relationship between gastric mill structures with food preferences and their contribution to the brachyuran phylogeny are briefly discussed.

An atlas of larval organogenesis in the European shore crab Carcinus maenas L. (Decapoda, Brachyura, Portunidae)

“…A complex filter press is already present in the Zoea I of C. maenas (data not shown). Similar observations were made for the first zoeal stages of the decapod species Maja brachydactyla [ 89 ], Uca vocator, and Panopeus occidentalis [ 90 ], which also possess a well-developed pyloric filter. On the contrary, early life history stages of other brachyuran species were reported to possess a less well-developed pyloric filter system in early zoeal stages ( Ucides cordatus , [ 91 ]; Dyspanopeus sayi , [ 92 ]), and a pyloric filter appears to be absent in the facultative lecitotrophic larval stages of Sesarma curacaoense, which use reserves stored in a yolk sac for nutrition during their pelagic phase [ 93 ].…”

Structure of the stomach cuticle in adult and larvae of the spider crab Maja brachydactyla (Brachyura, Decapoda)

“…That “dorsal tooth” might correspond to the epithelium variation we observed in M. brachydactyla because gastric mill teeth are absent in the zoeal stages in all other brachyuran species that have been studied. The cardio‐pyloric valve also transform during the molt to megalopa: the general morphology of the valve is modified, the characteristic long thickened setae of the zoeae disappear as reported by (Castejón, Rotllant, et al, ), and in this study, we also observed that the cuticle of the cardio‐pyloric valve increases in thickness. This transformation suggest that the cardio‐pyloric valve might modify its role from the zoeal stages, or that cardio‐pyloric valve requires a different morphology due to the transformation of the cardiac stomach.…”

“…The most significant ontogenic change in the stomach of M. brachydactyla occurs during the molt to megalopa, a transitional stage between the pelagic zoea and the benthic juvenile (Anger, ). We observed that the transformation of the stomach includes the appearance of the ossicle system, cardiac sacs, and gastric mill teeth, which also occurs in other brachyurans (Abrunhosa & Melo, ; Abrunhosa, Melo, & Abrunhosa, ; Abrunhosa, Simith, Monteiro, de Souza Junior, & Oliva, ; Castejón, Ribes, Durfort, Rotllant, & Guerao, 2015; Castejón, Rotllant, et al, ; Jantrarotai & Sawanyatiputi, ; Lumasag, Quinitio, Aguilar, Baldevarona, & Saclauso, ; Melo, Abrunhosa, & Sampaio, ). The cuticle of the newly formed ossicles and gastric mill teeth differs from the cuticle of the previous zoeal stages and the cuticle of other stomach structures as the cardiac sacs.…”

“…This specialization also involves the degree of mineralization. The cardiac sacs of M. brachydactyla have elastic noncalcified cuticle while gastric mill teeth are hard and calcified (Castejón, Rotllant, et al, ) as reported in other decapods (see review by Ceccaldi, 1989). Heeren and Mitchell () reported that the stomach cuticle in the adult of the crab Pseudocarcinus gigas varies in composition and structure; specifically, cardiac sacs (noncalcicified), mid‐region of the cardiac stomach (rich in setae), gastric mill (thick and irregular) and pyloric stomach (thick and noncalcified).…”

Micro-computed tomography and histology to explore internal morphology in decapod larvae

“…Micro-CT reveals that gastric mill teeth are sharp in the megalopa, as reported by scanning electron microscopy in a previous study on M . brachydactyla 34 . Micro-CT reveals that the midgut gland has a morphology based on blind-end tubules, while histology shows several epithelial cell types, as occur in adult decapods 27 , 29 – 31 .…”