Amphiporus bimaculatus

Amphiporus bimaculatus

Biological Flags

  • Ecosystem: Marine
Languages: English

Overview

General Description

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

Body not very small.  Proboscis sheath usually reaches nearly or quite to posterior end of body. Proboscis large; central stylet well developed.  Ocelli usually numerous.  Basis of central stylet but half as long as the slender stylet itself. Usually 4 pouches of accessory stylets.  Dorsal surface deep brownish orange with 2 conspicuous oval or dark brown spots on head; ventral surface pale orange or flesh-color.

Description

External Appearance

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)
The color of this species is very striking.  The whole dorsal surface back of the head is deep brownish orange, somewhat paler behind.  The head is without color, or of a very much paler color than the rest of the dorsal surface, and in the center of this pale area two oval, black or very dark brown spots lie side by side.  These are very characteristic, and are conspicuous even in alcoholic specimens.  The black spots sometimes occupy a considerable portion of the pale area, and are sometimes sharply angular in front.  In the median line of the body the color is slightly paler than elsewhere and in the center of the paler stripe is a dark, but inconspicuous, longitudinal line.  The pale stripe and dark line both fade out at a point about 1/5 the distance towards the posterior end of the body.  The brain lobes appear as pinkish bodies just posterior to the black cephalic spots.  The whole ventral surface is of a homogeneous, pale orange or flesh color, with the exception of pinkish spots marking the position of the brain, and a slightly paler stripe below the anterior portion of the proboscis sheath.

Proboscis and Rhynchocoel System

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)
Proboscis:
The proboscis is remarkably large, and its constituent layers are very sharply defined.  the proboscis sheath has a correspondingly massive development, and reaches to the very extremity of the body.  The stylet apparatus of the proboscis is very characteristic of the species, because of the extreme minuteness of the basis of the central stylet.  The central stylet itself is very long and slender, while the length of its basis is but half as great.  The basis is constricted in the middle, and is 2/3 as wide as long. There are usually four pouches of accessory stylets.  these pouches are not evenly distributed on the circumference, for two lie close together on one side of the proboscis, the other two on the opposite side.  there are usually five to seven slender stylets in each of the four pooches.  Most of the stylets are much smaller than the central stylet.  measurements of the stylets of one individual about 100 mm long are: central stylet 0.12 mm long, 0.015 mm wide near base; basis of central stylet 0.06 mm long 0.04 mm wide; largest accessory stylet, less than 0.1 mm long.  The proboscis is provided with 16 large nerves.The mouth and proboscis open together.  There are three large communicating blood lacunae in the head, one on the right, one on the left, and one dorsal to the rhynchodaeum.

Excretory System

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

Nephridia:

The nephridia reach forward close to the posterior ends of the cerebral sense organs.  anteriorly there is a tangle of small vessels, but farther back these unite into a single large, branched canal which runs close beside the blood vessels above the lateral nerve on each side.  From these canals a pair of large efferent ducts pass avow the lateral never cord, and open to the exterior of the body just below the lateral margin.

Sensory Organs

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

Ocelli:

The eyes are rather large, and number 25 to 30 or upwards on each side.  the majority lie in an irregular marginal row beside and in front of each of the black cephalic spots.  At the posterior end of each marginal cluster the ocelli are more closely and more irregularly placed, and often occupy several rows. In addition to theses marginal clusters a closely set group of about a half dozen smaller ocelli is situated in the light area lateral to the posterior end of each of the dark cephalic spots.  these ocelli lie deeper in the tissues of the head, and near the brain.

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

Cerebral sense organs:

Remarkable for their large size, being fully as large as either of the brain lobes.  They lie lateral to the brain, slightly behind the commissures, and in the angle between the dorsal and ventral lobes.  A large process form the posterior end of the dorsal lobe furnishes the sense organs of the same side with an abundant innervation.  Their posterior ends extend backwards beyond the dorsal brain lobes, against the poster faces of which they are closely pressed.  Behind the dorsal brain lobe the sense organs lie directly dorsal to the lateral nerve-cords and are bathed on their internal borders by large blood lacunae.  A section through this point is not very different from a corresponding section of a Heteronemertean.  Of the Alaska Metanemerteans here recorded this i the only one in which the cerebral sense organs lie posterior to the brain commissures.  The canal by which each sense organ communicates with the exterior is o large size, runs anteriorly in front of the brain, and opens on the ventro-lateral aspect of the head.

Reproductive System

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

Reproductive glands:

These occur both above and below the intestinal canal.  Although the sexual products were very immature in one of the specimens sectioned, yet the efferent ducts of the gland were formed as far outward as the basement layer of the cuts.  Here each duct ended in a swollen chamber lined with cylindrical epithelial cells.

Glands

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

Sub-muscular glands:

Present along anterior portion of esophageal region, but not very abundant.A broad and profusely branched intestinal caecum runs forward from the intestine well toward the brain region.  The caecum lies well beneath the esophagus and sends off numerous pouch-like branches dorsally above the lateral nerve cords.

Size

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

The individuals of this species varied from 40 to 150 mm in length.  The largest were about 6 mm wide and 2 mm thick.

Ecology

Habitat

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

Habitat:

The species was collected at Victoria, B.C. on the piles of the wharf; at Sitka among hydroids, etc., near low water (W. E. Ritter), and a finely preserved specimen from Puget Sound, State of Washington, was given to me by Prof. Trevor Kincaid. 

Taxonomic Notes

Current name is Nipponnemertes bimaculata or Collarenemertes bimaculata

References

Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.
Coe, W. R. (1904).  Nemerteans of the Pacific coast of North America. Part II. Harriman Alaska Series. 11, 111–220.