Effects of Neuroendocrine Centers on Germ and Germline Cells in Dendrobaena atheca Cernosvitov (Annelida: Lumbricidae)

Abstract

The aim of the present comprehensive experimental study was to reveal the effects of the removal and the regeneration of the main neuroendocrine centers in the oogonia, oocytes and trophocytes in Dendrobaena atheca. Various types of serial sections of ovaries and cephalic regions were obtained. Four histological staining techniques were employed. In controlled preparations, the neurosecretory activities of A-cells and C-cells showed correlation with cellular activities of oogonia, oocytes and trophocytes. In experimental preparations, removal of A-cells caused abnormalities in oocytes and trophocytes. The regeneration of A-cells restored vitellogenesis and repaired abnormalities. In both preparations, C-cells remained aldehyde-fuchsin (AF)-positive. B-cells and U-cells remained AF-negative. The oogonia showed continuous mitotic divisions. Regenerated A-cells appeared in week 3, increased in number, but could not stop the abnormalities, as hormones were not transported due to the lack or scarcity of blood capillaries. Therefore, abnormalities increased extremely. Then, they stopped, decreased, and were repaired due to hormonal transport via fully reconstructed blood capillary plexuses. The main conclusions are: (1) oocytes and trophocytes are controlled by A-cells, since they exhibited prominent changes during the removal and regeneration of A-cells; (2) oogonia are controlled by C-cells, as they showed correlation of activities with C-cells and were not affected by the removal and regeneration of A-cells; (3) B-cells and U-cells remained inactive; hence, they have no role in oogonia divisions and vitellogenesis; and (4) delayed hormonal effects of regenerated A-cells were due to the lack or scarcity of blood capillaries. Therefore, fully reconstructed blood capillary beds in the A-cells area are indispensable for hormonal diffusion, transport and effectivity.

Keywords

main neuroendocrine centers - C-cells - fully reconstructed blood capillary plexuses - germ cells - germline cells

• References

• 1 Durchon M. Recherches experimentale sur deux aspects de la reproduction chez les annelids. Polychetes: l'epitoque et la stolonisation. Annales des sciences naturelles Zoologie et Biologie Animale, XI 1952; 14: 117-206
• 2 Durchon M. L'endocrinologie des Vers et des Mollusques. Masson, Paris: 1967
• 3 Clark RB. Endocrinology and the reproductive biology of the Polychaetes. Oceanogr Mar Biol Annu Rev 1965; 3: 211-255
• 4 Hagadorn IR. Neurosecretion in the Hirudinea and its possible role in reproduction. Am Zool 1966; 6 (02) 251-261
• 5 Olive PJW, Bentley M. Hormonal control of oogenesis, ovulation and spawning in the annual reproductive cycle of the polychaete, Nephtys hombergii (Savigny, 1818) (Nephtyidae). International journal of Invertebrate Reproduction 1980; 2 (04) 205-221
• 6 Kulkarni GK, Anand CSK. Functional significance of supraesophageal and subesophageal ganglia in oogenesis of the freshwater leech, Hirudo birmanica (Blanchard, 1894). Comp Biochem Physiol Part A Physiol 1992; 103 (03) 545-550
• 7 Parthasarathi K, Ranganathan LS. Influence of pressmud on the development of the ovary, oogenesis and neurosecretory cells of the earthworm, Eudilus eugeniae (Kinberg). Afr Zool 2000; 35 (02) 281-286
• 8 Siekierska E. The structure of the ovary and oogenesis in gonadotropin-deprived earthworm, Dendrobaena veneta (Rosa). Zool Pol 2002; 47 (3–4): 37-48
• 9 Khalid VA. Seasonal changes in the histology of the ovary and its relation with neurosecretory activity in the earthworm, Dendrobaena atheca Cernosvitov. M. Sc. Thesis, Department of Biology, Faculty of Science, University of Zakho, Zakho, Kurdistan Regional Government, Iraq. 2014
• 10 Kiret ZT. The effects of the removal of the principal neurosecretory centers on the ovaries of the earthworm, Dendrobaena atheca Cernosvitov, (Annelida: Oligochaeta: Lumbricidae). M. Sc. Thesis, Department of Biology, Faculty of Science, University of Zakho, Zakho, Kurdistan Regional Government, Iraq. 2016
• 11 Gorgees NS. Study on the neurosecretory system of Dendrobaena atheca Cernosvitov and its role in regeneration. M. Sc. Thesis, Department of Biology, College of Science, University of Mosul, Mosul, Iraq. 1974
• 12 Baid IC, Gorgees NS. Presence of elementary neurohaemal organs in the lumbricid worm, Dendrobaena atheca Cernosvitov. J Anim Morphol Physiol 1975; 22 (02) 129-133
• 13 Baid IC, Gorgees NS. On the neurosecretory system of Dendrobaena atheca Cernosvitov. J Morphol 1977; 153 (02) 163-185
• 14 Gorgees NS, Baid IC. Presence of neurosecretory cells in the vegetative nervous system of Dendrobaena atheca Cernosvitov. Experientia 1975; 31 (04) 430-431
• 15 Golding DW. The infracerebral gland in Nephtys--a possible neuroendocrine complex. Gen Comp Endocrinol 1970; 14 (01) 114-126
• 16 Swiatek P. Ovary cord structure and oogenesis in Hirudo medicinalis and Haemopis sanguisuga (Clitellata, Annelida): remarks on different ovaries organization in Hirudinea. Zoomorphology 2008; 127: 213-226
• 17 Swiatek P, Krok F, Bielecki A. Germline cysts are formed during oogenesis in Eropobdella octaculata (Annelida, Clitellata, Erpobdellidae). Invertebr Reprod Dev 2010; 54: 53-63
• 18 Chaudhri PS, Banik D. Cytology and histology of the cerebral neurosecretory systems in some tropical earthworm species. J Cytol Histol 2015; 6: 1-7
• 19 Gorgees NS, Khalid VA. Histomorphology of the ovaries of the earthworm, Dendrobaena atheca Cernosvitov (Annelida, Clitellata: Oligochaeta). Journal of Morphological Sciences 2017; 34 (03) 178-185
• 20 Luna LG. Mnanual of histologic staining methods of the armed forces institute of pathology. 3rd ed. McGraw-Hill; New York: 1968
• 21 Galigher AE, Kozloff EN. Essentials of practical microtechnique. Lea and Febiger; Philadelphia: 1971
• 22 Culling CFA, Alliston RT, Barr WT. Cellular pathology techniques. 4th ed. London: Butterworth and Co. Ltd.; 1985
• 23 Al-Hajj HA. . Light microscope techniques: theory and practice, Jordan book center, Aman, Jordan. 1998