Larval development of the parasitic barnacle Heterosaccus papillosus (Cirripedia: Rhizocephala: Sacculinidae) studied under laboratory conditions

Abstract

Larval development of the parasitic barnacle Heterosaccus papillosus (Cirripedia: Rhizocephala: Sacculinidae) is described from larvae reared in the laboratory. Lecithotrophic nauplii of H. papillosus reached the cypris stage in 3.5 days, at 22^238C. The development included ¢ve naupliar and the single cypris stage, thus following the typical pattern in the Rhizocephala Kentrogonida. Like the nauplii of all sacculinids, those of H. papillosus had a single pigmented nauplius eye, unsegmented frontolateral horns each with two long spines and a tubercle between the furcal rami, but they lack a £otation collar and have no seta on the antennal basipod. The male larvae are larger than female ones, the mean lengths in the two sexes never overlap. The most interesting feature of this species are the morphological di¡erences between the male and female larvae. In the male nauplii III to V the anterior body margin is noticeably convex, that is not characteristic for female larvae. The male cyprid also has a more acuited anterior region, whereas that of the female is rounded.

Synchronism of naupliar development of Sacculina carcini Thompson, 1836 (Pancrustacea, Rhizocephala) revealed by precise monitoring

“…The method of counting antennulary setae may vary according to the publications. Walossek et al [8], Rybakov et al [11] and Ponomarenko et al [12] numbered antennulary setae from S1 for the preaxial seta to S5 for the postaxial seta. Collis and Walker [7] numbered from postaxial to preaxial.…”

“…Frontal horns are short, directed rearward (Figs. 1a, 2a), with a triangular shape and an apical [7] b Walossek et al [8] c Korn et al [9] d Korn and Rybakov [10] e Rybakov et al [11] f Ponomarenko et al [12] Larval instar Species anterior spine, without terminal fringe (Fig. 3b).…”

“…After this work, investigators began to count exuviae and fix rhizocephalan larvae samples more frequently. Five naupliar instars were subsequently described in other Sacculinidae species: Polyascus polygenea [9], Sacculina pilosella [10] and Heterosaccus papillosus [12]. Five instars were also found in Peltrogastridae: Peltogasterella sulcatus, P. gracilis [11] and Peltogaster reticulatus [26].…”

“…An ovoid shape and frontal horns pointing rearward are N1 specific characters and are common to the N1 instar of all Rhizocephala [8][9][10][11][12], Thoracica [31], and Acrothoracica [39,40].…”

“…Four naupliar instars have been described for S. carcini [6,7], but several descriptions of other Rhizocephala species count five naupliar instars: Briarosaccus tenellus [8], Polyascus polygenea [9], Sacculina pilosella [10], Peltogasterella gracilis and P. sulcata [11], and Heterosaccus papillosa [12]. The number of naupliar instars in Rhizocephala is a matter of some debate [11,13] and our aim was to monitor larval development precisely to determine the exact number of naupliar instars.…”