Cystisoma pellucida, Willemoes-Suhm, 1874
- Dataset
- Pelagic Invertebrates
- Rank
- SPECIES
Classification
- class
- Crustacea
- order
- Amphipoda
- family
- Cystisomatidae
- genus
- Cystisoma
- species
- Cystisoma pellucida
general
Type Locality:
Off Cape St. Vincent, 35°47' N, 8°23' W. [Zeidler, 2003] .morphology
The eyes occupy the dorsal and partly lateral surfaces. [Willemoes-Suhm, 1874] .
biology
Notes:
Zeidler (2003) describes this family [Cystisomatidae] in a new superfamily, Cystisomatoidea.There has been some speculation as to the correct description of this species. Willemoes-Suhm's description was received by the Royal Society of London on February 27th, 1873, and an abbreviated version was published in the Society's Proceedings in 1873, and lastly a more detailed description with figures in the Transactions in 1874. Thus, the correct citation for this species is Willemoes-Suhm, 1873.
One of the most distinctive species of Cystisoma distinguished by the characteristic shape of the first antennae and the exopods and uropods, because of the presence of a swollen gland. In addition, the prehensile nature of pereopod 7 with its small dactyl is also a distinctive feature of this species. [Zeidler, 2003] .
diagnostic
The head is slightly more in length than height. The eyes occupy the dorsal and partly lateral surfaces, leaving free the relatively broad, slightly convex remaining part of the head. There are 13-15 marginal denticles. Antennae I in females are attached (lateral view) at the level of the lower border of the eyes or lower and their length is approximately the same as that of the head. The head in males is relatively lower and the antennae adjacent and much longer than the head. In females the tip of the flagellum is bulged due to the presence of a highly developed apical gland. The ventral denticles comprise four to seven pairs, more often five-six pairs. The mandibles have one highly developed central denticle. The coxal spines of pereopods I-II are strong, long, and very acute. The 2nd segment of pereopods I is equal in length to the rest of the leg, with denticles present along the entire anterior margin and the distal part of the posterior margin; the process of the 5th segment is equal to the basal part of the segment or slightly longer than it, with denticulate margins, and extends to the base of the claw; the 6th segment has a straight denticulate posterior margin while the anterior margin is barely convex with two denticulate keels terminating distally in large denticles along both sides of the claw; the claw is evenly curved and slightly longer than 1/3 of the 6th segment. The 2nd segment of pereopds II is just a little shorter than pereopods I and slightly longer than the rest of the leg; the 5th segment is distally broadened; the process on the posterior margin of the 5th segment is distinctly longer than the rest of the segment, its width at the base more than half the segmental width here, its margins denticulate, its tip extending to the base of the claw; the 6th segment is narrow, longer than the 5th and its ornamentation similar to that in pereopods I; the claw is almost straight and 1/3 the length of the 6th segment. The surface of the distal segments of both these pereopods bears sparse setae. The 2nd segment of pereopods III is carinate and equal to the whole pereopods II in length, being 10 times or more longer than wide, with strong denticles on the posterior margin and weakly denticulate anterior chela; the 4th and 5th segments are equal in length and coarsely denticulate posteriorly; the 6th segment is the same length as the preceding segments but narrower and more finely denticulate posteriorly, its distal end bulged in the mature female because of the developed gland; the claw is barely curved and about 1/5 the length of the 6th segment; the surface of the 4th-6th segments has sparse groups of thin setae. Pereopods IV are longer than pereopods III; the 2nd segment is slightly broader than successive ones; the 6th segment is longer than the 5th. Pereopods V are the longest due to elongation of the distal segments; the 2nd segment is denticulate on both sides and the distal denticle of the anterior margin reaches almost to the end of the 3rd segment; the 5th segment is longer than the 4th, anteriorly denticulate like it except for the narrowed distal part, evenly curved forward; the 6th segment is narrow, highly elongated, and in a folded condition reaches the middle of the 4th segment. Pereopods VI are shorter than pereopods V by half the length of their 6th segment. Pereopods VII have narrow 2nd-5th segments and extend to the end of the 4th segment of pereopods VI or are slightly longer; the 2nd segment is slightly constricted distallyand five-six times longer than wide; the 4th and 5th segments are about 2/3 the length of the 2nd segment; the medial surface of the 5th-6th segments has transverse rows of thin setae; the 6th segment in mature females is bulged and clavate because of the highly developed gland, its maximum width occurring slightly before the distal end, the medial surface covered with setae, and the anterior prominence of the distal margin separated from the base of the claw by a notch; the base of the claw rises above the notch and the thick, deeply curved claw rests with its tip in the anterior prominence, thus closing the place for the egg. The urosome (with uropods) is longer than the pleon. The basipodite of uropods I is four times longer than wide; the endopodite is short and proximally broad; the exopodite in females is much longer, in males slightly longer than the endopodite; in females it is almost half the length of the basipodites, distally bulged, but with an acute apex. The basipodite of uropods III is slightly broadened distally and the ratio of length to maximum width 3:1; the exopodite is slightly more than half the length of the basipodite. [Willemoes-Suhm, 1874].
distribution
Widely distributed in the Atlantic (from 45° N to 35° S) and Indian Oceans, and in the Indo-West Pacific. In the Pacific Ocean it was found off southern California and in the waters of Tasmania at 43° S, and 150° E. [Willemoes-Suhm, 1874]
Zeidler (1992) recorded specimens of this species off the coast of Australia.
look_alikes
Willemoes-Suhm, 1874: 634 (Thaumatops); Woltereck, 1903: 452 (Thaumatops); Stephensen, 1918: 64 (Thaumatops); Spandl, 1927: 172 (Thaumatops); barnard, 1932: 272; Pirlot, 1938: 364. --? neptunus Guerin-Menewille, 1842: 215. -longipes type sp. B. Bovallius, 1889: 47 (Thaumatops). --parkinsoni Stephensen, 1918: 27 (Thaumatops).
size
Body length up to 85 mm. [Willemoes-Suhm, 1874].