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A Contribution to the Life History of Bucephalus longicornutus (Manter, 1954)

Description

Description

(Based on 50 living and 10 fixed and stained specimens. Body, tail stem and furcae dimensions are given in Table I, p. 15).

A cercaria is small, opaque, and consists of a body, tail stem and furcae (Text-fig. 3, A). Body tapered anteriorly, pear-shaped and depressed when contracted (Text-fig. 3, A; 4, D), elongate and cylindrical when expanded (Text-fig. 4, A; 4, F). Greatest width contracted is at about mid-body level. Small, diagonally arranged, blunt spines are distributed over anterior half of body, and these merge with irregularly shaped cuticular plates which form a mosaic over posterior half of body (Text-fig. 3, C). Numerous, irregularly shaped cystogenous granules, 4μ to 15μ by 2μ to 9μ,? are distributed throughout parenchyma and impart opacity to body. These granules are concentrated in posterior half of body, becoming sparser anterior to pharynx. Central region of body is almost completely devoid of granules and accordingly less opaque. Flask-shaped cystogenous organ, 32μ to 35μ long by 22μ to 25μ at its widest point, is situated near anterior extremity (Text-fig. 3, A). Its external surface is partly covered by granules of similar appearance and texture to cystogenous granules in parenchyma. Neck of cystogenous organ encloses posterior half of a narrow duct at posterior end of which, and within cystogenous organ, is a mass of gland cells. This duct of cystogenous organ opens anteriorly by a small pore which is surrounded by four lips. Neutral red stains cystogenous granules in body stain dull pink to orange indicating neutrality, and cystogenous organ bright red indicating acidity.

An H-shaped ganglionic mass lies just posterior to cystogenous organ (Text-fig. 4, A, C). Anterior and longitudinal nerve trunks arising from this were not seen.

Mouth is a small transverse slit, 5μ to 6μ wide, surrounded by cuticular plates, situated 30μ to 40μ from posterior extremity depending on state of contraction of body. Little or no prepharynx. Pharynx more or less spherical, 12μ to 16μ in diameter, followed by a short oesophagus; intestine sacculate, up to 75μ long by 20μ to 25μ wide, and lined by a cuboidal epithelium. Peristaltic contractions of intestine occur, but no food inclusions seen in intestine.

Usual number of body wall layers present (Text-fig. 3, F). A band of muscles (2μ?thick) lies immediately within cuticle but separate longitudinal and circular fibres could not be seen. Parenchyma contains a few oblique muscle fibres. Mucus cells surround oesophagus.

Rudimentary genital pore is situated 10μ?from posterior extremity. Genital anlagen consists of two lobed masses of densely staining nuclei posterior to pharynx, each about 30μ long by 10μ wide (Text-fig. 4, A and C).

Excretory pore is at posterior extremity of body. Excretory vesicle is saccular and extends to left of pharynx. Excretory tubules open into excretory vesicle approximately midway along its length. Flame cell formula is 2[(3 + 3 + 3) + (3 + 3 + 3)] = 36 (Text-fig. 4, B). Elimination of liquid from the excretory vesicle takes place as indicated in Text-fig. 5, A-C.

Tail stem is unspined. A parenchymatous layer within the cuticle is continuous with an axial strand of parenchyma and muscle fibres. A single row of cystogenous granules lies within cuticle along posterior surface of tail stem, apart from axial strand region where granules may be four or five rows deep. A few scattered granules are distributed through axial strand. Lumen of tail stem contains a few oily droplets.

page 15

Furcae are sub-circular in section, unspined, tapered distally and flattened against tail stem proximally. Highly contractile, varying between 1.3 and 18 times as long as body. Two rows of cystogenous granules, 6μ wide by 2μ long in ventral view, by 6μ tall in lateral view, lie along ventral surface of furcae (Text-fig. 3, D and E).

Text-fig. 5.—Bucephalus longicornutus. Elimination of liquid from the excretory vesicle. For abbreviations see p. 9.

Text-fig. 5.—Bucephalus longicornutus. Elimination of liquid from the excretory vesicle. For abbreviations see p. 9.

Table I.—Body, tail stem and furcae dimensions of cercariae (measurements in mm).
Average Range of 50 specimens
Body length contracted 0.150 0.120–0.168
Body length expanded 0.250 0.210–0.290
Tail stem width 0.100 0.085–0.110
Tail stem length 0.044 0.036–0.049
Greatest body width contracted 0.096 0.090–0.108
Greatest body width expanded 0.060 0.056–0.068
Furca contracted 0.275 0.200–0.286
Furca expanded 3.900 3.810–4.100
Width of axial strand 0.026 0.020–0.032

Table II.—Previous Reports of Bucephalid Cercariae from Bivalve Molluscs.
Date Author Host Name given to Species Locality
1827 von Baer Unio pictorum Bucephalus polymorphus Europe (F)
1827 von Baer Anodonta anatina B. polymorphus Europe (F)
1827 von Baer A. cellensis B. polymorphus Europe (F)page 16
1848 Siebold A. cellensis B. polymorphus Europe (F)
1854 Lacaze-Duthiers Ostrea edulis B. haimeanus Mediterranean (S)
1854 Lacaze-Duthiers Cardium rusticum B. haimeanus Mediterranean (S)
1857 Pagenstecher A. anatina B. polymorphus Europe (F)
1863 Claparede Found free swimming cercaria B. haimeanus Normandy (S)
1874 McCrady Crassostrea virginica B. cuculus Carolina (S)
1878 Ulicny A. cellensis B. intermedius 1 Europe (F)
1881 Ercolani U. pictorum Cercaria bucephalus 1 Europe (F)
1881 Levinsen Modiolaria discors B. crux Egedesminde (S)
1882 Ercolani A. anatina C. bucephalus 1 Europe (F)
1883 Ziegler B. polymorphus Europe (F)
1888 Huet Cardium edule B. haimeanus Normandy (S)
1890 Nelson Crassostrea virginica "Gregarinoid parasites" New Jersey, U.S.A. (S)
1893 Huet Mactra solida B. haimeanus Normandy (S)
1893 Nelson Crassostrea virginica B. cuculus New Jersey, U.S.A. (S) Europe (S)
1894 Vaullegeard Tapes pullastra B. haimeanus
1894 Vaullegeard Tapes decussatus B. haimeanus Europe (S)
1899 Kelly Unionidae B. polymorphus Mississippi R. (F)
1903 Haswell Mytilus latus B. sp. New Zealand (S)
1904, 05 Johnstone Cardium edule B. haimeanus England (S)
1905, 06 09 Tennent Crassostrea virginica B. haimeanus 2 East Coast, U.S.A. (S)
1906 Pelseneer Syndosmya alba B. haimeanus Europe (S)
1906 Pelseneer Cardium edule B. haimeanus Europe (S)
1907 Pelseneer Mactra solida B. haimeanus Europe (S)
1907 Pelseneer Mactra subtruncata B. haimeanus Europe (S)
1907 Pelseneer Donax trunculus B. haimeanus Europe (S)
1909 Sinitzin Dreissensia polymorpha B. polymorphus Warsaw (F)
1909 Sinitzin A. mutabilis B. polymorphus Warsaw (F)
1909 Sinitzin Tapes rugatus B. haimeanus Black Sea (S)
1911 Sinitzin Tapes rugatus C. hydriformis 3 Black Sea (S)
1911 Lebour Cardium edule B. haimeanus England (S)page 17
1911 Lebour S. alba B. syndosmyae England (S)
1924 Wunder B. polymorphus Europe (F)
1925 Miller Pinna carnea Cercaria N Tortugas (S)
1928 Faust Modiola capensis Bucephalopsis modiolae Sth. Africa (S)
1929 Woodhead Elliptio dilatatus Bucephalus papillosum 4,8 Michigan (F)
1930 Woodhead Eurynia iris B. elegans 8 Michigan (F)
1933 Roughley O. commercialis B. haimeanus N.S.W. (S)
1933 Roughley O. angasi B. haimeanus N.S.W. (S)
1934 Ozaki and Ishibashi Pinctada martensi B. margaritae Japan (S)
1934 Palombi Tapes decussatus Bucephalopsis haimeana 6 Naples (S)
1934 Palombi Tapes aureus B. haimeana 6 Naples (S)
1934 Wesenberg-Lund Bucephalus polymorphus Europe (F)
1935 Cole Mytilus edulis B. mytili England (S)
1936 Woodhead A. grandis C. argi Michigan (F)
1936 Woodhead Lampsilis siliquoidea C. basi 5 Michigan (F)
1936 Woodhead Eurynia iris C. scioti Michigan (F)
1939 Rees Cardium edule B. haimeanus England (S)
1949 Andreu Tapes aureus Bucephalopsis haimeana 6 Spain (S)
1952 Chubrik Mytilus latus Prosorhynchus squamatus 7 Arctic? (S)
1952 Kniskern L. siliquoidea Rhipidocotyle septpapillata 8 Michigan (F)
1954? Ozaki ? Bucephalus itabo? Japan (S)
1954 Hopkins Crassostrea virginica B. cuculus U.S.A. (S)
1956 Cable Donax denticulatus C. caribbea XLII Puerto Rico (S)
1956 Cable Tellina lintea C. caribbea XLII Puerto Rico (S)
1958 Hopkins Donax variabilis B. loeschi Mustang Is. (S)
1960 Ozaki Caecella chinensis P. caecellae Japan (S)
1960 Ozaki Gryphaea gigas P. magakii Japan (S)
1961 Angel Velesunionis ambiguus C. velesunionis Australia (F)
1961 Holliman Mulinia lateralis C. apalachiensis Florida (S)
1961 Laird Ostrea belcheri unidentified sp. Pakistan (S)

Key to Table II
F Fresh water species.
S Marine species.
1 Considered as synonyms of B. polymorphus.page 18
2 Synonymous with B. cuculus
3 B. haimeanus of Sinitzin, 1909.
4 Now R. papillosum
5 Synonymous with R. septpapillata
6 Bucephalopsis haimeanus
7 Adult status not determined experimentally but based on morphological resemblances.
8 Adult status determined experimentally.