Paraleiopus macrochelis Silva-Brum, 1978

Araújo-Silva, Catarina De L. & Larsen, Kim, 2010, Tanaidacea from Brazil. II. A revision of the subfamily Hemikalliapseudinae (Kalliapseudidae; Tanaidacea; Crustacea) using phylogenetic methods, Zootaxa 2555, pp. 30-48 : 44

Paraleiopus macrochelis Silva-Brum, 1978

( Figs. 5 B, 6 A–I)

Description of manca II. Length, 0.51 mm.

Body ( Fig. 5 B). Slender similar to the adult (about 7.5 times longer than broad) but cylindrical.

Pleotelson ( Fig. 6 B). Similar proportions as in the adult.

Cheliped ( Fig. 6 D) remarkably similar to the adult but with far fewer setae, none on which setules could be observed. Exopod of similar proportions as in the adult but with fewer distal setae.

Pereopod 1 ( Fig. 6 E) also much like adult but with far fewer setae. Propodus also with fewer heavy spiniform setae. Anlage for sensory apparatus visible.

Pereopod 2 and 3 ( Fig. 6 F, 6G) also like in the adult but with far fewer setae.

Pereopod 4 and 5 ( Fig. 6 H, 6I) with large, 5 articulated, and setose exopod; articles of successively smaller size.

Pereopod 6 not developed in the manca II larval stage.

Pleopods not developed in the manca II larval stage.

Uropod ( Fig. 6 B) Basal article longer and wider than individual endopod articles. Exopod as in adult but with fewer setae; endopod with about 10 articles but with few setae.

Remarks on the ontogeny of the pereopodal exopod. The function of the cheliped and pereopod 1 exopod has been attributed to assist in respiration ( Dennell 1937) or feeding ( Drumm 2005) but while the role of the exopod in respiration is not logical (given the many taxa that lack a cheliped exopod), its function in feeding is better supported ( Drumm 2005).

The pereopod exopods of the manca stages of the kalliapseudids are most interesting; their phylogeny significance have been debated by several authors ( Larwood 1954, Lang 1956a, Guţu & Heard 2002, Hansknecht et al. 2002, Santos 2007). Menzies (1953) was the first who described the presence of an exopod on the posterior pereopods of the manca stage in the Kalliapseudidae or even in the Tanaidacea . However, such an exopod is not restricted to this family ( Guţu 1989) and the patterns of development are far from clear and certainly not identical among the species. For example, no exopods are presence on the posterior pereopods on the manca of Psammokalliapseudes ( Lang 1956a: 222) . The manca of the Paraleiopus species mentioned above, does display these exopods and these are multiarticulated and very large (half as long as entire basis) while the anterior exopods are far smaller relative to the basis, consist of only two articles and a peduncle, and are only equipped with terminal setae. The exopods of the posterior pereopods are not retained in adulthood of Paraleiopus while the exopods of the cheliped and anterior pereopod are retained. The same situation is found in the family Sphyrapodidae . However, A. petronius does not display anterior exopods, neither in the adult nor the manca I larvae. Nevertheless the Acutihumerus manca I does display large posterior exopods (apparently uniarticulate but it should be mentioned that the articulations in the manca I larvae are very indistinct).

It is puzzling that some species display anterior exopods in adulthood while losing the posterior ones ( Acutihumerus never displays anterior exopods in any ontogenetic stage but does display posterior exopods as a manca). It is also notable that the anterior and posterior exopods are so strikingly different in morphology and one wonders if we are really dealing with a homologous structure. The impact of this character on the phylogeny would be very interesting to examine but the condition of the manca is only known for a few species and thus not included in the analysis above.

Figures

FIGURE 6. Paraleiopus macrochelis Silva-Brum, 1978. Manca II. A, antennas; B, telson and uropods; C, maxilliped; D, cheliped; E, pereopod 1; F, pereopod 2; G, pereopod 3; H, pereopod 4; I, pereopod 5. Scale bars = 0.1 mm.

FIGURE 5. A, Acutihumerus petronius n. sp. Manca I larvae. B. Paraleiopus macrochelis Silva-Brum, 1978. Manca II. Scale bars = 0.1 mm and 0.2 mm