Peraclis michaelsarsi, Bonnevie, 1913
- Dataset
- Pelagic Invertebrates
- Rank
- SPECIES
Classification
- class
- Gastropoda
- order
- Thecosomata
- family
- Periclididae
- genus
- Peraclis
- species
- Peraclis michaelsarsi
diagnostic
Male: The body is somewhat compressed laterally, the pleon is shorter than the pereon, the posterior angles of epimerons I-III are round, and the entire body, especially its anterior part, is covered with thin setae, which are solitary on the pleon and urosome. The head is somewhat shorter than the first three somites of the pereon, large, round, and its height more than its length. The entire surface of the head is covered with thin setae, located in the angles of the facets of the eyes. Antennae I are shorter than antennae II; the 1st segment of the peduncle is strong, its length just a little more than its width, and both distal segments half the length of the 1st; the 1st segment of the flagellum is equal to the entire peduncle of the antennae and, like the remaining segments (12), is densely armed with thin setae. Antennae II are attached to the lower anterior angle of the head; the flagellum consists of 13 segments. The mandibles have a broad denticulate cutting edge and a three-segmented palp; the left mandible has an accessory - small plate. The narrow outer lobes of the maxillipeds taper sharply distally and the fused inner lobes are barely discernible. The 2nd segment of pereopods I is equal in length to all the other segments together; the 4th segment slightly broadens distally and its lower distal angle is straight; the 5th segment is highly broadened distally and its lower distal angle stretched into a very short chisel-like process bearing a long and strong terminal spine; the narrowly oval 6th segment has a slightly curved posterior margin compactly pressed against the distal margin of the 5th segment to form the subchela; the claw is strong, curved, with short setae in the middle of its concave posterior margin. Pereopods II are somewhat longer than pereopods I; the 2nd segment is shorter than all the successive segments together; the short 5th segment has a well-developed distal process exceeding the length of the segment, its posterior margin bearing numerous short spinules, and the anterior side, with a dolabriform depression bearing a long strong terminal spine; the 6th segment is almost linear and three times longer than wide; the claw is deeply curved. Pereopods III and IV are equal in length; the 2nd segment is broadened distally and twice wider than at the base; the 5th segment is somewhat longer than the 4th; the 6th segment is equal to the 5th, only slightly narrower, its posterior margin straight; the claw is weakly curved and 1/4 the length of the 6th segment; the surface of the segments is covered with short setae, particularly abundant in the proximal parts of the legs. Pereopods V, VI and VII are similar in structure and equal in length; the 5th segment is longer than the 4th but much shorter than the 3rd and 4th segments together; the 6th segment is shorter than the 5th but only slightly narrower; the claw is strong and 1/3 the length of the 6th segment; the surface of the segments, particularly in the proximal part of the pereopods, is covered with numerous setae. Both margins of the basipodite of uropods I bear strong setae; the rami are narrowly lanceolate, the outer ramus somewhat longer than the inner. The basipodite of uropods II is half as narrow as uropods I and the broad basipodite of uropods III has a slightly curved outer margin and a straight inner margin; the exopodite is longer than the endopodite and 3/4 the length of the basipodite. The telson is triangular, its width at the base equal to its length, which is half that of the basipodite of uropods III. Female: The body is somewhat broader than in the male. The head is larger and in length equal to the first three somites of the pereon, but its height almost two times its length. The 1st segment of the peduncle of antennae I is large, semicircular, much longer than the next two segments together; the one-segmented flagellum somewhat exceeds the peduncle in length. Antennae II are rudimentary and consist of just two small segments. Pereopods I and II are identical in structure to the male. Pereopods III and IV are somewhat longer; the 2nd segment is much longer than in pereopods II, narrows proximally, and is almost 2.5 times broader in the distal part; the 5th segment is longer than the 4th; the 6th segment is shorter and much narrower than the 5th; the curved claw is 1/3 the length of the 6th segment. Pereopods V-VII are shorter than III and IV; the 6th segment broadens distally; the strong curved claw together with the broadened part of the 6th segment forms a unique prehensile organ. The basipodite of uropods I is relatively broader than in the male and three times longer than wide. The structure of the other legs does not differ significantly in the two sexes. The oostegites are located on somites II-V of the pereon, irregularly triangular in shape, and much longer than the gill sacs. [Bovallius, 1887].
diagnostic
Symmetrical tentacles, without sheath, the lips and footlobes form trumpet-shaped proboscis. Wings fused into swimming disc. Central nervous system with separate abdominal ganglion. Lateral and median lips are fused at lateral points where they meet. [van der Spoel, 1976]
distribution
Distribution in the Atlantic Ocean from 57° N up to 37° 33' S in the Mediterranean Sea. In the Pacific Ocean it was found at 14° 52' S, 76° 47' W (1 male). The species is rare; reports usually pertain to isolated finds. [Bovallius, 1887].
distribution
Type Locality: 48°29'N 13°55'W. [van der Spoel, 1976]
Distribution: Only record south of Iceland. Northern distribution when synonymous with P. valdiviae. [van der Spoel, 1976]
habitat
Mesopelagic [Bonnevie, 1913]
look_alikes
Procymbulia michaelsarsi, Bonnevie, 1913
size
Unknown shell length, swimming disc could not be measured. About 0.5cm in height. [Bonnevie, 1913]