Reish, Donald J. (1954). The life history and ecology of the polychaetous annelid Nereis grubei (Kinberg). Occasional Papers of the Allan Hancock Foundation. 14: 1-75.

60614

Reish, Donald J.

1954

14: 1-75

Publication

http://digitallibrary.usc.edu/cdm/ref/collection/p15799coll82/id/18604

World Polychaeta Database (WPolyDb)

Summary: "1. Culture techniques for handling atokes, epitokes, and developing larvae were described. Fertilized eggs of N. grubei were reared to sexual maturity by the use of a compressed air circulating aquarium. 2. Both sexes lost the majority of the green body wall pigment with the approach of epitoky. Increased blood supply in the natatory region gave a red appearance to the epitokal specimens. An increase in size occurred in both the lens and retina of the eye after the onset of epitoky. 3. The number of pre-natatory segments in N. grubei was constant, 14 in the male and 16 in the female. The modifications of the parapodia were typical for the epitokal nereids. All biramous pre-natatory parapodia contained epitokal notopodial homogomph falcigerous setae which were distinctive to N. grubei. No changes of systematic importance were observed in the paragnaths during metomorphosis. 4. The pharynx consisted of simple cuboidal epithelium surrounded by a single layer of long pharyngeal muscle cells. The peritoneum was simple squamous in nature and was similar throughout the digestive tract. No changes were observed in the pharynx during epitokal formation. 5. The esophagus was composed of simple cuboidal epithelium which may or may not have circular and longitudinal muscles surrounding it. The digestive glands were lined with loosely packed, simple columnar epithelium. Deposition or secretion of yellow-brown granules occurred within the cells of the esophagus and digestive glands. The origin, nature, and function of these granules are unknown. 6. The epithelium of the intestine consisted of simple columnar cells except near the posterior end. Here there was a gradual transition into simple cuboidal cells. Circular muscles surrounded the epithelium. Comparison of the diameter of the sub-epitokes with that of the epitoke indicated a three-fold reduction in size. The simple columnar cells of the intestinal epithelium were frequently dome-like in shape at their free margin. These cells appeared colorless and empty. No changes were observed in the simple cuboidal cells of the posterior intestinal region. 7. Formation of eggs and sperm took place in the ligules of the parapodia. The ova developed from segment eight to near the posterior end, and the sperm formed from the first setigerous segment to near the posterior end. The genital elements passed from the ligule into the coelom where maturation was completed. 8. On the basis of laboratory and field observations it is apparent that N. grubei reproduces throughout the year. The male spawned out the papillae of the anal rosette, and the female emitted the eggs through paired ruptures in the lateral body wall near the posterior end. Laboratory observations indicated that both sexes spawn only once and die within a day. 9. The unfertilized ova ranged in size from 162 to 380/x in diameter. The sperm was 7.8/A in length. 10. Cleavage and development proceeded in the manner typical for the nereids. Three-segmented larvae were formed in 31 hours. Anal cirri and tentacles developed by 48 hours. The first pair of peristomial tentacles appeared at 80 hours. The fourth larval segment formed at the seventh day. Feeding began at nine days. Additional segments were formed at the rate of about one a day until the adult number was reached. One male was sexually matured at 96 days and one female at 98 days. The average length of time for N. grubei to mature in the laboratory was 28 to 29 weeks. 11. The outer portion of the proboscis is composed of simple columnar epithelia. These cells are covered by a continuous layer of secretum to which the paragnaths attach. Apparently, the paragnaths at the basal portion are formed by the fusion either of small flecks or layers of horny material. As this material is worn off the apex, the new material is gradually moved outward. 12. The development of the parapodia from formation to epitokal modification of setigerous segments 2, 5, 10, 20, 45, and 70 was described. The convex nature of the dorsal lobe of the posterior parapodia was established soon after the formation of these parapodia and was retained throughout life in the female, but became straight in male epitokes. 13. The types, number, distribution, and succession of the setae of N. grubei were observed in segments 2, 5, 10, 20, 45, and 70. Unique homogomph falcigerous setae appeared in the pre-natatory parapodia of the epitokes during the early stages of metamorphosis. The atokal notopodial homogomph falcigerous setae were formed soon after the development of its parapodium. The setae increased in size by replacement and persisted until metamorphosis. The shape and structure of this seta was constant throughout life. 14. Growth in N. grubei, as measured by weight, proceeded at a regular rate until the approach of sexual maturity. The worms ceased eating about two weeks before attainment of maturity. The loss of weight during metamorphosis averaged 37% for ten specimens. 15. The body length, the number of segments, and the number of paragnaths on areas I and VI were analyzed statistically for the atoke and epitoke stages. Comparisons were made of laboratory-reared specimens with worms collected from nature. The body length and number of segments were smaller and fewer for the laboratory specimens as compared to the worms taken at Point Fermin. A significant difference in the number of paragnaths on areas I and VI was observed in the cultured specimens as compared to those from nature. There was a marked similarity between the offspring of Ft and F2B. No explanations were advanced to account for either differences or similarities in these observations. 16. Nereis grubei occurs in all horizons of the intertidal region at Point Fermin, San Pedro, California. 17. The associations in which N. grubei occur indicate that they require protection from the surf and material on which to construct their tube. Nereis grubei occur commonly in the Cladophora trichotoma and Gigartina canaliculata associations. Animal associations are not an important element in the ecology of N. grubei in southern California. 18. Nereis grubei in nature can eat a variety of food depending upon what association it inhabits. The principal food at Point Fermin is Cladophora trichotoma and Gigartina canaliculata. Individuals collected from Limnoria tripunctata-iniected pilings had eaten detritus and L. tripunctata. 19. In feeding, the jaws grasp the food with the palpi assisting. The food is pulled to the tube entrance and engulfed. The jaws, by a pumping action, particularly with the long filaments, pass the food into the intestine

California quadrant

Annelida

RIS (EndNote, Reference Manager, ProCite, RefWorks)
BibTex (BibDesk, LaTeX)

[Back to search]