Serrula acuta, Schockaert & Curini-Galletti & Ridder & Volonterio & Artois, 2009

Schockaert, Ernest R., Curini-Galletti, Marco, Ridder, Wouter De, Volonterio, Odile & Artois, Tom, 2009, A new family of lithophoran Proseriata (Platyhelminthes), with the description of seven new species from the Indo-Pacific and South America, and the proposal of three new genera, Zoological Journal of the Linnean Society 155 (4), pp. 759-773 : 767-768

SERRULA ACUTA SP. NOV.

Diagnoses: Serrula byronensis : species of Serrula with an unpaired seminal vesicle, a prepenial vagina, and a copulatory bursa. The needles are pointed: 14-Mm long, and 5–6-Mm wide at the base. The precerebral diverticle ends at the statocyst.

Serrula maxillaria : species of Serrula with a single seminal vesicle. Atrial needles are 13-Mm long and 3-Mm wide over the whole length, and have a truncated and serrated distal end. The precerebral diverticle ends at the statocyst.

Serrula concharum : species of Serrula with paired seminal vesicles; needles are similar to those of S. maxillaria , 15-Mm long and 5-Mm wide. Pre-cerebral diverticle ends anteriorly of the statocyst.

Serrula acuta : species of Serrula with a single seminal vesicle?; slender pointed needles that are 25-Mm long, and are 6-Mm wide at the base. No data on the living animal.

Occurrence: Serrula byronensis: Byron Bay , Australia (New South Wales); exposed intertidal at Tallum Beach , mid-fine sand (October 1993).

Serrula maxillaria: Cairns , Australia (Queensland); protected beach at Yorkney’s Knob , with fine to midfine sand (October 1993).

Serrula concharum: Eaglehawk Neck, Australia (Tasmania); exposed intertidal, with fine sand, and with a high density of Mesodesmatidae bivalves of the genus Paphies Lesson, 1830 (October 1993) .

Serrula acuta : same locality as S. maxillaria .

Material studied: Drawings from the living animals, except for S. acuta . One whole mount of each species (designated as holotypes, QM G 230108–230111). Sections of one individual of S. byronensis of very poor quality, and without relevant information (except the epidermis) (UH 393).

Etymology: The genus name refers to the serrate end of the needles in two of the species (Latin serrula: little saw). The species epithet of S. byronensis refers to the place where it has been found; that of S. concharum refers to the co-occurrence with many shells (Latin concha: shell); the needles of S. maxillaria show some resemblance to the maxillae of crustaceans; the needles of S. acuta are very slender and pointed (Latin acuta : pointed).

Description: These four species are described from only one living individual of each species, and from the whole mounts. Therefore, our knowledge of a number of important characters is lacking. Nevertheless, we consider it worthwhile to describe them, hoping that more abundant material may be found in the future.

The four species are relatively small: only about 1-mm long. They have the usual anterior sensory bristles, but also have long bristles at the caudal end. Serrula byron also has prominent adhesive papillae ( Figs 13 , 14 ). The precerebral gut diverticle reaches far in front of the statocyst in S. concharum , whereas it ends roughly above the statocyst in S. byronensis and S. maxillaria (and is unknown in S. acuta ). Cnidocysts were seen in the anterior part of the gut in S. maxillaria .

The globular and ventrally directed pharynx is placed at the first quarter of the body; the ovaries, located anterior to the pharynx, are preceded by a single pair of testes. All vitellarian follicles are behind the pharynx, and the posteriormost follicles are found in front of the copulatory bursa in S. byronensis , and in front of the copulatory organ in the other species. The female pore is located at some distance behind the seminal vesicle ( Fig. 14 ). The copulatory organ is directed forwards, with a small prostate vesicle on which the two needles are attached. Serrula concharum has a pair of seminal vesicles; the other species have an unpaired seminal vesicle. Only in S. byron has a prepenial copulatory bursa been observed, with a vagina just in front of the copulatory organ. We could not determine whether the vagina and the male pore are combined or not. As far as the whole mount reveals, S. acuta has a single seminal vesicle, whereas a copulatory bursa is absent. Without sections, it cannot be said if a genitointestinal connection or a resorbing bursa is present.

The hard parts of the copulatory organ ( Fig. 15 ) consist of two spines that we interpret as the equivalent of the needles in the male atrium of the other representatives of Meidiamidae . Except in S. acuta , each of the two needles sits on a base, evidently formed by two muscles that ‘flank’ the prostate vesicle at either side. Because of the lack of sections, the hypothesis that these bases are muscles is yet to be confirmed. The form and size of the needles are given in the diagnoses.

Figures

Figure 13. Living specimens of the species of Serrula. A, Serrula byronensis sp. nov.; B, Serrula maxillaria sp. nov.; C, Serrula concharum sp. nov. Refer to the Appendix for a list of abbreviations.

Figure 14. Posteriormost body part in live animals. A, Serrula byronensis sp. nov.; B, Serrula maxillaria sp. nov.; C, Serrula concharum sp. nov. Refer to the Appendix for a list of abbreviations.

Figure 15. The needles and the muscular supports of the copulatory organ in the species of Serrula. A, Serrula byronensis sp. nov.; B, Serrula maxillaria sp. nov.; C, Serrula concharum sp. nov.; D, Serrula acuta sp. nov. Refer to the Appendix for a list of abbreviations.