Development of polarized female germline cysts in the polychaete, Ophryotrocha labronica

Abstract

Polarized oogenic cysts are clonal syncytia in which cellular compartments (cystocytes) differentiate as either oocytes or nurse cells-supportive germ cells that transport material to the oocyte through cytoplasmic bridges. Although polarized cysts have evolved independently in several animal phyla, most research on this phenomenon has focused on insects, particularly Drosophila melanogaster. To provide a foundation for comparative studies of cyst polarization, we have examined the coelomic development of polarized cysts in an annelid worm, Ophryotrocha labronica, using a variety of microscopic techniques. This species has elegantly simple cysts, each consisting of two interconnected cells (one oocyte and one nurse cell) free of somatic follicular tissue. These cysts arise from segmental ovaries, but are released to the coelom early in oogenesis, where they carry out most of their development. Although the oocyte remains transcriptionally active through oogenesis, nurse cells in this species are robust biosynthetic factories, with highly polyploid nuclei, enormous nucleoli, numerous mitochondria, and abundant rough endoplasmic reticulum. Ultimately, the nurse cell dumps its cytoplasm into oocyte, detaches, and undergoes programmed cell death. Although in insects, and possibly some polychaetes, the overall polarity of the cyst is linked to the specification of future embryonic axes in the oocyte, in Ophryotrocha this appears not to be the case. Our findings provide a detailed analysis of cyst development, addressing earlier misconceptions in the literature and adding new insights. This foundation shows the potential of Ophryotrocha labronica as a model system for further experimental analysis of nurse cell-oocyte differentiation.

The Ovary of Tubifex tubifex (Clitellata, Naididae, Tubificinae) Is Composed of One, Huge Germ-Line Cyst that Is Enriched with Cytoskeletal Components

“…Although female germ-line cysts in the fruit fly are the best known, they are only one specific example of female cyst organization. To show the diversity of female cyst organization in animals and for comparative purposes, we chose several others that have been studied in this aspect, species such as the polychaetous annelid Ophryotrocha labronica [ 11 , 12 ], the nematode Caenorhabditis elegans [ 22 , 23 , 43 – 47 ], the aphid Stomaphis quercus [ 48 ] and among vertebrates the frog Xenopus laevis [ 13 ]. A comparison of several aspects of the composition of female germ-line cysts, such as its spatial organization, mode of interconnections between cyst components, participation of the cytoskeleton in cyst stability and oogenesis between T .…”

“…The main differences are the number of interconnected cells and the spatial pattern of cell distribution – the cyst architecture. The simplest, two-celled cysts have been found in some insects such as Forficula auricularia [ 10 ] and in the polychaete annelid Ophryotrocha labronica ( Table 1 ) [ 11 , 12 ], 16-celled cysts are known from the ovaries of Drosophila melanogaster [ 8 ] and Xenopus laevis [ 13 ], whereas as many as 250 cells have been found in the female cyst in the Strepsiptera [ 14 , 15 ].…”

Preparation of the planarian Schmidtea mediterranea for high-resolution histology and transmission electron microscopy

“…Additionally, one of us (JLB) has successfully used a rapid, cold procedure for processing annelid worms 39,40 . We therefore began our trials with S. mediterranea by dehydrating specimens through a graded series of ethanol dilutions, over 10 minutes at −20°C.…”

Zespoły komórek płciowych w gametogenezie zwierząt - geneza, organizacja i funkcjonowanie

“…W takich zespołach oocyty kontynuują oogenezę, gromadzą materiały zapasowe, otaczane są osłonami jajowymi i wchodzą w kolejne etapy mejozy, a komórki odżywcze nie kontynuują mejozy, nie rosną tak znacząco jak oocyty, ale za to są często komórkami poliploidalnymi. Główną funkcją komórek odżywczych jest bowiem synteza, a następnie transport makrocząsteczek i organelli do oocytu (bądź oocytów), podczas gdy jądro komórkowe oocytu pozostaje często nieaktywne transkrypcyjnie [25,51,54,[91][92][93]. Poliploidyzacja jąder komórkowych w komórkach odżywczych jest charakterystyczna dla wielu owadów, przykładowo u D. melanogaster materiał genetyczny w komórkach odżywczych jest zwielokrotniany 12 razy, a u motyli 16 razy [25].…”