Cetacean strandings along the Pacific and Caribbean coasts of Nicaragua from 2014 to 2021

Documenting marine mammal strandings provides important information needed to understand the occurrence and distribution patterns of species. Here, we report on strandings of cetaceans on the Pacific (n = 11) and Caribbean (n = 2) coasts of Nicaragua, documented opportunistically from 2014 to 2021. Strandings included three species of baleen whale (blue whale Balaenoptera musculus, Bryde’s whale Balaenoptera edeni, humpback whale Megaptera novaeangliae) and five species of toothed whale (dwarf sperm whale Kogia sima, Guiana dolphin Sotalia guianensis, pantropical spotted dolphin Stenella attenuata, spinner dolphin Stenella longirostris, Cuvier’s beaked whale Ziphius cavirostris). These are the first published accounts of blue whales, Bryde’s whales, dwarf sperm whales, and Cuvier’s beaked whales in Nicaraguan waters. Limited resources and the advanced decomposition of animals prevented necropsies in most cases, the identification of the causes of mortality in all cases, and the species identification of two dolphins. Information derived from these stranding events offers new insights into the occurrence of marine mammals on the Pacific and Caribbean coasts of Nicaragua and Central America.

Deep-sea predator niche segregation revealed by combined cetacean biologging and eDNA analysis of cephalopod prey

Fundamental insight on predator-prey dynamics in the deep sea is hampered by a lack of combined data on hunting behavior and prey spectra. Deep-sea niche segregation may evolve when predators target specific prey communities, but this hypothesis remains untested. We combined environmental DNA (eDNA) metabarcoding with biologging to assess cephalopod community composition in the deep-sea foraging habitat of two top predator cetaceans. Risso’s dolphin and Cuvier’s beaked whale selectively targeted distinct epi/meso- and bathypelagic foraging zones, holding eDNA of 39 cephalopod taxa, including 22 known prey. Contrary to expectation, extensive taxonomic overlap in prey spectra between foraging zones indicated that predator niche segregation was not driven by prey community composition alone. Instead, intraspecific prey spectrum differences may drive differentiation for hunting fewer, more calorific, mature cephalopods in deeper waters. The novel combination of methods presented here holds great promise to disclose elusive deep-sea predator-prey systems, aiding in their protection.

Antimicrobial Activity of Lactococcus lactis subsp. lactis Isolated from a Stranded Cuvier’s Beaked Whale (Ziphius cavirostris) against Gram-Positive and -Negative Bacteria

In the present study, we isolated and characterized Lactococcus lactis (L. lactis) subsp. lactis from a female Cuvier’s beaked whale (Ziphius cavirostris) stranded in Shizuoka, Japan. Only five isolates (CBW1-5), grown on Lactobacilli de Man Rogosa Sharpe (MRS) agar plates prepared using 50% artificial seawater, were positive in L. lactis species-specific primer PCR. Their 16S rRNA sequences were highly similar to those of L. lactis subsp. lactis JCM 5805T. The Gram reaction, motility, gas production from glucose, catalase production, and growth conditions were consistent with those of the type strain. Additionally, carbohydrate utilization of the strains was consistent with previously reported marine organism-derived strains. The pH-neutralized cell-free culture supernatant of strain CBW2 inhibited the growth of Bacillus subtilis subsp. subtilis ATCC 6051 and Vibrio alginolyticus ATCC 17749, whereas protease treatment eliminated or diminished its inhibitory activity. The strain possesses a precursor of the nisin structural gene (nisA), which showed 100% homology with nisin Z, and nisin biosynthesis-related genes (nisB, nisC, nisT, nisP, nisF, nisI, and nisRK), suggesting that the strain produces a nisin-like substance. This study provides fundamental information on whale-derived L. lactis subsp. lactis which may be useful for reducing the carriage of B. subtilis subsp. subtilis and V. alginolyticus.

First records of Cuvier’s beaked whale (Ziphius cavirostris, G. Cuvier 1823) strandings along the Tunisian coast

The Cuvier’s beaked whale (Ziphius cavirostris) is the only member of the Ziphiidae family with a regular occurrence in the Mediterranean Sea. Much of the knowledge of this species in the Mediterranean has come from stranding data. This note reports the first records of strandings of Cuvier’s beaked whales along the Tunisian coast. The two strandings described are about two specimens, likely adult animals. The first specimens was 530 cm long and beached at El Hicha (Gulf of Gabès, south Tunisia) on March 5th, 2019. The second specimens was 630 cm long and it was reported in Ras Angla (Bizerte, north Tunisia) on June 6th, 2019. Since this species faces multiple threats in the Mediterranean basin, this contribution is intended to extend previous knowledge of this species in the region and to push towards major efforts to be undertaken to fill the knowledge gaps regarding occurrence of Cuvier’s beaked whale along northern Tunisia.

First assessment of POPs and cytochrome P450 expression in Cuvier’s beaked whales (Ziphius cavirostris) skin biopsies from the Mediterranean Sea

The Cuvier's beaked whale (Ziphius cavirostris) is one of the least known cetacean species worldwide. The decreasing population trend and associated threats has led to the IUCN categorising the Mediterranean subpopulation as Vulnerable on the Red List of Threatened Species. This study aimed to investigate for the first time the ecotoxicological status of Cuvier's beaked whale in the NW Mediterranean Sea. The study sampled around the 20% of the individuals belonging to the Ligurian subpopulation, collecting skin biopsies from free-ranging specimens. The levels of polychlorinated biphenyl (PCBs), polybrominated diphenyl ethers (PBDEs) and induction of cytochrome's P450 (CYP1A1 and CYP2B isoforms) were evaluated. Results highlighted that the pattern of concentration for the target contaminants was PCBs > PBDEs and the accumulation values were linked to age and sex, with adult males showing significantly higher levels than juvenile. Concerns raised by the fact that 80% of the individuals had PCB levels above the toxicity threshold for negative physiological effects in marine mammals. Therefore, these findings shed light on this silent and serious threat never assessed in the Mediterranean Cuvier’s beaked whale population, indicating that anthropogenic pressures, including chemical pollution, may represent menaces for the conservation of this species in the Mediterranean Sea.