Description of the larval and adult hindgut tract of the common spider crab Maja brachydactyla Balss, 1922 (Brachyura, Decapoda, Malacostraca)

Abstract

Arthropods are the most diversified animals on Earth. The morphology of the digestive system has been widely studied in insects; however, crustaceans have received comparatively little attention. This study describes the hindgut tract of the common spider crab Maja brachydactyla Balss, 1922 in larvae and adults using dissection, light and electron microscopical analyses. The hindgut tract maintains a similar general shape in larvae and adults. Major differences among stages are found in the morphology of epithelial cells and microspines, the thickness of the cuticle and connective-like tissue, and the presence of rosette glands (only in adults). Here we provide the description of the sub-cellular structure of the folds, epithelium (conformed by tendon cells), musculature, and microspines of the hindgut of larvae and adults of M. brachydactyla.The morphological features of the hindgut of M. brachydactyla is compared with those of other arthropods (Insecta, Myriapoda and Arachnida). Our results suggest that the morphology of the hindgut is associated mainly with transport of faeces. In adults, the hindgut may also exert an osmoregulatory function, as described in other arthropods. At difference from holometabolous insets, the hindgut of M. brachydactyla (Decapoda) does not undergo a true metamorphic change during development, but major changes observed between larval and adult stages might respond to the different body size between life stages.

Morphological description of the midgut tract and midgut–hindgut junction in the larvae of the spider crab Maja brachydactyla Balss, 1922 (Malacostraca: Decapoda)

“…The midgut tract of the larval stages of the common spider crab M. brachydactyla is a short and simple tube positioned anteriorly, between the stomach and the hindgut tract, as observed in adults from the same species (Castejón et al, 2021). The midgut tract as a simple tube, internally lined by a simple columnar epithelium, is shared by the larvae of several decapod taxa, including other brachyuran species (Jantrarotai and Sawanyatiputi, 2005;Spitzner et al, 2018), anomurans (Williams, 1944;Abrunhosa and Kittaka, 1997), astacideans (Factor, 1981), achelatans (Mikami et al, 1994), and carideans (Tziouveli et al, 2011;Sonakowska-Czajka et al, 2021).…”

“…This species has been a useful model to describe several digestive organs during the larval stages, e.g. oesophagus (Castejón et al, 2018b), stomach (Castejón et al, 2015b(Castejón et al, , 2019b, midgut gland (Castejón et al, 2019a), midgut caeca (Castejón et al, 2022), and hindgut tract (Castejón et al, 2021).…”

Morphological and histological description of the midgut caeca in true crabs (Malacostraca: Decapoda: Brachyura): origin, development and potential role

“…In crustaceans, the digestive organs derived from the ectoderm germ layer are the esophagus, stomach, and the hindgut tract (including the anus), and all those organs have an epithelium covered by a cuticle lining [ 24 , 25 ]. Moreover, the TEM observations reveal an special cell type called “tendon cells”, characterized by dense packs of filaments crossing the entire cell height to connect the upper cuticle with the underlying muscle fibres [ 48 , 51 , 74 ]. In M. brachydactyla , both cuticle lining and packs of filaments were identified in the epithelia of the esophagus, stomach, and hindgut tract [ 28 , 48 , 50 , 51 ], but neither the cuticle lining or the packs of filaments were found in the epithelial cells of the midgut caeca as presented in this study.…”

“…The thickening of the different tissue layers during development could be related with the increment of the size of the organ, i.e. a larger organ will requires larger musculature for their motility and larger connective for their sustainability [ 51 ].…”

“…The common spider crab has been useful to study the ontogeny of the digestive organs in brachyurans, e.g. oesophagus [ 48 ], stomach [ 49 , 50 ], midgut gland [ 20 ], and hindgut tract [ 51 ].…”