[in Japanese]

View full abstract

The anomuran crab, Lithodes longispina SAKAI (Fig. 1), is a species allied to Lithodes turritus and L. aequispina. This crab has been taken from the bottoms, 400-900m deep, off Boso Peninsula and Sagami Bay from March 1969 to March 1971 (Fig. 2, Table 1). Width of carapace ranges from 9.3 to 12.5 cm in the female and from 9.4 to 13.5 cm in the male (Fig. 3). The spawning period of this crab seems to continue from August to October (Fig. 4). The number of incubating eggs was correlated to the carapace width of the crab at the coefficy of correlation, 0.859. The number of eggs ranges from 3,900 to 11,200 per individual female from 9.8 cm to 11.9 cm in carapace width (Fig. 5).

View full abstract

This paper deals with the anandromous phenomena of megalopa of Varuna litterata (FABRICIUS) (Grapsidae, Varuninae), which was observed at the river mouth of the Hikiji-Gawa, situated on the north-east coast of Sagami Bay. The phenomena were observed in the daytime during the period from Oct. 9th to Nov. 7th of 1972. Tidal influence to the river reaches about 2 km from the river mouth. The adult crab is very rarely found on the northern areas of Sagami Bay, where may be the northern limit of distribution of this species. Each of the megalopa reaches the river mouth from off shore before full tide. The number of megalopa increases to the greatest at the time of full tide after the new moon or the full moon day. The megalopa continues to swim swiftly up the stream, keeping the distance between 10 to 30 cm from the shore. The swarm of megalopae thus reaches even 2 km beyond the limit of tidal influence. The length of carapace of the megalopa varies from 3.7 mm to 4.5 mm, the average size being 4.1 mm.

View full abstract

Eriocheir japonica mates during the period from the middle of October to the latter part of March and the peak of mating period is from the middle of January to that of February. The mating occus in the inter tidal zone of the neap tide. This crabs usually chose a region nearer the full tide line as a mating place. The mating time is during the tide rising. The crabs showing sexual behavior are more than 3.9cm in carapace width and the smaller crabs which are less than 3.9 cm in carapace width passes the winter in the river. This species changes its nature a few days after having reached the tidal zone and losts its nocternal disposition and comes to behave to the rhythum of an ebb and flow even in the day time. The crabs chose the partners by snipping one another. The opposite sex is recognizd by the degree of the intensity of snipping back. The male crabs living in the river have the second pleopods, but lost them when these crabs come down to the tidal zone for mating. In the laboratory the mating behavior of Eriocheir japonica easily can be observed, by keeping the male and female crabs obtained from the inter tidal zone in aquariums separately, in which 25-30 % sea water is preserved about a week befor pairing. The mating occurs in 25-30 % sea water, in pure sea water and also in fresh water.

View full abstract

The present author obtained three living specimens of megalopa from Sagami Bay by surface collection, in October of 1970. These larvae have been reared in the aquarium until moulted to the young crabs, which are identified to Hemigrapsus penicillatus. The adult crab is very common in japan, found usually on the rocky and muddy beaches as well as on the beach of pebbles on river-mouth. The larval features of these specimens have been observed and illustrated in this short report, comparing with the larvae of some other related crabs already reported.

View full abstract

[in Japanese]

View full abstract

The larvae of Chasmagnathus convexus reared in the laboratory were obtained from tow ovigerous crabs collected in Ise Bay in April 1972 and fed Artemia nauplii. This species consists of four zoeal stages and one megalopa stage in the complete development. Twenty eight days were taken until the young crab metamorphosed. 1. The zoea stage. The carapace is 0.6 mm in length. It possesses a rostral and a dorsal spine, and a pair of lateral spines on the carapace. The abdomen is composed of six distinct segments. There are a pair of lateral knobs on either side of the second segment, and the same little paired spines on the third and the fourth segment. The paired larval appendages; antennae, mandible, maxillae and maxillipeds, are observed. Numbers of black chromatophores are seen on the surface of the body, and a few pale yellowish green chromatophores only on the abdomen. The additional changes in number are found through the four zoeal stages in following parts: (1) Swimming hairs of the first and the second maxillipeds, (2) segments of the abdomen. (3) setae on the telson, (4) setae on the coxopodite, the basipodite and the scaphognathite of the maxillae, (5) aesthetes on the top of the first antenna, (6) chromatophores. In the second or the third zoeal stage, the rudiments of five parts of the megalopa stage; (1) endopodite of the second antenna, (2) pereiopod, (3) pleopod, (4) third maxilliped, (5) gill can be observed. They are develop in length in the fourth zoeal stage. 2. The megalopa stage The carapace is 1.7 mm in length, 1.4 mm in width, and is in good shape. The dorsal surface of the carapace is smooth and bald. The front bears four appendixes with round tops. The short rostral spine is projecting downwards. The dactylus of the fourth ambulatory leg bears three long feelers at the distal portion. The abdomen is divided into seven distinct segments. The seventh segment is rectangular and its posterior margin swells out, with one point emarginating on its central portion 3. The first young crab stage The general aspect of the body is similar to that of the adult crab. The carapace is 3.5 mm in length and 3.3 mm in width. Many black chromatophores arid pale yellowish green ones are observed on the surface of the carapace and the ambulatory legs.

View full abstract

The paleo-ecological method of studies for the fossil barnacles collected from the Narita formation of Japan proper is discussed in this paper, referring to the ecological information of barnacles in a living state. The fossil barnacles obtained from the pleistocene beds keep well-defined coloring on the shell plates. Typical hosts of the fossil barnacles are pelecypode species. In the case that the fossil barnacles had been removed from certain hosts, the original hosts are possible to presume by the ornamentati on printing the fossil barnacle bases. It is known that the shell plates of barnacles in a living state are almost attacked with boring algae (Parke & Moore, 1935). The same evidences are also founded in the barnacles obtained from various pleistocene beds at the Narita formation.

View full abstract