Laonice cricketae Sikorski & Pavlova, 2016, sp. nov.

Laonice cricketae sp. nov.

(Figures 3 A–F, 5)

Laonice cirrata — Kirkegaard 1959: 18 (partim).

Holotype: R/V "Galathea" Eksp., Guinea Bay, St. 92, 06°40ʼS, 11°36ʼE, 380 m, 0 9 Dec. 1950 (ZMUC-POL- 642).

Description. Anterior fragment of 1.9 mm width with 48 chaetigers.

Prostomium obviously fused to the peristomium by the anterior margin (very conspicuous fold connecting the anterolateral corner of prostomium and peristomium presented on Fig. 3 B, arrow). Prostomium triangular (Fig. 3 A–B) with two large eyespots in the posterior, with large cylindrical occipital papilla. Caruncle well developed, extending only to the border between chaetiger 1 and 2. Nuchal organ extending chaetiger 20.

Branchiae present until chaetiger 39. Branchiae longer than notopodial postchaetal lobes on chaetiger 2, becoming significantly longer on subsequent chaetigers posteriorly (Fig. 3 D–E), over twice as long as notopodial postchaetal lobes. Branchiae long enough to reach bases of branchiae on opposite side of body. Notopodial postchaetal lobes with acute upper tips up to and including the fifth segment. No acute tips from chaetiger 6, no peaks on the lateral margins of notopodial postchaetal lobes. Notopodial postchaetal lobes later become rounded (not extended upwards). Transverse dorsal membranes absent but there are prominent transverse dorsal ciliary bands (two per segment) on six segments posterior to nuchal organ. Neuropodial postchaetal lobes with acute upper tips up to and including the third segment (Fig. 3 C).Tips on neuropodial postchaetal lobes disappear from chaetiger 4 and the lobes become rounded. Genital pouches present until chaetiger 40.

Noto- and neuropodial capillaries arranged in two vertical rows. Neuropodial hooded hooks bidentate in side view (Fig. 3 F); but main fang is surmounted by pair of apical teeth. Hooded hooks appear on chaetiger 43, up to 7 per fascicle. Notopodial hooks are not detected. Sabre chaetae detected from chaetiger 24, up to 3 per neuropodium

Pygidium unknown.

Methyl green staining pattern. No special pattern detected, but in ethanol dorsal ciliary bands lighten much faster than the dorsal body surface.

Distribution. Off the mouth of Congo River, 380 m (Fig. 5).

Etymology. The name is given after the nickname of Dr. Mary E. Petersen.

Remarks. This species should be compared to the Laonice species having prostomium and peristomium fused anteriorly, and without transverse dorsal membranes on the middle segments: species such as L. cirrata; L. brevicornis (Kinberg, 1866); L. antarcticae Hartman, 1953; L. quadridentata Blake & Kudenov, 1978; L. shamrockensis; and probably L. asaccata Sigvaldadottir & Desbruyeres, 2003. First, it should be noted that the possible synonymization of L. petersenae Radashevsky & Lana, 2009 with L. quadridentata has been discussed by Greaves et al (2011, p. 18) based on examination of type material, but the species L. petersenae was not formally synonymized with L. quadridentata. Formally L. petersenae was synonymized with L. brevicornis in Sikorski (2011). It means that following Greaves et al. (2011) L. quadridentata is a junior synonym of L. brevicornis revised in Sikorski 2011. There is really complete overlap of all morphological characters, including shape of hooded hooks, between descriptions of these two species. L. brevicornis has (unlike L. cricketae) tridentate hooks in side view, much more pronounced fusing of prostomium and peristomium, and GP from 3–17 or absent.

The whole combination of morphological characters makes the new species closest to L. cirrata, but the degree of fusion between prostomium and peristomium by anterior margin is much more prominent in L. cirrata, but not so obvious in L. cricketae. The new species differs from L. cirrata also by short nuchal organ (L. cirrata of a similar size has longer nuchal organ—minimum till chaetiger 22), by value of difference between the numbers of the last chaetiger with nuchal organ and the chaetiger of appearance of sabre chaetae: 4 compared to 1–12 in L. cirrata, by much longer branchiae (branchiae of chaetiger 2 are even longer than notopodial postchaetal lobes).

Degree of fusion of prostomium with peristomium at the anterior margin makes this species close to L. shamrockensis and L. asaccata. But this feature is the only one bringing them together. The main differences between L. cricketae and L. antarcticae are: the appearance of genital pouches in L. antarcticae from chaetiger 3–4 compared to 40 in L. cricketae, and the length of nuchal organ, to chaetiger 12–13 in L. antarcticae compared to 20 in L. cricketae.

L. cricketae resembles L. antarcticae in the pattern of fusing of prostomium and peristomium. L. japonica (Moore, 1907) may also look similar to L. cricketae due to the prostomium and peristomium being set quite close together and the similar values of the majority of numeric characters. However, GP appear from chaetiger 4 in L.

japonica compared to 40 in L. cricketae, there are more (up to 15) hooks per neuropodium in L. japonica compared to 7 in L. cricketae, and branchiae until chaetiger 4 are lower than notopodial postchaetal lobes in L. japonica, unlike L. cricketae.