| 1. |
- Hessler, Robert R, et al.
(författare)
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Reproductive system of Hutchinsoniella macracantha (Cephalocarida)
- 1995
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Ingår i: Journal of Crustacean Biology. - : Oxford University Press (OUP). - 0278-0372. ; 15, s. 493-522
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Tidskriftsartikel (refereegranskat)abstract
- Hutchinsoniella macracantha is a simultaneous hermaphrodite. The small, paired ovaries are cephalic. From each, a long oviduct runs posteriorly to the eighteenth trunk segment, where it loops forward and runs toward the sixth trunk segment. The paired, sausage-shaped testes are dorsal to the midgut in the anterior end of the abdomen. A vas deferens runs down from the anterior end of each testis to join the oviduct. A common gonoduct exits on the posterior face of the sixth thoracopod. The ovaries contain no nurse or follicle cells, although projections from the epithelial cells and oocytes intertwine in the core of the ovary. The mechanism for translocating oocytes along the oviduct is problematical; a conveyor belt hypothesis is offered. Vitellogenesis does not begin until the posterior loops of the oviduct. Only 1 pair of oocytes matures at a time. Spermatogonia are scattered over the length of the testes. Each multiplies to form a small cluster of simultaneously developing spermatocytes; there are no cytoplasmic bridges or nurse cells. Within the testes, sperm formation is asynchronous and continuous. In addition to the acrosome, nucleus, and aflagellar central rod, each sperm cell forms voluminous vacuoles in the remaining cytoplasm; the associated volume increase probably causes mature sperm to enter and move through the testicular central lumen into the vas deferens. There is no obvious morphological obstacle to self fertilization. Each huge (approximately 0.4 mm long) ovum is attached to the ninth thoracopod with cement secreted by glands located midventrally in the ninth thoracic segment
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| 2. |
- Elofsson, Rolf, et al.
(författare)
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Sensory structures associated with the cuticle of Hutchinsoniella macracantha (Crustacea, Cephalocarida)
- 1994
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Ingår i: Journal of Crustacean Biology. - 0278-0372. ; 14, s. 454-462
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Tidskriftsartikel (refereegranskat)abstract
- The body cuticle of the cephalocarid crustacean Hutchinsoniella macracantha Sanders, 1955, carries two types of small setae which differ in their external shape and number of ciliated sensory cells. It also has two types of pores, one being a gland opening, the other containing the tip of a cilium. The setae and the pore type containing a ciliated sensory cell are considered chemosensory organs.
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| 3. |
- Elofsson, Rolf, et al.
(författare)
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Tegumental glands of Hutchinsoniella macracantha (Cephalocarida)
- 1998
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Ingår i: Journal of Crustacean Biology. - 0278-0372. ; 18, s. 42-56
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Tidskriftsartikel (refereegranskat)abstract
- Three types of tegumental glands of Hutchinsoniella macracantha body, limb, and caudal, are described for the first time. Previously described salivary and cement glands also belong to this category. All have the same fundamental construction. They consist of 1 or 2 secretory cells opening into a short cuticular channel ending in a pore. The channel is Formed by a sheath or canal cell and an intermediate cell. The intermediate cell has an actin-like filament bundle encircling the duct. If is a type of tricellular tegumental gland common in crustaceans. The secretory cells can be very large, the caudal gland in the cerci being 0.5-0.6 mm in length. They are, at least distally, completely filled with secretory granules. Some contain enormous Golgi-like bodies. The secretory cells vary in cytological details and granular secretion, both within a pair and depending on body position. It is concluded that a common gross morphology of the tegumental glands of Hutchinsoniella houses different functions.
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| 4. |
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| 5. |
- Elofsson, Rolf, et al.
(författare)
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The digestive system of the cephalocarid Hutchinsoniella macracantha (Crustacea)
- 1992
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Ingår i: Journal of Crustacean Biology. - 0278-0372. ; 12, s. 571-591
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Tidskriftsartikel (refereegranskat)abstract
- The digestive tract of the cephalocarid Hutchinsoniella macracantha begins with an atrium oris, posterior to the mouth. The esophagus loops up through the head and ends with a valve to the midgut. The epithelial cells and cuticle of both these structures are connected with long, winding, apically distended microvilli. The midgut is a straight tube with a pair of diverticula anteriorly. Midgut epithelial cells have microvilli, light vesicles, and a peculiar endoplasmic reticulum that is produced into a palisade of extensions toward the apical surface. Outside the basal lamina are muscle and peri-intestinal cells which send fingerlike projections into the basal portion of the midgut epithelial cells. The rectum joins the midgut near the end of the eighteenth segment and consists of unspecialized epithelial cells. In spite of the simple gross morphology the digestive tract has a complicated musculature. Circular muscles follow the whole tract including the diverticula. Radial muscles attach to the esophagus and rectum. Many longitudinal muscles are found inside the circular muscles in the anterior part of the midgut but only a few outside posteriorly. Gland cells occur in the labrum and diverticula. Absorption of nutrients seems to be limited to the midgut epithelial cells. Metabolites are transported via their endoplasmic reticulum to that of the peri-intestinal cells.
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| 6. |
- Elofsson, Rolf, et al.
(författare)
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The intestinal musculature of Derocheilocaris typica (Crustacea, Mystacocarida) - A different and unique pattern.
- 2010
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Ingår i: Arthropod Structure & Development. - : Elsevier BV. - 1467-8039. ; 39, s. 242-250
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Tidskriftsartikel (refereegranskat)abstract
- An ultrastructural study of the intestine of Derocheilocaris typica revealed an organization of the midgut musculature, which is unique in the Crustacea. This species unusual anal skeletomusculature has also not been seen before. The intestinal musculature of D. typica displays different patterns in the fore-, mid-, and hindgut. Around the foregut, eight pairs of dilator muscles complement a contiguous carpet of circular muscles around the foregut. Their coordinated action serves to suck in food and pass it to the midgut. A pair of large glands, each consisting of three cells, opens into the foregut above the mouth. The midgut musculature differs from any previously described. Circular muscles give rise to thin, longitudinal protrusions and short longitudinal muscles. The distribution of all of them is irregular. Thus the short longitudinal muscles, which have a length of approximately one segment, vary from none to five within a segment. The last abdominal segment is exceptional, by having 15-20 short longitudinal muscles. The hindgut has three longitudinal muscle groups each consisting of three muscles, one dorsally and one on each side. The posterior end of the midgut and the hindgut suggests that they act together to achieve defecation. The importance of the peri-intestinal cells as part of the nutritional process is emphasized.
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| 7. |
- Elofsson, Rolf, et al.
(författare)
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The tegumental sensory organ and nervous system of Derocheilocaris typica (Crustacea : Mystacocarida)
- 2005
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Ingår i: Arthropod Structure & Development. - : Elsevier BV. - 1467-8039. ; 34:2, s. 139-152
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Tidskriftsartikel (refereegranskat)abstract
- A tegumental sensory organ is described in Derocheilocaris typica. It consists of sensory cells, the somata of which are situated in the rim of the central nervous system. They give rise to long dendrites, each of which transforms to one cilium. Three cilia surface in small pegs on the body. In the labrum there are seven peg sensilla with five and three with two cilia each that emerge in small pores into the atrium oris. The peg sensilla are distributed in a repetitious pattern on the body and labrum. A few pegs are found on some appendages. The cilia project through a distal pore to the environment. The mystacocarid type of tegumentary organ differs from that of the cephalocarids. The tegumental sensory organs may represent a new unimodal chemosensory organ within crustaceans. The central nervous system is described in detail including an electron microscopic analysis and our results are compared to an earlier light microscopic study. Nervous structures, not described before, are the stomatogastric nervous system, the abdominal ganglia, segmental nerves, a dorsal ganglion in the telson, and a 'neurohemal' organ in the thoracic ganglia. The brain organization is reinterpreted and it is characterized by its low degree of specialization.
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| 8. |
- Elofsson, Rolf, et al.
(författare)
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The ultrastructure of the striated muscles of Derocheilocaris typica (Mystacocarida, Crustacea).
- 2013
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Ingår i: Arthropod Structure & Development. - : Elsevier BV. - 1467-8039. ; 42:5, s. 361-368
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Tidskriftsartikel (refereegranskat)abstract
- The striated muscles of Derocheilocaris typica consist of mononucleated cells, each containing one filament bundle. Large muscles consist of two or more cells adjacent to each other. The mitochondria line up along the filament bundle on one side. The nucleus is situated in the mitochondrial row and has a small cytoplasmic area around it filled with glycogen. The sarcomeres are between 3 and 6 μm long. The Z-line and H band are present. Six thin filaments surround one thick filament. All muscles belong to the phasic type. The tubular system emanates from the ends of the muscle cell and penetrates the whole cell. The tubules are formed as cisterns, which also open at the cell membrane at the level of the I bands. They have sarcoplasmic cisterns on both sides forming a continuous triad system. Partially transformed epidermal cells mediate muscle insertions on the cuticle. Tendons are formed with the transformed epidermal cells being supplemented by fibroblasts forming collagen fibers. Dorsal and ventral abdominal muscles are innervated from the dorso-lateral nerve arising from the nerve chain. Each muscle cell receives one axon, which forms one synapse on the mitochondrial-free side of the muscles. Axons form terminal spines, which make axo-axonal synapses.
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| 9. |
- Elofsson, Rolf, et al.
(författare)
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Two microvillar organs, new to Crustacea, in the Mystacocarida.
- 2008
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Ingår i: Arthropod Structure & Development. - : Elsevier BV. - 1467-8039. ; 37:6, s. 522-534
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Tidskriftsartikel (refereegranskat)abstract
- The mystacocarid crustacean Derocheilocaris typica has two microvillar organs, one new, the other previously unappreciated in crustacean literature. The first is situated on the head-shield and consists of three pairs of cells: one with microvilli and a ballooned nucleus; one smaller and without special features; the third large and investing the other two and extending down to the foregut. We call this new organ the "cephalic microvillar organ" and discuss the value of the concept "dorsal organ", to which it might have been included. The second organ consists of about 21 cells that cover the proximal part of the dorsal surface of the labrum. The cells are alike, being characterized by an apical field of microvilli and a large residual body. This organ is here called the "labral microvillar organ". Both organs are neither sensory nor secretory and do not qualify for membership in any of the other recognized organ systems. We are unable to deduce their functions.
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| 10. |
- Hessler, Robert R, et al.
(författare)
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An excretory organ in the Mystacocarida (Crustacea)
- 2007
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Ingår i: Arthropod Structure & Development. - : Elsevier BV. - 1467-8039. ; 36, s. 171-181
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Tidskriftsartikel (refereegranskat)abstract
- An excretory antennal gland, composed of only eight cells, is found entirely in the limb in the mystacocarid Derocheilocaris typica. The end sac is composed of podocytes, valve cells and cap cells. The podocytes contain enormous residual vesicles. There are few pedicel complexes, and they arise directly from the cell surface without intermediate foot processes. The excretory duct is entirely lined with microvilli, which are separated from the lumen by a modified layer of thin cuticle. 2007 Elsevier Ltd. All rights reserved.
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