The Fine Structure of the Gastric Exocrine Cells of the Purple Sea Urchin, Strongylocentrotus purpuratus

Holland, Nicholas D.; Lauritis, J. A.

doi:10.2307/3224441

Cited by 13 publications

(6 citation statements)

References 14 publications

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“…They cytologically resemble the gastric exocrine (zymogen-like) cells described by Holland & Lauritis (1968) in the stomach of regular echinoids. All of their enterocytes secrete proteinaceous compounds.…”

Section: Discussionsupporting

confidence: 58%

“…Complex enterocytes are restricted to the anterior stomach (gastric caecum included). They cytologically resemble the gastric exocrine (zymogen-like) cells described by Holland & Lauritis (1968) in the stomach of regular echinoids. Though secretion of digestive enzymes by the stomach wall was not demonstrated, microscopical examinations and biochemical analyses of the gut content of E. cordatum showed that digestion occurs in the lumen of the distal stomach (DeRidder et a f .…”

Section: Discussionsupporting

confidence: 58%

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The Digestive Tract of the Spatangoid Echinoid Echinocardium cordatum (Echinodermata): Morphofunctional Study

DeRidder

Jangoux

1993

Acta Zoologica

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DcRidder. C. & Jungoux. M . 1993. The digestive tract of the spatangoid echinoid Echinocardium cordarum (Echinodermata): morphofunctional study.-Acra Zoologica (Stockholm) 74: 337-35 1.Echinocardium cordarum is a detritus-feeder. Its digestive tract has three functional parts: the mucus-secreting oesophagus where lubrication and sedimcnt compaction occur, the proteinsecreting stomach and gastric caecum where extracellular digestion occurs. and the absorptive non-secretory siphon. intestine, intestinal caecum and rectum. Each region harbours typical enterocytes. Acinar mucous glands occur in the posterior oesophagus prior to the incurrent aperture of the siphon; their secretions prevent sedimcnt grains from entering the siphon and may he stimulated hy epineural nerves running in the connective tissue layer. The siphon is a sucking organ. and its cytological features indicate that it is a site for absorption of dissolved organic matter. Enterocytes of the intestinal caecum show basal specializations. suggesting that it is a site of active exchange between coelom and gut. This caecum contains symbiotic sulphideoxidizing bacteria. Collagen fibres are well developed in organs subjected to severe deformations (c.g.. oesophagus and siphon); clastic-like fibres are conspicuous around haernal lacunae and at the attachment areas of gut-suspending mesenteries. Circular muscles are seen along the whole gut, whereas longitudinal muscles may be absent in areas such as the siphon. The bulky alimentary bolus that occurs in the ascending segments of the gut is transported by peristalsis; thc scattered sediment grains that occur in horizontal segments are presumably moved by the contractions of the gut-suspending mesenteries. C. DeRidder. Lahoraroire de Biologic marine (C. P. 16Ol15). Universire Lihre de Bruxelles, 50 av. F. D. Romevel.~~. A-10.50 Bruxelle.+, Belgium.

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Section: Discussionsupporting

confidence: 58%

Section: Discussionsupporting

confidence: 58%

The Digestive Tract of the Spatangoid Echinoid Echinocardium cordatum (Echinodermata): Morphofunctional Study

DeRidder

Jangoux

1993

Acta Zoologica

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“…For conventional TEM, six larvae were fixed every 30 min between 23 h and 25 h. Fixation was for 90 min at room temperature in 3% glutaraldehyde in 0.1 M phosphate buffer (pH 7.3) with 0.5 M sucrose [ 8 ]. Specimens were rinsed in three 5-min changes of 0.1 M phosphate buffer (pH 7.3) with 0.5 M sucrose and then post-fixed in 1% osmium tetroxide in 0.1 M phosphate buffer (pH 7.3) with 0.5 M sucrose at 4 °C for 1 h. After dehydration at room temperature in an ethanol series, larvae were transferred to propylene oxide, embedded in LX-112 resin, and oriented for cross sectioning.…”

Section: Methodsmentioning

confidence: 99%

Formation of the initial kidney and mouth opening in larval amphioxus studied with serial blockface scanning electron microscopy (SBSEM)

Holland

2018

EvoDevo

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BackgroundFor early larvae of amphioxus, Kaji et al. (Zool Lett 2:2, 2016) proposed that mesoderm cells are added to the rim of the forming mouth, giving it the quality of a coelomoduct without homology to the oral openings of other animals. They depended in part on non-serial transmission electron microscopic (TEM) sections and could not readily put fine structural details into a broader context. The present study of amphioxus larvae is based largely on serial blockface scanning electron microscopy (SBSEM), a technique revealing TEM-level details within an extensive anatomical volume that can be reconstructed in three dimensions.ResultsIn amphioxus larvae shortly before mouth formation, a population of compact mesoderm cells is present at the posterior extremity of the first left somite. As development continues, the more dorsal of these cells give rise to the initial kidney (Hatschek’s nephridium), while the more ventral cells become interposed between the ectoderm and endoderm in a localized region where the mouth will soon penetrate. SBSEM reveals that, after the mouth has opened, a majority of these mesoderm cells can still be detected, sandwiched between the ectoderm and endoderm; they are probably myoblasts destined to develop into the perioral muscles.ConclusionsSBSEM has provided the most accurate and detailed description to date of the tissues at the anterior end of amphioxus larvae. The present study supports the finding of Kaji et al. (2016) that the more dorsal of the cells in the posterior region of the first left somite give rise to the initial kidney. In contrast, the fate of the more ventral cells (called here the oral mesoderm) is less well understood. Although Kaji et al. (2016) implied that all of the oral mesoderm cells joined the rim of the forming mouth, SBSEM reveals that many of them are still present after mouth penetration. Even so, some of those cells go missing during mouth penetration and their fate is unknown. It cannot be ruled out that they were incorporated into the rim of the nascent mouth as proposed by Kaji et al. (2016). On the other hand, they might have degenerated or been shed from the larva during the morphogenetic interaction between the ectoderm and endoderm to form the mouth. The present SBSEM study, like Kaji et al. (2016), is based on static morphological data, and dynamic cell tracer experiments would be needed to decide among these possibilities.

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“…We regard the anterior stomach as beginning immediately distal to the junction of esophagus and stomach in the vicinity of the branching-off point of the primary siphon (some irregular taxa possess a secondary siphon [ 5 ]). A certain degree of histological specialization is known to exist in the anterior part of the stomach in "regular" taxa [ 24 , 26 , 27 ]. The primary siphon, although a derivative of the entire stomach and therefore also present in the anterior stomach, is not considered here, primarily because histological techniques not used in this study have been shown to be essential in determining presence or absence of the primary siphon [ 28 ].…”

Section: Resultsmentioning

confidence: 99%

Origin and evolutionary plasticity of the gastric caecum in sea urchins (Echinodermata: Echinoidea)

et al. 2010

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BackgroundThe digestive tract of many metazoan invertebrates is characterized by the presence of caeca or diverticula that serve secretory and/or absorptive functions. With the development of various feeding habits, distinctive digestive organs may be present in certain taxa. This also holds true for sea urchins (Echinodermata: Echinoidea), in which a highly specialized gastric caecum can be found in members of a derived subgroup, the Irregularia (cake urchins, sea biscuits, sand dollars, heart urchins, and related forms). As such a specialized caecum has not been reported from "regular" sea urchin taxa, the aim of this study was to elucidate its evolutionary origin.ResultsUsing morphological data derived from dissection, magnetic resonance imaging, and extensive literature studies, we compare the digestive tract of 168 echinoid species belonging to 51 extant families. Based on a number of characters such as topography, general morphology, mesenterial suspension, and integration into the haemal system, we homologize the gastric caecum with the more or less pronounced dilation of the anterior stomach that is observed in most "regular" sea urchin taxa. In the Irregularia, a gastric caecum can be found in all taxa except in the Laganina and Scutellina. It is also undeveloped in certain spatangoid species.ConclusionsAccording to our findings, the sea urchin gastric caecum most likely constitutes a synapomorphy of the Euechinoidea. Its occurrence in "regular" euechinoids is linked to the presence of an additional festoon of the anterior stomach in ambulacrum III. Both structures, the additional festoon and the gastric caecum, are absent in the sister taxon to the Euechinoidea, the Cidaroida. Since the degree of specialization of the gastric caecum is most pronounced in the predominantly sediment-burrowing irregular taxa, we hypothesize that its evolution is closely linked to the development of more elaborate infaunal lifestyles. We provide a comprehensive study of the origin and evolutionary plasticity of a conspicuous digestive tract structure, the gastric caecum, in a major taxon of the extant invertebrate macrozoobenthos.

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The Fine Structure of the Gastric Exocrine Cells of the Purple Sea Urchin, Strongylocentrotus purpuratus

Cited by 13 publications

References 14 publications

The Digestive Tract of the Spatangoid Echinoid Echinocardium cordatum (Echinodermata): Morphofunctional Study

The Digestive Tract of the Spatangoid Echinoid Echinocardium cordatum (Echinodermata): Morphofunctional Study

Formation of the initial kidney and mouth opening in larval amphioxus studied with serial blockface scanning electron microscopy (SBSEM)

Origin and evolutionary plasticity of the gastric caecum in sea urchins (Echinodermata: Echinoidea)

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